Fabrication of highly hydrophobic two-component thermosetting polyurethane surfaces with silica nanoparticles

NASA Astrophysics Data System (ADS)

Yang, Guang; Song, Jialu; Hou, Xianghui

2018-05-01

Highly hydrophobic thermosetting polyurethane (TSU) surfaces with micro-nano hierarchical structures were developed by a simple process combined with sandpaper templates and nano-silica embellishment. Sandpapers with grit sizes varying from 240 to 7000 grit were used to obtain micro-scale roughness on an intrinsic hydrophilic TSU surface. The surface wettability was investigated by contact angle measurement. It was found that the largest contact angle of the TSU surface without nanoparticles at 102 ± 3° was obtained when the template was 240-grit sandpaper and the molding progress started after 45 min curing of TSU. Silica nanoparticles modified with polydimethylsiloxane were scattered onto the surfaces of both the polymer and the template to construct the desirable nanostructures. The influences of the morphology, surface composition and the silica content on the TSU surface wettability were studied by scanning electron microscopy (SEM), attenuated total reflection (ATR) infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The surface of the TSU/SiO2 nanocomposites containing 4 wt% silica nanoparticles exhibited a distinctive dual-scale structure and excellent hydrophobicity with the contact angle above 150°. The mechanism of wettability was also discussed by Wenzel model and Cassie-Baxter model.

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

PubMed

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of the effect of plasma treatment and gamma ray irradiation on PS-Cu nanocomposite films surface

NASA Astrophysics Data System (ADS)

Farag, O. F.

2018-06-01

Polystyrene-copper (PS-Cu) nanocomposite films were treated with DC N2 plasma and gamma rays irradiations. The plasma treatment of PS-Cu film surface was carried out at different treatment times, gas pressure 0.4 Torr and the applied power 3.5 W. On the other hand, the treatment with gamma rays irradiation were carried out at irradiation doses 10, 30 and 50 kGy. The induced changes in surface properties of PS-Cu films were investigated with UV-viss spectroscopy, scanning electron microscopy (SEM) and FTIR spectroscopy techniques. In addition, the wettability property, surface free energy, spreading coefficient and surface roughness of the treated samples were studied by measuring the contact angle. The UV-viss spectroscopy analysis revealed that the optical band gap decreases with increasing the treatment time and the irradiation dose for plasma and gamma treatments, respectively. SEM observations showed that the particle size of copper particles was increased with increasing the treatment time and the irradiation dose, but gamma treatment changes the copper particles size from nano scale to micro scale. The contact angle measurements showing that the wettability property, surface free energy, spreading coefficient and surface roughness of the treated PS-Cu samples were increased remarkably with increasing the treatment time and the irradiation dose for plasma and gamma treatments, respectively. The contact angle, surface free energy, spreading coefficient and surface roughness of the treated PS-Cu samples are more influenced by plasma treatment than gamma treatment.

Synthesis and Characterization of Hydrophobic Silica Thin Layer Derived from Methyltrimethoxysilane (MTMS)

NASA Astrophysics Data System (ADS)

Darmawan, Adi; Utari, Riyadini; Eka Saputra, Riza; Suhartana; Astuti, Yayuk

2018-01-01

This study investigated the synthesis and characterization of MTMS hydrophobic silica prepared by sol-gel method. In principle, silica xerogels and silica thin layer were obtained by reacting MTMS in ethanol solvent in some pH variations. The MTMS solution was used to modify the surface of the ceramic plate by dipcoating method to further be calcined at two different temperatures of 350°C and 500°C. The silica xerogels were analysed by FTIR, TGA-DSC and GSA to determine functional group characteristics, thermal properties and pore morphology respectively. Meanwhile, the silica thin layers were analysed their hydrophobic properties using water contact angle measurement and surface roughness determination using SEM. The results showed that the higher the pH used in the MTMS solution, the higher the resulting contact angle. The highest contact angle was obtained at pH 8.12 which reached 94.7° and 79.5° for silica thin layer calcined at 350°C and 500°C, respectively. The TGA results indicated that the methyl group survived up to 400°C and disappeared at 500°C which had implications on silica thin layer hydrophobic nature. GSA result exhibited that the silica xerogel had a close structure with a very low pore volume. While the SEM-EDX results displayed that the silica thin layer prepared at acidic pH had smoother surface morphology and became rough when prepared at an alkaline pH.

Cheap non-toxic non-corrosive method of glass cleaning evaluated by contact angle, AFM, and SEM-EDX measurements.

PubMed

Dey, Tania; Naughton, Daragh

2017-05-01

Glass surface cleaning is the very first step in advanced coating deposition and it also finds use in conserving museum objects. However, most of the wet chemical methods of glass cleaning use toxic and corrosive chemicals like concentrated sulfuric acid (H 2 SO 4 ), piranha (a mixture of concentrated sulfuric acid and 30% hydrogen peroxide), and hydrogen fluoride (HF). On the other hand, most of the dry cleaning techniques like UV-ozone, plasma, and laser treatment require costly instruments. In this report, five eco-friendly wet chemical methods of glass cleaning were evaluated in terms of contact angle (measured by optical tensiometer), nano-scale surface roughness (measured by atomic force microscopy or AFM), and elemental composition (measured by energy dispersive x-ray spectroscopy or SEM-EDX). These glass cleaning methods are devoid of harsh chemicals and costly equipment, hence can be applied in situ in close proximity with plantation such as greenhouse or upon subtle objects such as museum artifacts. Out of these five methods, three methods are based on the chemical principle of chelation. It was found that the citric acid cleaning method gave the greatest change in contact angle within the hydrophilic regime (14.25° for new glass) indicating effective cleansing and the least surface roughness (0.178 nm for new glass) indicating no corrosive effect. One of the glass sample showed unique features which were traced backed to the history of the glass usage.

Waterborne Superhydrophobic and Superoleophobic Coatings for the Protection of Marble and Sandstone

PubMed Central

Aslanidou, Dimitra; Lampakis, Dimitrios

2018-01-01

Silica nanoparticles were dispersed in an aqueous emulsion of alkoxy silanes and organic fluoropolymer. The dispersion was sprayed onto white marble and sandstone. The deposited composite coatings exhibited (i) superhydrophobicity and superoleophobicity, as evidenced by the high (>150°) static contact angles of water and oil drops as well as (ii) water and oil repellency according to the low (<7°) corresponding tilt contact angles. Apart from marble and sandstone, the coatings with extreme wetting properties were deposited onto concrete, silk, and paper, thus demonstrating the versatility of the method. The siloxane/fluoropolymer product was characterized using Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy and Scanning Electron Microscopy equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDX). Moreover, SEM and FT-IR were used to reveal the surface structures of the composite coatings and their transition from superhydrophobicity to superhydrophilicity which occurred after severe thermal treatment. The composite coatings slightly reduced the breathability of marble and sandstone and had practically no optical effect on the colour of the two stones. Moreover, the coatings offered good protection against water penetration by capillarity. PMID:29642652

Surface treatment of polypropylene (PP) film by 50 Hz dielectric barrier discharge produced in air and argon/air mixture at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Ujjwal Man, E-mail: umjoshi@gmail.com; Subedi, Deepak Prasad, E-mail: deepaksubedi2001@yahoo.com

Thin films of polypropylene (PP) are treated for improving hydrophilicity using non-thermal plasma generated by 50 Hz line frequency dielectric barrier discharge produced in air and argon/air mixture at atmospheric pressure. PP samples before and after the treatments are studied using contact angle measurements, surface free energy calculations and scanning electron microscopy (SEM). Distilled water (H{sub 2}O), glycerol (C{sub 3}H{sub 8}O{sub 3}) and diiodomethane (CH{sub 2}I{sub 2}) are used as test liquids. The contact angle measurements between test liquids and PP samples are used to determine total surface free energy using sessile drop technique. PP films show a remarkable increase inmore » surface free energy after plasma treatment. SEM analysis of the plasma-treated PP films shows that plasma treatment introduces greater roughness on the surface leading to the increased surface free energy. Furthermore, it is found that introducing a small quantity of argon can enhance the surface treatment remarkably.« less

The method of synthesizing of superhydrophobic surfaces by PECVD

NASA Astrophysics Data System (ADS)

Orazbayev, Sagi; Gabdullin, Maratbek; Ramazanov, Tlekkabul; Dosbolayev, Merlan; Zhunisbekov, Askar; Omirbekov, Dulat; Otarbay, Zhuldyz

2018-03-01

The aim of this work was to obtain superhydrophobic surfaces in a plasma medium. The experiment was carried out using the PECVD method in two different modes: constant and pulsing. The surface roughness was obtained by applying nanoparticles synthesized in plasma in a mixture of argon and methane. The resulting particles were deposited on the surface of silicon and glass materials. The contact angle increased linearly depending on the number of cycles, until it reached 160° at 150-160th cycles, after that the increase in cycles does not affect the contact angle, since the saturation process is in progress. Also the effect of the working gas composition on the hydrophobicity of the surface was studied. At low concentrations of methane (1%) only particles are synthesized in the working gas, and hydrophobicity is unstable, with an increase in methane concentration (7%) nanofilms are synthesized from nanoclusters, and surface hydrophobicity is relatively stable. In addition, a pulsing plasma mode was used to obtain superhydrophobic surfaces. The hydrophobicity of the sample showed that the strength of the nanofilm was stable in comparison with the sample obtained in the first mode, but the contact angle was lower. The obtained samples were examined using SEM, SPM, optical analysis, and their contact angles were determined.

Surface analysis of selected hydrophobic materials

NASA Astrophysics Data System (ADS)

Wisniewska, Sylwia Katarzyna

This dissertation contains a series of studies on hydrophobic surfaces by various surface sensitive techniques such as contact angle measurements, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Hydrophobic surfaces have been classified as mineral surfaces, organic synthetic surfaces, or natural biological surfaces. As a model hydrophobic mineral surface, elemental sulfur has been selected. The sulfur surface has been characterized for selected allotropic forms of sulfur such as rhombic, monoclinic, plastic, and cyclohexasulfur. Additionally, dextrin adsorption at the sulfur surface was measured. The structure of a dextrin molecule showing hydrophobic sites has been presented to support the proposed hydrophobic bonding nature of dextrin adsorption at the sulfur surface. As a model organic hydrophobic surface, primary fatty amines such as dodecylamine, hexadecylamine, and octadecylamine were chosen. An increase of hydrophobicity, significant changes of infrared bands, and surface topographical changes with time were observed for each amine. Based on the results it was concluded that hydrocarbon chain rearrangement associated with recrystallization took place at the surface during contact with air. A barley straw surface was selected as a model of biological hydrophobic surfaces. The differences in the contact angles for various straw surfaces were explained by the presence of a wax layer. SEM images confirmed the heterogeneity and complexity of the wax crystal structure. AFM measurements provided additional structural details including a measure of surface roughness. Additionally, straw degradation as a result of conditioning in an aqueous environment was studied. Significant contact angle changes were observed as soon as one day after conditioning. FTIR studies showed a gradual wax layer removal due to straw surface decomposition. SEM and AFM images revealed topographical changes and biological life development as part of the straw degradation process. Three different classes of hydrophobic surfaces have been studied, and in each case important surface chemistry issues have been identified that influence the hydrophobic state. Many of the studies are unique to the particular system, but common phenomena that influence the hydrophobic state of all of these surfaces include time dependence due to crystallization and chemical degradation (oxidation, hydration, biological activity).

A coating of silane modified silica nanoparticles on PET substrate film for inkjet printing

NASA Astrophysics Data System (ADS)

Wu, J.; Liu, L.; Jiang, B.; Hu, Z.; Wang, X. Q.; Huang, Y. D.; Lin, D. R.; Zhang, Q. H.

2012-04-01

The paper aims to design nanoporous coatings for inkjet printing and study its microstructure influence on the ink absorption. In the present work, two inkjet materials were prepared: one with unmodified nano-SiO2 (S_1), the other with silica coupling agent modified nano-SiO2 (S_2). The surface characteristic changing after modification was investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM). Wetting with contact angles was determined by the dynamic contact angle analysis test (DCAT). Through measurements, the dispersion of modified nano-SiO2 particles in the coating was superior to the dispersion of unmodified nano-SiO2 particles, surface roughness value (Ra) of S_1 was significantly higher than that of S_2, dynamic contact angle of S_2 is smaller than that of S_1 and ink droplet absorption in S_2 was much faster than in S_1. These results also reveal that the modification method is effective and offers a potential way to fabricate inkjet material with the advantages of microstructure and ink absorption over traditional methods.

Fabrication of a novel superhydrophobic and superoleophilic surface by one-step electrodeposition method for continuous oil/water separation

NASA Astrophysics Data System (ADS)

Xiang, Meisu; Jiang, Meihuizi; Zhang, Yanzong; Liu, Yan; Shen, Fei; Yang, Gang; He, Yan; Wang, Lilin; Zhang, Xiaohong; Deng, Shihuai

2018-03-01

A novel superhydrophobic and superoleophilic surface was fabricated by one-step electrodeposition on stainless steel meshes, and the durability and oil/water separation properties were assessed. Field emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), fourier transform infrared spectroscopy (FT-IR) and optical contact angle measurements were used to characterize surface morphologies, chemical compositions, and wettabilities, respectively. The results indicated that the as-prepared mesh preformed excellent superhydrophobicity and superoleophilicity with a high water contact angle (WCA) of 162 ± 1° and oil contact angle of (OCA) 0°. Meanwhile, the as-prepared mesh also exhibited continuous separation capacity of many kinds of oil/water mixtures, and the separation efficiency for lubrication oil/water mixture was about 98.6%. In addition, after 10 separation cycles, the as-prepared mesh possessed the WCAs of 155 ± 2°, the OCAs of 0° and the separation efficiency of 97.8% for lubrication oil/water mixtures. The as-prepared mesh also retained superhydrophobic and superoleophilic properties after abrading, immersing in salt solutions and different pH solutions.

Effect of plasma treatment (He/CH4) on glass surface for the reduction of powder flux adhesion in the spray drying process

NASA Astrophysics Data System (ADS)

Ramlan, Nadiah; Zamri, Nazirah Wahidah Mohd; Maskat, Mohd Yusof; Hoong, Chin Oi; Theng, Lau Yen; Zubairi, Saiful Irwan

2018-04-01

A 50Hz glow discharge He/CH4 plasma was generated and applied for the modification of glass surface to reduce powder adhesion on the wall of spray dryer. The hydrophobicity of the glass samples determined by the water droplet contact angle and adhesion weight on glass, dependent on the CH4 flow rate and plasma exposure time. There was a peak that appeared at 1470 cm-1 on the surface of treated glass indicating the presence of CH3 groups from ATR-FTIR data. Surface morphology analysis using scanning electron microscopy (SEM) showed changes of roughness in the surface-treated glass. The presence of alkyl group (CH3) that deposited on the glass surface is one of the factors that contribute to the increase in the surface roughness. The surface roughness will reflect the value of contact angle where hydrophobic surface are rougher compared to hydrophilic surface. The plasma treatment could enhance the value of the contact angle and thus reduced the adhesion on the spray dryer glass surface.

Effect of dielectric barrier discharge treatment on surface nanostructure and wettability of polylactic acid (PLA) nonwoven fabrics

NASA Astrophysics Data System (ADS)

Ren, Yu; Xu, Lin; Wang, Chunxia; Wang, Xiaona; Ding, Zhirong; Chen, Yuyue

2017-12-01

Polylactic acid (PLA) nonwoven fabrics are treated with atmospheric dielectric barrier discharge (DBD) plasma to improve surface wettability. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that micro- to nano-scale textures appear on the treated PLA surfaces dependent on the treatment time. X-ray photoelectron spectroscopy (XPS) analysis reveals that the DBD plasma treatments result in decreased carbon contents and increased oxygen contents as well as slightly increased nitrogen contents. The water contact angle decreases sharply with the increase of the DBD plasma treatment time. The super hydrophilic PLA surfaces (the water contact angle reached 0°) are obtained when the treatment time is longer than 90 s. Ninety days after the DBD plasma treatment, the XPS analysis shows that Csbnd O/Csbnd N and Cdbnd O/Osbnd Cdbnd O percentages decline for all treatment groups. However, the water contact angle is kept constant at 0° for the groups treated above 90 s, which could be due to the oxidized nano-structured layer on the DBD plasma treated PLA surfaces.

Electrospun nerve guide scaffold of poly(ε-caprolactone)/collagen/nanobioglass: an in vitro study in peripheral nerve tissue engineering.

PubMed

Mohamadi, Forouzan; Ebrahimi-Barough, Somayeh; Reza Nourani, Mohammad; Ali Derakhshan, Mohammad; Goodarzi, Vahabodin; Sadegh Nazockdast, Mohammad; Farokhi, Mehdi; Tajerian, Roksana; Faridi Majidi, Reza; Ai, Jafar

2017-07-01

Among various methods, nerve tissue engineering (NTE) is one of the applicable methods to reconstruct damaged nerve tissues. Electrospinning technique and biomaterials are often considered to fabricate fibrous tissue engineered conduits which have great similarity to the extracellular matrix on fiber structure. Polymer blending is one of the most effective methods for the production of new materials with outstanding features. In this study, conduit structures as main part of the peripheral nerve regeneration based on polymer blend nanocomposites poly(ε-caprolactone)/collagen/nanobioglass (PCL/collagen/NBG) were manufactured by electrospinning technique. Various properties of electrospun mats were investigated by using contact angle, tensile, degradation time, porosity, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and wide-angle X-ray scattering (WAXS). The SEM analysis was shown that size range and average pore size of polymer blend nanocomposite nanofibers were about 250-400 nm and 0.7 µm, respectively, with an optimum porosity of 62.5%. The XRD result was shown that synthesized nanoparticles of NBG had amorphous structures. Also, FTIR analysis indicated that good interaction between polymer-polymer macromolecules and polymer particles. The contact angle and tensile tests were indicated that electrospun webs showed good hydrophilicity and toughness properties. According to SEM, MTT assay and DAPI staining technique, the ability to support cell attachment and viability of samples were characterized. In vitro study indicated electrospun collagen/PCL/NBG nanofibrous conduit promoted Human Endometrial Stem cells (hEnSCs) adhesion and proliferation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1960-1972, 2017. © 2017 Wiley Periodicals, Inc.

Preparation of superhydrophobic copper surface by a novel silk-screen printing aided electrochemical machining method

NASA Astrophysics Data System (ADS)

Yan, X. Y.; Chen, G. X.; Liu, J. W.

2018-03-01

A kind of superhydrophobic copper surface with micro-nanocomposite structure has been successfully fabricated by employing a silk-screen printing aided electrochemical machining method. At first silk-screen printing technology has been used to form a column point array mask, and then the microcolumn array would be fabricated by electrochemical machining (ECM) effect. In this study, the drop contact angles have been studied and scanning electron microscopy (SEM) has been used to study the surface characteristic of the workpiece. The experiment results show that the micro-nanocomposite structure with cylindrical array can be successfully fabricated on the metal surface. And the maximum contact angle is 151° when the fluoroalkylsilane ethanol solution was used to modify the machined surface in this study.

Characterization of modified PVDF membrane by gamma irradiation for non-potable water reuse.

PubMed

Lim, Seung Joo; Kim, Tak-Hyun; Shin, In Hwan

2015-01-01

Poly(vinylidene fluorine) (PVDF) membranes were grafted by gamma-ray irradiation and were sulfonated by sodium sulfite to modify the surface of the membranes. The characteristics of the modified PVDF membranes were evaluated by the data of Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FE-SEM), the contact angle of the membrane surface and the water permeability. From the results of FT-IR, XPS and FE-SEM, it was shown that the modified membranes were successfully grafted by gamma-ray irradiation and were sulfonated. The content of oxygen and sulfur increased with the monomer concentration, while the content of fluorine sharply decreased. The pore size of the modified membranes decreased after gamma-ray irradiation. The contact angle and the water permeability showed that the hydrophilicity of the modified membranes played a role in determining the membrane performance. The feasibility study of the modified PVDF membranes for using non-potable water reuse were carried out using a laboratory-scale microfiltration system. Grey wastewater was used as the influent in the filtration unit, and permeate quality satisfied non-potable water reuse guidelines in the Republic of Korea.

Preparation of graphene oxide modified poly(m-phenylene isophthalamide) nanofiltration membrane with improved water flux and antifouling property

NASA Astrophysics Data System (ADS)

Yang, Mei; Zhao, Changwei; Zhang, Shaofeng; Li, Pei; Hou, Deyin

2017-02-01

Poly (m-phenylene isophthalamide)/graphene oxide (PMIA/GO) composite nanofiltartion (NF) membranes were prepared via a facile phase inversion method. Structures, surface properties and hydrophilicities of the membrane were analyzed using FT-IR, XPS, AFM, SEM, water contact angle and Zeta-potential measurements. FTIR spectra indicated the existence of hydrophilic carboxylic acid and hydroxyl groups in the GO molecules. SEM pictures revealed the large and finger-like micro-voids formed in the sublayer of the NF membranes after adding GO. The zeta-potential and water contact angle results proved that PMIA/GO composite membranes had more negatively charged and greater hydrophilic surfaces. The pure water flux of the PMIA/GO (0.3 wt% GO) composite membrane (125.2 (L/m2/h)) was 2.6 times as high as that of the pristine PMIA NF membrane (48.3 (L/m2/h)) at 0.8 MPa with slightly higher rejections to all tested dyes and better fouling resistance to bovine serum albumin (BSA). This study gave an effective method for preparing composite PMIA NF membranes with high water flux and excellent antifouling property, which showed potential application in water treatment.

Recycling of phenol from aqueous solutions by pervaporation with ZSM-5/PDMS/PVDF hollow fiber composite membrane

NASA Astrophysics Data System (ADS)

Li, Dan; Yao, Jie; Sun, Hao; Liu, Bing; van Agtmaal, Sjack; Feng, Chunhui

2018-01-01

Zeolite (ZSM-5)/polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) hollow fiber composite membrane was prepared by dynamic negative pressure. The influence of ZSM-5 silanization, coating time and concentration of ZSM-5 on the resulting pervaporation (PV) performance of composite membranes was investigated. The contact angle (CA) was used to measure surface hydrophobic property and it was found that the water contact angle of the membrane was increased significantly from 99° to 132° when the concentration of ZSM-5 increased from 0% to 50%. The morphology of the membrane was characterized by scanning electron microscope (SEM) and those SEM images illustrated that the thickness of the separating layer has obvious differences at varying coating times. Furthermore, the membranes were investigated in PV process to recycle phenol from aqueous solutions as feed mixtures. The impact of phenol concentration in feed, temperature and pressure of penetration side on the PV performance of membrane was studied systematically. When the ZSM-5 concentration was 40% and the coating time was 60 min, separation factor and phenol permeability were 4.56 and 5.78 g/(m2 h), respectively. ZSM-5/PDMS/PVDF membrane significantly improved the recovery efficiency of phenols.

Robust superhydrophobic needle-like nanostructured ZnO surfaces prepared without post chemical-treatment

NASA Astrophysics Data System (ADS)

Velayi, Elmira; Norouzbeigi, Reza

2017-12-01

Robust superhydrophobic ZnO surfaces with micro/nano hybrid hierarchical structures were synthesized on the stainless steel mesh by a facile single-step chemical bath deposition (CBD) method without using further low surface energy materials. The Taguchi L16 experimental design was applied to evaluate the effects of reaction time, type and concentration of the additive, type of the chelating agent, and the molar ratio of the chelating agent to the initial zinc (II) ions. The prepared sample at the optimal conditions exhibited a sustainable and time-independent superhydrophobic behavior with the water contact angle (WCA) of 162.8° ± 2.5° and contact angle hysteresis (CAH) of 1.8° ± 0.5°. The XRD, SEM, TEM and FTIR analyses were used to characterize the prepared samples. Surface characterization using scanning electron microscopy (SEM) indicated accumulation of micro/nano branched ZnO needles on the substrate with the average diameters of ∼85 nm. After 20 abrasion cycles the optimum sample indicated an excellent mechanical robustness via exposure to the pressure of 4.7 kPa. A suitable chemical resistance to the acidic and basic droplets with the pH range of 4 and 9 was observed.

Reduced graphene oxide growth on 316L stainless steel for medical applications

NASA Astrophysics Data System (ADS)

Cardenas, L.; MacLeod, J.; Lipton-Duffin, J.; Seifu, D. G.; Popescu, F.; Siaj, M.; Mantovani, D.; Rosei, F.

2014-07-01

We report a new method for the growth of reduced graphene oxide (rGO) on the 316L alloy of stainless steel (SS) and its relevance for biomedical applications. We demonstrate that electrochemical etching increases the concentration of metallic species on the surface and enables the growth of rGO. This result is supported through a combination of Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), density functional theory (DFT) calculations and static water contact angle measurements. Raman spectroscopy identifies the G and D bands for oxidized species of graphene at 1595 cm-1 and 1350 cm-1, respectively, and gives an ID/IG ratio of 1.2, indicating a moderate degree of oxidation. XPS shows -OH and -COOH groups in the rGO stoichiometry and static contact angle measurements confirm the wettability of rGO. SEM and AFM measurements were performed on different substrates before and after coronene treatment to confirm rGO growth. Cell viability studies reveal that these rGO coatings do not have toxic effects on mammalian cells, making this material suitable for biomedical and biotechnological applications.

Controllable stearic acid crystal induced high hydrophobicity on cellulose film surface.

PubMed

He, Meng; Xu, Min; Zhang, Lina

2013-02-01

A novel, highly hydrophobic cellulose composite film (RCS) with biodegradability was fabricated via solvent-vaporized controllable crystallization of stearic acid in the porous structure of cellulose films (RC). The interface structure and properties of the composite films were investigated with wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), FT-IR, solid-state (13)C NMR, water uptake, tensile testing, water contact angle, and biodegradation tests. The results indicated that the RCS films exhibited high hydrophobicity (water contact angle achieved to 145°), better mechanical properties in the humid state and lower water uptake ratio than RC. Interestingly, the stearic acid crystallization was induced by the pore wall of the cellulose matrix to form a micronano binary structure, resulting in a rough surface. The rough surface with a hierarchical structure containing micronanospace on the RCS film surface could trap abundant air, leading to the high hydrophobicity. Moreover, the RCS films were flexible, biodegradable, and low-cost, showing potential applications in biodegradable water-proof packaging.

Superhydrophobic surfaces: From nature to biomimetic through VOF simulation.

PubMed

Liu, Chunbao; Zhu, Ling; Bu, Weiyang; Liang, Yunhong

2018-04-01

The contact angle, surface structure and chemical compositions of Canna leaves were investigated. According to the surface structure of Canna leaves which observed by Scanning Electron Microscopy(SEM), the CFD (Computational Fluid Dynamics)model was established and the method of volume of fluid (VOF) was used to simulate the process of droplet impacting on the surface and established a smooth surface for comparison to verify that the surface structure was an important factor of the superhydrophobic properties. Based on the study of Canna leaf and VOF simulation of its surface structure, the superhydrophobic samples were processed successfully and showed a good superhydrophobic property with a contact angle of 156 ± 1 degrees. A high-speed camera (5000 frames per second) was used to assess droplet movement and determine the contact time of the samples. The contact time for the sample was 13.1 ms. The results displayed that the artificial superhydrophobic surface is perfect for the performance of superhydrophobic properties. The VOF simulation method was efficient, accurate and low cost before machining artificial superhydrophobic samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of Ambient Temperature on Hydrophobic Recovery Behavior of Silicone Rubber Composites

NASA Astrophysics Data System (ADS)

Peng, Xiangyang; Li, Zijian; Zheng, Feng; Zhang, Ni; Huang, Zhen; Fang, Pengfei

A series of silicone rubber samples with different cyclosiloxanes contents have been successfully prepared, and their hydrophobic recovery behaviors and mechanism were investigated in detail. The gas chromatography-mass spectroscopy technique after Soxhlet extraction was utilized to examine the low molecular weight siloxanes in the sample, SEM was used to observe the surface morphology of the silicone rubber influenced by plasma treatment, and contact angle measurement was applied to probe the hydrophobic recovery of the sample surface after plasma treatment at different storage temperatures. The storage time-dependent contact angle of water can be well fitted by the diffusion model calculated from Fick’s second law. The results imply that the hydrophobic recovery of silicone rubber is related to the diffusion of low molecular weight siloxanes, while larger content or higher temperature can induce faster hydrophobic recovery.

Directional self-cleaning superoleophobic surface.

PubMed

Zhao, Hong; Law, Kock-Yee

2012-08-14

In this work, we report the creation of a grooved surface comprising 3 μm grooves (height ~4 μm) separated by 3 μm from each other on a silicon wafer by photolithography. The grooved surface was then modified chemically with a fluorosilane layer (FOTS). The surface property was studied by both static and dynamic contact angle measurements using water, hexadecane, and a polyethylene wax ink as the probing liquids. Results show that the grooved surface is both superhydrophobic and superoleophobic. Its observed contact angles agree well with the calculated Cassie-Baxter angles. More importantly, we are able to make a replica of the composite wax ink-air interface and study it by SEM. Microscopy results not only show that the droplet of the wax ink "sits" on air in the composite interface but also further reveal that the ink drop actually pins underneath the re-entrant structure in the side wall of the grooved structure. Contact angle measurement results indicate that wetting on the grooved surface is anisotropic. Although liquid drops are found to have lower static and advancing contact angles in the parallel direction, the drops are found to be more mobile, showing smaller hysteresis and lower sliding angles (as compared to the FOTS wafer surface and a comparable 3-μm-diameter pillar array FOTS surface). The enhanced mobility is attributable to the lowering of the resistance against an advancing liquid because 50% of the advancing area is made of a solid strip where the liquid likes to wet. This also implies that the contact line for advancing is no longer smooth but rather is ragged, having the solid strip area leading the wetting and the air strip area trailing behind. This interpretation is supported by imaging the geometry of the contact lines using molten ink drops recovered from the sliding angle experiments in both the parallel and orthogonal directions. Because the grooved surface is mechanically stronger against mechanical abrasion, the self-cleaning effect exhibited in the parallel direction suggests that groove texturing is a viable approach to create mechanically robust, self-cleaning, superoleophobic surfaces.

Surface wettability of silicon substrates enhanced by laser ablation

NASA Astrophysics Data System (ADS)

Tseng, Shih-Feng; Hsiao, Wen-Tse; Chen, Ming-Fei; Huang, Kuo-Cheng; Hsiao, Sheng-Yi; Lin, Yung-Sheng; Chou, Chang-Pin

2010-11-01

Laser-ablation techniques have been widely applied for removing material from a solid surface using a laser-beam irradiating apparatus. This paper presents a surface-texturing technique to create rough patterns on a silicon substrate using a pulsed Nd:YAG laser system. The different degrees of microstructure and surface roughness were adjusted by the laser fluence and laser pulse duration. A scanning electron microscope (SEM) and a 3D confocal laser-scanning microscope are used to measure the surface micrograph and roughness of the patterns, respectively. The contact angle variations between droplets on the textured surface were measured using an FTA 188 video contact angle analyzer. The results indicate that increasing the values of laser fluence and laser pulse duration pushes more molten slag piled around these patterns to create micro-sized craters and leads to an increase in the crater height and surface roughness. A typical example of a droplet on a laser-textured surface shows that the droplet spreads very quickly and almost disappears within 0.5167 s, compared to a contact angle of 47.9° on an untextured surface. This processing technique can also be applied to fabricating Si solar panels to increase the absorption efficiency of light.

Topography and surface free energy of DPPC layers deposited on a glass, mica, or PMMA support.

PubMed

Jurak, Malgorzata; Chibowski, Emil

2006-08-15

An investigation of energetic properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) layers deposited on glass, mica, and PMMA (poly(methyl methacrylate)) surfaces was carried out by means of contact angles measurements (advancing and receding) for three probe liquids (diiodomethane, water, and formamide). DPPC was deposited on the surfaces from water (on glass and mica) or methanol (on PMMA) solutions. The topography of the tested surfaces was determined with a help of scanning electron microscopy (SEM) and atomic force microscopy (AFM). Using the measured contact angles, the total apparent surface free energy and its components of the studied layers were determined from van Oss et al.'s (Lifshitz-van der Waals and acid-base components, LWAB) and contact angle hysteresis (CAH) approaches. It allowed us to learn about changes in the surface free energy of the layers (hydrophobicity/hydrophilicity) depending on their number and kind of support. It was found that the changes in the energy greatly depended on the surface properties of the substrate as well as the statistical number of monolayers of DPPC. However, principal changes took place for first three monolayers.

Facile hydrophobicity/hydrophilicity modification of SMP surface based on metal constrained cracking

NASA Astrophysics Data System (ADS)

Han, Yu; Li, Peng; Zhao, Liangyu; Wang, Wenxin; Leng, Jinsong; Jin, Peng

2015-04-01

This study demonstrates an easy way to change surface characteristics, the water contact angle on styrene based shape memory polymer (SMP) surface alters before and after cracking formation and recovery. The contact angle of water on the original SMP surface is about 85 degree, after coating with Al and then kneading from side face at glass transition temperature Tg, cracking appeared both on Al film and SMP; cooling down and removing the Al film, cracks remain on SMP surface while the contact angle reduced to about 25 degree. When reheated above Tg, the cracks disappeared, and the contact angle go back to about 85 degree. The thin Al film bonded on SMP surface was coated by spurting, that constrains the deformation of SMP. Heating above Tg, there are complex interactions between soft SMP and hard metal film under kneading. The thin metal film cracked first with the considerable deformation of soft polymer, whereafter, the polymer was ripped by the metal cracks thus polymer cracked as well. Cracks on SMP can be fixed cooling down Tg, while reheated, cracks shrinking and the SMP recovers to its original smooth surface. Surface topography changed dramatically while chemical composition showed no change during the deformation and recovery cycle, as presented by SEM and EDS. Furthermore, the wetting cycle is repeatable. This facile method can be easily extended to the hydropobicity/hydrophilicity modification of other stimuli-responsive polymers and put forward many potential applications, such as microfluidic switching and molecule capture and release.

Grafting of poly (lactic acid) with maleic anhydride using supercritical carbon dioxide

NASA Astrophysics Data System (ADS)

Khankrua, R.; Pivsa-Art, S.; Hiroyuki, H.; Suttiruengwong, S.

2015-07-01

The aim of this work was to modify poly lactic acid (PLA) via free radical grafting with maleic anhydride (MA) by using supercritical carbon dioxide (SCCO2). Benzoyl peroxide (BPO) was used as an initiator. The solubility of MA in SCCO2 was first determined to estimate the suitable grafting conditions and equilibrium. From the solubility study of MA in SCCO2, it was found that the solubility of MA in SCCO2 increased with the increasing pressure and dissolution time. PLA films were first prepared by compression molding. The ratio of MA to BPO was 2:1. The reaction temperature and pressure were 70°C and 100 bar respectively. The grafting reaction and the degree of grafting were characterized by nuclear magnetic resonance (NMR) spectroscopy and titration, respectively. Scanning electron microscope (SEM) technique and contact angle were used to confirm the changes in physical properties of PLA film grafted MA. NMR spectrum indicated that the grafting of MA onto PLA was successively achieved. Degree of grafting by using SCCO2 was as high as 0.98%. This provided rather high grafting degree compared with other processes. SEM pictures showed the rough surface structure on modified PLA film. In addition, contact angle results showed an improvement of the hydrophilicity by maleic anhydride grafting onto polymers.

Preparation and Properties of Nano-Hydroxyapatite/Gelatin/Poly(vinyl alcohol) Composite Membrane.

PubMed

Liao, Haotian; Shi, Kun; Peng, Jinrong; Qu, Ying; Liao, Jinfeng; Qian, Zhiyong

2015-06-01

In this study, the bone-like composite membrane based on blends of gelatin (Gel), nano-hydroxyapatite (n-HA) and poly(vinyl alcohol) (PVA) was fabricated by solvent casting and evaporation methods. The effect of n-HA content and the ratio of Gel/PVA on the properties of the composite was investigated. The Gel/PVA and n-HA/Gel/PVA composite membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), water contact angle measurement and scanning electron microscopy (SEM). The mechanical properties of the composites were determined by tensile tests. The as prepared composite membranes exhibited hydrophobility, the water contact angle of composite membrane was 126.6 when its mass ratio of n-HA/Gel/PVA was 10/50/40. The tensile strength of composite membranes was greatly increased due to the introduction of n-HA, and the tensile strength was increased to 74.92 MPa when the mass ratio of n-HA/Gel/PVA was 10/50/40. SEM observation indicated that n-HA was dispersed in the membranes and a sea-island structure was formed in the n-HA/Gel/PVA composite membranes, resulting in a significant increase in tensile strength. The as-prepared n-HA/Gel/PVA composite membranes may be applied in the field of bone tissue engineering.

Induced wettability and surface-volume correlation of composition for bovine bone derived hydroxyapatite particles

NASA Astrophysics Data System (ADS)

Maidaniuc, Andreea; Miculescu, Florin; Voicu, Stefan Ioan; Andronescu, Corina; Miculescu, Marian; Matei, Ecaterina; Mocanu, Aura Catalina; Pencea, Ion; Csaki, Ioana; Machedon-Pisu, Teodor; Ciocan, Lucian Toma

2018-04-01

Hydroxyapatite powders characteristics need to be determined both for quality control purposes and for a proper control of microstructural features of bone reconstruction products. This study combines bulk morphological and compositional analysis methods (XRF, SEM-EDS, FT-IR) with surface-related methods (XPS, contact angle measurements) in order to correlate the characteristics of hydroxyapatite powders derived from bovine bone for its use in medical applications. An experimental approach for correlating the surface and volume composition was designed based on the analysis depth of each spectral method involved in the study. Next, the influences of powder particle size and forming method on the contact angle between water drops and ceramic surface were evaluated for identifying suitable strategies of tuning hydroxyapatite's wettability. The results revealed a preferential arrangement of chemical elements at the surface of hydroxyapatite particles which could induce a favourable material behaviour in terms of sinterability and biological performance.

Study on fabrication of the superhydrophobic sol-gel films based on copper wafer and its anti-corrosive properties

NASA Astrophysics Data System (ADS)

Fan, Youhua; Li, Changzhu; Chen, Zejun; Chen, Hong

2012-06-01

In the present study, superhydrophobic copper wafer was prepared by a sol-gel deposition method. Different molar ratios of vinyltrimethoxysilane (VTES), ethanol (EtOH), water (H2O) and ammonia water (NH3·OH) were involved in this research. The morphologies, chemical compositions and hydrophobicity of the films were analyzed by scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX), Fourier transfer infrared spectrometer (FTIR) and water contact angle measurement (CA). It was shown by the surface morphological study that different structures, such as pyramid-shaped protrusions, nipple-shaped protrusions or ball-shaped silica particles, were distributed on the copper substrate. The films had a high water contact angle larger than 155.4°. The durability properties revealed that the films had a good superhydrophobicity deposited in 3.5 wt.% sodium chloride solution for up to 14 days.

Hydrophilicity improvement in polyphenylsulfone nanofibrous filtration membranes through addition of polyethylene glycol

NASA Astrophysics Data System (ADS)

Kiani, Shirin; Mousavi, Seyed Mahmoud; Shahtahmassebi, Nasser; Saljoughi, Ehsan

2015-12-01

Novel hydrophilic polyphenylsulfone (PPSU) nanofibrous membrane was prepared by electrospinning of the PPSU solution blended with polyethylene glycol 400 (PEG 400). The influence of the PEG concentration on the membrane characteristics was studied using scanning electron microscopy (SEM), water contact angle measurement, and tensile test. Filtration performance of the membranes was investigated by measurement of pure water flux (PWF) and determination of the rejection values of the pollution indices during treatment of canned beans production wastewater. According to the results, blending the PPSU solution with 10 wt.% PEG 400 resulted in formation of a nanofibrous membrane with high porosity and increased mechanical strength which exhibited a low water contact angle of 8.9° and high water flux of 7920 L/m2h. Flux recovery of the mentioned membrane which was assessed by filtration of a solution containing bovine serum albumin (BSA) was 83% indicating a noticeable antifouling property.

Fabrication of hydrophobic structures on coronary stent surface based on direct three-beam laser interference lithography

NASA Astrophysics Data System (ADS)

Gao, Long-yue; Zhou, Wei-qi; Wang, Yuan-bo; Wang, Si-qi; Bai, Chong; Li, Shi-ming; Liu, Bin; Wang, Jun-nan; Cui, Cheng-kun; Li, Yong-liang

2016-05-01

To solve the problems with coronary stent implantation, coronary artery stent surface was directly modified by three-beam laser interference lithography through imitating the water-repellent surface of lotus leaf, and uniform micro-nano structures with the controllable period were fabricated. The morphological properties and contact angle (CA) of the microstructure were measured by scanning electron microscope (SEM) and CA system. The water repellency of stent was also evaluated by the contact and then separation between the water drop and the stent. The results show that the close-packed concave structure with the period of about 12 μm can be fabricated on the stent surface with special parameters (incident angle of 3°, laser energy density of 2.2 J·cm-2 and exposure time of 80 s) by using the three-beam laser at 1 064 nm, and the structure has good water repellency with CA of 120°.

Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching

PubMed Central

Nokes, Jolie M.; Sharma, Himanshu; Tu, Roger; Kim, Monica Y.; Chu, Michael; Siddiqui, Ali; Khine, Michelle

2016-01-01

We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the mismatch in stiffness between the stiff skin layer and bulk shrink film causes the formation of multiscale hierarchical wrinkles with nano-textured features. Scanning electron microscopy (SEM) images confirm the presence of these biomimetic structures. Contact angle (CA) and contact angle hysteresis (CAH) measurements, respectively, defined as values greater than 150° and less than 10°, verified the SH nature of the substrates. Furthermore, we demonstrate the ability to reliably pattern hydrophilic regions onto the SH substrates, allowing precise capture and detection of proteins in urine. Finally, we achieved self-driven microfluidics via patterning contrasting superhydrophilic microchannels on the SH Ar substrates to induce flow for biosensing. PMID:28773318

Nanotextured Shrink Wrap Superhydrophobic Surfaces by Argon Plasma Etching.

PubMed

Nokes, Jolie M; Sharma, Himanshu; Tu, Roger; Kim, Monica Y; Chu, Michael; Siddiqui, Ali; Khine, Michelle

2016-03-14

We present a rapid, simple, and scalable approach to achieve superhydrophobic (SH) substrates directly in commodity shrink wrap film utilizing Argon (Ar) plasma. Ar plasma treatment creates a stiff skin layer on the surface of the shrink film. When the film shrinks, the mismatch in stiffness between the stiff skin layer and bulk shrink film causes the formation of multiscale hierarchical wrinkles with nano-textured features. Scanning electron microscopy (SEM) images confirm the presence of these biomimetic structures. Contact angle (CA) and contact angle hysteresis (CAH) measurements, respectively, defined as values greater than 150° and less than 10°, verified the SH nature of the substrates. Furthermore, we demonstrate the ability to reliably pattern hydrophilic regions onto the SH substrates, allowing precise capture and detection of proteins in urine. Finally, we achieved self-driven microfluidics via patterning contrasting superhydrophilic microchannels on the SH Ar substrates to induce flow for biosensing.

A New Green Ionic Liquid-Based Corrosion Inhibitor for Steel in Acidic Environments.

PubMed

Atta, Ayman M; El-Mahdy, Gamal A; Al-Lohedan, Hamad A; Ezzat, Abdel Rahman O

2015-06-17

This work examines the use of new hydrophobic ionic liquid derivatives, namely octadecylammonium tosylate (ODA-TS) and oleylammonium tosylate (OA-TS) for corrosion protection of steel in 1 M hydrochloric acid solution. Their chemical structures were determined from NMR analyses. The surface activity characteristics of the prepared ODA-TS and OA-TS were evaluated from conductance, surface tension and contact angle measurements. The data indicate the presence of a double bond in the chemical structure of OA-TS modified its surface activity parameters. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements, scanning electron microscope (SEM), Energy dispersive X-rays (EDX) analysis and contact angle measurements were utilized to investigate the corrosion protection performance of ODA-TS and OA-TS on steel in acidic solution. The OA-TS and ODA-TS compounds showed good protection performance in acidic chloride solution due to formation of an inhibitive film on the steel surface.

Icephobicity of Leaves

NASA Astrophysics Data System (ADS)

Kavehpour, H. Pirouz; Shirazi, Elika T.; Alizadeh-Birjandi, Elaheh

2016-11-01

Ice adhesion and excessive accumulation on exposed structures and equipment are well known to cause serious problems in cold-climate regions; therefore, the development of coatings that can resist icing can solve many challenges in various areas of industry. This work was inspired by nature and ice-resistivity and superhydrophobicity of plants leaves. Kale is an example of a plant that can be harvested in winter. It shows superhydrophobic behavior, which is normally known as an advantage for cleaning the leaves, but we were able to show that its surface structure and high contact angle of water drops on kale leaves could delay the ice formation process making it a good candidate for an ice-repellent coating. We have performed in-depth experimental analyses on how different plants can prevent icing, and contact angle measurements and scanning electron microscopy (SEM) of the leaves were taken to further mimic their surface morphology.

Preparation and characterization of antibacterial electrospun chitosan/poly (vinyl alcohol)/graphene oxide composite nanofibrous membrane

NASA Astrophysics Data System (ADS)

Yang, Shuai; Lei, Peng; Shan, Yujuan; Zhang, Dawei

2018-03-01

In this paper, chitosan (CS)/poly (vinyl alcohol) (PVA)/graphene oxide (GO) composite nanofibrous membranes were prepared via electrospinning. Such nanofibrous membranes have been characterized and investigated for their morphological, structural, thermal stability, hydrophilic and antibacterial properties. SEM images showed that the uniform and defect-free nanofibers were obtained and GO sheets, shaping spindle and spherical, were partially embedded into nanofibers. FTIR, XRD, DSC and TGA indicated the good compatibility between CS and PVA. There were strong intermolecular hydrogen bonds between the chitosan and PVA molecules. Contact angle measurement indicated that while increasing the content of GO, the distance between fibers increased and water drop showed wetting state on the surface of nanofibrous membranes. As a result, the contact angle decreased significantly. Meanwhile, good antibacterial activity of the prepared nanofibrous membranes were exhibited against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.

Improvement in surface hydrophilicity and resistance to deformation of natural leather through O2/H2O low-temperature plasma treatment

NASA Astrophysics Data System (ADS)

You, Xuewei; Gou, Li; Tong, Xingye

2016-01-01

The natural leather was modified through O2/H2O low-temperature plasma treatment. Surface morphology was characterized by scanning electron microscopy (SEM) and the results showed that the pores on the leather surface became deeper and larger with enhanced permeability of water and vapor. XPS and FTIR-ATR was performed to determine the chemical composition of natural leather surface. Oxygen-containing groups were successfully grafted onto the surface of natural leather and oxygen content increased with longer treatment time. After O2/H2O plasma treatment, initial water contact angle was about 21° and water contact angles were not beyond 55° after being stored for 3 days. Furthermore, the tensile test indicated that the resistance to deformation had a prominent transform without sacrificing the tensile strength.

Controlled surface morphology and hydrophilicity of polycaprolactone toward human retinal pigment epithelium cells.

PubMed

Shahmoradi, Saleheh; Yazdian, Fatemeh; Tabandeh, Fatemeh; Soheili, Zahra-Soheila; Hatamian Zarami, Ashraf Sadat; Navaei-Nigjeh, Mona

2017-04-01

Applying scaffolds as a bed to enhance cell proliferation and even differentiation is one of the treatment of retina diseases such as age-related macular degeneration (AMD) which deteriorating photoreceptors and finally happening blindness. In this study, aligned polycaprolactone (PCL) nanofibers were electrospun and at different conditions and their characteristics were measured by scanning electron microscope (SEM) and contact angle. Response surface methodology (RSM) was used to optimize the diameter of fabricated nanofibers. Two factors as solution concentration and voltage value were considered as independent variables and their effects on nanofibers' diameters were evaluated by central composite design and the optimum conditions were obtained as 0.12g/mL and 20kV, respectively. In order to decrease the hydrophobicity of PCL, the surface of the fabricated scaffolds was modified by alkaline hydrolysis method. Contact time of the scaffolds and alkaline solution and concentration of alkaline solution were optimized using Box Behnken design and (120min and 5M were the optimal, respectively). Contact angle measurement showed the high hydrophilicity of treated scaffolds (with contact angle 7.48°). Plasma surface treatment was applied to compare the effect of using two kinds of surface modification methods simultaneously on hydrolyzed scaffolds. The RPE cells grown on scaffolds were examined by immunocytochemistry (ICC), MTT and continuous inspection of cellular morphology. Interestingly, Human RPE cells revealed their characteristic morphology on hydrolyzed scaffold well. As a result, we introduced a culture substrate with low diameter (185.8nm), high porosity (82%) and suitable hydrophilicity (with contact angle 7.48 degree) which can be promising for hRPE cell transplantation. Copyright © 2016. Published by Elsevier B.V.

Preparation of MTMS based transparent superhydrophobic silica films by sol-gel method.

PubMed

Venkateswara Rao, A; Latthe, Sanjay S; Nadargi, Digambar Y; Hirashima, H; Ganesan, V

2009-04-15

Superhydrophobic surfaces with water contact angle higher than 150 degrees generated a lot of interest both in academia and in industry because of the self-cleaning properties. Optically transparent superhydrophobic silica films were synthesized at room temperature (27 degrees C) using sol-gel process by a simple dip coating technique. The molar ratio of MTMS:MeOH:H(2)O (5 M NH(4)OH) was kept constant at 1:10.56:4.16, respectively. Emphasis is given to the effect of the surface modifying agents on the hydrophobic behavior of the films. Methyl groups were introduced in the silica film by post-synthesis grafting from two solutions using trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDZ) silylating agents in hexane solvent, individually. The percentage of silylating agents and silylation period was varied from 2.5 to 7.5% and 1 to 3 h, respectively. The TMCS modified films exhibited a very high water contact angle (166+/-2 degrees) in comparison to the HMDZ (138+/-2 degrees) modified films, indicating the water repellent behavior of the surface. When the TMCS and HMDZ modified films were heated at temperatures higher than 350 degrees C and 335 degrees C, respectively, the films became superhydrophilic; the contact angle for water on the films was smaller than 5 degrees. Further, the humidity study was carried out at a relative humidity of 85% at 30 degrees C temperature over 30 days. The films have been characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), % optical transmission, humidity tests and contact angle (CA) measurements.

An easy and environmentally-friendly approach to superamphiphobicity of aluminum surfaces

NASA Astrophysics Data System (ADS)

Deng, R.; Hu, Y. M.; Wang, L.; Li, Zh. H.; Shen, T.; Zhu, Y.; Xiang, J. Zh.

2017-04-01

Superamphiphobic Al surfaces were achieved via an easy and environmentally-friendly approach. Aqueous mixed solution of 0.7 M CuSO4 and 1 M NaCl was used to etch polished Al surfaces to fabricate a rough morphology distributed with microscale step-like pits. The uniformly distributed nanoscale petals covered on the microscale pits were obtained by subsequent 96 °C hot deionized water bathing for 13 min. Thus, the hierarchical micro/nanometer scale roughness was formed which provided the structural basic of superamphiphobic Al surfaces. By 1H, 1H, 2H, 2H-Perfluorodecyl-triethoxysilane (PFDTS) derivatization, desirable superamphiphobic Al surfaces were achieved with the highest static contact angles of 162° for water, 156° for peanut oil, respectively. Meanwhile, the sliding angles were lower than 10° for both water and peanut oil droplets. The as-prepared Al surfaces were investigated by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and optical contact angle measurements. The FE-SEM images of as-prepared Al surfaces showed a hierarchical micro/nanometer scale morphology. XPS analyses demonstrated the PFDTS derivitization on Al surfaces. The superamphiphobic Al surfaces presented good mechanical durability and chemical stability which have a wide range of applications in fields such as self-cleaning, anti-icing, anti-corrosion, oil transportation, energy harvesting, microfluidics, and so forth. The approach reported in this paper may easily realize the industrial production of superamphiphobic Al surfaces owing to the advantage of facile, low cost and environmentally-friendly.

A Rapid One-Step Process for Fabrication of Biomimetic Superhydrophobic Surfaces by Pulse Electrodeposition.

PubMed

Jiang, Shuzhen; Guo, Zhongning; Liu, Guixian; Gyimah, Glenn Kwabena; Li, Xiaoying; Dong, Hanshan

2017-10-25

Inspired by some typical plants such as lotus leaves, superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and hierarchical micro/nano structures. In this work, superhydrophobic surfaces on copper substrates were prepared by a rapid, facile one-step pulse electrodepositing process, with different duty ratios in an electrolyte containing lanthanum chloride (LaCl₃·6H₂O), myristic acid (CH₃(CH₂) 12 COOH), and ethanol. The equivalent electrolytic time was only 10 min. The surface morphology, chemical composition and superhydrophobic property of the pulse electrodeposited surfaces were fully investigated with SEM, EDX, XRD, contact angle meter and time-lapse photographs of water droplets bouncing method. The results show that the as-prepared surfaces have micro/nano dual scale structures mainly consisting of La[CH₃(CH₂) 12 COO]₃ crystals. The maximum water contact angle (WCA) is about 160.9°, and the corresponding sliding angle is about 5°. This method is time-saving and can be easily extended to other conductive materials, having a great potential for future applications.

A Rapid One-Step Process for Fabrication of Biomimetic Superhydrophobic Surfaces by Pulse Electrodeposition

PubMed Central

Jiang, Shuzhen; Guo, Zhongning; Liu, Guixian; Gyimah, Glenn Kwabena; Li, Xiaoying; Dong, Hanshan

2017-01-01

Inspired by some typical plants such as lotus leaves, superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and hierarchical micro/nano structures. In this work, superhydrophobic surfaces on copper substrates were prepared by a rapid, facile one-step pulse electrodepositing process, with different duty ratios in an electrolyte containing lanthanum chloride (LaCl3·6H2O), myristic acid (CH3(CH2)12COOH), and ethanol. The equivalent electrolytic time was only 10 min. The surface morphology, chemical composition and superhydrophobic property of the pulse electrodeposited surfaces were fully investigated with SEM, EDX, XRD, contact angle meter and time-lapse photographs of water droplets bouncing method. The results show that the as-prepared surfaces have micro/nano dual scale structures mainly consisting of La[CH3(CH2)12COO]3 crystals. The maximum water contact angle (WCA) is about 160.9°, and the corresponding sliding angle is about 5°. This method is time-saving and can be easily extended to other conductive materials, having a great potential for future applications. PMID:29068427

Fast enhancement on hydrophobicity of poplar wood surface using low-pressure dielectric barrier discharges (DBD) plasma

NASA Astrophysics Data System (ADS)

Chen, Weimin; Zhou, Xiaoyan; Zhang, Xiaotao; Bian, Jie; Shi, Shukai; Nguyen, Thiphuong; Chen, Minzhi; Wan, Jinglin

2017-06-01

The hydrophilicity of woody products leads to deformation and cracks, which greatly limits its applications. Low-pressure dielectric barrier discharge (DBD) plasma using hexamethyldisiloxane was applied in poplar wood surface to enhance the hydrophobicity. The chemical properties, micro-morphology, and contact angles of poplar wood surface before and after plasma treatment were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS), scanning electron microscope and energy dispersive analysis of X-ray (SEM-EDX), atomic force microscopy (AFM), and optical contact angle measurement (OCA). Moreover, tinfoil film was used as the base to reveal the enhancement mechanism. The results showed that hexamethyldisiloxane monomer is first broken into several fragments with active sites and hydrophobic chemical groups. Meanwhile, plasma treatment results in the formation of free radicals and active sites in the poplar wood surface. Then, the fragments are reacted with free radicals and incorporated into the active sites to form a network structure based on the linkages of Si-O-Si and Sisbnd Osbnd C. Plasma treatment also leads to the formation of acicular nano-structure in poplar wood surface. These facts synergistically enhance the hydrophobicity of poplar wood surface, demonstrating the dramatically increase in the equilibrium contact angle by 330%.

Direct and accurate measurement of size dependent wetting behaviors for sessile water droplets

PubMed Central

Park, Jimin; Han, Hyung-Seop; Kim, Yu-Chan; Ahn, Jae-Pyeong; Ok, Myoung-Ryul; Lee, Kyung Eun; Lee, Jee-Wook; Cha, Pil-Ryung; Seok, Hyun-Kwang; Jeon, Hojeong

2015-01-01

The size-dependent wettability of sessile water droplets is an important matter in wetting science. Although extensive studies have explored this problem, it has been difficult to obtain empirical data for microscale sessile droplets at a wide range of diameters because of the flaws resulting from evaporation and insufficient imaging resolution. Herein, we present the size-dependent quantitative change of wettability by directly visualizing the three phase interfaces of droplets using a cryogenic-focused ion beam milling and SEM-imaging technique. With the fundamental understanding of the formation pathway, evaporation, freezing, and contact angle hysteresis for sessile droplets, microdroplets with diameters spanning more than three orders of magnitude on various metal substrates were examined. Wetting nature can gradually change from hydrophobic at the hundreds-of-microns scale to super-hydrophobic at the sub-μm scale, and a nonlinear relationship between the cosine of the contact angle and contact line curvature in microscale water droplets was demonstrated. We also showed that the wettability could be further tuned in a size-dependent manner by introducing regular heterogeneities to the substrate. PMID:26657208

Three-dimensional ultrastructure of osteocytes assessed by focused ion beam-scanning electron microscopy (FIB-SEM).

PubMed

Hasegawa, Tomoka; Yamamoto, Tomomaya; Hongo, Hiromi; Qiu, Zixuan; Abe, Miki; Kanesaki, Takuma; Tanaka, Kawori; Endo, Takashi; de Freitas, Paulo Henrique Luiz; Li, Minqi; Amizuka, Norio

2018-04-01

The aim of this study is to demonstrate the application of focused ion beam-scanning electron microscopy, FIB-SEM for revealing the three-dimensional features of osteocytic cytoplasmic processes in metaphyseal (immature) and diaphyseal (mature) trabeculae. Tibiae of eight-week-old male mice were fixed with aldehyde solution, and treated with block staining prior to FIB-SEM observation. While two-dimensional backscattered SEM images showed osteocytes' cytoplasmic processes in a fragmented fashion, three-dimensional reconstructions of FIB-SEM images demonstrated that osteocytes in primary metaphyseal trabeculae extended their cytoplasmic processes randomly, thus maintaining contact with neighboring osteocytes and osteoblasts. In contrast, diaphyseal osteocytes extended thin cytoplasmic processes from their cell bodies, which ran perpendicular to the bone surface. In addition, these osteocytes featured thick processes that branched into thinner, transverse cytoplasmic processes; at some point, however, these transverse processes bend at a right angle to run perpendicular to the bone surface. Osteoblasts also possessed thicker cytoplasmic processes that branched off as thinner processes, which then connected with cytoplasmic processes of neighboring osteocytes. Thus, FIB-SEM is a useful technology for visualizing the three-dimensional structures of osteocytes and their cytoplasmic processes.

Preparation of highly hydrophobic cotton fabrics by modification with bifunctional silsesquioxanes in the sol-gel process

NASA Astrophysics Data System (ADS)

Przybylak, Marcin; Maciejewski, Hieronim; Dutkiewicz, Agnieszka

2016-11-01

The surface modification of cotton fabrics was carried out using two types of bifunctional fluorinated silsesquioxanes with different ratios of functional groups. The modification was performed either by one- or two-step process. Two methods, the sol-gel and the dip coating method were used in different configurations. The heat treatment and the washing process were applied after modification. The wettability of cotton fabric was evaluated by measuring water contact angles (WCA). Changes in the surface morphology were examined by scanning electron microscopy (SEM, SEM-LFD) and atomic force microscopy (AFM). Moreover, the modified fabrics were subjected to analysis of elemental composition of the applied coatings using SEM-EDS techniques. Highly hydrophobic textiles were obtained in all cases studied and one of the modifications resulted in imparting superhydrophobic properties. Most of impregnated textiles remained hydrophobic even after multiple washing process which shows that the studied modification is durable.

Filamentary superhydrophobic Teflon surfaces: Moderate apparent contact angle but superior air-retaining properties.

PubMed

Di Mundo, Rosa; Bottiglione, Francesco; Palumbo, Fabio; Notarnicola, Michele; Carbone, Giuseppe

2016-11-15

Micro-scale textured Teflon surfaces, resulting from plasma etching modification, show extremely high water contact angle values and fairly good resistance to water penetration when hit by water drops at medium-high speed. This behavior is more pronounced when these surfaces present denser and smaller micrometric reliefs. Tailoring the top of these reliefs with a structure which further stabilizes the air may further increase resistance to wetting (water penetration) under static and dynamic conditions. Conditions of the oxygen fed plasma were tuned in order to explore the possibility of obtaining differently topped structures on the surface of the polymer. Scanning Electron Microscopy (SEM) was used to explore topography and X-ray Photoelectron Spectroscopy (XPS) to assess chemical similarity of the modified surfaces. Beside the usual advancing and receding water contact angle (WCA) measurements, surfaces were subjected to high speed impacting drops and immersion in water. At milder, i.e. shorter time and lower input power, plasma conditions formation of peculiar filaments is observed on the top of the sculpted reliefs. Filamentary topped surfaces result in a lower WCA than the spherical ones, appearing in this sense less superhydrophobic. However, these surfaces give rise to the formation of a more pronounced air layer when placed underwater. Further, when hit by water drops falling at medium/high speed, they show a higher resistance to water penetration and a sensitively lower surface-liquid contact time. The contact time is as low as previously observed only on heated solids. This behavior may be ascribed to the cavities formed beneath the filaments which, similarly with the salvinia leaf structures, require a surplus of pressure to be filled by water. Also, it suggests a different concept of superhydrophobicity, which cannot be expected on the basis of the conventional water contact angle characterization. Copyright © 2016 Elsevier Inc. All rights reserved.

Dealloying, Microstructure and the Corrosion/Protection of Cast Magnesium Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sieradzki, Karl; Aiello, Ashlee; McCue, Ian

The purpose of this project was to develop a greater understanding of micro-galvanic corrosion effects in cast magnesium alloys using both experimental and computational methods. Experimental accomplishments have been made in the following areas of interest: characterization, aqueous free-corrosion, atmospheric corrosion, ionic liquid dissolution, rate kinetics of oxide dissolution, and coating investigation. Commercial alloys (AZ91D, AM60, and AZ31B), binary-phase alloys (αMg-2at.%Al, αMg-5at.%Al, and Mg-8at.%Al), and component phases (Mg, Al, β-Mg, β-1%Zn, MnAl3) were obtained and characterized using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Full immersion in aqueous chloride was used to characterize the corrosionmore » behavior of alloys. Rotating disc electrodes (RDEs) were used to observe accelerated long-term corrosion behavior. Al surface redistribution for freely corroded samples was analyzed using SEM, EDS, and lithium underpotential deposition (Li UPD). Atmospheric corrosion was observed using contact angle evolution, overnight pH monitoring, and surface pH evolution studies. Ionic liquid corrosion characterization was performed using linear sweep voltammetry and potentiostatic dissolution in 150° choline chloride-urea (cc-urea). Two surface coatings were investigated: (1) Li-carbonate and (2) cc-urea. Li-carbonate coatings were characterized using X-ray photoelectron spectroscopy (XPS), SEM, and aqueous free corrosion potential monitoring. Hydrophobic cc-urea coatings were characterized using contact angle measurements and electrochemical impedance spectroscopy. Oxide dissolution rate kinetics were studied using inductively coupled plasma mass spectroscopy (ICP-MS). Computational accomplishments have been made through the development of Kinetic Monte Carlo (KMC) simulations which model time- and composition-dependent effects on the microstructure due to spatial redistribution of alloying elements during corrosion.« less

[Observation of topography and analysis of surface contamination of titanium implant after roughness treatment].

PubMed

Cao, Hongdan; Yang, Xiaodong; Wu, Dayi; Zhang, Xingdong

2007-04-01

The roughness treatment of dental implant surface could improve the bone bonding and increase the success rate of implant, but the difference of diverse treatments is still unknown. In this study using scanning electron microscopy (SEM), energy disperse spectrometer (EDS) and the test of contact angle, we studied the microstructure, surface contamination and surface energy, and hence conducted a comparative analysis of the following surface roughness treatments: Polished Treatment (PT), Sandblasting with Alumina(SA), Sandblasting with Aluminia and Acid-etched (SAA), Sandblasting with Titanium Acid-etched (STA), Electro-erosion Treatment(ET). The result of SEM showed that the surface displayed irregularities after roughness treatments and that the surface properties of different roughness treatments had some distinctions. SAA and SA had some sharp edges and protrutions; the STA showed a regular pattern like honeycomb, but the ET sample treated by electric erosion exhibited the deeper pores of different sizes and the pores with a perforated secondary structure. The EDS indicated that the surface was contaminated after the treatment with foreign materials; the SA surface had some embedded contaminations even after acid etching. The measurement of water contact angle indicated that the morphology correlated with the surface treatments. These findings suggest that the distinction of surface structure and composition caused by different treatments may result in the disparity in biological behavior of dental implant.

Effect of liquid immersion of PEDOT: PSS-coated polyester fabric on surface resistance and wettability

NASA Astrophysics Data System (ADS)

Getnet Tadesse, Melkie; Loghin, Carmen; Chen, Yan; Wang, Lichuan; Catalin, Dumitras; Nierstrasz, Vincent

2017-06-01

Coating of textile fabrics with poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) is one of the methods used for obtaining functional or smart applications. In this work, we prepared PEDOT:PSS polymer with certain additives such as polyethylene glycol, methanol (MeOH), and ethylene glycol on polyester fabric substrates by a simple immersion process. Surface resistance was measured and analyzed with analysis of variance to determine the coating parameters at 95% confidence level. Fourier transform infrared (FTIR) analysis and scanning electron microscopy (SEM) study of the samples were performed. Contact angle and washing fastness measurements were conducted, to observe the wettability and washing fastness of the samples, respectively. Surface resistance values were decreased by a factor of 100, due to conductive enhancers. As the immersion time and temperature condition varies, surface resistance showed no difference, statistically. FTIR analysis supports the idea that the mechanism responsible for the conductivity enhancement is the partial replacement of PSS from PEDOT chain by forming a hydrogen bond with hydroxyl ion (OH) of the conductive enhancers. A SEM images showed that PEDOT:PSS is well distributed to the surface of the fabrics. Contact angle measurements showed morphology change in the samples. The conductivity was reasonably stable after 10 washing cycles. Altogether, an effective simple immersion of coated polyester fabric is presented to achieve functional textiles that offer a broad range of possible applications.

Nanooxide/Polymer Composites with Silica@PDMS and Ceria-Zirconia-Silica@PDMS: Textural, Morphological, and Hydrophilic/Hydrophobic Features.

PubMed

Sulym, Iryna; Goncharuk, Olena; Sternik, Dariusz; Terpilowski, Konrad; Derylo-Marczewska, Anna; Borysenko, Mykola V; Gun'ko, Vladimir M

2017-12-01

SiO 2 @PDMS and CeO 2 -ZrO 2 -SiO 2 @PDMS nanocomposites were prepared and studied using nitrogen adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), measurements of advancing and receding contact angles with water, and microcalorimetry. The pore size distributions indicate that the textural characteristics change after oxide modification by poly(dimethylsiloxane) (PDMS). Composites are characterized by mainly mesoporosity and macroporosity of aggregates of oxide nanoparticles or oxide@PDMS nanoparticles and their agglomerates. The FT-IR spectra show that PDMS molecules cover well the oxide surface, since the intensity of the band of free silanols at 3748 cm -1 decreases with increasing PDMS concentration and it is absent in the IR spectrum at C PDMS  ≥ 20 wt% that occurs due to the hydrogen bonding of the PDMS molecules to the surface hydroxyls. SEM images reveal that the inter-particle voids are gradually filled and aggregates are re-arranged and increase from 20 to 200 nm in size with the increasing polymer concentration. The highest hydrophobicity (contact angle θ = 140° at C PDMS  = 20-40 wt%) is obtained for the CeO 2 -ZrO 2 -SiO 2 @PDMS nanocomposites. The heat of composite immersion in water shows a tendency to decrease with increasing PDMS concentration.

Fabrication of anti-adhesion surfaces on aluminium substrates of rubber plastic moulds using electrolysis plasma treatment

NASA Astrophysics Data System (ADS)

Meng, Jianbing; Dong, Xiaojuan; Wei, Xiuting; Yin, Zhanmin

2015-04-01

An anti-adhesion surface with a water contact angle of 167° was fabricated on aluminium samples of rubber plastic moulds by electrolysis plasma treatment using mixed electrolytes of C6H5O7(NH4)3 and Na2SO4, followed by fluorination. To optimise the fabrication conditions, several important processing parameters such as the discharge voltage, discharge time, concentrations of supporting electrolyte and stearic acid ethanol solution were examined systematically. Using scanning electron microscopy (SEM) to analyse surfaces morphology, micrometer scale pits, and protrusions were found on the surface, with numerous nanometer mastoids contained in the protrusions. These binary micro/nano-scale structures, which are similar to the micro-structures of soil-burrowing animals, play a critical role in achieving low adhesion properties. Otherwise, the anti-adhesion behaviours of the resulting samples were analysed by the atomic force microscope (AFM), Fourier-transform infrared spectrophotometer (FTIR), electrons probe micro-analyzer (EPMA), optical contact angle meter, digital Vickers microhardness (Hv) tester, and electronic universal testing. The results show that the electrolysis plasma treatment does not require complex processing parameters, using a simple device, and is an environment-friendly and effective method. Under the optimised conditions, the contact angle (CA) for the modified anti-adhesion surface is up to 167°, the sliding angle (SA) is less than 2°, roughness of the sample surface is only 0.409μm. Moreover, the adhesion force and Hv are 0. 9KN and 385, respectively.

Ordered CdSe nanoparticles within self-assembled block copolymer domains on surfaces.

PubMed

Zou, Shan; Hong, Rui; Emrick, Todd; Walker, Gilbert C

2007-02-13

Hierarchical, high-density, ordered patterns were fabricated on Si substrates by self-assembly of CdSe nanoparticles within approximately 20-nm-thick diblock copolymer films in a controlled manner. Surface-modified CdSe nanoparticles formed well-defined structures within microphase-separated polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) domains. Trioctylphosphine oxide (TOPO)-coated CdSe nanoparticles were incorporated into PS domains and polyethylene glycol-coated CdSe nanoparticles were located primarily in the P2VP domains. Nearly close-packed CdSe nanoparticles were clearly identified within the highly ordered patterns on Si substrates by scanning electron microscopy (SEM). Contact angle measurements together with SEM results indicate that TOPO-CdSe nanoparticles were partially placed at the air/copolymer interface.

A critical study of the role of the surface oxide layer in titanium bonding

NASA Technical Reports Server (NTRS)

Dias, S.; Wightman, J. P.

1982-01-01

The molecular understanding of the role which the surface oxide layer of the adherend plays in titanium bonding is studied. The effects of Ti6-4 adherends pretreatment, bonding conditions, and thermal aging of the lap shear specimens were studied. The use of the SEM/EDAX and ESCA techniques to study surface morphology and surface composition was emphasized. In addition, contact angles and both infrared and visible reflection spectroscopy were used in ancillary studies.

A simple and low temperature process for super-hydrophilic rutile TiO 2 thin films growth

NASA Astrophysics Data System (ADS)

Mane, R. S.; Joo, Oh-Shim; Min, Sun-Ki; Lokhande, C. D.; Han, Sung-Hwan

2006-11-01

We investigate an environmentally friendly aqueous solution system for rutile TiO2 violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO2 with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO2 films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

Topography and surface energy dependent calcium phosphate formation on Sol-Gel derived TiO2 coatings.

PubMed

Järn, Mikael; Areva, Sami; Pore, Viljami; Peltonen, Jouko; Linden, Mika

2006-09-12

Heterogeneous nucleation and growth of calcium phosphate (CaP) on sol-gel derived TiO(2) coatings was investigated in terms of surface topography and surface energy. The topography of the coatings was derived from AFM measurements, while the surface energy was determined with contact angle measurements. The degree of precipitation was examined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The precipitation of CaP was found to be dependent on both topography and surface energy. A high roughness value when combining the RMS roughness parameter S(q) with the number of local maxima per unit area parameter S(ds) enhances CaP formation. The hydrophilicity of the coating was also found to be of importance for CaP formation. We suggest that the water contact angle, which is a direct measure of the hydrophilicity of the surface, may be used to evaluate the surface energy dependent precipitation kinetics rather than using the often applied Lewis base parameter.

The fabrication and property of hydrophilic and hydrophobic double functional bionic chitosan film.

PubMed

Wang, Xiaohong; Xi, Zhen; Liu, Zhongxin; Yang, Liang; Cao, Yang

2011-11-01

A new kind of hydrophobic bionic chitosan film was fabricated by simulating the surface structure of lotus leaf. The titanium oxide nanotube array was used as templates. Scanning electron microscopy (SEM) images show that one side of this films have nano-scale rough surface with spherical protrusions alike the surface of lotus leaf. The diameter of the protrusions is about 100 nm, which is equal to diameter of the titanium oxide nanotube. The water contact angle of chitosan films is up to 120 degrees and it is hydrophobic. The other side of the film is flat and the contact angle is 70 degrees. That indicated that the hydrophilism of natural materials is connected with the surface structures. The double functional chitosan films, one side is hydrophilic, the other is hydrophobic, can be made by an easy method. This method is non-toxic and clean. The double functional chitosan film will improve the application of chitosan films in medicine.

Super-hydrophobic multi-walled carbon nanotube coatings for stainless steel.

PubMed

De Nicola, Francesco; Castrucci, Paola; Scarselli, Manuela; Nanni, Francesca; Cacciotti, Ilaria; De Crescenzi, Maurizio

2015-04-10

We have taken advantage of the native surface roughness and the iron content of AISI 316 stainless steel to directly grow multi-walled carbon nanotube (MWCNT) random networks by chemical vapor deposition (CVD) at low-temperature (1000°C) without the addition of any external catalysts or time-consuming pre-treatments. In this way, super-hydrophobic MWCNT films on stainless steel sheets were obtained, exhibiting high contact angle values (154°C) and high adhesion force (high contact angle hysteresis). Furthermore, the investigation of MWCNT films with scanning electron microscopy (SEM) reveals a two-fold hierarchical morphology of the MWCNT random networks made of hydrophilic carbonaceous nanostructures on the tip of hydrophobic MWCNTs. Owing to the Salvinia effect, the hydrophobic and hydrophilic composite surface of the MWCNT films supplies a stationary super-hydrophobic coating for conductive stainless steel. This biomimetical inspired surface not only may prevent corrosion and fouling, but also could provide low friction and drag reduction.

Fabrication of hydrophobic compressed oil palm trunk surface by sol-gel process

NASA Astrophysics Data System (ADS)

Muzakir, Syafiqah; Salim, Nurjannah; Huda Abu Bakar, Nurul; Roslan, Rasidi; Sin, Lim Wan; Hashim, Rokiah

2018-04-01

Improvement of the robustness of hydrophobic surfaces is crucial to achieving commercial applications of these surfaces in such various areas as self-cleaning, water repellency and corrosion resistance. Compressed oil palm trunk (OPT) panel is one of potential product which can be used as panelling and indoor furniture application. By adding hydrophobic properties to compressed oil palm trunk panel might increase the application of compressed oil palm trunk especially for outdoor application. In this study, fabrication is using the sol-gel technique. Sol-gel was prepared by adding ethanol with Hexadecyl Trimethyl Ammonium Bromide (CTAB) solution with Tetraethyl Orthosilicate (TEOS) with surface modification of chlorotrimethylsilane (CTMS). The surface with hydrophobic coating was undergone surface analysis with contact angle machine with the aid of software SCA 20 and the determined of the morphology of surface with scanning electron microscope (SEM). The produced compressed oil palm trunk surfaces exhibited promising hydrophobic properties with a contact angle of 104° and the relatively better mechanical robustness.

Replication of surface nano-structure of the wing of dragonfly ( Pantala Flavescens) using nano-molding and UV nanoimprint lithography

NASA Astrophysics Data System (ADS)

Cho, Joong-Yeon; Kim, Gyutae; Kim, Sungwook; Lee, Heon

2013-07-01

The hydrophobicity of a dragonfly's wing originates from the naturally occurring nano-structure on its surface. The nano-structure on a dragonfly's wing consists of an array of nano-sized pillars, 100 nm in diameter. We re-create this hydrophobicity on various substrates, such as Si, glass, curved acrylic polymer, and flexible PET film, by replicating the nano-structure using UV curable nano-imprint lithography (NIL) and PDMS molding. The success of the nano-structure duplication was confirmed using scanning electron microscopy (SEM). The hydrophobicity was measured by water-based contact angle measurements. The water contact angle of the replica made of UV cured polymer was 135° ± 2°, which was slightly lower than that of the original dragonfly's wing (145° ± 2°), but much higher than that of the UV cured polymer surface without any nano-sized pillars (80°). The hydrophobicity was further improved by applying a coating of Teflon-like material.

Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

PubMed

Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

2016-05-20

An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparation of enhanced hydrophobic poly(L-lactide-co-ɛ-caprolactone) films surface and its blood compatibility

NASA Astrophysics Data System (ADS)

Kim, Seung Il; Lim, Jin Ik; Jung, Youngmee; Mun, Cho Hay; Kim, Ji Heung; Kim, Soo Hyun

2013-07-01

Hydrophobicity-enhanced poly(L-lactide-co-ɛ-caprolactone) (PLCL) (50:50) films were cast by using the solvent-nonsolvent casting method. PLCL (50:50) was synthesized by the well-known random copolymerization process and confirmed by 1H NMR analysis. The molecular weight of the synthesized PLCL was measured by gel permeation chromatography (GPC). Number-average (Mn), weight-average (Mw) molecular weights and polydispersity (Mw/Mn) were 7 × 104, 1.2 × 105, and 1.7, respectively. PLCL films were cast in vacuum condition with various nonsolvents and nonsolvent ratios. Tetrahydrofuran (THF) was used as the solvent and three different alcohols were used as the nonsolvent: methanol, ethanol, and isopropyl alcohol (IPA). Surface hydrophobicity was confirmed by water contact angle. The water contact angle was increased from 81° ± 2° to 107° ± 2°. Water contact angle was influenced by surface porosity and topography. The prepared film surfaces were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The change of crystalline property was characterized by X-ray diffraction (XRD). Platelet adhesion tests on the modified PLCL film surfaces were evaluated by platelet-rich plasma (PRP). The modified film surface exhibited enhanced hydrophobicity and reduced platelet adhesion ratio depending on the surface topography. One of the candidate products proposed as a potential blood compatible material showed a markedly reduced platelet adhesion property.

Fabrication of anti-adhesion surfaces on aluminium substrates of rubber plastic moulds using electrolysis plasma treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Jianbing, E-mail: jianbingmeng@126.com; Dong, Xiaojuan; Wei, Xiuting

An anti-adhesion surface with a water contact angle of 167° was fabricated on aluminium samples of rubber plastic moulds by electrolysis plasma treatment using mixed electrolytes of C{sub 6}H{sub 5}O{sub 7}(NH{sub 4}){sub 3} and Na{sub 2}SO{sub 4}, followed by fluorination. To optimise the fabrication conditions, several important processing parameters such as the discharge voltage, discharge time, concentrations of supporting electrolyte and stearic acid ethanol solution were examined systematically. Using scanning electron microscopy (SEM) to analyse surfaces morphology, micrometer scale pits, and protrusions were found on the surface, with numerous nanometer mastoids contained in the protrusions. These binary micro/nano-scale structures, whichmore » are similar to the micro-structures of soil-burrowing animals, play a critical role in achieving low adhesion properties. Otherwise, the anti-adhesion behaviours of the resulting samples were analysed by the atomic force microscope (AFM), Fourier-transform infrared spectrophotometer (FTIR), electrons probe micro-analyzer (EPMA), optical contact angle meter, digital Vickers microhardness (Hv) tester, and electronic universal testing. The results show that the electrolysis plasma treatment does not require complex processing parameters, using a simple device, and is an environment-friendly and effective method. Under the optimised conditions, the contact angle (CA) for the modified anti-adhesion surface is up to 167°, the sliding angle (SA) is less than 2°, roughness of the sample surface is only 0.409μm. Moreover, the adhesion force and H{sub v} are 0. 9KN and 385, respectively.« less

A novel and expeditious method to fabricate superhydrophobic metal carboxylate surface

NASA Astrophysics Data System (ADS)

Li, Feng; Geng, Xingguo; Chen, Zhi; Zhao, Lei

2012-01-01

This article has presented a novel method to fabricate superhydrophobic metal carboxylate surface on substrates like copper, ferrum, etc. This method markedly shortened the fabrication time to less than one second. The superhydrophobic effect is even better that the contact angle (CA) is 170±1° and the sliding angle (SA) <2°. Scanning electron microscopy (SEM) images showed micro-nano flower-like structures. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed that the flower-like structures are composed of Cu[CH3(CH2)12COO]2. The ethanol solution containing fatty acid and metal salt plays a key role in this method. This method has tremendous potentials in industrial production of superhydrophobic materials.

Facile fabrication of corrosion-resistant superhydrophobic and superoleophilic surfaces with MnWO(4):Dy(3+) microbouquets.

PubMed

Li, Taohai; Li, Quanguo; Yan, Jing; Li, Feng

2014-04-21

Superhydrophobic and superoleophilic MnWO4:Dy(3+) microbouquets were successfully fabricated via a facile hydrothermal process. The surface morphologies and chemical composition were investigated by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The wettability of the as-synthesized MnWO4:Dy(3+) microbouquet film was studied by measuring the water contact angle (CA). A static CA for water of 165° and a very low sliding angle (SA) were observed, which were closely related to both the MnWO4:Dy(3+) microbouquet structure and chemical modification. Furthermore, the as-prepared MnWO4:Dy(3+) surface showed superhydrophobicity for some corrosive liquids such as aqueous basic and salt solutions.

Fabrication of superhydrophobic surface on zinc substrate by 3-trifluoromethylbenzene diazonium tetrafluoroborate salts

NASA Astrophysics Data System (ADS)

Li, Hong; Huang, Chengya; Zhang, Long; Lou, Wanqiu

2014-09-01

In this study we report a new and efficient method of fabricating superhydrophobic surface on zinc plate modified with 3-trifluoromethylbenzene diazonium tetrafluoroborate salts (CF3BD), which shows a water contact angle of 160° for a 4 μl water droplet and a low sliding angle of about 1°. The morphology and chemical composition of as-prepared superhydrophobic zinc surfaces are investigated by means of scanning electron microscopy (SEM), electron probe microanalyzer (EPMA) and FT-IR spectrum. The results show that the organic layers formed on zinc plate surface are provided with the special hierarchical porous microstructure and the low surface energy, which lead to the superhydrophobicity surface on the modified zinc.

Novel synergistic transparent k-Carrageenan/Xanthan gum/Gellan gum hydrogel film: Mechanical, thermal and water barrier properties.

PubMed

Balasubramanian, R; Kim, Sam Soo; Lee, Jaewoong

2018-06-24

The aim is to develop novel synergistic transparent k-Carrageenan/Xanthan gum/Gellan gum (k-C/X/G) hydrogel films with different weight ratio composition and to study the effect of these compositions on the physical properties of the films. The structure and morphological properties of the films were investigated by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimeter (DSC). Results for FT-IR, DSC and SEM analysis showed a clear interaction between k-C, X, and G to form a new material. The mechanical, thermal and water barrier properties such as water vapor permeability (WVP), water contact angle (WCA) and moisture content were determined. The temperature at 5% weight loss (T 5% ) are in the range of 64.2-121.9 °C. The WVP exhibits are in the range of 1.8-2.4, contact angle are in the range of 32-65.8° and moisture content 16.5-21.51. The hydrogel film had good tensile strength of 19.1-31.0 MPa and elongation at break of 13-19% and tensile modulus of 1.6-2.4 GPa. The UV results indicate that the films were very transparent. The range of properties of the ternary k-C/X/G hydrogel films suggest that the presence molecular interaction and cross linking within the blends. Copyright © 2018. Published by Elsevier B.V.

Identification of the mechanism that confers superhydrophobicity on 316L stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Escobar, Ana M.; Llorca-Isern, Nuria; Rius-Ayra, Oriol

This study develops a rapid method to confer superhydrophobicity on 316L stainless steel surfaces with an amphiphilic reagent such as dodecanoic acid. The highest contact angle (approaching 173°) was obtained after forming hierarchical structures with a non-aqueous electrolyte by an electrolytic process. Our goal was to induce superhydrophobicity directly on 316L stainless steel substrates and to establish which molecules cause the effect. The superhydrophobic behaviour is analysed by contact angle measurements, scanning electron microscopy (SEM), IR spectroscopy and atomic force microscopy (AFM). The growth mechanism is analysed using FE-SEM, TOF-SIMS and XPS in order to determine the molecules involved inmore » the reaction and the growth. The TOF-SIMS analysis revealed that the Ni{sup 2+} ions react with lauric acid to create an ester on the stainless steel surface. - Highlights: • This study develops a rapid and facile approach to impart superhydrophobicity properties to 316L stainless steel surfaces with an amphiphilic reagent such as dodecanoic acid. Surface character changes from superhydrophilicity to superhydrophobicity. • This process changes the surface character from superhydrophilicity to superhydrophobicity. • The process based on electrolysis of a nickel salt in lauric acid provides superhydrophobic behaviour in 316L stainless steel. • The growth mechanism is proposed as a mode island (Volmert- Weber mode). • TOF-SIMS and XPS provided the identification of the molecules involved in the surface modification reaction on AISI 316L inducing superhydrophobicity.« less

Antibacterial properties of nano-silver coated PEEK prepared through magnetron sputtering.

PubMed

Liu, Xiuju; Gan, Kang; Liu, Hong; Song, Xiaoqing; Chen, Tianjie; Liu, Chenchen

2017-09-01

We aimed to investigate the cytotoxicity and antibacterial properties of nano-silver-coated polyetheretherketone (PEEK) produced through magnetron sputtering and provide a theoretical basis for its use in clinical applications. The surfaces of PEEKs were coated with nano-silver at varying thicknesses (3, 6, 9, and 12nm) through magnetron sputtering technology. The resulting coated PEEK samples were classified into the following groups according to the thickness of the nano-silver coating: PEEK-3 (3nm), PEEK-6 (6nm), PEEK-9 (9nm), PEEK-12 (12nm), and PEEK control group. The surface microstructure and composition of each sample were observed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive spectrum (EDS) analysis. The water contact angle of each sample was then measured by contact angle meters. A cell counting kit (CCK-8) was used to analyze the cytotoxicity of the mouse fibroblast cells (L929) in the coated groups (n=5) and group test samples (n=6), negative control (polyethylene, PE) (n=6), and positive control group (phenol) (n=6). The antibacterial properties of the samples were tested by co-culturing Streptococcus mutans and Straphylococcus aureus. The bacteria that adhered to the surface of samples were observed by SEM. The antibacterial adhesion ability of each sample was then evaluated. SEM and AFM analysis results showed that the surfaces of control group samples were smooth but compact. Homogeneous silver nano-particles (AgNPs) and nano-silver coating were uniformly distributed on the surface of the coated group samples. Compared with the control samples, the nano-silver coated samples had a significant increase in surface roughness (P<0.05) as the thickness of their nano-silver coating increased. EDS analysis showed that not only C and O but also Ag were present on the surface of the coated samples. Moreover, the water contact angle of modified samples significantly increased after nano-silver coating modification (P<0.01). CCK-8 cytotoxicity test results showed that coated samples did not exhibit cytotoxicity. The antibacterial experimental results showed that the nano-silver coating can significantly improve the antibacterial activity and bacterial adhesion ability of the PEEK samples. The compact and homogeneous nano-silver coating was successfully prepared on the surface of PEEK through magnetron sputtering. The nano-silver coated PEEKs demonstrated enhanced antibacterial activities and bacterial adhesion abilities and had no cytotoxic effects. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Effect of Nylon and Polyester Peel Ply Surface Preparation on the Bond Quality of Composite Laminates

NASA Astrophysics Data System (ADS)

Moench, Molly K.

The preparation of the surfaces to be bonded is critical to the success of composite bonds. Peel ply surface preparation is attractive from a manufacturing and quality assurance standpoint, but is a well known example of the extremely system-specific nature of composite bonds. This study examined the role of the surface energy, morphology, and chemistry left by peel ply removal in resulting bond quality. It also evaluated the use of contact angle surface energy measurement techniques for predicting the resulting bond quality of a prepared surface. The surfaces created by preparing three aerospace fiber-reinforced composite prepregs were compared when prepared with a nylon vs a polyester peel ply. The prepared surfaces were characterized with contact angle measurements with multiple fluids, scanning electron microscopy (SEM), and x-ray electron spectroscopy. The laminates were bonded with aerospace grade film adhesives. Bond quality was assessed via double cantilever beam testing followed by optical and scanning electron microscopy of the fracture surfaces.The division was clear between strong bonds (GIC of 600- 1000J/m2 and failure in cohesion) and weak bonds (GIC of 80-400J/m2 and failure in adhesion). All prepared laminates showed the imprint of the peel ply texture and evidence of peel ply remnants after fabric removal, either through SEM or XPS. Within an adhesive system, large amounts of SEM-visible peel ply material transfer correlated with poor bond quality and cleaner surfaces with higher bond quality. The both sides of failed weak bonds showed evidence of peel ply remnants under XPS, showing that at least some failure is occurring through the remnants. The choice of adhesive was found to be significant. AF 555 adhesive was more tolerant of peel ply contamination than MB 1515-3. Although the bond quality results varied substantially between tested combinations, the total surface energies of all prepared surfaces were very similar. Single fluid contact angle measurements/water break tests were therefore not predictive of bond quality, and are recommended against. The multiple fluids used allowed the construction of wettability envelopes, a more detailed look at the surface energy profile. The envelopes of nylon and polyester prepared systems were noticeably different, but while potentially useful for detecting changes or errors in surface preparation of known systems, they were not valid for predicting bond quality in new systems. Ultimately, it was determined that wetting is a necessary but not sufficient condition for bonding.

Characterization of sub-0.18-μm critical dimension pattern collapse for yield improvement

NASA Astrophysics Data System (ADS)

Zhong, Tom X.; Gurer, Emir; Lee, Ed C.; Bai, Hong; Gendron, Bill; Krishna, Murthy S.; Reynolds, Reese M.

1999-09-01

In this study, we demonstrate that surface-resist interface interactions are becoming more crucial in DUV lithography as we enter deep into the sub-wavelength era of smaller critical dimension (CD) size and high aspect ratio. This interaction reveals itself as an adhesion reduction of the resist film due to the smaller contact area between the feature and the substrate. Considerable yield improvements in a manufacturing environment can be realized if pattern collapsing of smaller features is prevented by means of proper priming. In addition, next generation photoresist processing equipments must be able to deliver excellent on-wafer results with minimum chemical consumption as environmental health and safety (EHS) requirements are better appreciated in the marketplace. HMDS is not only highly toxic but it is also a prime threat to CD control of most deep ultra violet (DUV) photoresists used for sub-0.18 micrometer design rules. The by-product NH3 created during priming process with HMDS can neutralize the photo-acid created during the exposure step. There are many technical opportunities in this usually neglected priming process step. In this study, we characterized sub-0.18 micrometer isolated line pattern collapse for UV5 resist on bare Si wafers by using a scanning electron microscope (SEM). The smallest line width printability on wafers primed with different contact angles was analyzed by using both top down and cross section SEM images. Our results show that there is a strong effect of substrate surface and film interface interaction on device yields. More specifically, there is a strong correlation between pattern integrity of features down to 115 nm and vapor prime process conditions. In general, wafers with higher contact angle can support smaller line widths. These results suggest that higher contact angle than the current specification will be required for sub-0.1 micrometer design rule for improved yield. An alternative material to HMDS will probably be needed due to more stringent future requirements and weak bonding characteristics of HMDS. Based on the result of this study, we propose an HMDS consumption reduction scheme for line-widths above 0.2 micrometer. There are many priming-related modular and system level technical enhancements that can be designed in the next generation photoresist processing tools in order to extend 248 nm lithography towards smaller feature sizes.

Impact of pre-incubation time of silk fibroin scaffolds in culture medium on cell proliferation and attachment.

PubMed

Amirikia, Mehdi; Shariatzadeh, Seyed Mohammad Ali; Jorsaraei, Seyed Gholam Ali; Soleimani Mehranjani, Malek

2017-12-01

Cell behaviours such as proliferation and attachment can be affected by the length of pre-incubation period of the scaffolds in the culture medium for long term. The aim of this study was to investigate the long term pre-incubation of 3D silk fibroin scaffolds in complete culture medium on cell attachment and proliferation. After the preparation of silk fibroin scaffolds by the technique of freeze drying, the scaffolds were pre-incubated in complete culture medium for 2 d, 6 d or 10 d before apical papilla stem cells (SCAP) seeding. Modifications of the scaffold surface and wettability were examined by FE-SEM and water contact angle, respectively. Results showed a decrease both in roughness and water contact angle as pre-incubation time increases. DNA measurement after 18h and 10 d cell seeding showed a significant increase of DNA concentration which represents better attachment and proliferation with pre-incubation time increase. Qualitative examination, live&dead assay or H&E staining method after 30h and 10 d cell seeding respectively, indicated that pre-incubation of scaffolds has time dependent effect on cell proliferation and attachment. This suggests that improvement of cell attachment and proliferation may be mediated by differences in the amount of wettability (decreased water contact angle) after exposure of scaffold to culture medium for long term which, in turn, causes more protein adsorption in the surface of silk fibroin scaffold (decreased roughness). Copyright © 2017. Published by Elsevier Ltd.

Insitu grown superhydrophobic Zn-Al layered double hydroxides films on magnesium alloy to improve corrosion properties

NASA Astrophysics Data System (ADS)

Zhou, Meng; Pang, Xiaolu; Wei, Liang; Gao, Kewei

2015-05-01

A hierarchical superhydrophobic zinc-aluminum layered double hydroxides (Zn-Al LDHs) film has been fabricated on a magnesium alloy substrate via a facile hydrothermal crystallization method following chemical modification. The characteristics of the films were investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM), and energy dispersive spectroscopy (EDS). XRD patterns and SEM images showed that the micro/nanoscale hierarchical LDHs film surfaces composed of ZnO nanorods and Zn-Al LDHs nanowalls structures. The static contact angle (CA) for the prepared surfaces was observed at around 165.6°. The corrosion resistance of the superhydrophobic films was estimated by electrochemical impedance spectroscopy (EIS) and potentiondynamic polarization measurement. EIS and polarization measurements revealed that the superhydrophobic Zn-Al LDHs coated magnesium alloy had better corrosion resistance in neutral 3.5 wt.% NaCl solution.

Modeling contact angle hysteresis of a liquid droplet sitting on a cosine wave-like pattern surface.

PubMed

Promraksa, Arwut; Chen, Li-Jen

2012-10-15

A liquid droplet sitting on a hydrophobic surface with a cosine wave-like square-array pattern in the Wenzel state is simulated by using the Surface Evolver to determine the contact angle. For a fixed drop volume, multiple metastable states are obtained at two different surface roughnesses. Unusual and non-circular shape of the three-phase contact line of a liquid droplet sitting on the model surface is observed due to corrugation and distortion of the contact line by structure of the roughness. The contact angle varies along the contact line for each metastable state. The maximum and minimum contact angles among the multiple metastable states at a fixed viewing angle correspond to the advancing and the receding contact angles, respectively. It is interesting to observe that the advancing/receding contact angles (and contact angle hysteresis) are a function of viewing angle. In addition, the receding (or advancing) contact angles at different viewing angles are determined at different metastable states. The contact angle of minimum energy among the multiple metastable states is defined as the most stable (equilibrium) contact angle. The Wenzel model is not able to describe the contact angle along the three-phase contact line. The contact angle hysteresis at different drop volumes is determined. The number of the metastable states increases with increasing drop volume. Drop volume effect on the contact angles is also discussed. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

Electrical transport in AZO nanorods

NASA Astrophysics Data System (ADS)

Yildiz, A.; Cansizoglu, H.; Karabacak, T.

2015-10-01

Al-doped ZnO (AZO) nanorods (NRs) with different lengths were deposited by utilizing glancing angle deposition (GLAD) technique in a DC sputter system at room temperature. The structural and optical characteristics of the NRs were investigated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis-NIR spectroscopy measurements. A band gap of about 3.5 eV was observed for the NRs. A novel capping process utilizing varying deposition angles was used to introduce a blanket metal top contact for the electrical characterization of NRs. Current-voltage (I-V) measurements were used to properly evaluate the approximate resistivity of a single NR. The electrical conduction was found to be governed by the thermally activated transport mechanism. Activation energy was determined as 0.14 eV from temperature dependent resistivity data.

Novel method for controllable fabrication of a superhydrophobic CuO surface on AZ91D magnesium alloy.

PubMed

She, Zuxin; Li, Qing; Wang, Zhongwei; Li, Longqin; Chen, Funan; Zhou, Juncen

2012-08-01

A novel method for controllable fabrication of a superhydrophobic CuO surface on AZ91D magnesium alloy is reported in this paper. Hierarchical structure composed of micro/nano-featherlike CuO was obtained by electrodeposition of Cu-Zn alloy coating and subsequently an electrochemical anodic treatment in alkaline solution. After modification with lauric acid, the surface became hydrophobicity/superhydrophobicity. The formation of featherlike CuO structures was controllable by varying the coating composition. By applying SEM, ICP-AES, and water contact angle analysis, the effects of coating composition on the surface morphology and hydrophobicity of the as-prepared surfaces were detailedly studied. The results indicated that at the optimal condition, the surface showed a good superhydrophobicity with a water contact angle as high as 155.5 ± 1.3° and a sliding angle as low as about 3°. Possible growth mechanism of featherlike CuO hierarchical structure was discussed. Additionally, the anticorrosion effect of the superhydrophobic surface was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. The interface model for anticorrosion mechanism of superhydrophobic surface in corrosive medium was proposed. Besides, the mechanical stability test indicated that the resulting superhydrophobic surfaces have good mechanical stability.

Application of fluorinated nanofluid for production enhancement of a carbonate gas-condensate reservoir through wettability alteration

NASA Astrophysics Data System (ADS)

Sakhaei, Zahra; Azin, Reza; Naghizadeh, Arefeh; Osfouri, Shahriar; Saboori, Rahmatollah; Vahdani, Hosein

2018-03-01

Condensate blockage phenomenon in near-wellbore region decreases gas production rate remarkably. Wettability alteration using fluorinated chemicals is an efficacious way to vanquish this problem. In this study, new synthesized fluorinated silica nanoparticles with an optimized condition and mean diameter of 50 nm is employed to modify carbonate rock surface wettability. Rock characterization tests consisting Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive x-ray Spectroscopy (EDX) were utilized to assess the nanofluid adsorption on rock surface after treatment. Contact angle, spontaneous imbibition and core flooding experiments were performed to investigate the effect of synthesized nanofluid adsorption on wettability of rock surface and liquid mobility. Results of contact angle experiments revealed that wettability of rock could alter from strongly oil-wetting to the intermediate gas-wetting even at elevated temperature. Imbibition rates of oil and brine were diminished noticeably after treatment. 60% and 30% enhancement in pressure drop of condensate and brine floods after wettability alteration with modified nanofluid were observed which confirm successful field applicability of this chemical.

Structure and properties of moisture-resistant konjac glucomannan films coated with shellac/stearic acid coating.

PubMed

Wei, Xueqin; Pang, Jie; Zhang, Changfeng; Yu, Chengcheng; Chen, Han; Xie, Bingqing

2015-03-15

A series of moisture-resistant konjac glucomannan films were prepared by coating shellac/stearic acid emulsion on deacetylated konjac glucomannan films (dKGM). The effect of stearic acid content on structure and properties of the coated films were investigated by field emission scanning electron microscopy (FE SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet spectroscopy (UV), water vapor permeability (WVP), water uptake, water contact angle, and tensile testing. The results revealed that shellac in the coating adhered intimately to the surface of dKGM film, and provided a substrate for the dispersion of stearic acid which played an important role in enhancement of the moisture barrier properties and mechanical properties of the coated films. The WVP of the coated films decreased from 2.63×10(-11) to 0.37×10(-11)g/(msPa) and the water contact angle increased from 68° to 101.2° when stearic acid content increased from 0wt% to 40wt%, showing the potential applications in food preservation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Determining efficacy of monitoring devices on ceramic bond to resin composite

PubMed Central

Osorio, Estrella; Aguilera, Fátima S.; Osorio, Raquel; García-Godoy, Franklin; Cabrerizo-Vilchez, Miguel A.; Toledano, Manuel

2012-01-01

Objectives: This paper aims to assess the effectiveness of 3D nanoroughness and 2D microroughness evaluations, by their correlation with contact angle measurements and shear bond strength test, in order to evaluate the effect of two different acids conditioning on the bonding efficacy of a leucite-based glass-ceramic to a composite resin. Study Design: Ceramic (IPS Empress) blocks were treated as follows: 1) no treatment, 2) 37% phosphoric acid (H3PO4), 15 s, 3) 9% hydrofluoric acid (HF), 5 min. Micro- and nano-roughness were assessed with a profilometer and by means of an atomic force microscopy (AFM). Water contact angle (CA) measurements were determined to assess wettability of the ceramic surfaces with the asixymetric drop shape analysis contact diameter technique. Shear bond strength (SBS) was tested to a resin composite (Z100) with three different adhesive systems (Scotchbond Multipurpose Plus, Clearfil New Bond, ProBOND). Scanning electron microscopy (SEM) images were performed. Results: Nanoroughness values assessed in 50x50 μm areas were higher for the HF group, these differences were not detected by profilometric analysis. HF treatment created the nano- roughest surfaces and the smallest CA (p<0.05), producing the highest SBS to the composite resin with all tested adhesive systems (p<0.05). No differences existed between the SBS produced by the adhesive systems evaluated with any of the surface treatments tested. Conclusions: Nano-roughness obtained in a 50x50 µm scan size areas was the most reliable data to evaluate the topographical changes produced by the different acid treatments on ceramic surfaces. Key words:Dental ceramic, acid etching, bonding efficacy, resin composite, adhesive systems, contact angle, roughness. PMID:22549693

Boron nitride nanotubes as novel fillers for improving the properties of dental adhesives.

PubMed

Degrazia, Felipe Weidenbach; Leitune, Vicente Castelo Branco; Samuel, Susana Maria Werner; Collares, Fabrício Mezzomo

2017-07-01

This study aimed to evaluate the physical-chemical properties of experimental dental adhesives containing boron nitride nanotubes (BNNTs) as inorganic fillers. An experimental adhesive resin was prepared using HEMA-BisGMA, 66/33wt% (control). Inorganic BNNT fillers were first analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and then incorporated into the adhesive at different concentration (0.05, 0.075, 0.1, 0.15wt%). Degree of conversion (DC), ultimate strength, contact angle, surface free energy (SFE) microhardness, softening in solvent and bioactivity were assessed. Scanning and transmission electron microscopy (SEM and TEM) showed BNNTs with diameter ranging from 5 to 10nm with close end tips. No changes in DC were observed after incorporating BNNTs up to 0.15wt%. The contact angles of water and α-bromonaphthalene increased (p<0.05) and consequently the SFE decreased after incorporating BNNTs to the polymer matrix. Microhardness and solvent degradation strength increased after incorporation of 0.075, 0.1 and 0.15wt% BNNTs. Mineral deposition was found after 7days of immersion on adhesive specimens after incorporation of BNNT. The incorporation of BNNTs up to 0.15wt% improved the chemical and mechanical properties of dental adhesives and promoted mineral deposition. Incorporation of boron nitride nanotubes into adhesive resin materials improved physical-chemical properties and increased mineral deposition on its surface allowing enhanced properties of the resin-dentin interface. Thus, the novel adhesive material is promising as a dental adhesive and may contribute to the stability of the dentin-resin bonding. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Diamond Bur Grit Size on Composite Repair.

PubMed

Valente, Lisia L; Silva, Manuela F; Fonseca, Andrea S; Münchow, Eliseu A; Isolan, Cristina P; Moraes, Rafael R

2015-06-01

This study investigated the effect of diamond bur grit size on the repair bond strength of fresh and aged resin composites. Blocks of microhybrid composite (Opallis, FGM) were stored in distilled water at 37°C for 24 h (fresh composite) or subjected to 5000 thermal cycles (aged composite). The surfaces were roughened using diamond-coated, flame-shaped carbide burs with medium grit (#3168), fine grit (#3168F), or extra-fine grit (#3168FF). The control group underwent no surface treatment. Surface roughness, water contact angle, and surface topography by scanning electron microscopy (SEM) were evaluated (n = 3). Samples were restored with resin composite and sectioned into beam-shaped specimens, which were subjected to microtensile bond testing. Failure modes were classified using a stereomicroscope. Data were statistically analyzed using the Student- Newman-Keuls test and two-way ANOVA, with significance set at p < 0.05. Higher surface roughness was observed for groups treated with the medium- and fine-grit burs; aged composites were rougher than fresh composites. The water contact angle formed on the aged composite was lower than that on the fresh composite. The highest repair bond strength was observed for the fine-grit bur group, and the lowest was recorded for control. Interfacial failures were more predominant. SEM images showed that the surfaces treated with fine- and extra-fine-grit burs had a more irregular topography. Surface roughening of fresh or aged resin composites with diamond burs improved retention of the repair material. Fine-grit burs generally performed better than medium- and extra-fine-grit burs.

Behavior of Human Bone Marrow-Derived Mesenchymal Stem Cells on Various Titanium-Based Coatings

PubMed Central

Qu, Chengjuan; Kaitainen, Salla; Kröger, Heikki; Lappalainen, Reijo; Lammi, Mikko J.

2016-01-01

The chemical composition and texture of titanium coatings can influence the growth characteristics of the adhered cells. An enhanced proliferation of the human mesenchymal stem cells (hMSCs) would be beneficial. The present study was aimed to investigate whether titanium deposited at different atmospheres would affect the cell growth properties, cellular morphology, and expression of surface markers of hMSCs. Titanium-based coatings were deposited on silicon wafers under oxygen, nitrogen, or argon atmospheres by ultra-short pulsed laser deposition using two different gas pressures followed by heating at 400 °C for 2 h. The characteristics of the coated surfaces were determined via contact angle, zeta potential, and scanning electron microscopy (SEM) techniques. Human MSCs were cultivated on differently coated silicon wafers for 48 h. Subsequently, the cell proliferation rates were analyzed with an MTT assay. The phenotype of hMSCs was checked via immunocytochemical stainings of MSC-associated markers CD73, CD90, and CD105, and the adhesion, spreading, and morphology of hMSCs on coated materials via SEM. The cell proliferation rates of the hMSCs were similar on all coated silicon wafers. The hMSCs retained the MSC phenotype by expressing MSC-associated markers and fibroblast-like morphology with cellular projections. Furthermore, no significant differences could be found in the size of the cells when cultured on all various coated surfaces. In conclusion, despite certain differences in the contact angles and the zeta potentials of various titanium-based coatings, no single coating markedly improved the growth characteristics of hMSCs. PMID:28773947

A highly accurate dynamic contact angle algorithm for drops on inclined surface based on ellipse-fitting.

PubMed

Xu, Z N; Wang, S Y

2015-02-01

To improve the accuracy in the calculation of dynamic contact angle for drops on the inclined surface, a significant number of numerical drop profiles on the inclined surface with different inclination angles, drop volumes, and contact angles are generated based on the finite difference method, a least-squares ellipse-fitting algorithm is used to calculate the dynamic contact angle. The influences of the above three factors are systematically investigated. The results reveal that the dynamic contact angle errors, including the errors of the left and right contact angles, evaluated by the ellipse-fitting algorithm tend to increase with inclination angle/drop volume/contact angle. If the drop volume and the solid substrate are fixed, the errors of the left and right contact angles increase with inclination angle. After performing a tremendous amount of computation, the critical dimensionless drop volumes corresponding to the critical contact angle error are obtained. Based on the values of the critical volumes, a highly accurate dynamic contact angle algorithm is proposed and fully validated. Within nearly the whole hydrophobicity range, it can decrease the dynamic contact angle error in the inclined plane method to less than a certain value even for different types of liquids.

Equilibrium contact angle or the most-stable contact angle?

PubMed

Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A

2014-04-01

It is well-established that the equilibrium contact angle in a thermodynamic framework is an "unattainable" contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid-liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie-Baxter equations accordingly or for the surface energy evaluation. © 2013 Elsevier B.V. All rights reserved.

Apparent contact angle and contact angle hysteresis on liquid infused surfaces.

PubMed

Semprebon, Ciro; McHale, Glen; Kusumaatmaja, Halim

2016-12-21

We theoretically investigate the apparent contact angle and contact angle hysteresis of a droplet placed on a liquid infused surface. We show that the apparent contact angle is not uniquely defined by material parameters, but also has a dependence on the relative size between the droplet and its surrounding wetting ridge formed by the infusing liquid. We derive a closed form expression for the contact angle in the limit of vanishing wetting ridge, and compute the correction for small but finite ridge, which corresponds to an effective line tension term. We also predict contact angle hysteresis on liquid infused surfaces generated by the pinning of the contact lines by the surface corrugations. Our analytical expressions for both the apparent contact angle and contact angle hysteresis can be interpreted as 'weighted sums' between the contact angles of the infusing liquid relative to the droplet and surrounding gas phases, where the weighting coefficients are given by ratios of the fluid surface tensions.

Enhancement of antibacterial activity in nanofillers incorporated PSF/PVP membranes

NASA Astrophysics Data System (ADS)

Pramila, P.; Gopalakrishnan, N.

2018-04-01

An attempt has been made to investigate the nanofillers incorporated polysulfone (PSF) and polyvinylpyrrolidone (PVP) polymer membranes prepared by phase inversion method. Initially, the nanofillers, viz, Zinc Oxide (ZnO) nanoparticle, Graphene Oxide-Zinc Oxide (GO-ZnO) nanocomposite were synthesized and then directly incorporated into PSF/PVP blend during the preparation of membranes. The prepared membranes have been subjected to FE-SEM, AFM, BET, contact angle, tensile test and anti-bacterial studies. Significant membrane morphologies and nanoporous properties have been observed by FE-SEM and BET, respectively. It has been observed that hydrophilicity, mechanical strength and water permeability of the ZnO and GO-ZnO incorporated membranes were enhanced than bare membrane. Antibacterial activity was assessed by measuring the inhibition zones formed around the membrane by disc-diffusion method using Escherichia coli (gram-negative) as a model bacterium. Again, it has been observed that nanofillers incorporated membrane exhibits high antibacterial performance compared to bare membrane.

Structure, wettability and thermal degradation of new fluoro-oligomer modified nanoclays.

PubMed

Valsecchi, R; Viganò, M; Levi, M; Turri, S

2008-04-01

Quaternary ammonium salts based on monofunctionalized Perfluoropolyether (PFPE) oligomers were synthesized and used for the cation exchange process of sodium Montmorillonite nanoclays. The new fluoromodified nanoclays were characterized through X-rays diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), termogravimetric analysis (TGA), differential scanning calorimetry (DSC), electronic microscopy (SEM-EDS), and contact angle measurements (CA). In particular XRD showed rather complex patterns (presence of higher order reflections) which allowed the calculation of basal spacings, regularly increasing with the molecular weight of the fluorinated macrocation. Both IR and SEM confirmed the presence of fluorinated segments at clays interface, while TGA showed a limited thermal stability with an onset of degradation temperature which seems not dependent on the molecular weight of the macrocation. CA measurements showed a peculiar behaviour, with evident dynamic hysteresis phenomena and surface tension components quite different from those of commercially available, organomodified clays.

Improved cell viability and hydroxyapatite growth on nitrogen ion-implanted surfaces

NASA Astrophysics Data System (ADS)

Shafique, Muhammad Ahsan; Murtaza, G.; Saadat, Shahzad; Uddin, Muhammad K. H.; Ahmad, Riaz

2017-08-01

Stainless steel 306 is implanted with various doses of nitrogen ions using a 2 MV pelletron accelerator for the improvement of its surface biomedical properties. Raman spectroscopy reveals incubation of hydroxyapatite (HA) on all the samples and it is found that the growth of incubated HA is greater in higher ion dose samples. SEM profiles depict uniform growth and greater spread of HA with higher ion implantation. Human oral fibroblast response is also found consistent with Raman spectroscopy and SEM results; the cell viability is found maximum in samples treated with the highest (more than 300%) dose. XRD profiles signified greater peak intensity of HA with ion implantation; a contact angle study revealed hydrophilic behavior of all the samples but the treated samples were found to be lesser hydrophilic compared to the control samples. Nitrogen implantation yields greater bioactivity, improved surface affinity for HA incubation and improved hardness of the surface.

Research on super-hydrophobic surface of biodegradable magnesium alloys used for vascular stents.

PubMed

Wan, Peng; Wu, Jingyao; Tan, LiLi; Zhang, Bingchun; Yang, Ke

2013-07-01

Micro-nanometer scale structure of nubby clusters overlay was constructed on the surface of an AZ31 magnesium alloy by a wet chemical method. The super-hydrophobicity was achieved with a water contact angle of 142° and a sliding angle of about 5°. The microstructure and composition of the super-hydrophobic surface were characterized by SEM and FTIR. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior, and the hemocompatibility of the super-hydrophobic surface was investigated by means of hemolytic and platelet adhesion tests. Results showed that the super-hydrophobic treatment could improve the corrosion resistance of magnesium alloys in PBS and inhibit blood platelet adhesion on the surface, which implied excellent hemocompatibility with controlled degradation. Copyright © 2013 Elsevier B.V. All rights reserved.

Preparation of Ag superhydrophobic surface on metal substrates

NASA Astrophysics Data System (ADS)

Li, J. Y.; Lu, S. X.; Xu, W. G.; Duan, Y. Q.; Yang, X. C.; Cheng, Y. Y.; He, G.; Cui, S.

2018-01-01

In this work, the facile approaches are developed for preparation the Ag superhydrophobic surfaces (SHSs) on zinc (Zn), copper (Cu) and aluminium (Al) substrates. The water contact angles (WCAs) of the Ag SHSs on Zn, Cu and Al substrates are 167°, 165° and 154°, respectively. Furthermore, the water sliding angle (WSA) of each surface is less than 1°. The morphology and chemical composition of the samples are characterized using scanning electron microscopy (SEM) and X-ray diffraction pattern (XRD). The as-prepared three kinds of SHSs possess the self-cleaning performance, which can quickly take the chalk away when the water droplets fall down the SHSs. In addition, the superhydrophobicity of the SHSs can well maintain after exposure to the air for 6 months, indicating that the surfaces can sustain good stability.

Synthesis and structural characterization of betaine- and imidazoline-based organoclays

NASA Astrophysics Data System (ADS)

Lazorenko, Georgy; Kasprzhitskii, Anton; Yavna, Victor

2018-01-01

The samples of organic-modified clays based on a Wyoming SWy-2 sodium montmorillonite (Na+-Mt) with the cationic surfactant hydroxyethylalkyl imidazoline (HEAI) and the amphoteric surfactant oleylamidopropyl betaine (OAPB) were synthesized via a cation exchange process. The obtained materials were characterized using XRD analysis, ATR-FTIR spectroscopy, SEM, BET and Water contact angle measurements. The potential sites of binding of OAPB and HEAI to the mineral surface were determined by the DFT calculations. For the variants of the structure of the complex, DFT calculations is performed and the interaction energy of the surfactant and clay mineral is estimated.

Synthesis and characterization of methyltrihydroxysilane water repellent

NASA Astrophysics Data System (ADS)

Abidin, A. Z.; Harjandi, M. N.; Wirawan, V.; Suharno, S. M.

2018-03-01

Methyltrihydroxysilane (CH3Si (OH)3) as a water repellent has been synthesized from trichloromethylsilane and ethanol by varying their composition, reaction condition, and the addition of nanosilica. The properties of the material have been characterized using FTIR for identification of raw materials and water repellent product, SEM for identification of water repellent coating surface, and tensiometer for measurement of water repellent contact angle. The FTIR spectra confirm the reaction of the water-repellent formation. The water repellent product was applied by spraying or dip coating on the automotive window surface. This study shows that the best ethanol composition is 91% and the best contact angle of synthesized water repellent material is 149,46°. This contact angle is higher than that of a commercial product, which shows it as a property of the superhydrophobic material. Water repellency properties increase as the composition of trichloromethylsilane increases. It shows that the increasing of trichloromethylsilane composition can also increase methyltrihydroxysilane formation. However, glass surface becomes opaque as the composition of trichloromethylsilane increase because methyltrihydroxysilane will create the Si-O-Si layer that has a white color. The addition of nanomaterial also increases the surface roughness, but a binder is required to bind nanomaterial to the water-repellent layer. For an application, dip coating has better water repellency than spraying. This is because dip coating method creates more homogenous nanomaterial precipitation on the surface. On the other hand, the level of transparency is worse. Therefore, the water repellent of trichloromethylsilane is recommended for applications that do not need clarity such bathroom glass wall.

Hysteresis of Contact Angle of Sessile Droplets on Smooth Homogeneous Solid Substrates via Disjoining/Conjoining Pressure.

PubMed

Kuchin, I; Starov, V

2015-05-19

A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr < θ < θa, which are different from the unique equilibrium contact angle θ ≠ θe, correspond to the state of slow "microscopic" advancing or receding motion of the liquid if θe < θ < θa or θr < θ < θe, respectively. This "microscopic" motion almost abruptly becomes fast "macroscopic" advancing or receding motion after the contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid-solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.

Contact angle distribution of particles at fluid interfaces.

PubMed

Snoeyink, Craig; Barman, Sourav; Christopher, Gordon F

2015-01-27

Recent measurements have implied a distribution of interfacially adsorbed particles' contact angles; however, it has been impossible to measure statistically significant numbers for these contact angles noninvasively in situ. Using a new microscopy method that allows nanometer-scale resolution of particle's 3D positions on an interface, we have measured the contact angles for thousands of latex particles at an oil/water interface. Furthermore, these measurements are dynamic, allowing the observation of the particle contact angle with high temporal resolution, resulting in hundreds of thousands of individual contact angle measurements. The contact angle has been found to fit a normal distribution with a standard deviation of 19.3°, which is much larger than previously recorded. Furthermore, the technique used allows the effect of measurement error, constrained interfacial diffusion, and particle property variation on the contact angle distribution to be individually evaluated. Because of the ability to measure the contact angle noninvasively, the results provide previously unobtainable, unique data on the dynamics and distribution of the adsorbed particles' contact angle.

Hydrophobization of epoxy nanocomposite surface with 1H,1H,2H,2H-perfluorooctyltrichlorosilane for superhydrophobic properties

NASA Astrophysics Data System (ADS)

Psarski, Maciej; Marczak, Jacek; Celichowski, Grzegorz; Sobieraj, Grzegorz B.; Gumowski, Konrad; Zhou, Feng; Liu, Weimin

2012-10-01

Nature inspires the design of synthetic materials with superhydrophobic properties, which can be used for applications ranging from self-cleaning surfaces to microfluidic devices. Their water repellent properties are due to hierarchical (micrometer- and nanometre-scale) surface morphological structures, either made of hydrophobic substances or hydrophobized by appropriate surface treatment. In this work, the efficiency of two surface treatment procedures, with a hydrophobic fluoropolymer, synthesized and deposited from 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) is investigated. The procedures involved reactions from the gas and liquid phases of the PFOTS/hexane solutions. The hierarchical structure is created in an epoxy nanocomposite surface, by filling the resin with alumina nanoparticles and micron-sized glass beads and subsequent sandblasting with corundum microparticles. The chemical structure of the deposited fluoropolymer was examined using XPS spectroscopy. The topography of the modified surfaces was characterized using scanning electron microscopy (SEM), and atomic force microscopy (AFM). The hydrophobic properties of the modified surfaces were investigated by water contact and sliding angles measurements. The surfaces exhibited water contact angles of above 150° for both modification procedures, however only the gas phase modification provided the non-sticking behaviour of water droplets (sliding angle of 3°). The discrepancy is attributed to extra surface roughness provided by the latter procedure.

Surface modification of several dental substrates by non-thermal, atmospheric plasma brush.

PubMed

Chen, Mingsheng; Zhang, Ying; Sky Driver, M; Caruso, Anthony N; Yu, Qingsong; Wang, Yong

2013-08-01

The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of four dental substrates. Specimens of dental substrates including dentin, enamel, and two composites Filtek Z250, Filtek LS Silorane were prepared (∼2mm thick, ∼10mm diameter). The prepared surfaces were treated for 5-45s with a non-thermal atmospheric plasma brush working at temperatures from 36 to 38°C. The plasma-treatment effects on these surfaces were studied with contact-angle measurement, X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM). The non-thermal atmospheric argon plasma brush was very efficient in improving the surface hydrophilicity of four substrates studied. The results indicated that water contact angle values decreased considerably after only 5s plasma treatment of all these substrates. After 30s treatment, the values were further reduced to <5°, which was close to a value for super hydrophilic surfaces. XPS analysis indicated that the percent of elements associated with mineral in dentin/enamel or fillers in the composites increased. In addition, the percent of carbon (%C) decreased while %O increased for all four substrates. As a result, the O/C ratio increased dramatically, suggesting that new oxygen-containing polar moieties were formed on the surfaces after plasma treatment. SEM surface images indicated that no significant morphology change was induced on these dental substrates after exposure to plasmas. Without affecting the bulk properties, a super-hydrophilic surface could be easily achieved by the plasma brush treatment regardless of original hydrophilicity/hydrophobicity of dental substrates tested. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Surface modification of several dental substrates by non-thermal, atmospheric plasma brush

PubMed Central

Chen, Mingsheng; Zhang, Ying; Driver, M. Sky; Caruso, Anthony N.; Yu, Qingsong; Wang, Yong

2013-01-01

Objective The purpose of this study was to reveal the effectiveness of non-thermal atmospheric plasma brush in surface wettability and modification of four dental substrates. Methods Specimens of dental substrates including dentin, enamel, and two composites Filtek Z250, Filtek LS Silorane were prepared (~2 mm thick, ~10 mm diameter). The prepared surfaces were treated for 5–45 s with a non-thermal atmospheric plasma brush working at temperatures from 36 to 38 °C. The plasma-treatment effects on these surfaces were studied with contact-angle measurement, X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM). Results The non-thermal atmospheric argon plasma brush was very efficient in improving the surface hydrophilicity of four substrates studied. The results indicated that water contact angle values decreased considerably after only 5 s plasma treatment of all these substrates. After 30 s treatment, the values were further reduced to <5°, which was close to a value for super hydrophilic surfaces. XPS analysis indicated that the percent of elements associated with mineral in dentin/enamel or fillers in the composites increased. In addition, the percent of carbon (%C) decreased while %O increased for all four substrates. As a result, the O/C ratio increased dramatically, suggesting that new oxygen-containing polar moieties were formed on the surfaces after plasma treatment. SEM surface images indicated that no significant morphology change was induced on these dental substrates after exposure to plasmas. Significance Without affecting the bulk properties, a super-hydrophilic surface could be easily achieved by the plasma brush treatment regardless of original hydrophilicity/hydrophobicity of dental substrates tested. PMID:23755823

Multifunctional surface modification of silk fabric via graphene oxide repeatedly coating and chemical reduction method

NASA Astrophysics Data System (ADS)

Cao, Jiliang; Wang, Chaoxia

2017-05-01

Multifunctional silk fabrics with electrical conductive, anti-ultraviolet and water repellent were successfully prepared by surface modification with graphene oxide (GO). The yellow-brown GO deposited on the surface of silk fabric was converted into graphitic black reduced graphene (RGO) by sodium hydrosulfite. The surface properties of silk fabrics were changed by repeatedly RGO coating process, which have been proved by SEM and XPS. The SEM results showed that the RGO sheets were successive form a continuously thin film on the surface of silk fabrics, and the deposition of GO or RGO also can be proved by XPS. The electrical conductivity was tested by electrical surface resistance value of the silk fabric, the surface resistance decreased with increasing of RGO surface modification times, and a low surface resistance value reached to 3.24 KΩ cm-1 after 9 times of modification, indicating the silk obtained excellent conductivity. The UPF value of one time GO modification silk fabric (silk-1RGO) was enhanced significantly to 24.45 in comparison to 10.40 of original silk. The contact angle of RGO coating silk samples was all above of 120°. The durability of RGO coated silk fabrics was tested by laundering. The electrical surface resistance of silk-4RGO (65.74 KΩ cm-1), silk-6RGO (15.54 KΩ cm-1) and silk-8RGO (3.86 KΩ cm-1) fabrics was up to 86.82, 22.30 and 6.57 KΩ cm-1 after 10 times of standard washing, respectively. The UPF value, contact angle and color differences of RGO modified silk fabric slightly changed before and after 10 times of standard washing. Therefore, the washing fastness of electric conduction, anti-ultraviolet and water repellent multifunctional silk fabrics was excellent.

Synthesis and characterization of novel fluoroalkyl-terminated hyperbranched polyurethane latex

NASA Astrophysics Data System (ADS)

Xu, Wei; Zhao, Weijia; Hao, Lifen; Wang, Sha; Pei, Mengmeng; Wang, Xuechuan

2018-04-01

Waterborne polyurethane (PU) emulsions are widely used in various fields and the demand for them is ever-increasing over the years. However, the hydrophilic chain extender inevitably bonded into the PU backbone can affect the water tolerance of PU. Thus, it is of great importance to improve PU water resistance effectively. Herein, novel fluoroalkyl-terminated hyperbranched polyurethane (HBPUF) latex was accordingly synthesized by graft reaction of perfluorohexyl ethyl alcohol and hyperbranched polyurethane (HBPU), which was previously obtained from interaction between hydroxyl-terminated hyperbranched polymer and PU prepolymer manufactured via the acetone process, as well as using neutralization, adding water, and high-speed stirring operations. We characterized the resultants and investigated its surface properties by IR, NMR, TEM, XRD, TGA, DSC, FE-SEM, AFM, XPS, and contact angle measurements, etc. IR and NMR tests confirmed that the fluorinated fragments had been grafted onto the tail end of HBPU. TEM, XRD, DSC, and FE-SEM results all accounted for the fact that there were multi-crystals in PU, HBPU and HBPUF. TGA results showed that thermal stabilities of the PU, HBPU, and HBPUF latex films were enhanced in turn. XPS and AFM analyses demonstrated that the fluorine-containing segments from the HBPUF terminals were prone to migrate and enrich on the film-air surface of the HBPUF latex film, which made water contact angle and water absorption of the HBPUF film be as 113.9° and 11.1%, respectively, compared to those of the PU film (77.8° and 136.2%). This research indicates that water resistance of the PU film can be efficiently enhanced by fluorinated polyurethane with novel fluoroalkyl-terminated hyperbranched structure.

Characterization and in vitro biocompatibility study of Ti-Si-N nanocomposite coatings developed by using physical vapor deposition

NASA Astrophysics Data System (ADS)

Trivedi, Pramanshu; gupta, Pallavi; Srivastava, Swati; Jayaganthan, R.; Chandra, Ramesh; Roy, Partha

2014-02-01

Amongst the Ti alloys used as orthopedic implant materials, Ti6Al4V is one of the widely used alloys. Magnetron sputtering was used to deposit nanocomposite coating of Ti-Si-N on the Ti6Al4V substrate at different power and then the coating structure and surface properties were characterized through contact angle measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). In vitro biocompatibility of the coatings was assessed by using mouse bone marrow mesenchymal stem cells (mBMMSC). Antibacterial studies were performed using Escherichia coli (E. coli) microorganisms. The osteogenic differentiation was also carried out in order to get gene expressions. The AFM results confirmed that the coatings deposited at 120 W was smoother as compared to other coatings developed at different power, along with optimum contact angle, also these coatings showed good antibacterial results. The fluorescent and viability results of 120 W sample confirmed their good biocompatibility as compared to the coatings deposited 20, 40, 60, and 100 W power. Hence, the coating deposited at 120 W exhibit desirable microstructural characteristics beneficial for surface modification of orthopedic implants.

Fabrication of multicolor fluorescent polyvinyl alcohol through surface modification with conjugated polymers by oxidative polymerization

NASA Astrophysics Data System (ADS)

Hai, Thien An Phung; Sugimoto, Ryuichi

2018-06-01

A simple method for the preparation of multicolor polyvinyl alcohol (PVA) by chemical oxidative polymerization is introduced. The PVA surface was successfully modified with conjugated polymers composed of 3-hexylthiophene (3HT) and fluorene (F). The incorporation of the 3HT/F copolymer onto the PVA surface was confirmed by Fourier-transform infrared (FT-IR), ultraviolet-visible (UV-vis), and fluorescence spectroscopies, X-ray diffraction (XRD), as well as thermogravimetric analysis (TGA), contact angle, and field-emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray (EDX) analysis. Different 3HT/F ratios on the PVA surface result in optical properties that include multicolor-emission and absorption behavior. The color of the resultant (3HT/F)-g-PVA shifted from red to blue, and the quantum yield increased with increasing F content. The surface hydrophobicity of the modified PVA increased significantly through grafting with the conjugated polymers, with the water contact angle increasing by 30° compared to pristine PVA. The PVA XRD peaks were less intense following surface modification. Thermogravimetric analyses reveal that the thermal stability of the PVA decreases as a result of grafting with the 3HT/F copolymers.

Vapor-liquid interfacial reaction to fabricate superhydrophilic and underwater superoleophobic thiol-ene/silica hybrid decorated fabric for oil/water separation

NASA Astrophysics Data System (ADS)

Li, Hongqiang; Liang, Tao; Lai, Xuejun; Su, Xiaojing; Zhang, Lin; Zeng, Xingrong

2018-01-01

With oil spill accidents and oil industrial wastewater increasing, oil/water separation has attracted much attention in recent years. Herein, we report the fabrication of superhydrophilic and underwater superoleophobic thiol-ene/silica hybrid decorated fabrics for oil/water separation via vapor-liquid interfacial reaction. It is based on sol-gel reaction of tetraethyl orthosilicate (TEOS) to generate silica and thiol-ene reaction between poly(ethylene glycol) dimethacrylate (PEGDMA) and trimethylolpropane tris(3-mercaptopropionate) (TTMP) to form crosslinked hydrophilic polymer on polyester fabric under the catalysis of butylamine/ammonia vapor. The chemical structure of the surfaces on thiol-ene/silica hybrid decorated fabric was confirmed by FTIR and XPS, and obvious micro-nano morphology and roughness were observed with SEM and AFM. The water contact angle of the fabric attained 0° in 0.36 s, and the underwater oil contact angle reached up to 160°. Importantly, the fabric exhibited high separation efficiency at 99.5%, fast water flux above 71600 Lm-2h-1 and excellent recyclability in oil/water separation. Our findings open a new strategy to fabricate organic-inorganic hybrid superhydrophobic and underwater superoleophobic materials for oil/water separation.

The Effects of Biopolymers Composite Based Waste Cooking Oil and Titanium Dioxide Fillers as Superhydrophobic Coatings.

NASA Astrophysics Data System (ADS)

Marsi, N.; Rus, A. Z. M.

2017-08-01

This project presents the effect of biopolymer composite surface coating on TiO2 fillers by analysing the static water contact angle, SEM micrographs, porosity, density and refractive index of biopolymer doped with different loading of TiO2. The different ratio loading of 0.5, 1.0, 1.5, 2.0 and 2.5 (wt/wt%) TiO2 can be used to improve the material properties in practical use for outdoor application especially to enhance the stability of surface coating. It is found that the smooth surfaces with a low ratio loading of TiO2 fillers on biopolymer composite surface coating increases the static water contact angle up to 162.29°. It is interpreted with respect to nano- features existing on the surface of the water repellent creates a thin superhydrphobic layer. The relationship between porosity and density is indirectly proportional where the higher the loading of TiO2 filler produce the lower porosity up to 0.86% of the surface coating. The movement from shorter to longer of wavelength was observed before and after exposure indicates that there are optimization of absorption of UV-B radiation as the amount of delocalisation.

Small angle X-ray scattering analysis of the effect of cold compaction of Al/MoO3 thermite composites.

PubMed

Hammons, Joshua A; Wang, Wei; Ilavsky, Jan; Pantoya, Michelle L; Weeks, Brandon L; Vaughn, Mark W

2008-01-07

Nanothermites composed of aluminum and molybdenum trioxide (MoO(3)) have a high energy density and are attractive energetic materials. To enhance the surface contact between the spherical Al nanoparticles and the sheet-like MoO(3) particles, the mixture can be cold-pressed into a pelleted composite. However, it was found that the burn rate of the pellets decreased as the density of the pellets increased, contrary to expectation. Ultra-small angle X-ray scattering (USAXS) data and scanning electron microscopy (SEM) were used to elucidate the internal structure of the Al nanoparticles, and nanoparticle aggregate in the composite. Results from both SEM imaging and USAXS analysis indicate that as the density of the pellet increased, a fraction of the Al nanoparticles are compressed into sintered aggregates. The sintered Al nanoparticles lost contrast after forming the larger aggregates and no longer scattered X-rays as individual particles. The sintered aggregates hinder the burn rate, since the Al nanoparticles that make them up can no longer diffuse freely as individual particles during combustion. Results suggest a qualitative relationship for the probability that nanoparticles will sinter, based on the particle sizes and the initial structure of their respective agglomerates, as characterized by the mass fractal dimension.

Predictive factors for the failure of endoscopic stent-in-stent self-expandable metallic stent placement to treat malignant hilar biliary obstruction

PubMed Central

Sugimoto, Mitsuru; Takagi, Tadayuki; Suzuki, Rei; Konno, Naoki; Asama, Hiroyuki; Watanabe, Ko; Nakamura, Jun; Kikuchi, Hitomi; Waragai, Yuichi; Takasumi, Mika; Sato, Yuki; Hikichi, Takuto; Ohira, Hiromasa

2017-01-01

AIM To investigate the factors predictive of failure when placing a second biliary self-expandable metallic stents (SEMSs). METHODS This study evaluated 65 patients with an unresectable malignant hilar biliary obstruction who were examined in our hospital. Sixty-two of these patients were recruited to the study and divided into two groups: the success group, which consisted of patients in whom a stent-in-stent SEMS had been placed successfully, and the failure group, which consisted of patients in whom the stent-in-stent SEMS had not been placed successfully. We compared the characteristics of the patients, the stricture state of their biliary ducts, and the implemented endoscopic retrograde cholangiopancreatography (ERCP) procedures between the two groups. RESULTS The angle between the target biliary duct stricture and the first implanted SEMS was significantly larger in the failure group than in the success group. There were significantly fewer wire or dilation devices (ERCP catheter, dilator, or balloon catheter) passing the first SEMS cell in the failure group than in the success group. The cut-off value of the angle predicting stent-in-stent SEMS placement failure was 49.7 degrees according to the ROC curve (sensitivity 91.7%, specificity 61.2%). Furthermore, the angle was significantly smaller in patients with wire or dilation devices passing the first SEMS cell than in patients without wire or dilation devices passing the first SEMS cell. CONCLUSION A large angle was identified as a predictive factor for failure of stent-in-stent SEMS placement. PMID:28974893

Predictive factors for the failure of endoscopic stent-in-stent self-expandable metallic stent placement to treat malignant hilar biliary obstruction.

PubMed

Sugimoto, Mitsuru; Takagi, Tadayuki; Suzuki, Rei; Konno, Naoki; Asama, Hiroyuki; Watanabe, Ko; Nakamura, Jun; Kikuchi, Hitomi; Waragai, Yuichi; Takasumi, Mika; Sato, Yuki; Hikichi, Takuto; Ohira, Hiromasa

2017-09-14

To investigate the factors predictive of failure when placing a second biliary self-expandable metallic stents (SEMSs). This study evaluated 65 patients with an unresectable malignant hilar biliary obstruction who were examined in our hospital. Sixty-two of these patients were recruited to the study and divided into two groups: the success group, which consisted of patients in whom a stent-in-stent SEMS had been placed successfully, and the failure group, which consisted of patients in whom the stent-in-stent SEMS had not been placed successfully. We compared the characteristics of the patients, the stricture state of their biliary ducts, and the implemented endoscopic retrograde cholangiopancreatography (ERCP) procedures between the two groups. The angle between the target biliary duct stricture and the first implanted SEMS was significantly larger in the failure group than in the success group. There were significantly fewer wire or dilation devices (ERCP catheter, dilator, or balloon catheter) passing the first SEMS cell in the failure group than in the success group. The cut-off value of the angle predicting stent-in-stent SEMS placement failure was 49.7 degrees according to the ROC curve (sensitivity 91.7%, specificity 61.2%). Furthermore, the angle was significantly smaller in patients with wire or dilation devices passing the first SEMS cell than in patients without wire or dilation devices passing the first SEMS cell. A large angle was identified as a predictive factor for failure of stent-in-stent SEMS placement.

Structural and wetting properties of porous anodic alumina templates prepared by different electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suchitra, S. M., E-mail: suchitra.ph14f03@nitk.edu.in; Reddy, P. Ramana; Udayashankar, N. K.

2016-05-06

Porous anodic alumina (PAA) has been extensively studied in recent years due to their unique properties and applications for manufacturing nanostructured materials. In this article, we report our studies on structural and wetting properties of PAA membranes prepared using different electrolytes such as sulphuric, oxalic and phosphoric acids. The morphological parameters such as pore diameter and porosity were measured using SEM and analysed using image-J software. The structural investigation of PAA membranes was carried out through X-ray diffraction analysis and it was confirmed that PAA membranes were amorphous in nature. The wetting behaviour of PAA membranes were measured using contactmore » angle measurement technique. The results show that PAA membranes were hydrophilic in nature with contact angles 26.03°, 35.21° and 42.0° for sulphuric, oxalic and phosphoric acids respectively.« less

Interactive stereo electron microscopy enhanced with virtual reality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bethel, E.Wes; Bastacky, S.Jacob; Schwartz, Kenneth S.

2001-12-17

An analytical system is presented that is used to take measurements of objects perceived in stereo image pairs obtained from a scanning electron microscope (SEM). Our system operates by presenting a single stereo view that contains stereo image data obtained from the SEM, along with geometric representations of two types of virtual measurement instruments, a ''protractor'' and a ''caliper''. The measurements obtained from this system are an integral part of a medical study evaluating surfactant, a liquid coating the inner surface of the lung which makes possible the process of breathing. Measurements of the curvature and contact angle of submicronmore » diameter droplets of a fluorocarbon deposited on the surface of airways are performed in order to determine surface tension of the air/liquid interface. This approach has been extended to a microscopic level from the techniques of traditional surface science by measuring submicrometer rather than millimeter diameter droplets, as well as the lengths and curvature of cilia responsible for movement of the surfactant, the airway's protective liquid blanket. An earlier implementation of this approach for taking angle measurements from objects perceived in stereo image pairs using a virtual protractor is extended in this paper to include distance measurements and to use a unified view model. The system is built around a unified view model that is derived from microscope-specific parameters, such as focal length, visible area and magnification. The unified view model ensures that the underlying view models and resultant binocular parallax cues are consistent between synthetic and acquired imagery. When the view models are consistent, it is possible to take measurements of features that are not constrained to lie within the projection plane. The system is first calibrated using non-clinical data of known size and resolution. Using the SEM, stereo image pairs of grids and spheres of known resolution are created to calibrate the measurement system. After calibration, the system is used to take distance and angle measurements of clinical specimens.« less

Direct determination of three-phase contact line properties on nearly molecular scale

DOE PAGES

Winkler, P. M.; McGraw, R. L.; Bauer, P. S.; ...

2016-05-17

Wetting phenomena in multi-phase systems govern the shape of the contact line which separates the different phases. For liquids in contact with solid surfaces wetting is typically described in terms of contact angle. While in macroscopic systems the contact angle can be determined experimentally, on the molecular scale contact angles are hardly accessible. Here we report the first direct experimental determination of contact angles as well as contact line curvature on a scale of the order of 1nm. For water nucleating heterogeneously on Ag nanoparticles we find contact angles around 15 degrees compared to 90 degrees for the corresponding macroscopicallymore » measured equilibrium angle. The obtained microscopic contact angles can be attributed to negative line tension in the order of –10 –10 J/m that becomes increasingly dominant with increasing curvature of the contact line. Furthermore, these results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects.« less

A contact angle hysteresis model based on the fractal structure of contact line.

PubMed

Wu, Shuai; Ma, Ming

2017-11-01

Contact angle is one of the most popular concept used in fields such as wetting, transport and microfludics. In practice, different contact angles such as equilibrium, receding and advancing contact angles are observed due to hysteresis. The connection among these contact angles is important in revealing the chemical and physical properties of surfaces related to wetting. Inspired by the fractal structure of contact line, we propose a single parameter model depicting the connection of the three angles. This parameter is decided by the fractal structure of the contact line. The results of this model agree with experimental observations. In certain cases, it can be reduced to other existing models. It also provides a new point of view in understanding the physical nature of the contact angle hysteresis. Interestingly, some counter-intuitive phenomena, such as the binary receding angles, are indicated in this model, which are waited to be validated by experiments. Copyright © 2017 Elsevier Inc. All rights reserved.

Contact angle hysteresis on doubly periodic smooth rough surfaces in Wenzel's regime: The role of the contact line depinning mechanism

NASA Astrophysics Data System (ADS)

Iliev, Stanimir; Pesheva, Nina; Iliev, Pavel

2018-04-01

We report here on the contact angle hysteresis, appearing when a liquid meniscus is in contact with doubly sinusoidal wavelike patterned surfaces in Wenzel's wetting regime. Using the full capillary model we obtain numerically the contact angle hysteresis as a function of the surface roughness factor and the equilibrium contact angle for a block case and a kink case contact line depinning mechanism. We find that the dependencies of the contact angle hysteresis on the surface roughness factor are different for the different contact line depinning mechanisms. These dependencies are different also for the two types of rough surfaces we studied. The relations between advancing, receding, and equilibrium contact angles are investigated. A comparison with the existing asymptotical, numerical, and experimental results is carried out.

Contact angle hysteresis on doubly periodic smooth rough surfaces in Wenzel's regime: The role of the contact line depinning mechanism.

PubMed

Iliev, Stanimir; Pesheva, Nina; Iliev, Pavel

2018-04-01

We report here on the contact angle hysteresis, appearing when a liquid meniscus is in contact with doubly sinusoidal wavelike patterned surfaces in Wenzel's wetting regime. Using the full capillary model we obtain numerically the contact angle hysteresis as a function of the surface roughness factor and the equilibrium contact angle for a block case and a kink case contact line depinning mechanism. We find that the dependencies of the contact angle hysteresis on the surface roughness factor are different for the different contact line depinning mechanisms. These dependencies are different also for the two types of rough surfaces we studied. The relations between advancing, receding, and equilibrium contact angles are investigated. A comparison with the existing asymptotical, numerical, and experimental results is carried out.

Development of PVA/gelatin nanofibrous scaffolds for Tissue Engineering via electrospinning

NASA Astrophysics Data System (ADS)

Perez-Puyana, V.; Jiménez-Rosado, M.; Romero, A.; Guerrero, A.

2018-03-01

The electrospinning process is an emerging and relatively easy technique to prepare three-dimensional matrices with micro- and nanofibers. To achieve it, aqueous polymer solutions from synthetic or natural polymers are used. PVA was selected as polymer and gelatin because of its biocompatibility and biodegradability. A complete characterization of the polymeric solutions (density, surface tension, etc) was previously performed. Subsequently, a standard electrospinning process (15 kV, 0.4 ml h-1 and 10 cm) was carried out to obtain scaffolds. The influence of the polymer concentration and the protein addition was observed by performing FTIR analyses and studied by analyzing the water contact angle and SEM images.

A novel strategy for durable superhydrophobic coating on glass substrate via using silica chains to fix silica particles

NASA Astrophysics Data System (ADS)

Huang, Qi-Zhang; Fang, Yue-Yun; Liu, Peng-Yi; Zhu, Yan-Qing; Shi, Ji-Fu; Xu, Gang

2018-01-01

The practical application of superhydrophobic coatings on glass is usually restricted by their poor wear resistance due to the insufficient adhesion. A double-silica-layered structure was proposed to reinforce the coating adhesion on glass substrate. The wettability, surface morphologies, and chemical composition were investigated by water contact angle measurement, scanning electron microscopy (SEM), and fourier transformed infrared (FTIR) spectroscopy. The prepared superhydrophobic coating displays a good wear-resistance by emery paper and sand abrasion, which also has excellent thermal stability and UV resistance. This strategy shows a bright future for durable superhydrophobic coating on glass.

Preparation of the Lentinus edodes-based porous biomass carbon by hydrothermal method for capacitive desalination

NASA Astrophysics Data System (ADS)

Yan, Junbin; Zhang, Hexuan; Xie, Zhengzheng; Liu, Jianyun

2017-08-01

Biomass carbon materials were prepared by hydrothermal method using Lentinus edodes, followed by activation by ZnCl2 at high carbonization temperature. SEM and contact angle test show that ZnCl2 has a significant effect on the surface morphology and properties of porous carbon materials. Using the porous carbon as electrodes of the capacitor, the specific capacitance of the porous carbon material was found to be 247.6 F/g. The desalination amount of porous carbon material in capacitor cell was 12.9 mg/g, being the 1.9 times of that of the commercial activated carbon.

Applicability of contact angle techniques used in the analysis of contact lenses, part 1: comparative methodologies.

PubMed

Campbell, Darren; Carnell, Sarah Maria; Eden, Russell John

2013-05-01

Contact angle, as a representative measure of surface wettability, is often employed to interpret contact lens surface properties. The literature is often contradictory and can lead to confusion. This literature review is part of a series regarding the analysis of hydrogel contact lenses using contact angle techniques. Here we present an overview of contact angle terminology, methodology, and analysis. Having discussed this background material, subsequent parts of the series will discuss the analysis of contact lens contact angles and evaluate differences in published laboratory results. The concepts of contact angle, wettability and wetting are presented as an introduction. Contact angle hysteresis is outlined and highlights the advantages in using dynamic analytical techniques over static methods. The surface free energy of a material illustrates how contact angle analysis is capable of providing supplementary surface characterization. Although single values are able to distinguish individual material differences, surface free energy and dynamic methods provide an improved understanding of material behavior. The frequently used sessile drop, captive bubble, and Wilhelmy plate techniques are discussed. Their use as both dynamic and static methods, along with the advantages and disadvantages of each technique, is explained. No single contact angle technique fully characterizes the wettability of a material surface, and the application of complimenting methods allows increased characterization. At present, there is not an ISO standard method designed for soft materials. It is important that each contact angle technique has a standard protocol, as small protocol differences between laboratories often contribute to a variety of published data that are not easily comparable.

Apparent and microscopic dynamic contact angles in confined flows

NASA Astrophysics Data System (ADS)

Omori, Takeshi; Kajishima, Takeo

2017-11-01

An abundance of empirical correlations between a dynamic contact angle and a capillary number representing a translational velocity of a contact line have been provided for the last decades. The experimentally obtained dynamic contact angles are inevitably apparent contact angles but often undistinguished from microscopic contact angles formed right on the wall. As Bonn et al. ["Wetting and spreading," Rev. Mod. Phys. 81, 739-805 (2009)] pointed out, however, most of the experimental studies simply report values of angles recorded at some length scale which is quantitatively unknown. It is therefore hard to evaluate or judge the physical validity and the generality of the empirical correlations. The present study is an attempt to clear this clutter regarding the dynamic contact angle by measuring both the apparent and the microscopic dynamic contact angles from the identical data sets in a well-controlled manner, by means of numerical simulation. The numerical method was constructed so that it reproduced the fine details of the flow with a moving contact line predicted by molecular dynamics simulations [T. Qian, X. Wang, and P. Sheng, "Molecular hydrodynamics of the moving contact line in two-phase immiscible flows," Commun. Comput. Phys. 1, 1-52 (2006)]. We show that the microscopic contact angle as a function of the capillary number has the same form as Blake's molecular-kinetic model [T. Blake and J. Haynes, "Kinetics of liquid/liquid displacement," J. Colloid Interface Sci. 30, 421-423 (1969)], regardless of the way the flow is driven, the channel width, the mechanical properties of the receding fluid, and the value of the equilibrium contact angle under the conditions where the Reynolds and capillary numbers are small. We have also found that the apparent contact angle obtained by the arc-fitting of the interface behaves surprisingly universally as claimed in experimental studies in the literature [e.g., X. Li et al., "An experimental study on dynamic pore wettability," Chem. Eng. Sci. 104, 988-997 (2013)], although the angle deviates significantly from the microscopic contact angle. It leads to a practically important point that it suffices to measure arc-fitted contact angles to make formulae to predict flow rates in capillary tubes.

Facile surface modification of glass with zwitterionic polymers for improving the blood compatibility

NASA Astrophysics Data System (ADS)

Zhang, Lingling; Chen, Xiaojuan; Liu, Pingsheng; Wang, Jing; Zhu, Haomiao; Li, Li

2018-06-01

A facile procedure to modify glass film with zwitterionic polymers for improving the blood compatibility was introduced. The glass slides were first silanized with 3-methacryloxypropyltrimethoxysilane (MPT) to generate methacrylate groups on the surface. Then, N, N’-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a sulfobetaine zwitterionic monomer, was polymerized on the silanized glass substrates by free-radical polymerization in order to graft the zwitterionic polymers onto the substrates. X-ray Photoelectron Spectroscopy (XPS), water contact angle, scanning electron microscope (SEM) and atomic force microscopy (AFM) were utilized to analyze the surface properties of the grafted glass. The blood compatibility of the grafted glass was verified by whole blood contacting and platelet adhesion experiments in vitro. The results showed that the zwitterionic polymers were successfully grafted on the glass surface, and consequently significantly inhibited the platelet adhesion and whole blood cell attachment.

University of Maryland MRSEC - Facilities: SEM/STM/AFM

Science.gov Websites

MRSEC Templates Opportunities Search Home » Facilities » SEM/STM/AFM Shared Experimental Facilities conducting and non conducting samples. The sample stage permits electronic device imaging under operational Specifications: Image Modes - STM, STS, MFM, EFM, SKPM, contact- and non-contact AFM Three Sample Contacts 0.1 nm

Diminution of contact angle hysteresis under the influence of an oscillating force.

PubMed

Manor, Ofer

2014-06-17

We suggest a simple quantitative model for the diminution of contact angle hysteresis under the influence of an oscillatory force invoked by thermal fluctuations, substrate vibrations, acoustic waves, or oscillating electric fields. Employing force balance rather than the usual description of contact angle hysteresis in terms of Gibbs energy, we highlight that a wetting system, such as a sessile drop or a bubble adhered to a solid substrate, appears at long times to be partially or fully independent of contact angle hysteresis and thus independent of static friction forces, as a result of contact line pinning. We verify this theory by studying several well-known experimental observations such as the approach of an arbitrary contact angle toward the Young contact angle and the apparent decrease (or increase) in an advancing (or a receding) contact angle under the influence of an external oscillating force.

Apparent-contact-angle model at partial wetting and evaporation: impact of surface forces.

PubMed

Janeček, V; Nikolayev, V S

2013-01-01

This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20° larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

Apparent-contact-angle model at partial wetting and evaporation: Impact of surface forces

NASA Astrophysics Data System (ADS)

Janeček, V.; Nikolayev, V. S.

2013-01-01

This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20∘ larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

Hydrophobic to superhydrophobic surface modification using impacting particulate sprays

NASA Astrophysics Data System (ADS)

Lau, Chun Yat; Vuong, Thach; Wang, Jingming; Muradoglu, Murat; Liew, Oi Wah; Ng, Tuck Wah

2014-08-01

The roughening or structuring of inherently hydrophobic surfaces to possess microscopic and nanoscopic features can transform them to exhibit superhydrophobicity. The use of impacting particulate sprays here eschews specialized reagents and equipments; is simple, inexpensive, and rapid to implement; creates highly repeatable outcomes; and permits selective region transformation via simple masking. With PTFE, the contact angle transforms from 90° to 150°, in which SEM examination reveals erosive wear mechanisms that are dependent on the impingement angle. The process tends to cause the sample to bulge upwards from the treated surface due to elongation there, and can be mitigated by using lower impingement angles in the particulate spray. A finite element model created enables this characteristic to be related to the action of locked-in surface traction forces. The use of adhesive bonding to a rigid base is shown to be an alternative method to reduce the bulging. A second finite model developed allows knowledge of the right adhesive needed for this. In developing substrates for biochemical analysis, the approach offers very small possibilities for unintended synergistic interactions.

Contact detection for nanomanipulation in a scanning electron microscope.

PubMed

Ru, Changhai; To, Steve

2012-07-01

Nanomanipulation systems require accurate knowledge of the end-effector position in all three spatial coordinates, XYZ, for reliable manipulation of nanostructures. Although the images acquired by a scanning electron microscope (SEM) provide high resolution XY information, the lack of depth information in the Z-direction makes 3D nanomanipulation time-consuming. Existing approaches for contact detection of end-effectors inside SEM typically utilize fragile touch sensors that are difficult to integrate into a nanomanipulation system. This paper presents a method for determining the contact between an end-effector and a target surface during nanomanipulation inside SEM, purely based on the processing of SEM images. A depth-from-focus method is used in the fast approach of the end-effector to the substrate, followed by fine contact detection. Experimental results demonstrate that the contact detection approach is capable of achieving an accuracy of 21.5 nm at 50,000× magnification while inducing little end-effector damage. Copyright © 2012 Elsevier B.V. All rights reserved.

Influence of spin creepage and contact angle on curve squeal: A numerical approach

NASA Astrophysics Data System (ADS)

Zenzerovic, I.; Kropp, W.; Pieringer, A.

2018-04-01

Curve squeal is a loud tonal sound that may arise when a railway vehicle negotiates a tight curve. Due to the nonlinear nature of squeal, time-domain models provide a higher degree of accuracy in comparison to frequency-domain models and also enable the determination of squeal amplitudes. In the present paper, a previously developed engineering time-domain model for curve squeal is extended to include the effects of the contact angle and spin creepage. The extensions enable the evaluation of more realistic squeal cases with the computationally efficient model. The model validation against Kalker's variational contact model shows good agreement between the models. Results of studies on the influence of spin creepage and contact angle show that the contact angle has a significant influence on the vertical-lateral dynamics coupling and, therefore, influences both squeal amplitude and frequency. Spin creepage mainly influences processes in the contact, therefore influencing the tangential contact force amplitude. In the combined spin-contact angle study the spin creepage value is kinematically related to the contact angle value. Results indicate that the influence of the contact angle is dominant over the influence of spin creepage. In general, results indicate that the most crucial factors in squeal are those that influence the dynamics coupling: the contact angle, wheel/rail contact positions and friction.

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

PubMed

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Development of Thin Films as Potential Structural Cathodes to Enable Multifunctional Energy-Storage Structural Composite Batteries for the U.S. Army’s Future Force

DTIC Science & Technology

2011-09-01

glancing angle X - ray diffraction (GAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and electrochemical...Emission SEM FWHM full width at half maximum GAXRD glancing angle X - ray diffraction H3COCH2CH2OH 2-methoxyethanol LiMn2O4 lithium manganese oxide...were characterized by scanning electron microscopy (SEM), X - ray diffraction (XRD), and atomic force microscopy (AFM). In addition,

[Determination of contact angle of pharmaceutical excipients and regulating effect of surfactants on their wettability].

PubMed

Hua, Dong-dong; Li, He-ran; Yang, Bai-xue; Song, Li-na; Liu, Tiao-tiao; Cong, Yu-tang; Li, San-ming

2015-10-01

To study the effects of surfactants on wettability of excipients, the contact angles of six types of surfactants on the surface of two common excipients and mixture of three surfactants with excipients were measured using hypsometry method. The results demonstrated that contact angle of water on the surface of excipients was associated with hydrophilcity of excipients. Contact angle was lowered with increase in hydrophilic groups of excipient molecules. The sequence of contact angle from small to large was starch < sodium benzoate < polyvinylpyrrolidone < sodium carboxymethylcellulose < sodium alginate < chitosan < hydroxypropyl methyl cellulose

Contact angle and local wetting at contact line.

PubMed

Li, Ri; Shan, Yanguang

2012-11-06

This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.

Light transfer through windows with external condensation

NASA Astrophysics Data System (ADS)

Zhu, Keyong; Li, Shaoling; Pilon, Laurent

2018-03-01

This study investigates systematically light transfer through windows supporting cap-shaped droplets on their external face. The presence of such droplets may have negative effects on the conversion efficiency of solar cells, distorts image quality of lenses, or hinders visibility through windows and windshields. Here, the directional-hemispherical transmittance was predicted by the Monte Carlo ray-tracing method. The droplets were monodisperse or polydisperse randomly distributed on the outside face of optically smooth windows. For nonabsorbing droplets, the diameter and size distribution did not have a significant effect on the window directional-hemispherical transmittance. The latter was nearly independent of contact angle for incident angle θi ≤ 30°. However, the directional-hemispherical transmittance decreased monotonously with increasing incident angle and droplet contact angle for contact angle θc ≤ 70° to reach a minimum at a contact angle θc,min beyond which it increased with increasing contact angle before reaching a plateau at large contact angles. This was attributed to total internal reflection at the back window/air and droplet/air interfaces. For absorbing droplets, the normal-hemispherical transmittance decreased significantly with increasing droplet contact angle, mean diameter, polydispersity, and projected surface area coverage due to strong absorption within the droplets. Moreover, the normal-hemispherical transmittance decreased with increasing contact angle for θc< 90° and remained constant and independent of the droplets' absorption index, mean diameter, and contact angle for θc ≥ 90°. Finally, Analytical expressions for the upper and lower bounds of the normal-hemispherical transmittance as a function of droplet contact angle, optical properties, and projected surface area coverage were derived.

High performance membrane-electrode assembly based on a surface-modified membrane

NASA Astrophysics Data System (ADS)

Han, Sangil; Lee, Jang Woo; Kwak, Chan; Chai, Geun Seok; Son, In Hyuk; Jang, Moon Yup; An, Sung Guk; Cho, Sung Yong; Kim, Jun Young; Kim, Hyung Wook; Serov, Alexey Alexandrovych; Yoo, Youngtai; Nam, Kie Hyun

A surface-modified membrane is prepared using a sputtering technique that deposits gold directly on a Nafion ® 115 membrane surface that is roughened with silicon carbide paper. The surface-modified membranes are characterized by means of a scanning electron microscope (SEM), differential scanning calorimetry (DSC), and water contact-angle analysis. A single direct methanol fuel cell (DMFC) with a surface-modified membrane exhibits enhanced performance (160 mW cm -2), while a bare Nafion ® 115 cell yields 113 mW cm -2 at 0.4 V and an operating temperature of 70 °C. From FE-SEM images and CO ad stripping voltammograms, it is also found that the gold layer is composed of clusters of porous nodule-like particles, which indicates that an anode with nodule-like gold leads to the preferential oxidation of carbon monoxide. These results suggest that the topology of gold in the interfacial area and its electrocatalytic nature may be the critical factors that affect DMFC performance.

Surface analysis of graphite fiber reinforced polyimide composites

NASA Technical Reports Server (NTRS)

Messick, D. L.; Progar, D. J.; Wightman, J. P.

1983-01-01

Several techniques have been used to establish the effect of different surface pretreatments on graphite-polyimide composites. Composites were prepared from Celion 6000 graphite fibers and the polyimide LARC-160. Pretreatments included mechanical abrasion, chemical etching and light irradiation. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used in the analysis. Contact angle of five different liquids of varying surface tensions were measured on the composites. SEM results showed polymer-rich peaks and polymer-poor valleys conforming to the pattern of the release cloth used durng fabrication. Mechanically treated and light irradiated samples showed varying degrees of polymer peak removal, with some degradation down to the graphite fibers. Minimal changes in surface topography were observed on concentrations of surface fluorine even after pretreatment. The light irradiation pretreatment was most effective at reducing surface fluorine concentrations whereas chemical pretreatment was the least effective. Critical surface tensions correlated directly with the surface fluorine to carbon ratios as calculated from XPS.

Chitin butyrate coated electrospun nylon-6 fibers for biomedical applications

NASA Astrophysics Data System (ADS)

Pant, Hem Raj; Kim, Han Joo; Bhatt, Lok Ranjan; Joshi, Mahesh Kumar; Kim, Eun Kyo; Kim, Jeong In; Abdal-hay, Abdalla; Hui, K. S.; Kim, Cheol Sang

2013-11-01

In this study, we describe the preparation and characterizations of chitin butyrate (CB) coated nylon-6 nanofibers using single-spinneret electrospinning of blends solution. The physicochemical properties of nylon-6 composite fibers with different proportions of CB to nylon-6 were determined using FE-SEM, TEM, FT-IR spectroscopy, and water contact angle measurement. FE-SEM and TEM images revealed that the nylon-6 and CB were immiscible in the as-spun nanofibers, and phase separated nanofiber morphology becomes more pronounced with increasing amounts of CB. The bone formation ability of composite fibers was evaluated by incubating in biomimetic simulated body fluid. In order to assay the cytocompatibility and cell behavior on the composite scaffolds, osteoblast cells were seeded on the matrix. Results suggest that the deposition of CB layer on the surface of nylon-6 could increase its cell compatibility and bone formation ability. Therefore, as-synthesized nanocomposite fibrous mat has great potentiality in hard tissue engineering.

Enhancement of anticorrosion property of 304 stainless steel using silane coatings

NASA Astrophysics Data System (ADS)

Akhtar, Sultan; Matin, Asif; Madhan Kumar, A.; Ibrahim, Ahmed; Laoui, Tahar

2018-05-01

In the present work, silane coatings based on glycidoxypropyltrimethoxysilane/methyltrimethoxysilane (GPTMS/MTMS) and silica nanoparticles were prepared by a sol-gel method. A simple dip-coating method was applied for film deposition and the effect of immersion time and number of immersion cycles on corrosion behavior of 304 stainless steel (SS) was investigated. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS) was used to study the surface morphology and elemental composition of the modified surfaces. The corrosion behavior of the coated and uncoated SS substrates was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.6 M sodium chloride solution. Our results showed that the presence of coatings improved the anti-corrosion property of SS substrates. The coating with a dipping time of 10 min and 3 dipping cycles exhibited the best protection efficiency compared to other coatings and the uncoated substrate. SEM/EDS findings and contact angle measurements supported the conclusions drawn from the corrosion study.

Beyond Cassie equation: Local structure of heterogeneous surfaces determines the contact angles of microdroplets

PubMed Central

Zhang, Bo; Wang, Jianjun; Liu, Zhiping; Zhang, Xianren

2014-01-01

The application of Cassie equation to microscopic droplets is recently under intense debate because the microdroplet dimension is often of the same order of magnitude as the characteristic size of substrate heterogeneities, and the mechanism to describe the contact angle of microdroplets is not clear. By representing real surfaces statistically as an ensemble of patterned surfaces with randomly or regularly distributed heterogeneities (patches), lattice Boltzmann simulations here show that the contact angle of microdroplets has a wide distribution, either continuous or discrete, depending on the patch size. The origin of multiple contact angles observed is ascribed to the contact line pinning effect induced by substrate heterogeneities. We demonstrate that the local feature of substrate structure near the contact line determines the range of contact angles that can be stabilized, while the certain contact angle observed is closely related to the contact line width. PMID:25059292

Synthesis of a fluorine-free polymeric water-repellent agent for creation of superhydrophobic fabrics

NASA Astrophysics Data System (ADS)

Shen, Keke; Yu, Miao; Li, Qianqian; Sun, Wei; Zhang, Xiting; Quan, Miao; Liu, Zhengtang; Shi, Suqing; Gong, Yongkuan

2017-12-01

A non-fluorinated polymeric alkylsilane, poly(isobutyl methacrylate-co-3-methacryloxypropyltrimethoxysilane) (PIT), is designed and synthesized to replace the commercial long-chain perfluoroalkylsilane (FAS) water-repellent agent. The superhydrophobic polyester fabrics are prepared by anchoring sol-gel derived silica nanoparticles onto alkali-treated polyester fabric surfaces and subsequently hydrophobilizing with PIT, using FAS as control. The surface chemical composition, surface morphology, wetting behavior and durability of the modified polyester fabrics are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectrophotometer (XPS) and video-based contact angle goniometer, respectively. The results show that a porous silica layer could be successfully fabricated onto the surface of polyester fabric through base-catalyzed sol-gel process with tetraethoxysilane (TEOS) as precursor, incorporating additional nanostructured roughness essential for superhydrophobicity. At the same time, such a silica primer layer could provide both secondary reactive moieties (-Si - OH) for the subsequent surface hydrophobization and acceptable adhesion at the silica-polyester fabric interface. When silica modified polyester fabric (SiO2@ fabric) is hydrophobized by PIT solution (10 mg/mL), excellent water-repellency could be obtained. The water contact angle is up to 154° and the sliding angle is about 5°. Compared with small molecule water-repellent agent FAS, PIT modified SiO2@ fabric exhibits greatly improved solvent resistance under ultra-sonication, abrasion and simulated laundering durability. The anti-stain property of PIT-modified SiO2@ fabric is also evaluated by using different aqueous colored solutions.

Forefoot angle at initial contact determines the amplitude of forefoot and rearfoot eversion during running.

PubMed

Monaghan, Gail M; Hsu, Wen-Hao; Lewis, Cara L; Saltzman, Elliot; Hamill, Joseph; Holt, Kenneth G

2014-09-01

Clinically, foot structures are assessed intrinsically - relation of forefoot to rearfoot and rearfoot to leg. We have argued that, from a biomechanical perspective, the interaction of the foot with the ground may influence forces and torques that are propagated through the lower extremity. We proposed that a more appropriate measure is an extrinsic one that may predict the angle the foot makes with ground at contact. The purposes of this study were to determine if the proposed measure predicts contact angles of the forefoot and rearfoot and assess if the magnitude of those angles influences amplitude and duration of foot eversion during running. With the individual in prone, extrinsic clinical forefoot and rearfoot angles were measured relative to the caudal edge of the examination table. Participants ran over ground while frontal plane forefoot and rearfoot contact angles, forefoot and rearfoot eversion amplitude and duration were measured. Participants were grouped twice, once based on forefoot contact inversion angle (moderatemedian) and once based on rearfoot contact inversion angle (moderatemedian). The forefoot and rearfoot extrinsic clinical angles predicted, respectively, the forefoot and rearfoot angles at ground contact. Large forefoot contact angles were associated with greater amplitudes (but not durations) of forefoot and rearfoot eversion during stance. Rearfoot contact angles, however, were associated with neither amplitudes nor durations of forefoot and rearfoot eversion. Possible mechanisms for the increased risk of running injuries associated with large forefoot angles are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

A method to measure internal contact angle in opaque systems by magnetic resonance imaging.

PubMed

Zhu, Weiqin; Tian, Ye; Gao, Xuefeng; Jiang, Lei

2013-07-23

Internal contact angle is an important parameter for internal wettability characterization. However, due to the limitation of optical imaging, methods available for contact angle measurement are only suitable for transparent or open systems. For most of the practical situations that require contact angle measurement in opaque or enclosed systems, the traditional methods are not effective. Based upon the requirement, a method suitable for contact angle measurement in nontransparent systems is developed by employing MRI technology. In the Article, the method is demonstrated by measuring internal contact angles in opaque cylindrical tubes. It proves that the method also shows great feasibility in transparent situations and opaque capillary systems. By using the method, contact angle in opaque systems could be measured successfully, which is significant in understanding the wetting behaviors in nontransparent systems and calculating interfacial parameters in enclosed systems.

A thermodynamic model of contact angle hysteresis.

PubMed

Makkonen, Lasse

2017-08-14

When a three-phase contact line moves along a solid surface, the contact angle no longer corresponds to the static equilibrium angle but is larger when the liquid is advancing and smaller when the liquid is receding. The difference between the advancing and receding contact angles, i.e., the contact angle hysteresis, is of paramount importance in wetting and capillarity. For example, it determines the magnitude of the external force that is required to make a drop slide on a solid surface. Until now, fundamental origin of the contact angle hysteresis has been controversial. Here, this origin is revealed and a quantitative theory is derived. The theory is corroborated by the available experimental data for a large number of solid-liquid combinations. The theory is applied in modelling the contact angle hysteresis on a textured surface, and these results are also in quantitative agreement with the experimental data.

Contact angle adjustment in equation-of-state-based pseudopotential model.

PubMed

Hu, Anjie; Li, Longjian; Uddin, Rizwan; Liu, Dong

2016-05-01

The single component pseudopotential lattice Boltzmann model has been widely applied in multiphase simulation due to its simplicity and stability. In many studies, it has been claimed that this model can be stable for density ratios larger than 1000. However, the application of the model is still limited to small density ratios when the contact angle is considered. The reason is that the original contact angle adjustment method influences the stability of the model. Moreover, simulation results in the present work show that, by applying the original contact angle adjustment method, the density distribution near the wall is artificially changed, and the contact angle is dependent on the surface tension. Hence, it is very inconvenient to apply this method with a fixed contact angle, and the accuracy of the model cannot be guaranteed. To solve these problems, a contact angle adjustment method based on the geometry analysis is proposed and numerically compared with the original method. Simulation results show that, with our contact angle adjustment method, the stability of the model is highly improved when the density ratio is relatively large, and it is independent of the surface tension.

Contact angle adjustment in equation-of-state-based pseudopotential model

NASA Astrophysics Data System (ADS)

Hu, Anjie; Li, Longjian; Uddin, Rizwan; Liu, Dong

2016-05-01

The single component pseudopotential lattice Boltzmann model has been widely applied in multiphase simulation due to its simplicity and stability. In many studies, it has been claimed that this model can be stable for density ratios larger than 1000. However, the application of the model is still limited to small density ratios when the contact angle is considered. The reason is that the original contact angle adjustment method influences the stability of the model. Moreover, simulation results in the present work show that, by applying the original contact angle adjustment method, the density distribution near the wall is artificially changed, and the contact angle is dependent on the surface tension. Hence, it is very inconvenient to apply this method with a fixed contact angle, and the accuracy of the model cannot be guaranteed. To solve these problems, a contact angle adjustment method based on the geometry analysis is proposed and numerically compared with the original method. Simulation results show that, with our contact angle adjustment method, the stability of the model is highly improved when the density ratio is relatively large, and it is independent of the surface tension.

Effect of nanoparticle size on sessile droplet contact angle

NASA Astrophysics Data System (ADS)

Munshi, A. M.; Singh, V. N.; Kumar, Mukesh; Singh, J. P.

2008-04-01

We report a significant variation in the static contact angle measured on indium oxide (IO) nanoparticle coated Si substrates that have different nanoparticle sizes. These IO nanoparticles, which have well defined shape and sizes, were synthesized by chemical vapor deposition in a horizontal alumina tube furnace. The size of the IO nanoparticles was varied by changing the source material, substrate temperature, and the deposition time. A sessile droplet method was used to determine the macroscopic contact angle on these IO nanoparticle covered Si substrate using two different liquids: de-ionized water and diethylene glycol (DEG). It was observed that contact angle depends strongly on the nanoparticle size. The contact angle was found to vary from 24° to 67° for de-ionized water droplet and from 15° to 60° for DEG droplet, for the nanoparticle sizes varying from 14 to 620 nm. The contact angle decreases with a decrease in the particles size. We have performed a theoretical analysis to determine the dependence of contact angle on the nanoparticle size. This formulation qualitatively shows a similar trend of decrease in the contact angle with a decrease in nanoparticle size. Providing a rough estimate of nanoparticle size by sessile droplet contact angle measurement is the novelty in this work.

Drop rebound after impact: the role of the receding contact angle.

PubMed

Antonini, C; Villa, F; Bernagozzi, I; Amirfazli, A; Marengo, M

2013-12-31

Data from the literature suggest that the rebound of a drop from a surface can be achieved when the wettability is low, i.e., when contact angles, measured at the triple line (solid-liquid-air), are high. However, no clear criterion exists to predict when a drop will rebound from a surface and which is the key wetting parameter to govern drop rebound (e.g., the "equilibrium" contact angle, θeq, the advancing and the receding contact angles, θA and θR, respectively, the contact angle hysteresis, Δθ, or any combination of these parameters). To clarify the conditions for drop rebound, we conducted experimental tests on different dry solid surfaces with variable wettability, from hydrophobic to superhydrophobic surfaces, with advancing contact angles 108° < θA < 169° and receding contact angles 89° < θR < 161°. It was found that the receding contact angle is the key wetting parameter that influences drop rebound, along with surface hydrophobicity: for the investigated impact conditions (drop diameter 2.4 < D0 < 2.6 mm, impact speed 0.8 < V < 4.1 m/s, Weber number 25 < We < 585), rebound was observed only on surfaces with receding contact angles higher than 100°. Also, the drop rebound time decreased by increasing the receding contact angle. It was also shown that in general care must be taken when using statically defined wetting parameters (such as advancing and receding contact angles) to predict the dynamic behavior of a liquid on a solid surface because the dynamics of the phenomenon may affect surface wetting close to the impact point (e.g., as a result of the transition from the Cassie-Baxter to Wenzel state in the case of the so-called superhydrophobic surfaces) and thus affect the drop rebound.

Measuring contact angle and meniscus shape with a reflected laser beam.

PubMed

Eibach, T F; Fell, D; Nguyen, H; Butt, H J; Auernhammer, G K

2014-01-01

Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

Measuring contact angle and meniscus shape with a reflected laser beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eibach, T. F.; Nguyen, H.; Butt, H. J.

2014-01-15

Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collectedmore » on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.« less

Low-temperature oxidizing plasma surface modification and composite polymer thin-film fabrication techniques for tailoring the composition and behavior of polymer surfaces

NASA Astrophysics Data System (ADS)

Tompkins, Brendan D.

This dissertation examines methods for modifying the composition and behavior of polymer material surfaces. This is accomplished using (1) low-temperature low-density oxidizing plasmas to etch and implant new functionality on polymers, and (2) plasma enhanced chemical vapor deposition (PECVD) techniques to fabricate composite polymer materials. Emphases are placed on the structure of modified polymer surfaces, the evolution of polymer surfaces after treatment, and the species responsible for modifying polymers during plasma processing. H2O vapor plasma modification of high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), polycarbonate (PC), and 75A polyurethane (PU) was examined to further our understanding of polymer surface reorganization leading to hydrophobic recovery. Water contact angles (wCA) measurements showed that PP and PS were the most susceptible to hydrophobic recovery, while PC and HDPE were the most stable. X-ray photoelectron spectroscopy (XPS) revealed a significant quantity of polar functional groups on the surface of all treated polymer samples. Shifts in the C1s binding energies (BE) with sample age were measured on PP and PS, revealing that surface reorganization was responsible for hydrophobic recovery on these materials. Differential scanning calorimetry (DSC) was used to rule out the intrinsic thermal properties as the cause of reorganization and hydrophobic recovery on HDPE, LDPE, and PP. The different contributions that polymer cross-linking and chain scission mechanisms make to polymer aging effects are considered. The H2O plasma treatment technique was extended to the modification of 0.2 microm and 3.0 microm track-etched polycarbonate (PC-TE) and track-etched polyethylene terephthalate (PET-TE) membranes with the goal of permanently increasing the hydrophilicity of the membrane surfaces. Contact angle measurements on freshly treated and aged samples confirmed the wettability of the membrane surfaces was significantly improved by plasma treatment. XPS and SEM analyses revealed increased oxygen incorporation onto the surface of the membranes, without any damage to the surface or pore structure. Contact angle measurements on a membrane treated in a stacked assembly suggest the plasma effectively modified the entire pore cross section. Plasma treatment also increased water flux through the membranes, with results from plasma modified membranes matching those from commercially available hydrophilic membranes (treated with wetting agent). Mechanisms for the observed modification are discussed in terms of OH and O radicals implanting oxygen functionality into the polymers. Oxidizing plasma systems (O2, CO2, H2O vapor, and formic acid vapor) were used to modify track-etched polycarbonate membranes and explore the mechanisms and species responsible for etching polycarbonate during plasma processing. Etch rates were measured using scanning electron microscopy; modified polycarbonate surfaces were further characterized using x-ray photoelectron spectroscopy and water contact angles. Etch rates and surface characterization results were combined with optical emission spectroscopy data used to identify gas-phase species and their relative densities. Although the oxide functionalities implanted by each plasma system were similar, the H2O vapor and formic acid vapor plasmas yielded the lowest contact angles after treatment. The CO2, H2O vapor, and formic acid vapor plasma-modified surfaces were, however, found to be similarly stable one month after treatment. Overall, etch rate correlated directly to the relative gas-phase density of atomic oxygen and, to a lesser extent, hydroxyl radicals. PECVD of acetic acid vapor (CH3COOH) was used to deposit films on PC-TE and silicon wafer substrates. The CH3COOH films were characterized using XPS, wCA, and SEM. This modification technique resulted in continuous deposition and self-limiting deposition of a-CxO yHz films on Si wafers and PC-TE, respectively. The self-limiting deposition on PC-TE revealed that resulting films have minimal impact on 3D PC structures. This technique would allow for more precise fabrication of patterned or nano-textured PC. PECVD is used to synthesize hydrocarbon/fluorocarbon thin films with compositional gradients by continuously changing the ratio of gases in a C 3F8/H2 plasma. The films are characterized using variable angle spectroscopic ellipsometry (VASE), Fourier transform infrared spectroscopy (FTIR), XPS, wCA, and SEM. These methods revealed that shifting spectroscopic signals can be used to characterize organization in the deposited film. Using these methods, along with gas-phase diagnostics, film chemistry and the underlying deposition mechanisms are elucidated, leading to a model that accurately predicts film thickness.

Synergistic effect of Chitosan-Zinc Oxide Hybrid Nanoparticles on antibiofouling and water disinfection of mixed matrix polyethersulfone nanocomposite membranes.

PubMed

Munnawar, Iqra; Iqbal, Sadia S; Anwar, Muhammad N; Batool, Mehwish; Tariq, Sheraz; Faitma, Nosheen; Khan, Asim L; Khan, Asad U; Nazar, Umair; Jamil, Tahir; Ahmad, Nasir M

2017-11-01

Antifouling polyethersulfone (PES) membranes for water disinfection were fabricated by incorporating varying concentrations of carbohydrate polymer chitosan and Zinc oxide hybrid nanoparticles (CS-ZnO HNPS). The CS-ZnO HNPS were prepared using chemical precipitation method and were characterized using SEM, XRD and FTIR. The membranes were then fabricated by incorporating nanoparticles of CS-ZnO HNPS with three different concentrations of 5%, 10% and 15% w/w in the casting solution of PES through phase inversion method. The influence of nano-sized CS-ZnO HNPS on the properties of PES was characterized to study morphology, contact angle, water retention, surface roughness and permeability flux. The membranes with the maximum concentrations of 15% HNPS resulted in larger mean pore sizes and lowest contact angle value as compare to the pristine PES membrane. The prepared membranes exhibited significant water permeability, hydrophilicity and prevention against microbial fouling. The prepared membranes were observed to have significant antibacterial as well as antifungal properties due to the synergistic effect of chitosan and ZnO against both bacteria of the type of S. Aureus, B. Cereus, E. coli, and fungi such as S. typhi, A. fumigatus and F. solani. Copyright © 2017. Published by Elsevier Ltd.

Selective generation of laser-induced periodic surface structures on Al2O3-ZrO2-Nb composites

NASA Astrophysics Data System (ADS)

Kunz, Clemens; Bartolomé, José F.; Gnecco, Enrico; Müller, Frank A.; Gräf, Stephan

2018-03-01

Laser-induced periodic surface structures (LIPSS) were selectively fabricated on the metal phase of Al2O3-nZrO2-Nb (78.3-1.7-20 vol.%) ceramic matrix composites. For this purpose, sample surfaces were irradiated with fs-laser pulses (τ = 300 fs, λ = 1025 nm) of different laser peak fluences ranging from 0.23 to 0.40 J/cm2. The structured surfaces were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and by measuring the water contact angle. Well-pronounced LIPSS with a period of Λ ≈ 750 nm and a height of h ≈ 263 nm were found solely on the metal phase of the composite when applying the highest fluence whereas no structural and chemical modifications were found on the surface of the ceramic matrix. This can be explained by the different light absorption behaviour of both phases, which results in different ablation thresholds. The water contact angle of composite surfaces was successfully reduced from 68.4° for untreated samples to 40.9° for structured samples. Selectively structured composites with adjustable wettability are of particular interest for biomedical and tribological applications.

A dense and strong bonding collagen film for carbon/carbon composites

NASA Astrophysics Data System (ADS)

Cao, Sheng; Li, Hejun; Li, Kezhi; Lu, Jinhua; Zhang, Leilei

2015-08-01

A strong bonding collagen film was successfully prepared on carbon/carbon (C/C) composites. The surface conditions of the modified C/C composites were detected by contact angle measurements, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectra. The roughness, optical morphology, bonding strength and biocompatibility of collagen films at different pH values were detected by confocal laser scanning microscope (CLSM), universal test machine and cytology tests in vitro. After a 4-h modification in 30% H2O2 solution at 100 °C, the contact angle on the surface of C/C composites was decreased from 92.3° to 65.3°. Large quantities of hydroxyl, carboxyl and carbonyl functional groups were formed on the surface of the modified C/C composites. Then a dense and continuous collagen film was prepared on the modified C/C substrate. Bonding strength between collagen film and C/C substrate was reached to 8 MPa level when the pH value of this collagen film was 2.5 after the preparing process. With 2-day dehydrathermal treatment (DHT) crosslinking at 105 °C, the bonding strength was increased to 12 MPa level. At last, the results of in vitro cytological test showed that this collagen film made a great improvement on the biocompatibility on C/C composites.

Preparation of Superhydrophobic Film on Ti Substrate and Its Anticorrosion Property

PubMed Central

Zhu, Min; Tang, Wenchuan; Huang, Luyao; Zhang, Dawei; Du, Cuiwei; Yu, Gaohong; Chen, Ming; Chowwanonthapunya, Thee

2017-01-01

Superhydrophobic films were fabricated on a titanium substrate with or without anodizing by using a self-assembling method. Firstly, the pretreatments of mechanical polishing/anodizing or mechanical polishing only were conducted, respectively. Subsequently, the preparation of polydopamine film layer, deposition of nano-silver particles, and post modification of 1H,1H,2H,2H-perfluorodecanethiol were performed on the surface of the pretreated substrate. The surface morphologies, compositions, wettability, and corrosion resistance of the films were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), water contact angle measurements, and electrochemical tests, respectively. Meanwhile, the effect of the deposition time in the silver nitrate solution on the hydrophobicity of the specimen surface was investigated. The result showed that with the increase of deposition time, the hydrophobic property enhanced gradually. The surface deposited for 7 h exhibited an optimum hydrophobic effect, which was characterized with a large water contact angle (WCA) of 154°, and the surface was rather rough and covered by a relatively uniform layer of micro-nano silver particles. The excellent hydrophobicity was attributed to a rough stratified microstructure along with the low surface energy. The electrochemical measurements showed that the existence of the superhydrophobic film can effectively enhance the corrosion resistance of Ti samples. PMID:28772987

Fabrication of TiO2/EP super-hydrophobic thin film on filter paper surface.

PubMed

Gao, Zhengxin; Zhai, Xianglin; Liu, Feng; Zhang, Ming; Zang, Deli; Wang, Chengyu

2015-09-05

A composite filter paper with super-hydrophobicity was obtained by adhering micro/nano structure of amorphous titanium dioxide on the filter paper surface with modifying low surface energy material. By virtue of the coupling agent, which plays an important part in bonding amorphous titanium dioxide and epoxy resin, the structure of super-hydrophobic thin film on the filter paper surface is extremely stable. The microstructure of super-hydrophobic filter paper was characterized by scanning electron microscopy (SEM), the images showed that the as-prepared filter paper was covered with uniform amorphous titanium dioxide particles, generating a roughness structure on the filter paper surface. The super-hydrophobic performance of the filter paper was characterized by water contact angle measurements. The observations showed that the wettability of filter paper samples transformed from super-hydrophilicity to super-hydrophobicity with the water contact angle of 153 ± 1°. Some experiments were also designed to test the effect of water-oil separation and UV-resistant by the super-hydrophobic filter paper. The prepared super-hydrophobic filter paper worked efficiently and simply in water-oil separation as well as enduringly in anti-UV property after the experiments. This method offers an opportunity to the practical applications of the super-hydrophobic filter paper. Copyright © 2015 Elsevier Ltd. All rights reserved.

The adhesion performance of epoxy coating on AA6063 treated in Ti/Zr/V based solution

NASA Astrophysics Data System (ADS)

Zhu, Wen; Li, Wenfang; Mu, Songlin; Yang, Yunyu; Zuo, Xi

2016-10-01

An environment-friendly titanium/zirconium/vanadium-based (Ti/Zr/V) conversion coating was prepared on aluminum alloy 6063 (AA6063). The epoxy powder coatings were applied on the AA6063 samples with/without Ti/Zr/V conversion coatings via electrostatic spraying. The morphology and composition of the conversion coating were studied by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The surface free energy components of AA6063 samples were measured by a static contact angle measuring device with Owens method. The adhesion properties of the epoxy coating on AA6063 treated with different conversion times were evaluated using a pull-off tester. The Ti/Zr/V conversion coating was mainly composed of metal oxide (TiO2, ZrO2, V2O5, Al2O3, etc.), metal fluoride (ZrF4, AlF3, etc.) and metal organic complex. The formation time of this conversion coating was reduced to 50 s. After such surface treatment, the samples' surface roughness was increased and the contact angle with water was decreased. Both the surface free energy and the work of adhesion were increased. The adhesion strength between the epoxy coating and AA6063 was enhanced significantly.

Induced superhydrophobic and antimicrobial character of zinc metal modified ceramic wall tile surfaces

NASA Astrophysics Data System (ADS)

Özcan, Selçuk; Açıkbaş, Gökhan; Çalış Açıkbaş, Nurcan

2018-04-01

Hydrophobic surfaces are also known to have antimicrobial effect by restricting the adherence of microorganisms. However, ceramic products are produced by high temperature processes resulting in a hydrophilic surface. In this study, an industrial ceramic wall tile glaze composition was modified by the inclusion of metallic zinc powder in the glaze suspension applied on the pre-sintered wall tile bodies by spraying. The glazed tiles were gloss fired at industrially applicable peak temperatures ranging from 980 °C to 1100 °C. The fired tile surfaces were coated with a commercial fluoropolymer avoiding water absorption. The surfaces were characterized with SEM, EDS, XRD techniques, roughness, sessile water drop contact angle, surface energy measurements, and standard antimicrobial tests. The surface hydrophobicity and the antimicrobial activity results were compared with that of unmodified, uncoated gloss fired wall tiles. A superhydrophobic contact angle of 150° was achieved at 1000 °C peak temperature due to the formation of micro-structured nanocrystalline zinc oxide granules providing a specific surface topography. At higher peak temperatures the hydrophobicity was lost as the specific granular surface topography deteriorated with the conversion of zinc oxide granules to the ubiquitous willemite crystals embedded in the glassy matrix. The antimicrobial efficacy also correlated with the hydrophobic character.

Preparation of Superhydrophobic Film on Ti Substrate and Its Anticorrosion Property.

PubMed

Zhu, Min; Tang, Wenchuan; Huang, Luyao; Zhang, Dawei; Du, Cuiwei; Yu, Gaohong; Chen, Ming; Chowwanonthapunya, Thee

2017-06-08

Superhydrophobic films were fabricated on a titanium substrate with or without anodizing by using a self-assembling method. Firstly, the pretreatments of mechanical polishing/anodizing or mechanical polishing only were conducted, respectively. Subsequently, the preparation of polydopamine film layer, deposition of nano-silver particles, and post modification of 1H,1H,2H,2H-perfluorodecanethiol were performed on the surface of the pretreated substrate. The surface morphologies, compositions, wettability, and corrosion resistance of the films were investigated with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), water contact angle measurements, and electrochemical tests, respectively. Meanwhile, the effect of the deposition time in the silver nitrate solution on the hydrophobicity of the specimen surface was investigated. The result showed that with the increase of deposition time, the hydrophobic property enhanced gradually. The surface deposited for 7 h exhibited an optimum hydrophobic effect, which was characterized with a large water contact angle (WCA) of 154°, and the surface was rather rough and covered by a relatively uniform layer of micro-nano silver particles. The excellent hydrophobicity was attributed to a rough stratified microstructure along with the low surface energy. The electrochemical measurements showed that the existence of the superhydrophobic film can effectively enhance the corrosion resistance of Ti samples.

Organic-Inorganic Hydrophobic Nanocomposite Film with a Core-Shell Structure

PubMed Central

Liu, Peng; Chen, Ying; Yu, Zhiwu

2016-01-01

A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO2–Al2O3–TiO2 nanoparticles, which is grafted with methacryloxy propyl trimethoxyl silane (KH570), and wrapped by fluoride and siloxane polymers. The synthesized samples are characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrscopy, X-ray diffractometry (XRD), contact angle meter (CA), and scanning electron microscope (SEM). The results indicate that the novel organic-inorganic hydrophobic nanocomposite with a core-shell structure was synthesized successfully. XRD analysis reveals the nanocomposite film has an amorphous structure, and FTIR analysis indicates the nanoparticles react with a silane coupling agent (methacryloxy propyl trimethoxyl silane KH570). Interestingly, the morphology of the nanoparticle film is influenced by the composition of the core. Further, comparing with the film synthesized by silica nanoparticles, the film formed from SiO2–Al2O3–TiO2 nanoparticles has higher hydrophobic performance, i.e., the contact angle is greater than 101.7°. In addition, the TEM analysis reveals that the crystal structure of the particles can be changed at high temperatures. PMID:28774141

Ultrasonic Spray Pyrolysis Deposited Copper Sulphide Thin Films for Solar Cell Applications

PubMed Central

Firat, Y. E.; Yildirim, H.; Erturk, K.

2017-01-01

Polycrystalline copper sulphide (CuxS) thin films were grown by ultrasonic spray pyrolysis method using aqueous solutions of copper chloride and thiourea without any complexing agent at various substrate temperatures of 240, 280, and 320°C. The films were characterized for their structural, optical, and electrical properties by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), atomic force microscopy (AFM), contact angle (CA), optical absorption, and current-voltage (I-V) measurements. The XRD analysis showed that the films had single or mixed phase polycrystalline nature with a hexagonal covellite and cubic digenite structure. The crystalline phase of the films changed depending on the substrate temperature. The optical band gaps (Eg) of thin films were 2.07 eV (CuS), 2.50 eV (Cu1.765S), and 2.28 eV (Cu1.765S–Cu2S). AFM results indicated that the films had spherical nanosized particles well adhered to the substrate. Contact angle measurements showed that the thin films had hydrophobic nature. Hall effect measurements of all the deposited CuxS thin films demonstrated them to be of p-type conductivity, and the current-voltage (I-V) dark curves exhibited linear variation. PMID:29109807

A fiber-optic technique for the measurement of contact angle in a clearance-fit pin-loaded hole

NASA Technical Reports Server (NTRS)

Prabhakaran, R.; Naik, R. A.

1987-01-01

A fiber-optic technique for measuring contact angle during pin loading of a specimen is proposed. The experimental design and procedures for loading a 49.8-mm-diameter instrumented pin into an quasi-isotropic graphite-epoxy specimen are described. The optical fiber was located just above the surface of the pin outer diameter in order to obtain accurate pin-hole contact-angle measurements at increasing load levels. The movement of the optical fiber through the no-contact, contact, and no-contact regions is discussed; the photodiode output decreased monotonically as the fiber moved from the no-contact to the contact region and then decreased monotonically as the fiber moved from the contact region to the no-contact region. Variations in the contact angle measurements are examined as function of applied load level. The measurements are compared to contact angle values obtained using a finite element analysis and an electrical technique; it is determined that the data correlate well.

Investigation of the Dynamic Contact Angle Using a Direct Numerical Simulation Method.

PubMed

Zhu, Guangpu; Yao, Jun; Zhang, Lei; Sun, Hai; Li, Aifen; Shams, Bilal

2016-11-15

A large amount of residual oil, which exists as isolated oil slugs, remains trapped in reservoirs after water flooding. Numerous numerical studies are performed to investigate the fundamental flow mechanism of oil slugs to improve flooding efficiency. Dynamic contact angle models are usually introduced to simulate an accurate contact angle and meniscus displacement of oil slugs under a high capillary number. Nevertheless, in the oil slug flow simulation process, it is unnecessary to introduce the dynamic contact angle model because of a negligible change in the meniscus displacement after using the dynamic contact angle model when the capillary number is small. Therefore, a critical capillary number should be introduced to judge whether the dynamic contact model should be incorporated into simulations. In this study, a direct numerical simulation method is employed to simulate the oil slug flow in a capillary tube at the pore scale. The position of the interface between water and the oil slug is determined using the phase-field method. The capacity and accuracy of the model are validated using a classical benchmark: a dynamic capillary filling process. Then, different dynamic contact angle models and the factors that affect the dynamic contact angle are analyzed. The meniscus displacements of oil slugs with a dynamic contact angle and a static contact angle (SCA) are obtained during simulations, and the relative error between them is calculated automatically. The relative error limit has been defined to be 5%, beyond which the dynamic contact angle model needs to be incorporated into the simulation to approach the realistic displacement. Thus, the desired critical capillary number can be determined. A three-dimensional universal chart of critical capillary number, which functions as static contact angle and viscosity ratio, is given to provide a guideline for oil slug simulation. Also, a fitting formula is presented for ease of use.

In Situ Local Contact Angle Measurement in a CO2-Brine-Sand System Using Microfocused X-ray CT.

PubMed

Lv, Pengfei; Liu, Yu; Wang, Zhe; Liu, Shuyang; Jiang, Lanlan; Chen, Junlin; Song, Yongchen

2017-04-11

The wettability of porous media is of major interest in a broad range of natural and engineering applications. The wettability of a fluid on a solid surface is usually evaluated by the contact angle between them. While in situ local contact angle measurements are complicated by the topology of porous media, which can make it difficult to use traditional methods, recent advances in microfocused X-ray computed tomography (micro-CT) and image processing techniques have made it possible to measure contact angles on the scale of the pore sizes in such media. However, the effects of ionic strength, CO 2 phase, and flow pattern (drainage or imbibition) on pore-scale contact angle distribution are still not clear and have not been reported in detail in previous studies. In this study, we employed a micro-CT scanner for in situ investigation of local contact angles in a CO 2 -brine-sand system under various conditions. The effects of ionic strength, CO 2 phase, and flow pattern on the local contact-angle distribution were examined in detail. The results showed that the local contact angles vary over a wide range as a result of the interaction of surface contaminants, roughness, pore topology, and capillarity. The wettability of a porous surface could thus slowly weaken with increasing ionic strength, and the average contact angle could significantly increase when gaseous CO 2 (gCO 2 ) turns into supercritical CO 2 (scCO 2 ). Contact angle hysteresis also occurred between drainage and imbibition procedures, and the hysteresis was more significant under gCO 2 condition.

(CH3)3SiCl/SiCl4 azeotrope grows superhydrophobic nanofilaments.

PubMed

Gao, Lichao; McCarthy, Thomas J

2008-01-15

We describe the vapor-phase reaction (at room temperature and 40-45% relative humidity) of silicon wafers with the azeotropic mixture of trimethylchlorosilane and tetrachlorosilane. Water contact angle analysis indicates that surfaces become nearly perfectly hydrophobic (thetaA/thetaR > or =176 degrees/> or =176 degrees) after 2 min of reaction. SEM analysis at various reaction times shows the growth of nanofilaments with diameters of approximately 30 nm. X-ray photoelectron spectroscopy of oxidized titanium surfaces that were exposed to the azeotrope vapor indicates that the product is derived from a approximately 10:1 ratio of SiCl4 and (CH3)3SiCl. A mechanism for filament growth is proposed.

Preparation of active antibacterial LDPE surface through multistep physicochemical approach II: graft type effect on antibacterial properties.

PubMed

Bílek, František; Sulovská, Kateřina; Lehocký, Marián; Sáha, Petr; Humpolíček, Petr; Mozetič, Miran; Junkar, Ita

2013-02-01

Three monomers (allylamine, N-allylmethylamine and N,N-dimethylallylamine) were used for grafting onto air plasma activated LDPE surface. Antibacterial agent triclosan was anchored on such substrates. Influence of graft type on the antibacterial properties was determined. Increase of antibacterial activity and amount of deposited antibacterial agent for N-allylmethylamine and N,N-dimethylallylamine monomers were examined. Surface characteristics were measured by means of static contact angle measurement with surface energy evaluation, ATR-FTIR spectroscopy, XPS and SEM characterization analysis. Antibacterial properties were tested in vitro by inhibition zone method on agar plates for Staphylococcus aureus and Escherichia coli strains. Copyright © 2012 Elsevier B.V. All rights reserved.

Optical, wetting and electrical properties of functionalized fulleropyrrolidine thin films

NASA Astrophysics Data System (ADS)

Abdulrazack, Parveen; Venkatesan, Sughanya; Chellasamy, Manoharan; Samuthira, Nagarajan

2017-12-01

Fulleropyrrolidine derivatives acts as an electron acceptor in the fabrication of solar cells and other optoelectronic devices. In this investigation thin film of functionalized fulleropyrrolidines were fabricated and studied their photo-physical properties. Surface morphology of the thin films was investigated through AFM and FE-SEM. The results suggested that large dependence on structure vs molecular packing. The long alkyl chain substituted C60 were assembled in the form of nanorods. C60- C60 intermolecular distance were measured, the films were with good absorption and exhibits n-type semiconducting behavior. The films were having high contact angle and can be effectively used for fabricating semiconducting devices with self- cleaning property.

Impregnation transition in a powder

NASA Astrophysics Data System (ADS)

Raux, Pascal; Cockenpot, Heloise; Quere, David; Clanet, Christophe

2011-11-01

When an initially dry pile of micrometrical grains comes into contact with a liquid, one can observe different behaviors, function of the wetting properties. If the contact angle with the solid is low, the liquid will invade the pile (impregnation), while for higher contact angles, the grains will stay dry. We present an experimental study of this phenomenon: a dry pile of glass beads is deposed on the liquid surface, and we vary the contact angle of the liquid on the grains. We report a critical contact angle below which impregnation always occurs, and develop a model to explain its value. Different parameters modifying this critical contact angle are also investigated. Collaboration with Marco Ramaioli, Nestle Research Center, Lausanne, Switzerland.

Molecular Modeling of Three Phase Contact for Static and Dynamic Contact Angle Phenomena

NASA Astrophysics Data System (ADS)

Malani, Ateeque; Amat, Miguel; Raghavanpillai, Anilkumar; Wysong, Ernest; Rutledge, Gregory

2012-02-01

Interfacial phenomena arise in a number of industrially important situations, such as repellency of liquids on surfaces, condensation, etc. In designing materials for such applications, the key component is their wetting behavior, which is characterized by three-phase static and dynamic contact angle phenomena. Molecular modeling has the potential to provide basic insight into the detailed picture of the three-phase contact line resolved on the sub-nanometer scale which is essential for the success of these materials. We have proposed a computational strategy to study three-phase contact phenomena, where buoyancy of a solid rod or particle is studied in a planar liquid film. The contact angle is readily evaluated by measuring the position of solid and liquid interfaces. As proof of concept, the methodology has been validated extensively using a simple Lennard-Jones (LJ) fluid in contact with an LJ surface. In the dynamic contact angle analysis, the evolution of contact angle as a function of force applied to the rod or particle is characterized by the pinning and slipping of the three phase contact line. Ultimately, complete wetting or de-wetting is observed, allowing molecular level characterization of the contact angle hysteresis.

An algorithm for selecting the most accurate protocol for contact angle measurement by drop shape analysis.

PubMed

Xu, Z N

2014-12-01

In this study, an error analysis is performed to study real water drop images and the corresponding numerically generated water drop profiles for three widely used static contact angle algorithms: the circle- and ellipse-fitting algorithms and the axisymmetric drop shape analysis-profile (ADSA-P) algorithm. The results demonstrate the accuracy of the numerically generated drop profiles based on the Laplace equation. A significant number of water drop profiles with different volumes, contact angles, and noise levels are generated, and the influences of the three factors on the accuracies of the three algorithms are systematically investigated. The results reveal that the above-mentioned three algorithms are complementary. In fact, the circle- and ellipse-fitting algorithms show low errors and are highly resistant to noise for water drops with small/medium volumes and contact angles, while for water drop with large volumes and contact angles just the ADSA-P algorithm can meet accuracy requirement. However, this algorithm introduces significant errors in the case of small volumes and contact angles because of its high sensitivity to noise. The critical water drop volumes of the circle- and ellipse-fitting algorithms corresponding to a certain contact angle error are obtained through a significant amount of computation. To improve the precision of the static contact angle measurement, a more accurate algorithm based on a combination of the three algorithms is proposed. Following a systematic investigation, the algorithm selection rule is described in detail, while maintaining the advantages of the three algorithms and overcoming their deficiencies. In general, static contact angles over the entire hydrophobicity range can be accurately evaluated using the proposed algorithm. The ease of erroneous judgment in static contact angle measurements is avoided. The proposed algorithm is validated by a static contact angle evaluation of real and numerically generated water drop images with different hydrophobicity values and volumes.

Calculation of contact angles at triple phase boundary in solid oxide fuel cell anode using the level set method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Xiaojun; Hasegawa, Yosuke; CREST, JST

2014-10-15

A level set method is applied to characterize the three dimensional structures of nickel, yttria stabilized zirconia and pore phases in solid oxide fuel cell anode reconstructed by focused ion beam-scanning electron microscope. A numerical algorithm is developed to evaluate the contact angles at the triple phase boundary based on interfacial normal vectors which can be calculated from the signed distance functions defined for each of the three phases. Furthermore, surface tension force is estimated from the contact angles by assuming the interfacial force balance at the triple phase boundary. The average contact angle values of nickel, yttria stabilized zirconiamore » and pore are found to be 143°–156°, 83°–138° and 82°–123°, respectively. The mean contact angles remained nearly unchanged after 100 hour operation. However, the contact angles just after reduction are different for the cells with different sintering temperatures. In addition, standard deviations of the contact angles are very large especially for yttria stabilized zirconia and pore phases. The calculated surface tension forces from mean contact angles were close to the experimental values found in the literature. Slight increase of surface tensions of nickel/pore and nickel/yttria stabilized zirconia were observed after operation. Present data are expected to be used not only for the understanding of the degradation mechanism, but also for the quantitative prediction of the microstructural temporal evolution of solid oxide fuel cell anode. - Highlights: • A level set method is applied to characterize the 3D structures of SOFC anode. • A numerical algorithm is developed to evaluate the contact angles at the TPB. • Surface tension force is estimated from the contact angles. • The average contact angle values are found to be 143o-156o, 83o-138o and 82o-123o. • Present data are expected to understand degradation and predict evolution of SOFC.« less

One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance

PubMed Central

Yao, Qiufang; Wang, Chao; Fan, Bitao; Wang, Hanwei; Sun, Qingfeng; Jin, Chunde; Zhang, Hong

2016-01-01

In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance. PMID:27775091

Method of Preparation AZP4330 PR Pattern with Edge Slope 40°

NASA Astrophysics Data System (ADS)

Wu, Jie; Zhao, Hongyuan; Yu, Yuanwei; Zhu, Jian

2018-03-01

When the edge which is under the multi-film is more steep or angular, the stress in the multilayer film near the edge is concentrated, this situation will greatly reduce the reliability of electronic components. And sometimes, we need some special structure such as a slope with a specific angle in the MEMS, so that the metal line can take the signal to the output pad through the slope instead of deep step. To cover these problems, the lithography method of preparing the structure with edge slope is studied. In this paper, based on the Kirchhoff scalar diffraction theory we try to change the contact exposure gap and the post-baking time at the specific temperature to find out the effect about the edge angle of the photoresist. After test by SEM, the results were presented by using AZP4330 photoresist, we can get the PR Pattern with edge slope 40° of the process and the specific process parameters.

One-step solvothermal deposition of ZnO nanorod arrays on a wood surface for robust superamphiphobic performance and superior ultraviolet resistance

NASA Astrophysics Data System (ADS)

Yao, Qiufang; Wang, Chao; Fan, Bitao; Wang, Hanwei; Sun, Qingfeng; Jin, Chunde; Zhang, Hong

2016-10-01

In the present paper, uniformly large-scale wurtzite-structured ZnO nanorod arrays (ZNAs) were deposited onto a wood surface through a one-step solvothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and differential thermal analysis (DTA). ZNAs with a diameter of approximately 85 nm and a length of approximately 1.5 μm were chemically bonded onto the wood surface through hydrogen bonds. The superamphiphobic performance and ultraviolet resistance were measured and evaluated by water or oil contact angles (WCA or OCA) and roll-off angles, sand abrasion tests and an artificially accelerated ageing test. The results show that the ZNA-treated wood demonstrates a robust superamphiphobic performance under mechanical impact, corrosive liquids, intermittent and transpositional temperatures, and water spray. Additionally, the as-prepared wood sample shows superior ultraviolet resistance.

Surface modification of paper on a continuous atmospheric-pressure-plasma system

NASA Astrophysics Data System (ADS)

Cruz-Barba, Luis Emilio

Plasma technologies for the continuous modification of materials in atmospheric-pressure-plasma conditions were used to evaluate the surface modification of paper under different plasma conditions. The generation of hydrophobic layers was used to characterize the efficiency of the originally designed system for future application in the paper industry. Generation of hydrophobic layers was carried out by deposition of thin layers from fluorine containing gases, as well as cross-linking of pre-deposited thin layers of hydrophobic materials, such as fluoropolymers and silicones, in a continuous system plasma reactor (CSPR). Physical and chemical characterization of these layers was carried out by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), contact angle goniometry, and water absorption evaluations. Pure gaseous CF4 and a CF4/CH4 mixture were used to deposit fluorinated layers, rendering paper surfaces with low to moderate relative surface atomic contents of fluorine (2.5 to 16.3%). Morphological characterization revealed that the deposition consists of small clusters of fluorinated species scattered on the surface. Contact angle evaluations (50°--70°) indicated a reduction in the water affinity of the paper. Thin layers of fluoropolymer pre-deposited on paper surfaces were cross-linked in the presence of CF4, CF4/CH4, and NH 3 plasmas. All of the gases proved to be effective for the cross-linking under different conditions. These cross-linked layers were determined to maintain the original polymer structure, consisting mainly of CF2-CF 2 and small quantities of CFx. Surface characterization by AFM indicated lower roughness values compared to the untreated additive-free paper (45.1 vs 67.1 nm). Paper samples treated by this approach showed a highly hydrophobic character with up to 160° contact angles, and water absorption was reduced by as much as 61.6%. Silicone layers were cross-linked in the presence of argon and oxygen plasmas. Characterization of the silicone-coated paper indicated, as in the case of fluoropolymers, the retention of the original chemical structure. Surface roughness values (AFM) were in the range of 11.8 to 18.2 nm, evidence of a very smooth surface. High hydrophobicity levels were reached, as shown by contact angles of up to 126°, and water absorption showed a maximum reduction of 76.8%.

Experimental study of contact edge roughness on sub-100 nm various circular shapes

NASA Astrophysics Data System (ADS)

Lee, Tae Y.; Ihm, Dongchul; Kang, Hyo C.; Lee, Jum B.; Lee, Byoung H.; Chin, Soo B.; Cho, Do H.; Song, Chang L.

2005-05-01

The measurement of edge roughness has become a hot issue in the semiconductor industry. Especially the contact roughness is being more critical as design rule shrinks. Major vendors offer a variety of features to measure the edge roughness in their CD-SEMs. For the line and space patterns, features such as Line Edge Roughness (LER) and Line Width Roughness (LWR) are available in current CD-SEMs. However the features currently available in commercial CD-SEM cannot provide a proper solution in monitoring the contact roughness. We had introduced a new parameter R, measurement algorithm and definition of contact edge roughness to quantify CER and CSR in previous paper. The parameter, R could provide an alternative solution to monitor contact or island pattern roughness. In this paper, we investigated to assess optimum number of CD measurement (1-D) and fitting method for CER or CSR. The study was based on a circular contact shape. Some new ideas to quantify CER or CSR were also suggested with preliminary experimental results.

Pore-scale Analysis of the effects of Contact Angle Hysteresis on Blob Mobilization in a Pore Doublet

NASA Astrophysics Data System (ADS)

Hsu, Shao-Yiu; Glantz, Roland; Hilpert, Markus

2011-11-01

The mobilization of residual oil blobs in porous media is of major interest to the petroleum industry. We studied the Jamin effect, which hampers the blob mobilization, experimentally in a pore doublet model and explain the Jamin effect through contact angle hysteresis. A liquid blob was trapped in one of the tubes of the pore doublet model and then subjected to different pressure gradients. We measured the contact angles (in 2D and 3D) as well as the mean curvatures of the blob. Due to gravity effects and hysteresis, the contact angles of the blob were initially (zero pressure gradient) non-uniform and exhibited a pronounced altitude dependence. As the pressure gradient was increased, the contact angles became more uniform and the altitude dependence of the contact angle decreased. At the same time, the mean curvature of the drainage interface increased, and the mean curvature of the imbibition interface decreased. The pressure drops across the pore model, which we inferred with our theory from the measured contact angles and mean curvatures, were in line with the directly measured pressure data. We not only show that a trapped blob can sustain a finite pressure gradient but also develop methods to measure the contact angles and mean curvatures in 3D.

Crumb waste tire rubber surface modification by plasma polymerization of ethanol and its application on oil-well cement

NASA Astrophysics Data System (ADS)

Xiaowei, Cheng; Sheng, Huang; Xiaoyang, Guo; Wenhui, Duan

2017-07-01

Crumb waste tire rubber (WTR) was pretreated by oxygen low temperature plasma (LTP) and modified by LTP polymerization process of ethanol monomer to improve the adhesion property with oil-well cement matrix and the mechanical properties of cement. The surface properties of modified crumb WTR and the mechanical properties and structures of modified oil-well cement were investigated by means of contact angle measurement, dispersion test, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), mechanics performance tests, permeability test and scanning electron microscopy (SEM). It was demonstrated that LTP treatment changed both the surface composition and roughness. The contact angle of pretreated crumb WTR dramatically fell from 122° to 34°, and sample with ethanol LPT polymer film decreased even further to 11°. The ATR-FTIR and XPS analysis results demonstrated that hydrophilic groups, such as -COOH, C-OH, and -CHO, were introduced on the WTR surface. The oxygen atomic percent increased from 8.11% to 14.50% and 24.83%. The mechanical properties, porosity and permeability of raw cement were compared to samples modified by untreated crumb WTR, pretreated crumb WTR and ethanol LTP polymerization treated crumb WTR. It was found that after 28 days, the compressive strength of the samples with the untreated crumb WTR decreased to 80% with respect to raw cement. The tensile strength and flexural strength also had a slight reduction compared with the raw cement. On the contrary, after 28 days, the tensile strength of cement modified by LTP polymerization treated WTR increased 11.03% and 13.36%, and the flexural strength increased 9.65% and 7.31%, respectively. A decrease in the compressive strength also occurred but was inconspicuous. A tight interface bonding for ethanol LTP polymerization treated WTR with cement matrix was observed via an SEM image.

Study on Tribological Properties of CoCrMo Alloys against Metals and Ceramics as Bearing Materials for Artificial Cervical Disc

NASA Astrophysics Data System (ADS)

Xiang, Dingding; Song, Jian; Wang, Song; Liao, Zhenhua; Liu, Yuhong; Tyagi, Rajnesh; Liu, Weiqiang

2018-02-01

CoCrMo alloys are believed to be a kind of potential material for artificial cervical disc. However, the tribological properties of CoCrMo alloys against different metals and ceramics are not systematically studied. In this study, the tribological behaviors of CoCrMo alloys against metals (316L, Ti6Al4V) and ceramics (Si3N4, ZrO2) were focused under dry friction and 25 wt.% newborn calf serum (NCS)-lubricated conditions using a ball-on-disc apparatus under reciprocating motion. The microstructure, composition and hardness of CoCrMo alloys were characterized using x-ray diffraction, scanning electron microscopy (SEM) and hardness testers, respectively. The contact angles of the CoCrMo alloys with deionized water and 25 wt.% NCS were measured by the OCA contact angle measuring instrument. The maximum wear width, wear depth and wear volume were measured by three-dimensional white light interference. The morphology and the EDX analysis of the wear marks on CoCrMo alloys were examined by SEM to determine the basic mechanism of friction and wear. The dominant wear mechanism in dry friction for CoCrMo alloys against all pairings was severe abrasive wear, accompanied with a lot of material transfer. Under 25 wt.% NCS-lubricated condition, the wear mechanism for CoCrMo alloys against ceramics (Si3N4, ZrO2) was also mainly severe abrasive wear. However, severe abrasive wear and electrochemical corrosion occurred for the CoCrMo-316L pairing under lubrication. Severe abrasive wear, adhesive wear and electrochemical corrosion occurred for the CoCrMo-Ti6Al4V pairing under lubrication. According to the results, the tribological properties of CoCrMo alloys against ceramics were better than those against metals. The CoCrMo-ZrO2 pairing displayed the best tribological behaviors and could be taken as a potential candidate bearing material for artificial cervical disc.

Water repellent porous silica films by sol-gel dip coating method.

PubMed

Rao, A Venkateswara; Gurav, Annaso B; Latthe, Sanjay S; Vhatkar, Rajiv S; Imai, Hiroaki; Kappenstein, Charles; Wagh, P B; Gupta, Satish C

2010-12-01

The wetting of solid surfaces by water droplets is ubiquitous in our daily lives as well as in industrial processes. In the present research work, water repellent porous silica films are prepared on glass substrate at room temperature by sol-gel process. The coating sol was prepared by keeping the molar ratio of methyltriethoxysilane (MTES), methanol (MeOH), water (H(2)O) constant at 1:12.90:4.74, respectively, with 2M NH(4)OH throughout the experiments and the molar ratio (M) of MTES/Ph-TMS was varied from 0 to 0.22. A simple dip coating technique is adopted to coat silica films on the glass substrates. The static water contact angle as high as 164° and water sliding angle as low as 4° was obtained for silica film prepared from M=0.22. The surface morphological studies of the prepared silica film showed the porous structure with pore sizes typically ranging from 200nm to 1.3μm. The superhydrophobic silica films prepared from M=0.22 retained their superhydrophobicity up to a temperature of 285°C and above this temperature the films became superhydrophilic. The porous and water repellent silica films are prepared by proper alteration of the Ph-TMS in the coating solution. The prepared silica films were characterized by surface profilometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared (FT-IR) spectroscopy, humidity tests, chemical aging tests, static and dynamic water contact angle measurements. Copyright © 2010 Elsevier Inc. All rights reserved.

Determination of contact angle from the maximum height of enlarged drops on solid surfaces

NASA Astrophysics Data System (ADS)

Behroozi, F.

2012-04-01

Measurement of the liquid/solid contact angle provides useful information on the wetting properties of fluids. In 1870, the German physicist Georg Hermann Quincke (1834-1924) published the functional relation between the maximum height of an enlarged drop and its contact angle. Quincke's relation offered an alternative to the direct measurement of contact angle, which in practice suffers from several experimental uncertainties. In this paper, we review Quincke's original derivation and show that it is based on a hidden assumption. We then present a new derivation that exposes this assumption and clarifies the conditions under which Quincke's relation is valid. To explore Quincke's relation experimentally, we measure the maximum height of enlarged water drops on several substrates and calculate the contact angle in each case. Our results are in good agreement with contact angles measured directly from droplet images.

Structural plastron in relict Gondwanan moss bugs (Hemiptera: Coleorrhyncha: Peloridiidae) and its possible implications for systematics, biogeography and for the standard definition of plastron.

PubMed

Hartung, Viktor; Medebach, Ingo; Walheim, Stefan

2016-09-01

Peloridiidae are a family of small hemipterans who live and feed on bryophytes of temperate forests in some regions of the Southern Hemisphere. They are often submerged in water and would require adaptations for respiration to tolerate periods of inundation. Here we report water-repelling cuticular structures on the tergites of thorax and abdomen and on the ventral surface of tegmina in Peloridiidae. Our observations show that these body parts can hold an air bubble or layer which is in contact with spiracles. Thus, the described structures comply with the definition of a structural plastron. The micromorphology of these structures was studied with a SEM on adults and nymphs of several species and their hydrophobicity was tested in two species with a contact angle goniometer. Possible implications for the standard plastron definition are discussed, as well as its significance for systematics, origin and biogeography of the group. Copyright © 2016 Elsevier Ltd. All rights reserved.

Contact Angle Measurements: an Alternative Approach Towards Understanding the Mechanism of Increased Drug Dissolution from Ethylcellulose Tablets Containing Surfactant and Exploring the Relationship Between Their Contact Angles and Dissolution Behaviors.

PubMed

Liu, Tiaotiao; Hao, Jingqiang; Yang, Baixue; Hu, Beibei; Cui, Zhixiang; Li, Sanming

2018-05-01

The addition of surfactant in tablet was a well-defined approach to improve drug dissolution rate. While the selected surfactant played a vital role in improving the wettability of tablet by medium, it was equally important to improve the dissolution rate by permeation effect due to production of pores or the reduced inter-particle adhesion. Furthermore, understanding the mechanism of dissolution rate increased was significant. In this work, contact angle measurement was taken up as an alternative approach for understanding the dissolution rate enhancement for tablet containing surfactant. Ethylcellulose, as a substrate, was used to prepare tablet. Four surfactants, sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), dodecyltrimethylammonium bromide (DTAB), and sodium lauryl sulfonate (SLS), were used. Berberine hydrochloride, metformin hydrochloride, and rutin were selected as model drugs. The contact angle of tablet in the absence and presence of surfactant was measured to explore the mechanism. The dissolution test was investigated to verify the mechanism and to establish a correlation with the contact angle. The result showed that the mechanism was the penetration effect rather than the wetting effect. The dissolution increased with a reduction in the contact angle. DTAB was found to obtain the highest level of dissolution enhancement and the lowest contact angle, while SDS, SDBS, and SLS were found to be the less effective in both dissolution enhancement and contact angle decrease. Therefore, contact angle was a good indicator for dissolution behavior besides exploring the mechanism of increased dissolution, which shows great potential in formula screening.

Dynamic Measurement of Low Contact Angles by Optical Microscopy.

PubMed

Campbell, James M; Christenson, Hugo K

2018-05-16

Precise measurement of contact angles is an important challenge in surface science, in the design and characterization of materials and in many crystallization experiments. Here we present a novel technique for measuring the contact angles of droplets between about 2° and 30°, with the lowest experimental uncertainty at the lower end of this range, typically ±0.1°. The lensing effect of a droplet interface produces the appearance of bright circles in low-aperture light, whose diameter is related to the contact angle. The technique requires no specialized equipment beyond an ordinary optical microscope, and may be used to study the dynamic evolution of the contact angle in situ during an experiment.

Three-gradient regular solution model for simple liquids wetting complex surface topologies

PubMed Central

Akerboom, Sabine; Kamperman, Marleen

2016-01-01

Summary We use regular solution theory and implement a three-gradient model for a liquid/vapour system in contact with a complex surface topology to study the shape of a liquid drop in advancing and receding wetting scenarios. More specifically, we study droplets on an inverse opal: spherical cavities in a hexagonal pattern. In line with experimental data, we find that the surface may switch from hydrophilic (contact angle on a smooth surface θY < 90°) to hydrophobic (effective advancing contact angle θ > 90°). Both the Wenzel wetting state, that is cavities under the liquid are filled, as well as the Cassie–Baxter wetting state, that is air entrapment in the cavities under the liquid, were observed using our approach, without a discontinuity in the water front shape or in the water advancing contact angle θ. Therefore, air entrapment cannot be the main reason why the contact angle θ for an advancing water front varies. Rather, the contact line is pinned and curved due to the surface structures, inducing curvature perpendicular to the plane in which the contact angle θ is observed, and the contact line does not move in a continuous way, but via depinning transitions. The pinning is not limited to kinks in the surface with angles θkink smaller than the angle θY. Even for θkink > θY, contact line pinning is found. Therefore, the full 3D-structure of the inverse opal, rather than a simple parameter such as the wetting state or θkink, determines the final observed contact angle. PMID:27826512

The use of acetone to enhance the infiltration of HA nanoparticles into a demineralized dentin collagen matrix.

PubMed

Besinis, Alexandros; van Noort, Richard; Martin, Nicolas

2016-03-01

This study investigates the role of acetone, as a carrier for nano-hydroxyapatite (nano-HA) in solution, to enhance the infiltration of fully demineralized dentin with HA nanoparticles (NPs). Dentin specimens were fully demineralized and subsequently infiltrated with two types of water-based nano-HA solutions (one containing acetone and one without). Characterization of the dentin surfaces and nano-HA particles was performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface wettability and infiltration capacity of the nano-HA solutions were quantified by means of contact angle measurements and energy dispersive X-ray spectroscopy (EDS), respectively. Contact angle measurements were taken at baseline and repeated at regular intervals to assess the effect of acetone. The P and Ca levels of infiltrated dentin specimens were measured and compared to sound dentin and non-infiltrated controls. The presence of acetone resulted in an eight-fold decrease in the contact angles of the nano-HA solutions recorded on the surface of demineralized dentin compared to nano-HA solutions without acetone (one-way ANOVA, p<0.05). Perfect wetting of the demineralized dentin surface was achieved 5min after the application of the nano-HA solution containing acetone. Infiltration of demineralized dentin with the nano-HA solution containing acetone restored the lost mineral content by 50%, whereas the mean mineralization values for P and Ca in dentin treated with the acetone-free nano-HA solution were less than 6%. Acetone was shown to act as a vehicle to enhance the capacity to infiltrate demineralized dentin with HA NPs. The successful infiltration of dentin collagen with HA NPs provides a suitable scaffold, whereby the infiltrated HA NPs have the potential to act as seeds that may initiate heterogenous mineral growth when exposed to an appropriate mineral-rich environment. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of Atmospheric Plasma Treatment to Titanium Surface on Initial Osteoblast-Like Cell Spreading. .

PubMed

Kim, In-Hye; Son, Jun-Sik; Kwon, Tae-Yub; Kim, Kyo-Han

2015-01-01

Plasma treatments are becoming a popular method for modifying the characteristics of a range of substrate surfaces. Atmospheric pressure plasma is cost-efficient, safe and simple compared to high-pressure plasma. This study examined the effects of atmospheric pressure plasma to a titanium (Ti) surface on osteoblast-like cell (osteoblast) spreading and cellular networks. The characteristics of the Ti surface before and after the atmospheric plasma treatment were analyzed by X-ray photoemission spectroscopy (XPS), scanning electron microscopy (SEM), contact angle measurements, and an optical 3D profiling system. The morphology of osteoblasts attached to the Ti surfaces was observed by SEM and confocal laser scanning microscopy. The atmospheric pressure plasma made the Ti surfaces more hydrophilic. The osteoblasts that adhered to the untreated surface were round and spherical, whereas the cells covered a larger surface area on the plasma-treated surface. The plasma-treated Ti surface showed enhanced cell spreading and migration with more developed cellular networks. In conclusion, an atmospheric plasma treatment is a potential surface modifying method that can enhance the initial the cell affinity at the early stages in vitro.

Pore-scale water dynamics during drying and the impacts of structure and surface wettability

NASA Astrophysics Data System (ADS)

Cruz, Brian C.; Furrer, Jessica M.; Guo, Yi-Syuan; Dougherty, Daniel; Hinestroza, Hector F.; Hernandez, Jhoan S.; Gage, Daniel J.; Cho, Yong Ku; Shor, Leslie M.

2017-07-01

Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loam soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single-component, multiphase model. In our experiments, micromodels with higher contact angle surfaces took 4 times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. Lattice Boltzmann simulations accurately predicted pore-scale moisture retention patterns within micromodels with different structures and contact angles.

Preparation of superhydrophobic glass fiber and interfacially reinforced glass fiber/epoxy composites by grafting polysiloxane nanowires

NASA Astrophysics Data System (ADS)

Lv, Junwei; Wang, Bin; Ma, Qi; Li, Mengyao; Wang, Wenjing; Lu, Gaotaihang; Li, Hui; Zhao, Chunxia

2018-04-01

Ethyltrichlorosilane used as precursor reacted with glass fiber (GF) surface. Then polysiloxane was functionalized onto GF surface to improve GF’s hydrophobicity and interfacial properties of GF reinforced composites. Fourier transform infrared spectroscopy (FTIR) confirmed the successful grafting of polysiloxane onto GF’s surface. Energy dispersive spectroscopy (EDS) characterized the variation of chemical composition of GF surface. Scanning electron microscopy (SEM) images showed that the polysiloxane was grafted onto GF’s surface uniformly and the surface roughness of GF was enhanced obviously. Static contact angle analysis (SCA) revealed the significant improvement of surface hydrophobicity. Compared with the original GF composites, the interfacial shear strength (IFSS) increased by 36.52%. Meanwhile, we discovered a facile way to accomplish the experiment.

UV Grafting Modification of Polyethylene Separator for Liion Battery

NASA Astrophysics Data System (ADS)

Lv, Xiaoyuan; Li, Hua; Zhang, Zhiqiang; Chang, Hiunam; Jiang, Li; Liu, Hezhou

Polyethylene (PE) separator was modified by UV grafting methyl acrylate (MA) and nano-SiO2 composite layer. The structure of functional group and morphology of the separator were analyzed by Fourier transform infrared spectrum (FT-IR) and scanning electron microscope (SEM). The wetting behavior and the heat resistance of the separator were also investigated by contact angle test and thermal shrinkage test respectively. The results show that MA/nano-SiO2 composite layer is successfully grafted onto the PE separator, and the addition of the DI water and butanol can make the nano-SiO2 dispersed better and lead to a microporous structure of the grafting layer. The grafted separator has a better wettability and heat resistance than the pristine one.

Surface phenomena of hydroxyapatite film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants.

PubMed

Kim, Eun-Ju; Jeong, Yong-Hoon; Choe, Han-Cheol

2013-03-01

In this study, surface phenomena of hydroxyapatite (HA) film on the nanopore formed Ti-29Nb-xZr alloy by anodization for bioimplants have been investigated by electron beam physical vapor deposition (EB-PVD), field emission scanning electron microscope (FE-SEM), X-ray diffractometer (XRD), potentiostat and contact angle. The microstructure of Ti-29Nb-xZr alloys exhibited equiaxed structure and alpha" phase decreased, whereas beta phase increased as Zr content increased. The increment of Zr contents in HA coated nanotubular Ti-29Nb-xZr alloys showed good corrosion potential in 0.9% NaCI solution. The wettability of HA coated nanotubular surface was higher than that of non-coated samples.

Effects of PVDF concentration on the properties of PVDF membranes

NASA Astrophysics Data System (ADS)

Pramono, E.; Simamora, A. L.; Radiman, C. L.; Wahyuningrum, D.

2017-07-01

Polyvinylideneflouride (PVDF) is a good polymeric material for preparing ultrafiltration and microfiltration membranes due to its high mechanical properties and chemical resistance. The objective of this work is to study the effects of PVDF concentration on the membrane properties such as mechanical strength, permeability of water and permselectivity of T-500 and T-2000 dextran solutions. These membranes were also characterized by contact angle determination and its morphology was observed by scanning electron microscopy (SEM). From the experimental data, it can be concluded that PVDF concentration affects the surface properties, permeability and permselectivity of the produced membranes. Higher PVDF concentrations results in higher hydrophobicity, mechanical properties and rejection towards T-500 and T-2000 dextrans, but lower water flux.

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride.

PubMed

Carrasco-Guigón, Fernando Javier; Rodríguez-Félix, Dora Evelia; Castillo-Ortega, María Mónica; Santacruz-Ortega, Hisila C; Burruel-Ibarra, Silvia E; Encinas-Encinas, Jose Carmelo; Plascencia-Jatomea, Maribel; Herrera-Franco, Pedro Jesus; Madera-Santana, Tomas Jesus

2017-01-25

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films.

Fabrication of a superhydrophobic polyurethane foam and its application for continuous oil removal

NASA Astrophysics Data System (ADS)

Liu, Hai-Dong; Gu, Bin; Yuan, Wei-Feng; He, Qi

2018-02-01

A new polyurethane foam with superhydrophobicity and excellent lipophilicity is presented and demonstrated experimentally in this work. The superhydrophobic foam is synthesized by dip coating the polyurethane foam with a mixture solution of silicone resine and silicon dioxide nanoparticles. Its superhydrophobic and oleophilic capacity is characterized and verified via the SEM images, the water contact angle measurement, the adsorption tests and recyclability tests for water and some typical oils. Combining with the vacuum assisted oil-water separation technology (VAST), continuous recovery of oil spill at the lab scale is realized on the new superhydrophobic foam. Moreover, the break through pressure for water penetrating through the superhydrophobic foam is determined experimentally and referred as the maximum operation pressure in the VAST.

Synthesis, characterization and biological evaluation of poly [LA-co-(Glc-alt-Lys)] for nerve regeneration scaffold

NASA Astrophysics Data System (ADS)

Yin, Yi-Xia; Yi, Ji-Ling; Xie, Li-Juan; Yan, Qiong-Jiao; Dai, Hong-Lian; Li, Shi-Pu

2014-03-01

A novel nerve repairing material poly [LA-co-(Glc-alt-Lys)] (PLGL) was synthesized. The viability and growth of Schwann cells (SCs) co-cultured with poly (D, Llactic acid) (PDLLA) films (control group) and PLGL films were evaluated by MTTassay and SEM observation. Then, contact angle measurement, histological assessment and enzyme-linked immunosorbent assay (ELISA) testing on inflammatory-related cytokines such as IL-10 and TGF-β1 were performed. The results showed that, compared with PDLLA, PLGL films possesses better hydrophilicity, biocompatibility, degradation property and less inflammatory reaction. The present study indicated that PLGL scaffolds would meet the requirements of artificial nerve scaffold and have a potential application in the fields of nerve regeneration.

In situ assessment of the contact angles of nanoparticles adsorbed at fluid interfaces by multiple angle of incidence ellipsometry.

PubMed

Stocco, Antonio; Su, Ge; Nobili, Maurizio; In, Martin; Wang, Dayang

2014-09-28

Here multiple angle of incidence ellipsometry was successfully applied to in situ assess the contact angle and surface coverage of gold nanoparticles as small as 18 nm, coated with stimuli-responsive polymers, at water-oil and water-air interfaces in the presence of NaCl and NaOH, respectively. The interfacial adsorption of the nanoparticles was found to be very slow and took days to reach a fairly low surface coverage. For water-oil interfaces, in situ nanoparticle contact angles agree with the macroscopic equilibrium contact angles of planar gold surfaces with the same polymer coatings, whilst for water-air interfaces, significant differences have been observed.

Simultaneous Soft Sensing of Tissue Contact Angle and Force for Millimeter-scale Medical Robots

PubMed Central

Arabagi, Veaceslav; Gosline, Andrew; Wood, Robert J.; Dupont, Pierre E.

2013-01-01

A novel robotic sensor is proposed to measure both the contact angle and the force acting between the tip of a surgical robot and soft tissue. The sensor is manufactured using a planar lithography process that generates microchannels that are subsequently filled with a conductive liquid. The planar geometry is then molded onto a hemispherical plastic scaffolding in a geometric configuration enabling estimation of the contact angle (angle between robot tip tangent and tissue surface normal) by the rotation of the sensor around its roll axis. Contact force can also be estimated by monitoring the changes in resistance in each microchannel. Bench top experimental results indicate that, on average, the sensor can estimate the angle of contact to within ±2° and the contact force to within ±5.3 g. PMID:24241496

Validation of a Novel Technique and Evaluation of the Surface Free Energy of Food

PubMed Central

Senturk Parreidt, Tugce; Schmid, Markus; Hauser, Carolin

2017-01-01

Characterizing the physical properties of a surface is largely dependent on determining the contact angle exhibited by a liquid. Contact angles on the surfaces of rough and irregularly-shaped food samples are difficult to measure using a contact angle meter (goniometer). As a consequence, values for the surface energy and its components can be mismeasured. The aim of this work was to use a novel contact angle measurement method, namely the snake-based ImageJ program, to accurately measure the contact angles of rough and irregular shapes, such as food samples, and so enable more accurate calculation of the surface energy of food materials. In order to validate the novel technique, the contact angles of three different test liquids on four different smooth polymer films were measured using both the ImageJ software with the DropSnake plugin and the widely used contact angle meter. The distributions of the values obtained by the two methods were different. Therefore, the contact angles, surface energies, and polar and dispersive components of plastic films obtained using the ImageJ program and the Drop Shape Analyzer (DSA) were interpreted with the help of simple linear regression analysis. As case studies, the superficial characteristics of strawberry and endive salad epicarp were measured with the ImageJ program and the results were interpreted with the Drop Shape Analyzer equivalent according to our regression models. The data indicated that the ImageJ program can be successfully used for contact angle determination of rough and strongly hydrophobic surfaces, such as strawberry epicarp. However, for the special geometry of droplets on slightly hydrophobic surfaces, such as salad leaves, the program code interpolation part can be altered. PMID:28425932

A Contact Pressure Analysis Comparing an All-Inside and Inside-Out Surgical Repair Technique for Bucket-Handle Medial Meniscus Tears.

PubMed

Marchetti, Daniel Cole; Phelps, Brian M; Dahl, Kimi D; Slette, Erik L; Mikula, Jacob D; Dornan, Grant J; Bucci, Gabriella; Turnbull, Travis Lee; Singleton, Steven B

2017-10-01

To directly compare effectiveness of the inside-out and all-inside medial meniscal repair techniques in restoring native contact area and contact pressure across the medial tibial plateau at multiple knee flexion angles. Twelve male, nonpaired (n = 12), fresh-frozen human cadaveric knees underwent a series of 5 consecutive states: (1) intact medial meniscus, (2) MCL tear and repair, (3) simulated bucket-handle longitudinal tear of the medial meniscus, (4) inside-out meniscal repair, and (5) all-inside meniscal repair. Knees were loaded with a 1,000-N axial compressive force at 5 knee flexion angles (0°, 30°, 45°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated using thin film pressure sensors. No significant differences were observed between the inside-out and all-inside repair techniques at any flexion angle for contact area, mean contact pressure, and peak contact pressure (all P > .791). Compared with the torn meniscus state, inside-out and all-inside repair techniques resulted in increased contact area at all flexion angles (all P < .005 and all P < .037, respectively), decreased mean contact pressure at all flexion angles (all P < .007 and all P < .001, respectively) except for 0° (P = .097 and P = .39, respectively), and decreased peak contact pressure at all flexion angles (all P < .001, all P < .001, respectively) except for 0° (P = .080 and P = .544, respectively). However, there were significant differences in contact area and peak contact pressure between the intact state and inside-out technique at angles ≥45° (all P < .014 and all P < .032, respectively). Additionally, there were significant differences between the intact state and all-inside technique in contact area at 60° and 90° and peak contact pressure at 90° (both P < .005 and P = .004, respectively). Median values of intact contact area, mean contact pressure, and peak contact pressure over the tested flexion angles ranged from 498 to 561 mm 2 , 786 to 997 N/mm 2 , and 1,990 to 2,215 N/mm 2 , respectively. Contact area, mean contact pressure, and peak contact pressure were not significantly different between the all-inside and inside-out repair techniques at any tested flexion angle. Both techniques adequately restored native meniscus biomechanics near an intact level. An all-inside repair technique provided similar, native-state-restoring contact mechanics compared with an inside-out repair technique for the treatment of displaced bucket-handle tears of the medial meniscus. Thus, both techniques may adequately decrease the likelihood of cartilage degeneration. Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

More Fluorous Surface Modifier Makes it Less Oleophobic: Fluorinated-Siloxane Copolymer/PDMS Coatings

PubMed Central

Zhang, Wei; Zheng, Ying; Orsini, Lorenzo; Morelli, Andrea; Galli, Giancarlo; Chiellini, Emo; Carpenter, Everett E.; Wynne, Kenneth J.

2010-01-01

A copolyacrylate with semifluorinated and polydimethylsiloxane side chains (D5-3) was used as a surface modifier for a condensation cured PDMS coating. The decyl fluorous group is represented by “D”; “5” is a 5 kDa silicone, and “3” the mole ratio of fluorous to silicone side chain. Wetting behavior was assessed by dynamic contact angle (DCA) analysis using isopropanol, which differentiates silicone and fluorous wetting behavior. Interestingly, a maximum in surface oleophobicity was found at low D5-3 concentration (0.4 wt%). Higher concentrations result in decreased oleophobicity reflected in decreased contact angles. To understand this unexpected observation, dynamic light scattering (DLS) studies were initiated on a model system consisting of hydroxyl-terminated PDMS (18 kDa) containing varying amounts of D5-3. DLS revealed D5-3 aggregation as a function of temperature and concentration. A model is proposed by which D5-3 surface concentration is depleted via phase separation favoring D5-3 aggregation at concentrations >0.4 wt%, that is, the CMC. This model suggests increasing aggregate / micelle concentrations at increased D5-3 concentration. Bulk morphologies studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) support this model by showing increased aggregate concentrations with increased D5-3 >0.4 wt%. PMID:20000339

Preparation and characterization of novel PVDF nanofiltration membranes with hydrophilic property for filtration of dye aqueous solution

NASA Astrophysics Data System (ADS)

Nikooe, Naeme; Saljoughi, Ehsan

2017-08-01

In the present research, for the first time PVDF/Brij-58 blend nanofiltration membranes with remarkable performance in filtration of dye aqueous solution were prepared via immersion precipitation. A noticeable improvement in water permeation and fouling resistance of the PVDF membranes was achieved by using Brij-58 surfactant as a hydrophilic additive. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and water contact angle were applied for the investigation of membrane morphology, detection of the surface chemical composition and relative hydrophilicity/hydrophobicity, respectively. The membrane performance was studied and compared by determination of pure water flux (PWF) and filtration of synthetic reactive dye aqueous solutions as well as bovine serum albumin (BSA) as foulant model. It was found out that addition of 4 wt.% Brij-58 to the casting solution results in formation of membrane with remarkable hydrophilicity and fouling resistance (contact angle of 46° and flux recovery ratio (FRR) = 90%), higher porosity and consequently noticeable PWF (31.2 L/m2 h) and recognized dye rejection value (90%) in comparison with the pristine PVDF nanofiltration membrane. Addition of Brij-58 surfactant to the casting solution resulted in formation of NF membrane with higher hydrophilicity and permeability as well as higher dye rejection value in comparison with the addition of PEG 400 additive.

High throughput laser texturing of super-hydrophobic surfaces on steel

NASA Astrophysics Data System (ADS)

Gemini, Laura; Faucon, Marc; Romoli, Luca; Kling, Rainer

2017-03-01

Super-hydrophobic surfaces are nowadays of primary interest in several application fields, as for de-icing devices in the automotive and aerospace industries. In this context, laser surface texturing has widely demonstrated to be an easy one-step method to produce super-hydrophobic surfaces on several materials. In this work, a high average power (up to 40W), high repetition-rate (up to 1MHz), femtosecond infrared laser was employed to produce super-hydrophobic surfaces on 316L steel. The set of process and laser parameters for which the super-hydrophobic behavior is optimized, was obtained by varying the laser energy and repetition rate. The morphology of the textured surfaces was firstly analyzed by SEM and confocal microscope analyses. The contact angle was measured over time in order to investigate the effect of air environment on the hydrophobic properties and define the period of time necessary for the super-hydrophobic properties to stabilize. An investigation on the effect of after-processing cleaning solvents on the CA evolution was carried to assess the influence of the after-processing sample handling on the CA evaluation. Results show that the highest values of contact angle, that is the best hydrophobic behavior, are obtained at high repetition rate and low energy, this way opening up a promising scenario in terms of upscaling for reducing the overall process takt-time.

Preparation of Water-Repellent Glass by Sol-Gel Process Using Perfluoroalkylsilane and Tetraethoxysilane.

PubMed

Jeong, Hye-Jeong; Kim, Dong-Kwon; Lee, Soo-Bok; Kwon, Soo-Han; Kadono, Kohei

2001-03-01

Coating films on glass substrate were prepared by sol-gel process using alkoxide solutions containing perfluoroalkylsilane (PFAS) and tetraethoxysilane (TEOS). The physical properties of the coating films were characterized by SEM, FT-IR, and XRD. And their surface properties were investigated by measuring contact angles and atomic compositions. Transparent coating films with smooth surface and uniform thickness could be obtained. The contact angles of the coating films for water and methylene iodide are extremely high, at 118 degrees and 97 degrees, respectively, and their surface free energies are about 9.7 dyn/cm. It was found that the water-repellent glass prepared is very hydrophobic and exhibits excellent water-repellency. Hydrophobic perfluoroalkyl groups are preferentially enriched to the outermost layer at the coating film-air interface, and two layers probably exist in the coating film. The upper layer oriented toward the air is composed of mainly perfluoroalkyl groups originating from PFAS, and the lower layer is composed of mainly -OSiO- groups originating from TEOS. The heat treatment after drying step cannot influence the surface enrichment of the perfluoroalkyl group. The hydrolysis reaction should be more completely done before the dip coating step to obtain lower surface free energy. The burning temperature should be less than 300 degrees C because the perfluoroalkyl group begins to decompose from this temperature. Copyright 2001 Academic Press.

Facile way in fabricating a cotton fabric membrane for switchable oil/water separation and water purification

NASA Astrophysics Data System (ADS)

Li, Yubin; Feng, Ziliang; He, Yi; Fan, Yi; Ma, Jing; Yin, Xiangying

2018-05-01

With dopamine and NiFe2O4 particles, a novel modified cotton fabric (PDA-NiFe2O4@CF) was prepared by one-pot method. Surface morphology, composition of the PDA-NiFe2O4@CF were investigated with SEM, EDX, XRD and FT-IR, respectively. According to the results, the cotton fiber surface was well coated with NiFe2O4 particles. Subsequently, wetting behavior of the modified cotton fabric was determined. The PDA-NiFe2O4@CF is superamphiphilic in air, and a dual lyophobic behavior was indicated with an oil contact angle (OCA) of 153° under water and a water contact angle (WCA) of 145° under oil. The rough micro-nano scale surface structure and high-surface-energy compositions of the PDA-NiFe2O4@CF makes the surface to be easily covered by one medium and enables it to repel other unmixable medium simultaneously. Therefore, water-oil mixtures can be separated on demand. Besides, with the unusual dual lyophobic surface of PDA-NiFe2O4@CF, both two types of emulsions were separated by gravity driven. On the other hand, it was also found that the as-prepared PDA-NiFe2O4@CF had good adsorption performance for methylene blue.

Synthesis, characterization, and biocompatibility of alternating block polyurethanes based on PLA and PEG.

PubMed

Mei, Tingzhen; Zhu, Yonghe; Ma, Tongcui; He, Tao; Li, Linjing; Wei, Chiju; Xu, Kaitian

2014-09-01

A series of alternating block polyurethanes (abbreviated as PULA-alt-PEG) and random block polyurethanes (abbreviated as PULA-ran-PEG) based on poly(L-lactic acid) (PLA) and poly(ethylene glycol) (PEG) were synthesized. The differences of PULA-alt/ran-PEG chemical structure, molecular weight, distribution, thermal properties, mechanical properties and static contact angle were systematically investigated. The PULA-alt/ran-PEG polyurethanes exhibited low T(g) (-47.3 ∼ -34.4°C), wide mechanical properties (stress σ(t): 4.6-32.6 MPa, modulus E: 11.4-323.9 MPa and strain ε: 468-1530%) and low water contact angle (35.4-51.4°). Scanning electron microscope (SEM) observation showed that PULA-alt-PEG film displays rougher and more patterned surface morphology than PULA-ran-PEG does, due to more regular structures of PULA-alt-PEG. Hydrolytic degradation shows that degradation rate of random block polyurethane series PULA-ran-PEG is higher than the alternating counterpart PULA-alt-PEG. PLA segment degradation is faster than urethane linkage and PEG segment almost does not degrade in the buffer solution. Platelet adhesion study showed that all the polyurethanes possess excellent hemocompatibility. The cell culture assay revealed that PULA-alt/ran-PEG polyurethanes were cell inert and unfavorable for the attachment of rat glial cell due to the hydrophilic characters of the materials. © 2013 Wiley Periodicals, Inc.

Evaluation of wetting ability of five new saliva substitutes on heat-polymerized acrylic resin for retention of complete dentures in dry mouth patients: a comparative study

PubMed Central

Mohsin, Abdul Habeeb Bin; Reddy, Varalakshmi; Kumar, Praveen; Raj, Jeevan; Babu, Siva Santosh

2017-01-01

Introduction The aim of this study was to evaluate & compare the wetting ability of five saliva substitutes & distilled water on heat-polymerized acrylic resin. Contact angle of the saliva substitute on denture base can be taken as an indicator of wettability. Good wetting of heat-polymerized acrylic resin is critical for optimum retention of complete dentures. Methods Two hundred & forty samples of heat-polymerized acrylic resin were fabricated using conventional method. 240 samples divided into 6 groups with 40 samples in each group. Advancing & Receding contact angles were measured using Contact Angle Goniometer & DSA4 software analysis. Results Anova test was carried out to test the significance in difference of contact angle values in the six groups. The mean of advancing angle values & mean of receding angle values of all the six groups has shown statistically significant difference between the groups. The mean of angle of hysteresis values of all the six groups are statistically not significant between the groups. A multiple comparison using Bonferroni’s test was carried out to verify the significance of difference between the contact angles in a pair of groups. Statistically significant difference was seen when Aqwet (Group II) was compared to Distilled water (Group I), Wet Mouth (Group III), E-Saliva (Group IV), Biotene (Group V), and Moi-Stir (Group VI). Conclusion The contact angles of five saliva substitutes and distilled water were measured and compared. Group II (AQWET) has the lowest advancing and receding contact angle values and the highest angle of hysteresis on heat-polymerized acrylic resin. Based on contact angle values, Group II (AQWET) has the best wetting ability on heat-cured acrylic resins. The ability of saliva to wet the denture surface is one of the most important properties for complete denture retention in dry mouth cases. PMID:29187918

Design and fabrication of highly hydrophobic Mn nano-sculptured thin films and evaluation of surface properties on hydrophobicity

NASA Astrophysics Data System (ADS)

Hosseini, Somaye; Savaloni, Hadi; Gholipour-Shahraki, Mehran

2017-03-01

The wettability of solid surfaces is important from the aspects of both science and technology. The Mn nano-sculptured thin films were designed and fabricated by oblique angle deposition of Mn on glass substrates at room temperature. The obtained structure was characterized by field emission scanning electron microscopy and atomic force microscopy. The wettability of thin films samples was investigated by water contact angle (WCA). The 4-pointed helical star-shaped structure exhibits hydrophobicity with static WCAs of more than 133° for a 10-mg distilled water droplet. This sample also shows the rose petal effect with the additional property of high adhesion. The Mn nano-sculptured thin films also act as a sticky surface which is confirmed by hysteresis of the contact angle obtained from advancing and receding contact angles measurements. Physicochemical property of liquid phase could effectively change the contact angle, and polar solvents in contact with hydrophobic solid surfaces do not necessarily show high contact angle value.

Hysteresis of the Contact Angle of a Meniscus Inside a Capillary with Smooth, Homogeneous Solid Walls.

PubMed

Kuchin, Igor V; Starov, Victor M

2016-05-31

A theory of contact angle hysteresis of a meniscus inside thin capillaries with smooth, homogeneous solid walls is developed in terms of surface forces (disjoining/conjoining pressure isotherm) using a quasi-equilibrium approach. The disjoining/conjoining pressure isotherm includes electrostatic, intermolecular, and structural components. The values of the static receding θr, advancing θa, and equilibrium θe contact angles in thin capillaries were calculated on the basis of the shape of the disjoining/conjoining pressure isotherm. It was shown that both advancing and receding contact angles depend on the capillary radius. The suggested mechanism of the contact angle hysteresis has a direct experimental confirmation: the process of receding is accompanied by the formation of thick β-films on the capillary walls. The effect of the transition from partial to complete wetting in thin capillaries is predicted and analyzed. This effect takes place in very thin capillaries, when the receding contact angle decreases to zero.

Thermodynamic analysis of effects of contact angle on interfacial interactions and its implications for membrane fouling control.

PubMed

Chen, Jianrong; Shen, Liguo; Zhang, Meijia; Hong, Huachang; He, Yiming; Liao, Bao-Qiang; Lin, Hongjun

2016-02-01

Concept of hydrophobicity always fails to accurately assess the interfacial interaction and membrane fouling, which calls for reliable parameters for this purpose. In this study, effects of contact angle on interfacial interactions related to membrane fouling were investigated based on thermodynamic analysis. It was found that, total interaction energy between sludge foulants and membrane monotonically decreases and increases with water and glycerol contact angle, respectively, indicating that these two parameters can be reliable indicators predicting total interaction energy and membrane fouling. Membrane roughness decreases interaction strength for over 20 times, and effects of membrane roughness on membrane fouling should consider water and glycerol contact angle on membrane. It was revealed existence of a critical water and glycerol contact angle for a given membrane bioreactor. Meanwhile, diiodomethane contact angle has minor effect on the total interaction, and cannot be regarded as an effective indicator assessing interfacial interactions and membrane fouling. Copyright © 2015 Elsevier Ltd. All rights reserved.

CD-SEM real time bias correction using reference metrology based modeling

NASA Astrophysics Data System (ADS)

Ukraintsev, V.; Banke, W.; Zagorodnev, G.; Archie, C.; Rana, N.; Pavlovsky, V.; Smirnov, V.; Briginas, I.; Katnani, A.; Vaid, A.

2018-03-01

Accuracy of patterning impacts yield, IC performance and technology time to market. Accuracy of patterning relies on optical proximity correction (OPC) models built using CD-SEM inputs and intra die critical dimension (CD) control based on CD-SEM. Sub-nanometer measurement uncertainty (MU) of CD-SEM is required for current technologies. Reported design and process related bias variation of CD-SEM is in the range of several nanometers. Reference metrology and numerical modeling are used to correct SEM. Both methods are slow to be used for real time bias correction. We report on real time CD-SEM bias correction using empirical models based on reference metrology (RM) data. Significant amount of currently untapped information (sidewall angle, corner rounding, etc.) is obtainable from SEM waveforms. Using additional RM information provided for specific technology (design rules, materials, processes) CD extraction algorithms can be pre-built and then used in real time for accurate CD extraction from regular CD-SEM images. The art and challenge of SEM modeling is in finding robust correlation between SEM waveform features and bias of CD-SEM as well as in minimizing RM inputs needed to create accurate (within the design and process space) model. The new approach was applied to improve CD-SEM accuracy of 45 nm GATE and 32 nm MET1 OPC 1D models. In both cases MU of the state of the art CD-SEM has been improved by 3x and reduced to a nanometer level. Similar approach can be applied to 2D (end of line, contours, etc.) and 3D (sidewall angle, corner rounding, etc.) cases.

Evaluation of touch-sensitive screen tablet terminal button size and spacing accounting for effect of fingertip contact angle.

PubMed

Nishimura, T; Doi, K; Fujimoto, H

2015-08-01

Touch-sensitive screen terminals enabling intuitive operation are used as input interfaces in a wide range of fields. Tablet terminals are one of the most common devices with a touch-sensitive screen. They have a feature of good portability, enabling use under various conditions. On the other hand, they require a GUI designed to prevent decrease of usability under various conditions. For example, the angle of fingertip contact with the display changes according to finger posture during operation and how the case is held. When a human fingertip makes contact with an object, the contact area between the fingertip and contact object increases or decreases as the contact angle changes. A touch-sensitive screen detects positions using the change in capacitance of the area touched by the fingertip; hence, differences in contact area between the touch-sensitive screen and fingertip resulting from different forefinger angles during operation could possibly affect operability. However, this effect has never been studied. We therefore conducted an experiment to investigate the relationship between size/spacing and operability, while taking the effect of fingertip contact angle into account. As a result, we have been able to specify the button size and spacing conditions that enable accurate and fast operation regardless of the forefinger contact angle.

Contact mechanics of reverse total shoulder arthroplasty during abduction: the effect of neck-shaft angle, humeral cup depth, and glenosphere diameter.

PubMed

Langohr, G Daniel G; Willing, Ryan; Medley, John B; Athwal, George S; Johnson, James A

2016-04-01

Implant design parameters can be changed during reverse shoulder arthroplasty (RSA) to improve range of motion and stability; however, little is known regarding their impact on articular contact mechanics. The purpose of this finite element study was to investigate RSA contact mechanics during abduction for different neck-shaft angles, glenosphere sizes, and polyethylene cup depths. Finite element RSA models with varying neck-shaft angles (155°, 145°, 135°), sizes (38 mm, 42 mm), and cup depths (deep, normal, shallow) were loaded with 400 N at physiological abduction angles. The contact area and maximum contact stress were computed. The contact patch and the location of maximum contact stress were typically located inferomedially in the polyethylene cup. On average for all abduction angles investigated, reducing the neck-shaft angle reduced the contact area by 29% for 155° to 145° and by 59% for 155° to 135° and increased maximum contact stress by 71% for 155° to 145° and by 286% for 155° to 135°. Increasing the glenosphere size increased the contact area by 12% but only decreased maximum contact stress by 2%. Decreasing the cup depth reduced the contact area by 40% and increased maximum contact stress by 81%, whereas increasing the depth produced the opposite effect (+52% and -36%, respectively). The location of the contact patch and maximum contact stress in this study matches the area of damage seen frequently on clinical retrievals. This finding suggests that damage to the inferior cup due to notching may be potentiated by contact stresses. Increasing the glenosphere diameter improved the joint contact area and did not affect maximum contact stress. However, although reducing the neck-shaft angle and cup depth can improve range of motion, our study shows that this also has some negative effects on RSA contact mechanics, particularly when combined. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Effect of inclination and anteversion angles on kinematics and contact mechanics of dual mobility hip implants.

PubMed

Gao, Yongchang; Chen, Zhenxian; Zhang, Zhifeng; Chen, Shibin; Jin, Zhongmin

2018-06-12

Steep inclination and excessive anteversion angles of acetabular cups could result in adverse edge-loading. This, in turn, increases contact pressure and impingement risk for traditional artificial hip joints. However, the influence of high inclination and anteversion angles on both the kinematics and contact mechanics of dual mobility hip implants has rarely been examined. This study focuses on investigating both the kinematics and contact mechanics of a dual mobility hip implant under different inclination and anteversion angles using a dynamic explicit finite element method developed in a previous study. The results showed that an inclination angle of both the back shell and liner ranging from 30° to 70° had little influence on the maximum contact pressure and the accumulated sliding distance of inner and outer surfaces of the liner under normal walking gait. The same results were obtained for an anteversion angle of the liner varying between -20° and +20°. However, when the anteversion angle of the liner was beyond this range, the contact between the femoral neck and the inner rim of the liner occurred. Consequently, this caused a relative rotation at the outer articulation. This suggests that both inclination and modest anteversion angles have little influence on the kinematics and contact mechanics of dual mobility hip implants. However, too excessive anteversion angle could result in a rotation for this kind of hip implant at both articulations. Copyright © 2018 Elsevier Ltd. All rights reserved.

A two-angle model of dynamic wetting in microscale capillaries under low capillary numbers with experiments.

PubMed

Lei, Da; Lin, Mian; Li, Yun; Jiang, Wenbin

2018-06-15

An accurate model of the dynamic contact angle θ d is critical for the calculation of capillary force in applications like enhanced oil recovery, where the capillary number Ca ranges from 10 -10 to 10 -5 and the Bond number Bo is less than 10 -4 . The rate-dependence of the dynamic contact angle under such conditions remains blurred, and is the main target of this study. Featuring with pressure control and interface tracking, the innovative experimental system presented in this work achieves the desired ranges of Ca and Bo, and enables the direct optical measurement of dynamic contact angles in capillaries as tiny as 40 × 20 (width × height) μm and 80 × 20 μm. The advancing and receding processes of wetting and nonwetting liquids were tested. The dynamic contact angle was confirmed velocity-independent with 10 -9  < Ca < 10 -5 (contact line velocity V = 0.135-490 μm/s) and it can be described by a two-angle model with desirable accuracy. A modified two-angle model was developed and an empirical form was obtained from experiments. For different liquids contacting the same surface, the advancing angle θ adv approximately equals the static contact angle θ o . The receding angle θ rec was found to be a linear function of θ adv , in good agreement with our and other experiments from the literature. Copyright © 2018 Elsevier Inc. All rights reserved.

Automated contact angle estimation for three-dimensional X-ray microtomography data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klise, Katherine A.; Moriarty, Dylan; Yoon, Hongkyu

2015-11-10

Multiphase flow in capillary regimes is a fundamental process in a number of geoscience applications. The ability to accurately define wetting characteristics of porous media can have a large impact on numerical models. In this paper, a newly developed automated three-dimensional contact angle algorithm is described and applied to high-resolution X-ray microtomography data from multiphase bead pack experiments with varying wettability characteristics. The algorithm calculates the contact angle by finding the angle between planes fit to each solid/fluid and fluid/fluid interface in the region surrounding each solid/fluid/fluid contact point. Results show that the algorithm is able to reliably compute contactmore » angles using the experimental data. The in situ contact angles are typically larger than flat surface laboratory measurements using the same material. Furthermore, wetting characteristics in mixed-wet systems also change significantly after displacement cycles.« less

AFM Study of Surface Nanobubbles on Binary Self-Assembled Monolayers on Ultraflat Gold with Identical Macroscopic Static Water Contact Angles and Different Terminal Functional Groups.

PubMed

Song, Bo; Chen, Kun; Schmittel, Michael; Schönherr, Holger

2016-11-01

All experimental findings related to surface nanobubbles, such as their pronounced stability and the striking differences of macroscopic and apparent nanoscopic contact angles, need to be addressed in any theory or model of surface nanobubbles. In this work we critically test a recent explanation of surface nanobubble stability and their consequences and contrast this with previously proposed models. In particular, we elucidated the effect of surface chemical composition of well-controlled solid-aqueous interfaces of identical roughness and defect density on the apparent nanoscopic contact angles. Expanding on a previous atomic force microscopy (AFM) study on the systematic variation of the macroscopic wettability using binary self-assembled monolayers (SAMs) on ultraflat template stripped gold (TSG), we assessed here the effect of different surface chemical composition for macroscopically identical static water contact angles. SAMs on TSG with a constant macroscopic water contact angle of 81 ± 2° were obtained by coadsorption of a methyl-terminated thiol and a second thiol with different terminal functional groups, including hydroxy, amino, and carboxylic acid groups. In addition, surface nanobubbles formed by entrainment of air on SAMs of a bromoisobutyrate-terminated thiol were analyzed by AFM. Despite the widely differing surface potentials and different functionality, such as hydrogen bond acceptor or donor, and different dipole moments and polarizability, the nanoscopic contact angles (measured through the condensed phase and corrected for AFM tip broadening effects) were found to be 145 ± 10° for all surfaces. Hence, different chemical functionalities at identical macroscopic static water contact angle do not noticeably influence the apparent nanoscopic contact angle of surface nanobubbles. This universal contact angle is in agreement with recent models that rely on contact line pinning and the equilibrium of gas outflux due to the Laplace pressure and gas influx due to gas oversaturation in the aqueous medium.

Ultralow contact angle hysteresis and no-aging effects in superhydrophobic tangled nanofiber structures generated by controlling the pore size of a 99.5% aluminum foil

NASA Astrophysics Data System (ADS)

Lee, Sangmin; Hwang, Woonbong

2009-03-01

Superhydrophobic surfaces designed to improve hydrophobicity have high advancing contact angles corresponding to the Cassie state, but these surfaces also exhibit high contact angle hysteresis. We report here a simple and inexpensive method for fabricating superhydrophobic tangled nanofiber structures with ultralow contact angle hysteresis and no-aging degradation, based on a widening process. The resulting nanostructures are suitable for diverse applications including microfluidic devices for biological studies and industrial self-cleaning products for automobiles, ships and houses.

Wettability Control of Gold Surfaces Modified with Benzenethiol Derivatives: Water Contact Angle and Thermal Stability.

PubMed

Tatara, Shingo; Kuzumoto, Yasutaka; Kitamura, Masatoshi

2016-04-01

The water wettability of Au surfaces has been controlled using various benzenethiol derivatives including 4-methylbenzenethiol, pentafluorobenzenethiol, 4-flubrobenzenethiol, 4-methoxy-benzenethiol, 4-nitrobenzenethiol, and 4-hydroxybenzenethiol. The water contact angle of the Au surface modified with the benzenethiol derivative was found to vary in the wide range of 30.9° to 88.3°. The contact angle of the modified Au films annealed was also measured in order to investigate their thermal stability. The change in the contact angle indicated that the modified surface is stable at temperatures below about 400 K. Meanwhile, the activation energy of desorption from the modified surface was estimated from the change in the contact angle. The modified Au surface was also examined using X-ray photoelectron spectroscopy.

Impact of air and water vapor environments on the hydrophobicity of surfaces.

PubMed

Weisensee, Patricia B; Neelakantan, Nitin K; Suslick, Kenneth S; Jacobi, Anthony M; King, William P

2015-09-01

Droplet wettability and mobility play an important role in dropwise condensation heat transfer. Heat exchangers and heat pipes operate at liquid-vapor saturation. We hypothesize that the wetting behavior of liquid water on microstructures surrounded by pure water vapor differs from that for water droplets in air. The static and dynamic contact angles and contact angle hysteresis of water droplets were measured in air and pure water vapor environments inside a pressure vessel. Pressures ranged from 60 to 1000 mbar, with corresponding saturation temperatures between 36 and 100°C. The wetting behavior was studied on four hydrophobic surfaces: flat Teflon-coated, micropillars, micro-scale meshes, and nanoparticle-coated with hierarchical micro- and nanoscale roughness. Static advancing contact angles are 9° lower in the water vapor environment than in air on a flat surface. One explanation for this reduction in contact angles is water vapor adsorption to the Teflon. On microstructured surfaces, the vapor environment has little effect on the static contact angles. In all cases, variations in pressure and temperature do not influence the wettability and mobility of the water droplets. In most cases, advancing contact angles increase and contact angle hysteresis decreases when the droplets are sliding or rolling down an inclined surface. Copyright © 2015 Elsevier Inc. All rights reserved.

In vitro evaluation of the contact angle formed between AH Plus, Hybrid Root Seal and mineral trioxide aggregate Plus sealer with dentin and gutta-percha.

PubMed

Nikhil, Vineeta; Jaiswal, Shikha; Bajpai, Gauravi

2018-01-01

The purpose of this study was evaluation and comparison of the contact angle of new root canal sealers - Hybrid Root Seal, mineral trioxide aggregate (MTA) Plus, and the conventional AH Plus sealer with dentin and gutta-percha. Two groups (Group D - dentin and Group G - gutta-percha) of 18 samples each were further randomly divided into 3 subgroups based on the type of sealer used, that is, AH Plus, Hybrid Root Seal, and MTA Plus. Contact angle measurement device (Phoenix 300) was used to measure the contact angle of the sealers on both dentin and gutta-percha. The results thus obtained were analyzed using one-way analysis of variance and Student's t -test. MTA Plus recorded significantly higher values of contact angle on both the substrates, that is, dentin and gutta-percha when compared to AH Plus and Hybrid root canal sealer. The lowest value of contact angle in gutta-percha and dentin was shown by Hybrid root canal sealer and AH Plus, respectively. Both AH Plus and Hybrid Root Seal exhibited lower contact angle values, and hence, better wettability on both dentin and gutta-percha as compared to MTA Plus.

Color-gradient lattice Boltzmann model for simulating droplet motion with contact-angle hysteresis.

PubMed

Ba, Yan; Liu, Haihu; Sun, Jinju; Zheng, Rongye

2013-10-01

Lattice Boltzmann method (LBM) is an effective tool for simulating the contact-line motion due to the nature of its microscopic dynamics. In contact-line motion, contact-angle hysteresis is an inherent phenomenon, but it is neglected in most existing color-gradient based LBMs. In this paper, a color-gradient based multiphase LBM is developed to simulate the contact-line motion, particularly with the hysteresis of contact angle involved. In this model, the perturbation operator based on the continuum surface force concept is introduced to model the interfacial tension, and the recoloring operator proposed by Latva-Kokko and Rothman is used to produce phase segregation and resolve the lattice pinning problem. At the solid surface, the color-conserving wetting boundary condition [Hollis et al., IMA J. Appl. Math. 76, 726 (2011)] is applied to improve the accuracy of simulations and suppress spurious currents at the contact line. In particular, we present a numerical algorithm to allow for the effect of the contact-angle hysteresis, in which an iterative procedure is used to determine the dynamic contact angle. Numerical simulations are conducted to verify the developed model, including the droplet partial wetting process and droplet dynamical behavior in a simple shear flow. The obtained results are compared with theoretical solutions and experimental data, indicating that the model is able to predict the equilibrium droplet shape as well as the dynamic process of partial wetting and thus permits accurate prediction of contact-line motion with the consideration of contact-angle hysteresis.

Pinning of the Contact Line during Evaporation on Heterogeneous Surfaces: Slowdown or Temporary Immobilization? Insights from a Nanoscale Study.

PubMed

Zhang, Jianguo; Müller-Plathe, Florian; Leroy, Frédéric

2015-07-14

The question of the effect of surface heterogeneities on the evaporation of liquid droplets from solid surfaces is addressed through nonequilibrium molecular dynamics simulations. The mechanism behind contact line pinning which is still unclear is discussed in detail on the nanoscale. Model systems with the Lennard-Jones interaction potential were employed to study the evaporation of nanometer-sized cylindrical droplets from a flat surface. The heterogeneity of the surface was modeled through alternating stripes of equal width but two chemical types. The first type leads to a contact angle of 67°, and the other leads to a contact angle of 115°. The stripe width was varied between 2 and 20 liquid-particle diameters. On the surface with the narrowest stripes, evaporation occurred at constant contact angle as if the surface was homogeneous, with a value of the contact angle as predicted by the regular Cassie-Baxter equation. When the width was increased, the contact angle oscillated during evaporation between two boundaries whose values depend on the stripe width. The evaporation behavior was thus found to be a direct signature of the typical size of the surface heterogeneity domains. The contact angle both at equilibrium and during evaporation could be predicted from a local Cassie-Baxter equation in which the surface composition within a distance of seven fluid-particle diameters around the contact line was considered, confirming the local nature of the interactions that drive the wetting behavior of droplets. More importantly, we propose a nanoscale explanation of pinning during evaporation. Pinning should be interpreted as a drastic slowdown of the contact line dynamics rather than a complete immobilization of it during a transition between two contact angle boundaries.

Effect of acetabular cup abduction angle on wear of ultrahigh-molecular-weight polyethylene in hip simulator testing.

PubMed

Korduba, Laryssa A; Essner, Aaron; Pivec, Robert; Lancin, Perry; Mont, Michael A; Wang, Aiguo; Delanois, Ronald E

2014-10-01

The effect of acetabular component positioning on the wear rates of metal-on-polyethylene articulations has not been extensively studied. Placement of acetabular cups at abduction angles of more than 40° has been noted as a possible reason for early failure caused by increased wear. We conducted a study to evaluate the effects of different acetabular cup abduction angles on polyethylene wear rate, wear area, contact pressure, and contact area. Our in vitro study used a hip joint simulator and finite element analysis to assess the effects of cup orientation at 4 angles (0°, 40°, 50°, 70°) on wear and contact properties. Polyethylene bearings with 28-mm cobalt-chrome femoral heads were cycled in an environment mimicking in vivo joint fluid to determine the volumetric wear rate after 10 million cycles. Contact pressure and contact area for each cup abduction angle were assessed using finite element analysis. Results were correlated with cup abduction angles to determine if there were any differences among the 4 groups. The inverse relationship between volumetric wear rate and acetabular cup inclination angle demonstrated less wear with steeper cup angles. The largest abduction angle (70°) had the lowest contact area, largest contact pressure, and smallest head coverage. Conversely, the smallest abduction angle (0°) had the most wear and most head coverage. Polyethylene wear after total hip arthroplasty is a major cause of osteolysis and aseptic loosening, which may lead to premature implant failure. Several studies have found that high wear rates for cups oriented at steep angles contributed to their failure. Our data demonstrated that larger cup abduction angles were associated with lower, not higher, wear. However, this potentially "protective" effect is likely counteracted by other complications of steep cup angles, including impingement, instability, and edge loading. These factors may be more relevant in explaining why implants fail at a higher rate if cups are oriented at more than 40° of abduction.

Effect of surface texturing on superoleophobicity, contact angle hysteresis, and "robustness".

PubMed

Zhao, Hong; Park, Kyoo-Chul; Law, Kock-Yee

2012-10-23

Previously, we reported the creation of a fluorosilane (FOTS) modified pillar array silicon surface comprising ~3-μm-diameter pillars (6 μm pitch with ~7 μm height) that is both superhydrophobic and superoleophobic, with water and hexadecane contact angles exceeding 150° and sliding angles at ~10° owing to the surface fluorination and the re-entrant structure in the side wall of the pillar. In this work, the effects of surface texturing (pillar size, spacing, and height) on wettability, contact angle hysteresis, and "robustness" are investigated. We study the static, advancing, and receding contact angles, as well as the sliding angles as a function of the solid area fraction. The results reveal that pillar size and pillar spacing have very little effect on the static and advancing contact angles, as they are found to be insensitive to the solid area fraction from 0.04 to ~0.4 as the pillar diameter varies from 1 to 5 μm and the center-to-center spacing varies from 4.5 to 12 μm. On the other hand, sliding angle, receding contact angle, and contact angle hysteresis are found to be dependent on the solid area fraction. Specifically, receding contact angle decreases and sliding angle and hysteresis increase as the solid area fraction increases. This effect can be attributable to the increase in pinning as the solid area fraction increases. Surface Evolver modeling shows that water wets and pins the pillar surface whereas hexadecane wets the pillar surface and then penetrates into the side wall of the pillar with the contact line pinning underneath the re-entrant structure. Due to the penetration of the hexadecane drop into the pillar structure, the effect on the receding contact angle and hysteresis is larger relative to that of water. This interpretation is supported by studying a series of FOTS pillar array surfaces with varying overhang thickness. With the water drop, the contact line is pinned on the pillar surface and very little overhang thickness effect was observed. On the other hand, the hexadecane drop is shown to wet the pillar surface and the side wall of the overhang. It then pins at the lower edge of the overhang structure. A plot of the thickness of the overhang as a function of the static, advancing, and receding contact angles and sliding angle of hexadecane reveals that static, advancing, and receding contact angles decrease and sliding angle increases as the thickness of the overhang increases. A larger overhang effect is observed with octane due to its lower surface tension. The robustness of the pillar array surface against external pressure induced wetting and abrasion was modeled. Surface Evolver simulation (with the hexadecane drop) indicates that wetting breakthrough pressure as high as ~70 kPa is achievable with 0.5-μm-diameter pillar array FOTS surfaces. Mechanical modeling shows that bending of the pillars is the key failure by abrasion, which can be avoided with a short pillar structure. The path to fabricate a superoleophobic surface that can withstand the external force equivalent of a gentle cleaning blade (up to ~30 kPa) without wetting and abrasion failure is discussed.

Contact angle of unset elastomeric impression materials.

PubMed

Menees, Timothy S; Radhakrishnan, Rashmi; Ramp, Lance C; Burgess, John O; Lawson, Nathaniel C

2015-10-01

Some elastomeric impression materials are hydrophobic, and it is often necessary to take definitive impressions of teeth coated with some saliva. New hydrophilic materials have been developed. The purpose of this in vitro study was to compare contact angles of water and saliva on 7 unset elastomeric impression materials at 5 time points from the start of mixing. Two traditional polyvinyl siloxane (PVS) (Aquasil, Take 1), 2 modified PVS (Imprint 4, Panasil), a polyether (Impregum), and 2 hybrid (Identium, EXA'lence) materials were compared. Each material was flattened to 2 mm and a 5 μL drop of distilled water or saliva was dropped on the surface at 25 seconds (t0) after the start of mix. Contact angle measurements were made with a digital microscope at initial contact (t0), t1=2 seconds, t2=5 seconds, t3=50% working time, and t4=95% working time. Data were analyzed with a generalized linear mixed model analysis, and individual 1-way ANOVA and Tukey HSD post hoc tests (α=.05). For water, materials grouped into 3 categories at all time-points: the modified PVS and one hybrid material (Identium) produced the lowest contact angles, the polyether material was intermediate, and the traditional PVS materials and the other hybrid (EXA'lence) produced the highest contact angles. For saliva, Identium, Impregum, and Imprint 4 were in the group with the lowest contact angle at most time points. Modified PVS materials and one of the hybrid materials are more hydrophilic than traditional PVS materials when measured with water. Saliva behaves differently than water in contact angle measurement on unset impression material and produces a lower contact angle on polyether based materials. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Fabrication of super-hydrophobic duo-structures

NASA Astrophysics Data System (ADS)

Zhang, X. Y.; Zhang, F.; Jiang, Y. J.; Wang, Y. Y.; Shi, Z. W.; Peng, C. S.

2015-04-01

Recently, super-hydrophobicity has attracted increasing attention due to its huge potential in the practical applications. In this paper, we have presented a duo-structure of the combination of micro-dot-matrix and nano-candle-soot. Polydimethylsiloxane (PDMS) was used as a combination layer between the dot-matrix and the soot particles. Firstly, a period of 9-μm dot-matrix was easily fabricated on the K9 glass using the most simple and mature photolithography process. Secondly, the dot-matrix surface was coated by a thin film of PDMS (elastomer: hardener=10:1) which was diluted by methylbenzene at the volume ratio of 1:8. Thirdly, we held the PDMS modified surface over a candle flame to deposit a soot layer and followed by a gentle water-risen to remove the non-adhered particles. At last, the samples were baked at 85°C for 2 hours and then the duo-structure surface with both micro-size dot-matrix and nano-size soot particles was obtained. The SEM indicated this novel surface morphology was quite like a lotus leaf of the well-know micro-nano-binary structures. As a result, the contact angle meter demonstrated such surface exhibited a perfect super-hydrophobicity with water contact angle of 153° and sliding angle of 3°. Besides, just listed as above, the fabrication process for our structure was quite more easy, smart and low-cost compared with the other production technique for super-hydrophobic surfaces such as the phase separation method, electrochemical deposition and chemical vapor deposition etc. Hence, this super-hydrophobic duo-structure reported in this letter was a great promising candidate for a wide and rapid commercialization in the future.

Wettability and impact dynamics of water droplets on rice ( Oryza sativa L.) leaves

NASA Astrophysics Data System (ADS)

Kwon, Dae Hee; Huh, Hyung Kyu; Lee, Sang Joon

2014-03-01

We investigated the wettability and impact dynamics of water droplets on rice leaves at various leaf inclination angles and orientations. Contact angle, contact angle hysteresis (CAH), and roll-off angle ( α roll) of water droplets were measured quantitatively. Results showed that droplet motion exhibited less resistance along the longitudinal direction. Impact dynamic parameters, such as impact behaviors, maximum spreading factor, contact distance, and contact time were also investigated. Three different impact behaviors were categorized based on the normal component of Weber number irrespective of the inclination angle of the rice leaf. The asymmetric impact behavior induced by the tangential Weber number was also identified. Variation in the maximum spreading factor according to the normal Weber number was measured and compared with theoretical value obtained according to scaling law to show the wettability of the rice leaves. The contact distance of the impacting droplets depended on the inclination angle of the leaves. Along the longitudinal direction of rice leaves, contact distance was farther than that along the transverse direction. This result is consistent with the smaller values of CAH and α roll along the longitudinal direction.

Analysis of water microdroplet condensation on silicon surfaces

NASA Astrophysics Data System (ADS)

Honda, Takuya; Fujimoto, Kenya; Yoshimoto, Yuta; Mogi, Katsuo; Kinefuchi, Ikuya; Sugii, Yasuhiko; Takagi, Shu; Univ. of Tokyo Team; Tokyo Inst. of Tech. Team

2016-11-01

We observed the condensation process of water microdroplets on flat silicon (100) surfaces by means of the sequential visualization of the droplets using an environmental scanning electron microscope. As previously reported for nanostructured surfaces, the condensation process of water microdroplets on the flat silicon surfaces also exhibits two modes: the constant base (CB) area mode and the constant contact angle (CCA) mode. In the CB mode, the contact angle increases with time while the base diameter is constant. Subsequently, in the CCA mode, the base diameter increases with time while the contact angle remains constant. The dropwise condensation model regulated by subcooling temperature does not reproduce the experimental results. Because the subcooling temperature is not constant in the case of a slow condensation rate, this model is not applicable to the condensation of the long time scale ( several tens of minutes). The contact angle of water microdroplets ( several μm) tended to be smaller than the macro contact angle. Two hypotheses are proposed as the cause of small contact angles: electrowetting and the coalescence of sub- μm water droplets.

Magnetowetting and sliding motion of a sessile ferrofluid droplet in the presence of a permanent magnet.

PubMed

Nguyen, Nam-Trung; Zhu, Guiping; Chua, Yong-Chin; Phan, Vinh-Nguyen; Tan, Say-Hwa

2010-08-03

Motion of a droplet on a planar surface has applications in droplet-based lab on a chip technology. This paper reports the experimental results of the shape, contact angles, and motion of ferrofluid droplets driven by a permanent magnet on a planar homogeneous surface. The water-based ferrofluid in use is a colloidal suspension of single-domain magnetic nanoparticles. The effect of the magnetic field on the apparent contact angle of the ferrofluid droplet was first investigated. The results show that an increasing magnetic flux decreases the apparent contact angle of a sessile ferrofluid droplet. Next, the dynamic contact angle was investigated by observing the shape and the motion of a sessile ferrofluid droplet. The advancing and receding contact angles of the moving ferrofluid were measured at different moving speeds and magnetic field strengths. The measured contact angles were used to estimate the magnitude of the forces involved in the sliding motion. Scaling analysis was carried out to derive the critical velocity, beyond which the droplet is not able to catch up with the moving magnet.

Contact angle of a nanodrop on a nanorough solid surface.

PubMed

Berim, Gersh O; Ruckenstein, Eli

2015-02-21

The contact angle of a cylindrical nanodrop on a nanorough solid surface is calculated, for both hydrophobic and hydrophilic surfaces, using the density functional theory. The emphasis of the paper is on the dependence of the contact angle on roughness. The roughness is modeled by rectangular pillars of infinite length located on the smooth surface of a substrate, with fluid-pillar interactions different in strength from the fluid-substrate ones. It is shown that for hydrophobic substrates the trend of the contact angle to increase with increasing roughness, which was noted in all previous studies, is not universally valid, but depends on the fluid-pillar interactions, pillar height, interpillar distance, as well as on the size of the drop. For hydrophilic substrate, an unusual kink-like dependence of the contact angle on the nanodrop size is found which is caused by the change in the location of the leading edges of the nanodrop on the surface. It is also shown that the Wenzel and Cassie-Baxter equations can not explain all the peculiarities of the contact angle of a nanodrop on a nanorough surface.

Wettability of naturally aged silicone and EPDM composite insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubanski, S.M.; Vlastos, A.E.

1990-07-01

This paper reports the wettability of aged surfaces and of the bulk of naturally aged silicone and EPDM insulator housings and of silicone elastomer insulator coatings studied. The samples were taken either directly from the insulators or treated by exposing them to corona discharges and/or to saline pollution. The results show that the contact angles of the silicone rubber insulator surfaces are larger than the contact angles of the RTV silicone rubber coating and of the EPDM rubber insulator surfaces, especially when the surfaces are aged. When the insulators were exposed to corona discharges, the contact angles of the siliconemore » rubber insulators are reduced but after the exposure they recover with time. The contact angles of the EPDM rubber insulators, however, after the exposure, continue to reduce. When exposed to artificial saline pollution, the silicone rubber insulators show a limited recovery of their contact angles with time, while, when exposed to corona discharge, they show a recovery of the contact angle after the exposure. The time for recovery is dependent on the exposure time to the corona discharges.« less

Optical distortion correction of a liquid-gas interface and contact angle in cylindrical tubes

NASA Astrophysics Data System (ADS)

Darzi, Milad; Park, Chanwoo

2017-05-01

Objects inside cylindrical tubes appear distorted as seen outside the tube due to the refraction of the light passing through different media. Such an optical distortion may cause significant errors in geometrical measurements using optical observations of objects (e.g., liquid-gas interfaces, solid particles, gas bubbles) inside the tubes. In this study, an analytical method using a point-by-point correction of the optical distortion was developed. For an experimental validation, the method was used to correct the apparent profiles of the water-air interfaces (menisci) in cylindrical glass tubes with different tube diameters and wall thicknesses. Then, the corrected meniscus profiles were used to calculate the corrected static contact angles. The corrected contact angle shows an excellent agreement with the reference contact angles as compared to the conventional contact angle measurement using apparent meniscus profiles.

A review of factors that affect contact angle and implications for flotation practice.

PubMed

Chau, T T; Bruckard, W J; Koh, P T L; Nguyen, A V

2009-09-30

Contact angle and the wetting behaviour of solid particles are influenced by many physical and chemical factors such as surface roughness and heterogeneity as well as particle shape and size. A significant amount of effort has been invested in order to probe the correlation between these factors and surface wettability. Some of the key investigations reported in the literature are reviewed here. It is clear from the papers reviewed that, depending on many experimental conditions such as the size of the surface heterogeneities and asperities, surface cleanliness, and the resolution of measuring equipment and data interpretation, obtaining meaningful contact angle values is extremely difficult and such values are reliant on careful experimental control. Surface wetting behaviour depends on not only surface texture (roughness and particle shape), and surface chemistry (heterogeneity) but also on hydrodynamic conditions in the preparation route. The inability to distinguish the effects of each factor may be due to the interplay and/or overlap of two or more factors in each system. From this review, it was concluded that: Surface geometry (and surface roughness of different scales) can be used to tune the contact angle; with increasing surface roughness the apparent contact angle decreases for hydrophilic materials and increases for hydrophobic materials. For non-ideal surfaces, such as mineral surfaces in the flotation process, kinetics plays a more important role than thermodynamics in dictating wettability. Particle size encountered in flotation (10-200 microm) showed no significant effect on contact angle but has a strong effect on flotation rate constant. There is a lack of a rigid quantitative correlation between factors affecting wetting, wetting behaviour and contact angle on minerals; and hence their implication for flotation process. Specifically, universal correlation of contact angle to flotation recovery is still difficult to predict from first principles. Other advanced techniques and measures complementary to contact angle will be essential to establish the link between research and practice in flotation.

Measurement of contact-angle hysteresis for droplets on nanopillared surface and in the Cassie and Wenzel states: a molecular dynamics simulation study.

PubMed

Koishi, Takahiro; Yasuoka, Kenji; Fujikawa, Shigenori; Zeng, Xiao Cheng

2011-09-27

We perform large-scale molecular dynamics simulations to measure the contact-angle hysteresis for a nanodroplet of water placed on a nanopillared surface. The water droplet can be in either the Cassie state (droplet being on top of the nanopillared surface) or the Wenzel state (droplet being in contact with the bottom of nanopillar grooves). To measure the contact-angle hysteresis in a quantitative fashion, the molecular dynamics simulation is designed such that the number of water molecules in the droplets can be systematically varied, but the number of base nanopillars that are in direct contact with the droplets is fixed. We find that the contact-angle hysteresis for the droplet in the Cassie state is weaker than that in the Wenzel state. This conclusion is consistent with the experimental observation. We also test a different definition of the contact-angle hysteresis, which can be extended to estimate hysteresis between the Cassie and Wenzel state. The idea is motivated from the appearance of the hysteresis loop typically seen in computer simulation of the first-order phase transition, which stems from the metastability of a system in different thermodynamic states. Since the initial shape of the droplet can be controlled arbitrarily in the computer simulation, the number of base nanopillars that are in contact with the droplet can be controlled as well. We show that the measured contact-angle hysteresis according to the second definition is indeed very sensitive to the initial shape of the droplet. Nevertheless, the contact-angle hystereses measured based on the conventional and new definition seem converging in the large droplet limit. © 2011 American Chemical Society

Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference.

PubMed

Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

2015-09-01

Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008)JFLSA70022-112010.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the behavior of daughter droplets is significantly different in both branch channels. Also, it is found that the contact angle hysteresis is strengthened with decreasing the viscosity ratio, leading to an earlier droplet breakup and a decrease in the maximum length that the droplet can reach before the breakup. These simulation results manifest that the present multiphase LBM can be a useful substitute to Ba et al. [Phys. Rev. E 88, 043306 (2013)PLEEE81539-375510.1103/PhysRevE.88.043306] for modeling the contact angle hysteresis, and it can be easily implemented with higher computational efficiency.

Detailed statistical contact angle analyses; "slow moving" drops on inclining silicon-oxide surfaces.

PubMed

Schmitt, M; Groß, K; Grub, J; Heib, F

2015-06-01

Contact angle determination by sessile drop technique is essential to characterise surface properties in science and in industry. Different specific angles can be observed on every solid which are correlated with the advancing or the receding of the triple line. Different procedures and definitions for the determination of specific angles exist which are often not comprehensible or reproducible. Therefore one of the most important things in this area is to build standard, reproducible and valid methods for determining advancing/receding contact angles. This contribution introduces novel techniques to analyse dynamic contact angle measurements (sessile drop) in detail which are applicable for axisymmetric and non-axisymmetric drops. Not only the recently presented fit solution by sigmoid function and the independent analysis of the different parameters (inclination, contact angle, velocity of the triple point) but also the dependent analysis will be firstly explained in detail. These approaches lead to contact angle data and different access on specific contact angles which are independent from "user-skills" and subjectivity of the operator. As example the motion behaviour of droplets on flat silicon-oxide surfaces after different surface treatments is dynamically measured by sessile drop technique when inclining the sample plate. The triple points, the inclination angles, the downhill (advancing motion) and the uphill angles (receding motion) obtained by high-precision drop shape analysis are independently and dependently statistically analysed. Due to the small covered distance for the dependent analysis (<0.4mm) and the dominance of counted events with small velocity the measurements are less influenced by motion dynamics and the procedure can be called "slow moving" analysis. The presented procedures as performed are especially sensitive to the range which reaches from the static to the "slow moving" dynamic contact angle determination. They are characterised by small deviations of the computed values. Additional to the detailed introduction of this novel analytical approaches plus fit solution special motion relations for the drop on inclined surfaces and detailed relations about the reactivity of the freshly cleaned silicon wafer surface resulting in acceleration behaviour (reactive de-wetting) are presented. Copyright © 2014 Elsevier Inc. All rights reserved.

Preparation of hydrophobic coatings

DOEpatents

Branson, Eric D [Albuquerque, NM; Shah, Pratik B [Albuquerque, NM; Singh, Seema [Rio Rancho, NM; Brinker, C Jeffrey [Albuquerque, NM

2009-02-03

A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150.degree.. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.

Approach to the determination of the contact angle in hydrophobic samples with simultaneous correction of the effect of the roughness

NASA Astrophysics Data System (ADS)

Domínguez, Noemí; Castilla, Pau; Linzoain, María Eugenia; Durand, Géraldine; García, Cristina; Arasa, Josep

2018-04-01

This work presents the validation study of a method developed to measure contact angles with a confocal device in a set of hydrophobic samples. The use of this device allows the evaluation of the roughness of the surface and the determination of the contact angle in the same area of the sample. Furthermore, a theoretical evaluation of the impact of the roughness of a nonsmooth surface in the calculation of the contact angle when it is not taken into account according to Wenzel's model is also presented.

Measurement of Critical Contact Angle in a Microgravity Space Experiment

NASA Technical Reports Server (NTRS)

Concus, P.; Finn, R.; Weislogel, M.

1998-01-01

Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USML-2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

Measurement of Critical Contact Angle in a Microgravity Space Experiment

NASA Technical Reports Server (NTRS)

Concus, P.; Finn, R.; Weislogel, M.

1998-01-01

Mathematical theory predicts that small changes in container shape or in contact angle can give rise to large shifts of liquid in a microgravity environment. This phenomenon was investigated in the Interface Configuration Experiment on board the USMT,2 Space Shuttle flight. The experiment's "double proboscis" containers were designed to strike a balance between conflicting requirements of sizable volume of liquid shift (for ease of observation) and abruptness of the shift (for accurate determination of critical contact angle). The experimental results support the classical concept of macroscopic contact angle and demonstrate the role of hysteresis in impeding orientation toward equilibrium.

Investigating How Contact Angle Effects the Interaction between Water and a Hydrophobic Surface

NASA Astrophysics Data System (ADS)

Poynor, Adele; Neidig, Caitlyn

2012-02-01

By definition hydrophobic substances hate water. What happens when water is forced into contact with a hydrophobic surface? One theory is that an ultra-thin low-density region forms near the surface. Contact angle is a measure of how hydrophobic a surface is. We have employed an automated home-built Surface Plasmon Resonance (SPR) apparatus to investigate the effect of varying the contact angle on the depletion layer

The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint.

PubMed

Sopher, Ran S; Amis, Andrew A; Davies, D Ceri; Jeffers, Jonathan Rt

2017-01-01

Data about a muscle's fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep pennation angles. Inter-subject variability in muscle architecture affected ankle muscle and contact loads only slightly. The link between muscle architecture and function contributes to the understanding of the relationship between muscle structure and function.

The Development of using the digital projection method to measure the contact angle of ball screw

NASA Astrophysics Data System (ADS)

Chen, Chun-Jen; Jywe, Wenyuh; Liu, Yu-Chun; Jwo, Hsin-Hong

The ball screw frequently used to drive or translate the parts on the precision machine, such as machine tool and motorized stage. Therefore they were most frequently used on the precision machine, semiconductor equipment, medical instrument and aero industry. The main parts of ball screw are screw, ball and nut. The contact angle between the screw, ball and nut will affect the performance (include loading and noise) and lifecycle of a ball screw. If the actual contact angle and the designed contact angle are not the same, the friction between the ball, screw and nut will increase and it will result in the thermal increase and lifecycle decrease. This paper combines the traditional profile projector and commercial digital camera to build an imaging based and noncontact measurements system. It can implement the contact angle measurement quickly and accurately. Three different pitch angles of ball screws were completed tests in this paper. The angle resolution of this measurement system is about 0.001 degree and its accuracy is about 0.05 degree.

Contact angle control of sessile drops on a tensioned web

NASA Astrophysics Data System (ADS)

Park, Janghoon; Kim, Dongguk; Lee, Changwoo

2018-04-01

In this study, the influence of the change of tension applied to flexible and thin web substrate on the contact angle of sessile drop in roll-to-roll system was investigated. Graphene oxide and deionized water solutions were used in the experiments. Tension was changed to 29, 49, and 69 N, and the casting distance of the micropipette and the material was set to 10, 20, and 40 mm, and the droplet volume was set to 10, 20, and 30 μL, respectively. Statistical analysis of three variables and analysis of the variance methodology showed that the casting distance was most significant for the contact angle change, and the most interesting tension variable was also affected. The change in tension caused the maximum contact angle to change by 5.5°. The tension was not uniform in the width direction. When the droplet was applied in the same direction in the width direction, it was confirmed that the tension unevenness had great influence on the contact angle up to 11°. Finally, the casting distance, which has a large effect on the contact angle, was calibrated in the width direction to reduce the width direction contact angle deviation to 1%. This study can be applied to fine patterning research using continuous inkjet printing and aerosol jet printing, which are roll-to-roll processes based on droplet handling.

The comparison between two irrigation regimens on the dentine wettability for an epoxy resin based sealer by measuring its contact angle formed to the irrigated dentine.

PubMed

Mohan, Rayapudi Phani; Pai, Annappa Raghavendra Vivekananda

2015-01-01

The aim was to assess the influence of two irrigation regimens having ethylenediaminetetraacetic acid (EDTA) and ethylenediaminetetraacetic acid with cetrimide (EDTAC) as final irrigants, respectively, on the dentine wettability for AH Plus sealer by comparing its contact angle formed to the irrigated dentine. Study samples were divided into two groups (n = 10). The groups were irrigated with 3% sodium hypochlorite (NaOCl) solution followed by either 17% EDTA or 17% EDTAC solution. AH Plus was mixed, and controlled volume droplet (0.1 mL) of the sealer was placed on the dried samples. The contact angle was measured using a Dynamic Contact Angle Analyzer and results were analyzed using SPSS 21.0 and 2 sample t-test. There was a significant difference in the contact angle of AH Plus formed to the dentine irrigated with the above two regimens. AH Plus showed significantly lower contact angle with the regimen having EDTAC as a final irrigant than the one with EDTA (P < 0.05). An irrigation regimen consisting of NaOCl with either EDTA or EDTAC solution as a final irrigant influences the dentine wettability and contact angle of a sealer. EDTAC as a final irrigant facilitates better dentin wettability than EDTA for AH Plus to promote its better flow and adhesion.

Cleanability evaluation of ceramic glazes with nanometer far-infrared materials using contact angle measurement.

PubMed

Wang, Lijuan; Liang, Jinsheng; Di, Xingfu; Tang, Qingguo

2014-05-01

The cleanability of easy-to-clean ceramic glazes doped with nanometer far-infrared materials was compared with that of some high-quality household ceramic glazes from the market. The cleanability was evaluated by the contact angle measurement using a sessile drop method with a Dataphysics OCA-30 contact angle analyzer. The results showed that the difference of contact angles of water on the glazes before soiling and after cleaning could be used as a parameter for evaluating the cleanability of the glazes. The relationship between cleanability and surface properties, such as surface free energy and surface topography, was investigated. The surface free energy of the samples and their components were calculated using van Oss acid-base approach. By measuring advancing and receding contact angles, the contact angle hysteresis of the ceramic glazes due to the surface topography was investigated. It was shown that the cleanability of ceramic glazes containing nanometer far-infrared materials (NFIM) is better than that of household ceramic glazes from market, due to a higher ratio of electron-acceptor parameter to electron-donor parameter, which led to the effect of water hydration as well as better hydrophilic property and increased smoothness. The contact angle measurement not only accurately evaluates the cleanability of the ceramic glazes, but also has a contribution to the study of cleanability theory. Moreover, this method is simple, convenient and less sample-consumption.

Contact angle of sessile drops in Lennard-Jones systems.

PubMed

Becker, Stefan; Urbassek, Herbert M; Horsch, Martin; Hasse, Hans

2014-11-18

Molecular dynamics simulations are used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid-fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150,000 particles. For particle numbers below 10,000, a decrease of the contact angle is found. This is attributed to a dependence of the solid-liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid-fluid dispersive interaction energy at a contact angle of θ = 90° is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed that describes the contact angle as a function of the dispersive interaction, the temperature, and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term.

Contact angle measurement with a smartphone

NASA Astrophysics Data System (ADS)

Chen, H.; Muros-Cobos, Jesus L.; Amirfazli, A.

2018-03-01

In this study, a smartphone-based contact angle measurement instrument was developed. Compared with the traditional measurement instruments, this instrument has the advantage of simplicity, compact size, and portability. An automatic contact point detection algorithm was developed to allow the instrument to correctly detect the drop contact points. Two different contact angle calculation methods, Young-Laplace and polynomial fitting methods, were implemented in this instrument. The performance of this instrument was tested first with ideal synthetic drop profiles. It was shown that the accuracy of the new system with ideal synthetic drop profiles can reach 0.01% with both Young-Laplace and polynomial fitting methods. Conducting experiments to measure both static and dynamic (advancing and receding) contact angles with the developed instrument, we found that the smartphone-based instrument can provide accurate and practical measurement results as the traditional commercial instruments. The successful demonstration of use of a smartphone (mobile phone) to conduct contact angle measurement is a significant advancement in the field as it breaks the dominate mold of use of a computer and a bench bound setup for such systems since their appearance in 1980s.

Contact angle measurement with a smartphone.

PubMed

Chen, H; Muros-Cobos, Jesus L; Amirfazli, A

2018-03-01

In this study, a smartphone-based contact angle measurement instrument was developed. Compared with the traditional measurement instruments, this instrument has the advantage of simplicity, compact size, and portability. An automatic contact point detection algorithm was developed to allow the instrument to correctly detect the drop contact points. Two different contact angle calculation methods, Young-Laplace and polynomial fitting methods, were implemented in this instrument. The performance of this instrument was tested first with ideal synthetic drop profiles. It was shown that the accuracy of the new system with ideal synthetic drop profiles can reach 0.01% with both Young-Laplace and polynomial fitting methods. Conducting experiments to measure both static and dynamic (advancing and receding) contact angles with the developed instrument, we found that the smartphone-based instrument can provide accurate and practical measurement results as the traditional commercial instruments. The successful demonstration of use of a smartphone (mobile phone) to conduct contact angle measurement is a significant advancement in the field as it breaks the dominate mold of use of a computer and a bench bound setup for such systems since their appearance in 1980s.

Dynamic Contact Angle at the Nanoscale: A Unified View.

PubMed

Lukyanov, Alex V; Likhtman, Alexei E

2016-06-28

Generation of a dynamic contact angle in the course of wetting is a fundamental phenomenon of nature. Dynamic wetting processes have a direct impact on flows at the nanoscale, and therefore, understanding them is exceptionally important to emerging technologies. Here, we reveal the microscopic mechanism of dynamic contact angle generation. It has been demonstrated using large-scale molecular dynamics simulations of bead-spring model fluids that the main cause of local contact angle variations is the distribution of microscopic force acting at the contact line region. We were able to retrieve this elusive force with high accuracy. It has been directly established that the force distribution can be solely predicted on the basis of a general friction law for liquid flow at solid surfaces by Thompson and Troian. The relationship with the friction law provides both an explanation of the phenomenon of dynamic contact angle and a methodology for future predictions. The mechanism is intrinsically microscopic, universal, and irreducible and is applicable to a wide range of problems associated with wetting phenomena.

Failure Mechanisms of the Coating/Metal Interface in Waterborne Coatings: The Effect of Bonding

PubMed Central

Wan, Hongxia; Song, Dongdong; Li, Xiaogang; Zhang, Dawei; Gao, Jin; Du, Cuiwei

2017-01-01

Waterborne coating is the most popular type of coating, and improving its performance is a key point of research. Cathodic delamination is one of the major modes of failure for organic coatings. It refers to the weakening or loss of adhesion between the coating and substrate. Physical and chemical characteristics of coatings have been studied via scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and secondary ion mass spectrometry (SIMS). Early heterogeneous swelling at the metal-coating interface in non-defective coated metals was elucidated using frequency-dependent alternating-current scanning electrochemical microscopy. Two types of coatings (styrene-acrylic coating and terpolymer coating) were compared. The effects of thickness, surface roughness, and chemical bonding on cathodic delamination were investigated. PMID:28772757

Preparation and Characterization of Extruded Composites Based on Polypropylene and Chitosan Compatibilized with Polypropylene-Graft-Maleic Anhydride

PubMed Central

Carrasco-Guigón, Fernando Javier; Rodríguez-Félix, Dora Evelia; Castillo-Ortega, María Mónica; Santacruz-Ortega, Hisila C.; Burruel-Ibarra, Silvia E.; Encinas-Encinas, Jose Carmelo; Plascencia-Jatomea, Maribel; Herrera-Franco, Pedro Jesus; Madera-Santana, Tomas Jesus

2017-01-01

The preparation of composites of synthetic and natural polymers represent an interesting option to combine properties; in this manner, polypropylene and chitosan extruded films using a different proportion of components and polypropylene-graft-maleic anhydride (PPgMA) as compatibilizer were prepared. The effect of the content of the biopolymer in the polypropylene (PP) matrix, the addition of compatibilizer, and the particle size on the properties of the composites was analyzed using characterization by fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), tensile strength, and contact angle, finding that in general, the addition of the compatibilizer and reducing the particle size of the chitosan, favored the physicochemical and morphological properties of the films. PMID:28772464

Metal-organic framework superhydrophobic coating on Kevlar fabric with efficient drag reduction and wear resistance

NASA Astrophysics Data System (ADS)

Li, Deke; Guo, Zhiguang

2018-06-01

Superhydrophobic layers are extremely essential for protecting material surface in various applications. In this study, a stable superhydrophobic mixed matrix surface with a 152.2° contact angle can be fabricated through the technology of layer-by-layer hot-pressing (HoP), and then modified by 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) on the ZIF-8@Kevlar fabric surface. The morphology and chemical composition were analyzed by the means of SEM, XRD and FTIR. The obtained superhydrophobic coatings showed excellent antiwear performance and drag reduction under desired working conditions. Moreover, we successfully applied superhydrophobic F-ZIF-8@Kevlar fabric in the alcohol adsorbent with high removal capacity, and it can be reused for several times without serious efficiency loss.

Production and characterization of hydrophobic zinc borate by using palm oil

NASA Astrophysics Data System (ADS)

Acarali, Nil Baran; Tugrul, Nurcan; Derun, Emek Moroydor; Piskin, Sabriye

2013-11-01

Zinc borate (ZB) was synthesized using zinc oxide, boric acid synthesized from colemanite, and reference ZB as seed. The effects of reaction parameters such as reaction time, reactant ratio, and seed ratio on its yield were examined. Then, the effects of palm oil with solvents (isopropyl alcohol (IPA), ethanol, and methanol) added to the reaction on its hydrophobicity were explored. Reactions were carried out under determined reaction conditions with magnetically and mechanically stirred systems. The produced ZB was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and measurements of contact angle identified hydrophobicity. The results showed that hydrophobic ZB was successfully produced under determined reaction conditions. The change of process parameters influenced its yield and the usage of palm oil provided hydrophobicity.

A green synthesis method for large area silver thin film containing nanoparticles.

PubMed

Shinde, N M; Lokhande, A C; Lokhande, C D

2014-07-05

The green synthesis method is inexpensive and convenient for large area deposition of thin films. For the first time, a green synthesis method for large area silver thin film containing nanoparticles is reported. Silver nanostructured films are deposited using silver nitrate solution and guava leaves extract. The study confirmed that the reaction time plays a key role in the growth and shape/size control of silver nanoparticles. The properties of silver films are studied using UV-visible spectrophotometer, scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle, Fourier-transform Raman (FT-Raman) spectroscopy and Photoluminescence (PL) techniques. Finally, as an application, these films are used effectively in antibacterial activity study. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis and characterization of polyurethane-cellulose acetate blend membrane for chromium (VI) removal.

PubMed

Riaz, Tabinda; Ahmad, Adnan; Saleemi, Sidra; Adrees, Muhammad; Jamshed, Fahad; Hai, Abdul Moqeet; Jamil, Tahir

2016-11-20

Blended membranes of polyurethane and cellulose acetate were prepared, characterized and investigated for their performance. Various ratios of cellulose acetate were employed to prepare four different blend membranes. The characteristics of both pure and blend membranes were investigated and results were compared to distinguish their properties. Functional group analysis was carried out by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) of pure and blend samples. Contact angle measurement and water content were evaluated to determine the membrane hydrophilicity. Moreover, the membrane morphology was studied by scanning electron microscopy (SEM). The membrane permeation properties and ability to reject chromium (VI) ions were tested at various pH and pressure by utilizing different salt concentrations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Surface degradation of polymer insulators under accelerated climatic aging in weather-ometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, G.; McGrath, P.B.; Burns, C.W.

1996-12-31

Climatic aging experiments were conducted on two types of outdoor polymer insulators by using a programmable weather-ometer. The housing materials for the insulators were silicone rubber (SR) and ethylene propylene diene monomer (EPDM). The accelerated aging stresses were comprised of ultraviolet radiation, elevated temperature, temperature cycling, thermal shock and high humidity. Their effects on the insulator surface conditions and electrical performance wee examined through visual inspection and SEM studies, contact angle measurements, thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) analysis, and 50% impulse flashover voltage tests. The results showed a significant damage on the insulator surface caused by some ofmore » the imposed aging stresses. The EDS analysis suggested a photooxidation process that happened on the insulator surface during the aging period.« less

Gunshot residue patterns on skin in angled contact and near contact gunshot wounds.

PubMed

Plattner, T; Kneubuehl, B; Thali, M; Zollinger, U

2003-12-17

The goal of this study was the reproduction of shape and pattern of gunshot residues in near contact and contact gunshot wounds by a series of experimental gunshots on a skin and soft tissue model. The aim was to investigate the shape and direction of soot deposits with regard to the muzzle according to different muzzle-target angles, firing distances, type of ammunition and weapon and barrel length. Based on a review of the literature and on the results of the experiments the authors could make the following statements of gunshot residues in angled contact and close contact gunshot: (1) gunshot residues on the target surface can be differentiated in a "inner" and "outer powder soot zone"; (2) the outer powder soot zone is much less visible than the inner powder soot zone and may lack on human skin; (3) with increasing muzzle target distance both inner and outer powder soot halo increase in size and decrease in density; (4) in angled shots the inner powder soot halo shows an eccentric, elliptic shape which points towards the muzzle, regardless of ammunition, calibre and barrel length; (5) the outer powder soot points away from the muzzle in angled contact and close contact shots.

Wetting of biopolymer coatings: contact angle kinetics and image analysis investigation.

PubMed

Farris, Stefano; Introzzi, Laura; Biagioni, Paolo; Holz, Torsten; Schiraldi, Alberto; Piergiovanni, Luciano

2011-06-21

The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values (θ(0)) ranged from ∼91° for chitosan to ∼30° for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a three-parameter decay equation [θ(t) = θ(0) exp(kt(n))] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanism of surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses. © 2011 American Chemical Society

On the uniqueness of the receding contact angle: effects of substrate roughness and humidity on evaporation of water drops.

PubMed

Pittoni, Paola G; Lin, Chia-Hui; Yu, Teng-Shiang; Lin, Shi-Yow

2014-08-12

Could a unique receding contact angle be indicated for describing the wetting properties of a real gas-liquid-solid system? Could a receding contact angle be defined if the triple line of a sessile drop is not moving at all during the whole measurement process? To what extent is the receding contact angle influenced by the intrinsic properties of the system or the measurement procedures? In order to answer these questions, a systematic investigation was conducted in this study on the effects of substrate roughness and relative humidity on the behavior of pure water drops spreading and evaporating on polycarbonate (PC) surfaces characterized by different morphologies. Dynamic, advancing, and receding contact angles were found to be strongly affected by substrate roughness. Specifically, a receding contact angle could not be measured at all for drops evaporating on the more rugged PC surfaces, since the drops were observed strongly pinning to the substrate almost until their complete disappearance. Substrate roughness and system relative humidity were also found responsible for drastic changes in the depinning time (from ∼10 to ∼60 min). Thus, for measurement observations not sufficiently long, no movement of the triple line could be noted, with, again, the failure to find a receding contact angle. Therefore, to keep using concepts such as the receding contact angle as meaningful specifications of a given gas-liquid-solid system, the imperative to carefully investigate and report the inner characteristics of the system (substrate roughness, topography, impurities, defects, chemical properties, etc.) is pointed out in this study. The necessity of establishing methodological standards (drop size, measurement method, system history, observation interval, relative humidity, etc.) is also suggested.

Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

NASA Astrophysics Data System (ADS)

Polkowski, Wojciech; Sobczak, Natalia; Nowak, Rafał; Kudyba, Artur; Bruzda, Grzegorz; Polkowska, Adelajda; Homa, Marta; Turalska, Patrycja; Tangstad, Merete; Safarian, Jafar; Moosavi-Khoonsari, Elmira; Datas, Alejandro

2017-12-01

For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism.

Anomalous contact angle hysteresis of a captive bubble: advancing contact line pinning.

PubMed

Hong, Siang-Jie; Chang, Feng-Ming; Chou, Tung-He; Chan, Seong Heng; Sheng, Yu-Jane; Tsao, Heng-Kwong

2011-06-07

Contact angle hysteresis of a sessile drop on a substrate consists of continuous invasion of liquid phase with the advancing angle (θ(a)) and contact line pinning of liquid phase retreat until the receding angle (θ(r)) is reached. Receding pinning is generally attributed to localized defects that are more wettable than the rest of the surface. However, the defect model cannot explain advancing pinning of liquid phase invasion driven by a deflating bubble and continuous retreat of liquid phase driven by the inflating bubble. A simple thermodynamic model based on adhesion hysteresis is proposed to explain anomalous contact angle hysteresis of a captive bubble quantitatively. The adhesion model involves two solid–liquid interfacial tensions (γ(sl) > γ(sl)′). Young’s equation with γ(sl) gives the advancing angle θ(a) while that with γ(sl)′ due to surface rearrangement yields the receding angle θ(r). Our analytical analysis indicates that contact line pinning represents frustration in surface free energy, and the equilibrium shape corresponds to a nondifferential minimum instead of a local minimum. On the basis of our thermodynamic model, Surface Evolver simulations are performed to reproduce both advancing and receding behavior associated with a captive bubble on the acrylic glass.

A Langevin model for fluctuating contact angle behaviour parametrised using molecular dynamics.

PubMed

Smith, E R; Müller, E A; Craster, R V; Matar, O K

2016-12-06

Molecular dynamics simulations are employed to develop a theoretical model to predict the fluid-solid contact angle as a function of wall-sliding speed incorporating thermal fluctuations. A liquid bridge between counter-sliding walls is studied, with liquid-vapour interface-tracking, to explore the impact of wall-sliding speed on contact angle. The behaviour of the macroscopic contact angle varies linearly over a range of capillary numbers beyond which the liquid bridge pinches off, a behaviour supported by experimental results. Nonetheless, the liquid bridge provides an ideal test case to study molecular scale thermal fluctuations, which are shown to be well described by Gaussian distributions. A Langevin model for contact angle is parametrised to incorporate the mean, fluctuation and auto-correlations over a range of sliding speeds and temperatures. The resulting equations can be used as a proxy for the fully-detailed molecular dynamics simulation allowing them to be integrated within a continuum-scale solver.

Visualization of the equilibrium position of colloidal particles at fluid-water interfaces by deposition of nanoparticles

NASA Astrophysics Data System (ADS)

Sabapathy, Manigandan; Kollabattula, Viswas; Basavaraj, Madivala G.; Mani, Ethayaraja

2015-08-01

We present a general yet simple method to measure the contact angle of colloidal particles at fluid-water interfaces. In this method, the particles are spread at the required fluid-water interface as a monolayer. In the water phase a chemical reaction involving reduction of a metal salt such as aurochloric acid is initiated. The metal grows as a thin film or islands of nanoparticles on the particle surface exposed to the water side of the interface. Analyzing the images of particles by high resolution scanning microscopy (HRSEM), we trace the three phase contact line up to which deposition of the metal film occurs. From geometrical relations, the three phase contact angle is then calculated. We report the measurements of the contact angle of silica and polystyrene (PS) particles at different interfaces such as air-water, decane-water and octanol-water. We have also applied this method to measure the contact angle of surfactant treated polystyrene particles at the air-water interface, and we find a non-monotonic change of the contact angle with the concentration of the surfactant. Our results are compared with the well-known gel trapping technique and we find good comparison with previous measurements.We present a general yet simple method to measure the contact angle of colloidal particles at fluid-water interfaces. In this method, the particles are spread at the required fluid-water interface as a monolayer. In the water phase a chemical reaction involving reduction of a metal salt such as aurochloric acid is initiated. The metal grows as a thin film or islands of nanoparticles on the particle surface exposed to the water side of the interface. Analyzing the images of particles by high resolution scanning microscopy (HRSEM), we trace the three phase contact line up to which deposition of the metal film occurs. From geometrical relations, the three phase contact angle is then calculated. We report the measurements of the contact angle of silica and polystyrene (PS) particles at different interfaces such as air-water, decane-water and octanol-water. We have also applied this method to measure the contact angle of surfactant treated polystyrene particles at the air-water interface, and we find a non-monotonic change of the contact angle with the concentration of the surfactant. Our results are compared with the well-known gel trapping technique and we find good comparison with previous measurements. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03369a

Contact angle hysteresis on superhydrophobic stripes.

PubMed

Dubov, Alexander L; Mourran, Ahmed; Möller, Martin; Vinogradova, Olga I

2014-08-21

We study experimentally and discuss quantitatively the contact angle hysteresis on striped superhydrophobic surfaces as a function of a solid fraction, ϕS. It is shown that the receding regime is determined by a longitudinal sliding motion of the deformed contact line. Despite an anisotropy of the texture the receding contact angle remains isotropic, i.e., is practically the same in the longitudinal and transverse directions. The cosine of the receding angle grows nonlinearly with ϕS. To interpret this we develop a theoretical model, which shows that the value of the receding angle depends both on weak defects at smooth solid areas and on the strong defects due to the elastic energy of the deformed contact line, which scales as ϕS(2)lnϕS. The advancing contact angle was found to be anisotropic, except in a dilute regime, and its value is shown to be determined by the rolling motion of the drop. The cosine of the longitudinal advancing angle depends linearly on ϕS, but a satisfactory fit to the data can only be provided if we generalize the Cassie equation to account for weak defects. The cosine of the transverse advancing angle is much smaller and is maximized at ϕS ≃ 0.5. An explanation of its value can be obtained if we invoke an additional energy due to strong defects in this direction, which is shown to be caused by the adhesion of the drop on solid sectors and is proportional to ϕS(2). Finally, the contact angle hysteresis is found to be quite large and generally anisotropic, but it becomes isotropic when ϕS ≤ 0.2.

Wetting of soap bubbles on hydrophilic, hydrophobic, and superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Arscott, Steve

2013-06-01

Wetting of sessile bubbles on various wetting surfaces (solid and liquid) has been studied. A model is presented for the apparent contact angle of a sessile bubble based on a modified Young's equation--the experimental results agree with the model. Wetting a hydrophilic surface results in a bubble contact angle of 90° whereas using a superhydrophobic surface one observes 134°. For hydrophilic surfaces, the bubble angle diminishes with bubble radius whereas on a superhydrophobic surface, the bubble angle increases. The size of the plateau borders governs the bubble contact angle, depending on the wetting of the surface.

Estimation of bearing contact angle in-situ by X-ray kinematography

NASA Technical Reports Server (NTRS)

Fowler, P. H.; Manders, F.

1982-01-01

The mounted, preloaded contact angle of the structural bearings in the assembled design mechanical assembly was measured. A modification of the Turns method is presented, based upon the clarity and definition of moving parts achieved with X-ray technique and cinematic display. Contact angle is estimated by counting the number of bearings passing a given point as a function of number of turns of the shaft. Ball and pitch diameter variations are discussed. Ball train and shaft angle uncertainties are also discussed.

Superhydrophobic floatability of a hydrophilic object driven by edge effect

NASA Astrophysics Data System (ADS)

Chang, Feng-Ming; Sheng, Yu-Jane; Tsao, Heng-Kwong

2009-11-01

It is generally believed that a water-repellent surface is necessary for small insects to stand on water. Through a combined experimental and theoretical study, we demonstrate that an object with hydrophilic surface can float with apparent contact angle greater than 90° due to edge effect. The apparent contact angle rises with increasing loading even to a value typically displayed only by superhydrophobic surfaces. On the basis of free energy minimization, two regimes are identified. When buoyancy controls, the meniscus meets the object with the intrinsic contact angle. As surface tension dominates, however, contact angle is regulated by total force balance.

Repulsion-based model for contact angle saturation in electrowetting

PubMed Central

2015-01-01

We introduce a new model for contact angle saturation phenomenon in electrowetting on dielectric systems. This new model attributes contact angle saturation to repulsion between trapped charges on the cap and base surfaces of the droplet in the vicinity of the three-phase contact line, which prevents these surfaces from converging during contact angle reduction. This repulsion-based saturation is similar to repulsion between charges accumulated on the surfaces of conducting droplets which causes the well known Coulombic fission and Taylor cone formation phenomena. In our model, both the droplet and dielectric coating were treated as lossy dielectric media (i.e., having finite electrical conductivities and permittivities) contrary to the more common assumption of a perfectly conducting droplet and perfectly insulating dielectric. We used theoretical analysis and numerical simulations to find actual charge distribution on droplet surface, calculate repulsion energy, and minimize energy of the total system as a function of droplet contact angle. Resulting saturation curves were in good agreement with previously reported experimental results. We used this proposed model to predict effect of changing liquid properties, such as electrical conductivity, and system parameters, such as thickness of the dielectric layer, on the saturation angle, which also matched experimental results. PMID:25759748

Fabrication of zero contact angle ultra-super hydrophilic surfaces.

PubMed

Jothi Prakash, C G; Clement Raj, C; Prasanth, R

2017-06-15

Zero contact angle surfaces have been created with the combined effect of nanostructure and UV illumination. The contact angle of titanium surface has been optimized to 3.25°±1°. with nanotubular structures through electrochemical surface modification. The porosity and surface energy of tubular TiO 2 layer play critical role over the surface wettability and the hydrophilicity of the surface. The surface free energy has been enhanced from 23.72mJ/m 2 (bare titanium surface) to 87.11mJ/m 2 (nanotubular surface). Similar surface with TiO 2 nanoparticles coating shows superhydrophilicity with contact angle up to 5.63°±0.95°. This implies liquid imbibition and surface curvature play a crucial role in surface hydrophilicity. The contact angle has been further reduced to 0°±0.86° by illuminating the surface with UV radiation. Results shows that by tuning the nanotube morphology, highly porous surfaces can be fabricated to reduce contact angle and enhance wettability. This study provides an insight into the inter-relationship between surface structural factors and ultra-superhydrophilic surfaces which can help to optimize thermal hydraulic and self cleaning surfaces. Copyright © 2017. Published by Elsevier Inc.

Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

PubMed

Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

2015-12-15

Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

Repulsion-based model for contact angle saturation in electrowetting.

PubMed

Ali, Hassan Abdelmoumen Abdellah; Mohamed, Hany Ahmed; Abdelgawad, Mohamed

2015-01-01

We introduce a new model for contact angle saturation phenomenon in electrowetting on dielectric systems. This new model attributes contact angle saturation to repulsion between trapped charges on the cap and base surfaces of the droplet in the vicinity of the three-phase contact line, which prevents these surfaces from converging during contact angle reduction. This repulsion-based saturation is similar to repulsion between charges accumulated on the surfaces of conducting droplets which causes the well known Coulombic fission and Taylor cone formation phenomena. In our model, both the droplet and dielectric coating were treated as lossy dielectric media (i.e., having finite electrical conductivities and permittivities) contrary to the more common assumption of a perfectly conducting droplet and perfectly insulating dielectric. We used theoretical analysis and numerical simulations to find actual charge distribution on droplet surface, calculate repulsion energy, and minimize energy of the total system as a function of droplet contact angle. Resulting saturation curves were in good agreement with previously reported experimental results. We used this proposed model to predict effect of changing liquid properties, such as electrical conductivity, and system parameters, such as thickness of the dielectric layer, on the saturation angle, which also matched experimental results.

Preparation, anti-biofouling and drag-reduction properties of a biomimetic shark skin surface

PubMed Central

Pu, Xia; Li, Guangji; Huang, Hanlu

2016-01-01

ABSTRACT Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydrophobic mechanism of the shark skin surface microstructure, the effect of biomimetic shark skin surface microstructure on surface wettability was evaluated by recording water contact angle. Additionally, protein adhesion experiments and anti-algae adhesion performance testing experiments were used to investigate and evaluate the anti-biofouling properties of the surface microstructure of biomimetic shark skin. The recorded values of the water contact angle of differently microstructured surfaces revealed that specific microstructures have certain effects on surface wettability. The anti-biofouling properties of the biomimetic shark skin surface with microstructures were superior to a smooth surface using the same polymers as substrates. Moreover, the air layer fixed on the surface of the biomimetic shark skin was found to play a key role in their antibiont adhesion property. An experiment into drag reduction was also conducted. Based on the experimental results, the microstructured surface of the prepared biomimetic shark skin played a significant role in reducing drag. The maximum of drag reduction rate is 12.5%, which is higher than the corresponding maximum drag reduction rate of membrane material with a smooth surface. PMID:26941105

Preparation, anti-biofouling and drag-reduction properties of a biomimetic shark skin surface.

PubMed

Pu, Xia; Li, Guangji; Huang, Hanlu

2016-04-15

Shark skin surfaces show non-smoothness characteristics due to the presence of a riblet structure. In this study, biomimetic shark skin was prepared by using the polydimethylsiloxane (PDMS)-embedded elastomeric stamping (PEES) method. Scanning electron microscopy (SEM) was used to examine the surface microstructure and fine structure of shark skin and biomimetic shark skin. To analyse the hydrophobic mechanism of the shark skin surface microstructure, the effect of biomimetic shark skin surface microstructure on surface wettability was evaluated by recording water contact angle. Additionally, protein adhesion experiments and anti-algae adhesion performance testing experiments were used to investigate and evaluate the anti-biofouling properties of the surface microstructure of biomimetic shark skin. The recorded values of the water contact angle of differently microstructured surfaces revealed that specific microstructures have certain effects on surface wettability. The anti-biofouling properties of the biomimetic shark skin surface with microstructures were superior to a smooth surface using the same polymers as substrates. Moreover, the air layer fixed on the surface of the biomimetic shark skin was found to play a key role in their antibiont adhesion property. An experiment into drag reduction was also conducted. Based on the experimental results, the microstructured surface of the prepared biomimetic shark skin played a significant role in reducing drag. The maximum of drag reduction rate is 12.5%, which is higher than the corresponding maximum drag reduction rate of membrane material with a smooth surface. © 2016. Published by The Company of Biologists Ltd.

Surface analysis and mechanical behaviour mapping of vertically aligned CNT forest array through nanoindentation

NASA Astrophysics Data System (ADS)

Koumoulos, Elias P.; Charitidis, C. A.

2017-02-01

Carbon nanotube (CNT) based architectures have increased the scientific interest owning to their exceptional performance rendering them promising candidates for advanced industrial applications in the nanotechnology field. Despite individual CNTs being considered as one of the most known strong materials, much less is known about other CNT forms, such as CNT arrays, in terms of their mechanical performance (integrity). In this work, thermal chemical vapor deposition (CVD) method is employed to produce vertically aligned multiwall (VA-MW) CNT carpets. Their structural properties were studied by means of scanning electron microscopy (SEM), X-Ray diffraction (XRD) and Raman spectroscopy, while their hydrophobic behavior was investigated via contact angle measurements. The resistance to indentation deformation of VA-MWCNT carpets was investigated through nanoindentation technique. The synthesized VA-MWCNTs carpets consisted of well-aligned MWCNTs. Static contact angle measurements were performed with water and glycerol, revealing a rather super-hydrophobic behavior. The structural analysis, hydrophobic behavior and indentation response of VA-MWCNTs carpets synthesized via CVD method are clearly demonstrated. Additionally, cycle indentation load-depth curve was applied and hysteresis loops were observed in the indenter loading-unloading cycle due to the local stress distribution. Hardness (as resistance to applied load) and modulus mapping, at 200 nm of displacement for a grid of 70 μm2 is presented. Through trajection, the resistance is clearly divided in 2 regions, namely the MWCNT probing and the in-between area MWCNT - MWCNT interface.

[Preparation of poly(methyl acrylate) microfluidic chips surface-modified by hyperbranched polyamide ester and their application in the separation of biomolecules].

PubMed

Liu, Bing; Lin, Donge; Xu, Lin; Lei, Yanhui; Bo, Qianglong; Shou, Chongqi

2012-05-01

The surface of poly (methyl acrylate) (PMMA) microfluidic chips were modified using hyperbranched polyamide ester via chemical bonding. The contact angles of the modified chips were measured. The surface morphology was observed by scanning electron microscope (SEM) and stereo microscope. The results showed that the surface of the modified chips was coated by a dense, uniform, continuous, hydrophilic layer of hyperbranched polyamide ester. The hydrophilic of the chip surface was markedly improved. The contact angle of the chips modified decreased from 89.9 degrees to 29.5 degrees. The electro osmotic flow (EOF) in the modified microchannel was lower than that in the unmodified microchannel. Adenosine and L-lysine were detected and separated via the modified PMMA microfluidic chips. Compared with unmodified chips, the modified chips successfully separated the two biomolecules. The detection peaks were clear and sharp. The separation efficiencies of adenosine and L-lysine were 8.44 x 10(4) plates/m and 9.82 x 10(4) plates/m respectively, and the resolutions (Rs) was 5.31. The column efficiencies and resolutions of the modified chips were much higher than those of the unmodified chips. It was also observed that the modified chips possessed good reproducibility of migration time. This research may provide a new and effective method to improve the hydrophilicity of the PMMA surface and the application of PMMA microfluidic chips in the determination of trace biomolecules.

Comparison of self-cleaning properties of three titania coatings on float glass

NASA Astrophysics Data System (ADS)

Piispanen, Minna; Hupa, Leena

2011-11-01

This work compares the self-cleaning properties of experimental TiO2 and TiO2-Ag coatings on float glass with a commercial self-cleaning glass. In the experimental surfaces, TiO2 coating was applied to float glass via the sol-gel route, while TiO2-Ag coating was applied by the liquid flame spray method, which deposits TiO2-Ag composite nanoparticles on the surface. The effect of the coatings on the surface wettability and the activation time for achieving hydrophilicity was studied through water contact angle as a function of exposure time to UV light. The surface morphology was investigated by using scanning electron microscopy (SEM) and confocal optical microscopy. The photocatalytic activity of the coatings was examined with methylene blue and stearic acid degradation tests. Finally, the soil attachment to the surfaces was tested with a sebum-based model soil. The sol-gel TiO2 coating became superhydrophilic within a few hours, while the activation time needed for the commercial titania coated glass was several days. The surface with the TiO2-Ag nanoparticles did not show any marked changes in the water contact angle. The commercial titania coated and the sol-gel TiO2 surfaces showed self-cleaning properties and clearly lower attachment of soil than the uncoated and TiO2-Ag coated surfaces. The difference in the interaction of the surfaces with the organic contaminants was assumed to depend mainly on differences in the thickness of the coatings.

Flower-Like CuO/ZnO Hybrid Hierarchical Nanostructures Grown on Copper Substrate: Glycothermal Synthesis, Characterization, Hydrophobic and Anticorrosion Properties

PubMed Central

Beshkar, Farshad; Khojasteh, Hossein; Salavati-Niasari, Masoud

2017-01-01

In this work we have demonstrated a facile formation of CuO nanostructures on copper substrates by the oxidation of copper foil in ethylene glycol (EG) at 80 °C. On immersing a prepared CuO film into a solution containing 0.1 g Zn(acac)2 in 20 mL EG for 8 h, ZnO flower-like microstructures composed of hierarchical three-dimensional (3D) aggregated nanoparticles and spherical architectures were spontaneously formed at 100 °C. The as-synthesized thin films and 3D microstructures were characterized using XRD, SEM, and EDS techniques. The effects of sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG) 6000 as surfactants and stabilizers on the morphology of the CuO and ZnO structures were discussed. Possible growth mechanisms for the controlled organization of primary building units into CuO nanostructures and 3D flower-like ZnO architectures were proposed. The hydrophobic property of the products was characterized by means of water contact angle measurement. After simple surface modification with stearic acid and PDMS, the resulting films showed hydrophobic and even superhydrophobic characteristics due to their special surface energy and nano-microstructure morphology. Importantly, stable superhydrophobicity with a contact angle of 153.5° was successfully observed for CuO-ZnO microflowers after modification with PDMS. The electrochemical impedance measurements proved that the anticorrosion efficiency for the CuO/ZnO/PDMS sample was about 99%. PMID:28773056

Investigating the Synthesis and Characterization of a Novel "Green" H₂O₂-Assisted, Water-Soluble Chitosan/Polyvinyl Alcohol Nanofiber for Environmental End Uses.

PubMed

Pervez, Md Nahid; Stylios, George K

2018-06-01

The present work highlights the formation of a novel green nanofiber based on H₂O₂-assisted water-soluble chitosan/polyvinyl alcohol (W S CHT/PVA) by using water as an ecofriendly solvent and genipin used as a nontoxic cross-linker. The 20/80 blend ratio was found to have the most optimum uniform fiber morphology. W S CHT retained the same structure as W IS CHT. The prepared nanofibers were characterized by Scanning electron microscopy (SEM), Fourier transform spectroscopy (FTIR), Thermo gravimetric analysis (TGA), Differential scanning calorimeter (DSC), X-ray diffraction (XRD), Water Contact Angle (WCA) and Ultraviolet-visible spectroscopy (UV-vis). During electrospinning, the crystalline microstructure of the W S CHT/PVA underwent better solidification and after cross-linking there was an increase in the melting temperature of the fiber. Swelling ratio studies revealed noticeable increase in hydrophilicity with increase of W S CHT, which was further demonstrated by the decrease of contact angle from 64.74° to 14.68°. W S CHT/PVA nanofiber mats exhibit excellent UV blocking protection with less than 5% transmittance value and also showed improved in vitro drug release properties with stable release for longer duration (cross-linked fibers) and burst release for shorter duration (uncross linked) fibers. Finally our experimental data demonstrates excellent adsorption ability of Colour Index (C.I.) reactive black 5 (RB5) due to protonated amino groups.

Physicochemical and bioactive properties of innovative resin-based materials containing functional halloysite-nanotubes fillers.

PubMed

Degrazia, Felipe Weidenbach; Leitune, Vicente Castelo Branco; Takimi, Antonio Shigueaki; Collares, Fabrício Mezzomo; Sauro, Salvatore

2016-09-01

This study aimed to assess the degree of conversion, microhardness, solvent degradation, contact angle, surface free energy and bioactivity (e.g., mineral precipitation) of experimental resin-based materials containing, pure or triclosan-encapsulated, aluminosilicate-(halloysite) nanotubes. An experimental resin blend was prepared using bis-GMA/TEGDMA, 75/25wt% (control). Halloysite nanotubes (HNT) doped with or without triclosan (TCN) were first analyzed using transmission electron microscopy (TEM). HNT or HNT/TCN fillers were incorporated into the resin blend at different concentrations (5, 10, and 20wt%). Seven experimental resins were created and the degree of conversion, microhardness, solvent degradation and contact angle were assessed. Bioactive mineral precipitation induced by the experimental resins was evaluated through Raman spectroscopy and SEM-EDX. TEM showed a clear presence of TCN particles inside the tubular lumen and along the outer surfaces of the halloysite nanotubes. The degree of conversion, surface free energy, microhardness, and mineral deposition of polymers increased with higher amount of HNTs. Conversely, the higher the amount (20wt%) of TCN-loaded HNTs the lower the microhardness of the experimental resins. The incorporation of pure or TCN-loaded aluminosilicate-(halloysite) nanotubes into resin-based materials increase the bioactivity of such experimental restorative materials and promotes mineral deposition. Therefore, innovative resin-based materials containing functional halloysite-nanotube fillers may represent a valuable alternative for therapeutic minimally invasive treatments. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Flower-Like CuO/ZnO Hybrid Hierarchical Nanostructures Grown on Copper Substrate: Glycothermal Synthesis, Characterization, Hydrophobic and Anticorrosion Properties.

PubMed

Beshkar, Farshad; Khojasteh, Hossein; Salavati-Niasari, Masoud

2017-06-25

In this work we have demonstrated a facile formation of CuO nanostructures on copper substrates by the oxidation of copper foil in ethylene glycol (EG) at 80 °C. On immersing a prepared CuO film into a solution containing 0.1 g Zn(acac)₂ in 20 mL EG for 8 h, ZnO flower-like microstructures composed of hierarchical three-dimensional (3D) aggregated nanoparticles and spherical architectures were spontaneously formed at 100 °C. The as-synthesized thin films and 3D microstructures were characterized using XRD, SEM, and EDS techniques. The effects of sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG) 6000 as surfactants and stabilizers on the morphology of the CuO and ZnO structures were discussed. Possible growth mechanisms for the controlled organization of primary building units into CuO nanostructures and 3D flower-like ZnO architectures were proposed. The hydrophobic property of the products was characterized by means of water contact angle measurement. After simple surface modification with stearic acid and PDMS, the resulting films showed hydrophobic and even superhydrophobic characteristics due to their special surface energy and nano-microstructure morphology. Importantly, stable superhydrophobicity with a contact angle of 153.5° was successfully observed for CuO-ZnO microflowers after modification with PDMS. The electrochemical impedance measurements proved that the anticorrosion efficiency for the CuO/ZnO/PDMS sample was about 99%.

How pinning and contact angle hysteresis govern quasi-static liquid drop transfer.

PubMed

Chen, H; Tang, T; Zhao, H; Law, K-Y; Amirfazli, A

2016-02-21

This paper presents both experimental and numerical simulations of liquid transfer between two solid surfaces with contact angle hysteresis (CAH). Systematic studies on the role of the advancing contact angle (θa), receding contact angle (θr) and CAH in determining the transfer ratio (volume of the liquid transferred onto the acceptor surface over the total liquid volume) and the maximum adhesion force (Fmax) were performed. The transfer ratio was found to be governed by contact line pinning at the end of the transfer process caused by CAH of surfaces. A map based on θr of the two surfaces was generated to identify the three regimes for liquid transfer: (I) contact line pinning occurs only on the donor surface, (II) contact line pinning occurs on both surfaces, and (III) contact line pinning occurs only on the acceptor surface. With this map, an empirical equation is provided which is able to estimate the transfer ratio by only knowing θr of the two surfaces. The value of Fmax is found to be strongly influenced by the contact line pinning in the early stretching stage. For symmetric liquid bridges between two identical surfaces, Fmax may be determined only by θa, only by θr, or by both θa and θr, depending on the magnitude of the contact angles. For asymmetric bridges, Fmax is found to be affected by the period when contact lines are pinned on both surfaces.

Fabrication and characterization of biomaterial film from gland silk of muga and eri silkworms.

PubMed

Dutta, Saranga; Talukdar, Bijit; Bharali, Rupjyoti; Rajkhowa, Rangam; Devi, Dipali

2013-05-01

This study discusses the possibilities of liquid silk (Silk gland silk) of Muga and Eri silk, the indigenous non mulberry silkworms of North Eastern region of India, as potential biomaterials. Silk protein fibroin of Bombyx mori, commonly known as mulberry silkworm, has been extensively studied as a versatile biomaterial. As properties of different silk-based biomaterials vary significantly, it is important to characterize the non mulberry silkworms also in this aspect. Fibroin was extracted from the posterior silk gland of full grown fifth instars larvae, and 2D film was fabricated using standard methods. The films were characterized using SEM, Dynamic contact angle test, FTIR, XRD, DSC, and TGA and compared with respective silk fibers. SEM images of films reveal presence of some globules and filamentous structure. Films of both the silkworms were found to be amorphous with random coil conformation, hydrophobic in nature, and resistant to organic solvents. Non mulberry silk films had higher thermal resistance than mulberry silk. Fibers were thermally more stable than the films. This study provides insight into the new arena of research in application of liquid silk of non mulberry silkworms as biomaterials. Copyright © 2012 Wiley Periodicals, Inc.

O electrolyte for bio-application

NASA Astrophysics Data System (ADS)

Naddaf, M.; Almariri, A.

2014-09-01

Porous silicon (PS) has been prepared in the dark by anodic etching of n+-type (111) silicon substrate in a HF:HCl:C2H5OH:H2O2:H2O electrolyte. The processed PS layer is characterized by means of photoluminescence (PL) spectroscopy, scanning electron microscope (SEM), water contact angle (CA) measurements, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and micro-Raman scattering. The CA of fresh PS layer is found to be ~142°. On aging at ambient conditions, the CA decreases gently to reach ~133° after 3 month, and then it is stabilized for a prolonged time of aging. The visible PL emission from the PS layer also exhibits a good stability against aging time. The FTIR and XPS measurements and analysis show that the stable aged PS layer has rather SiO2-rich surface. The micro/nanostructure nature of the PS layer is revealed from SEM and micro-Raman results and correlated to CA results. Stable hydrophobic surface of oxidized PS layer is attractive for bio-applications. The efficiency of the produced PS layers as an entrapping template for specific immobilization of IgG2a antibody via physical absorption process is demonstrated.

Improved wettability and adhesion of polylactic acid/chitosan coating for bio-based multilayer film development

NASA Astrophysics Data System (ADS)

Gartner, Hunter; Li, Yana; Almenar, Eva

2015-03-01

The objective of this study was to investigate the effect of methyldiphenyl diisocyanate (MDI) concentration (0, 0.2, 1, 2, and 3%) on the wettability and adhesion of blend solutions of poly(lactic acid) (PLA) and chitosan (CS) when coated on PLA film for development of a bio-based multi-layer film suitable for food packaging and other applications. Characterization was carried out by attenuated total reflectance infrared spectrometry (ATR-FTIR), contact angle (θ), mechanical adhesion pull-off testing, and scanning electron microscopy (SEM). The θ of the PLA/CS blend shifted to a lower value (41-35°) with increasing MDI concentration showing that the surface tension was modified between the PLA/CS blend solution and PLA film and better wettability was achieved. The increase in MDI also resulted in an increased breaking strength (228-303 kPa) due to the increased H-bonding resulting from the more urethane groups formed within the PLA/CS blend as shown by ATR-FTIR. The improved adhesion was also shown by the increased number of physical entanglements observed by SEM. It can be concluded that MDI can be used to improve wettability and adhesion between PLA/CS coating and PLA film.

A study of the physical, chemical and biological properties of TiO2 coatings produced by micro-arc oxidation in a Ca-P-based electrolyte.

PubMed

dos Santos, Amanda; Araujo, Joyce R; Landi, Sandra M; Kuznetsov, Alexei; Granjeiro, José M; de Sena, Lidia Ágata; Achete, Carlos Alberto

2014-07-01

In this work, a porous and homogeneous titanium dioxide layer was grown on commercially pure titanium substrate using a micro-arc oxidation (MAO) process and Ca-P-based electrolyte. The structure and morphology of the TiO2 coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and profilometry. The chemical properties were studied using electron dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy. The wettability of the coating was evaluated using contact angle measurements. During the MAO process, Ca and P ions were incorporated into the oxide layer. The TiO2 coating was composed of a mixture of crystalline and amorphous structures. The crystalline part of the sample consisted of a major anatase phase and a minor rutile phase. A cross-sectional image of the coating-substrate interface reveals the presence of voids elongated along the interface. An osteoblast culture was performed to verify the cytocompatibility of the anodized surface. The results of the cytotoxicity tests show satisfactory cell viability of the titanium dioxide films produced in this study.

SD-SEM: sparse-dense correspondence for 3D reconstruction of microscopic samples.

PubMed

Baghaie, Ahmadreza; Tafti, Ahmad P; Owen, Heather A; D'Souza, Roshan M; Yu, Zeyun

2017-06-01

Scanning electron microscopy (SEM) imaging has been a principal component of many studies in biomedical, mechanical, and materials sciences since its emergence. Despite the high resolution of captured images, they remain two-dimensional (2D). In this work, a novel framework using sparse-dense correspondence is introduced and investigated for 3D reconstruction of stereo SEM images. SEM micrographs from microscopic samples are captured by tilting the specimen stage by a known angle. The pair of SEM micrographs is then rectified using sparse scale invariant feature transform (SIFT) features/descriptors and a contrario RANSAC for matching outlier removal to ensure a gross horizontal displacement between corresponding points. This is followed by dense correspondence estimation using dense SIFT descriptors and employing a factor graph representation of the energy minimization functional and loopy belief propagation (LBP) as means of optimization. Given the pixel-by-pixel correspondence and the tilt angle of the specimen stage during the acquisition of micrographs, depth can be recovered. Extensive tests reveal the strength of the proposed method for high-quality reconstruction of microscopic samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

Flow Visualization in Evaporating Liquid Drops and Measurement of Dynamic Contact Angles and Spreading Rate

NASA Technical Reports Server (NTRS)

Zhang, Neng-Li; Chao, David F.

2001-01-01

A new hybrid optical system, consisting of reflection-refracted shadowgraphy and top-view photography, is used to visualize flow phenomena and simultaneously measure the spreading and instant dynamic contact angle in a volatile-liquid drop on a nontransparent substrate. Thermocapillary convection in the drop, induced by evaporation, and the drop real-time profile data are synchronously recorded by video recording systems. Experimental results obtained from this unique technique clearly reveal that thermocapillary convection strongly affects the spreading process and the characteristics of dynamic contact angle of the drop. Comprehensive information of a sessile drop, including the local contact angle along the periphery, the instability of the three-phase contact line, and the deformation of the drop shape is obtained and analyzed.

Transmittance of transparent windows with non-absorbing cap-shaped droplets condensed on their backside

NASA Astrophysics Data System (ADS)

Zhu, Keyong; Huang, Yong; Pruvost, Jeremy; Legrand, Jack; Pilon, Laurent

2017-06-01

This study aims to quantify systematically the effect of non-absorbing cap-shaped droplets condensed on the backside of transparent windows on their directional-hemispherical transmittance and reflectance. Condensed water droplets have been blamed to reduce light transfer through windows in greenhouses, solar desalination plants, and photobioreactors. Here, the directional-hemispherical transmittance was predicted by Monte Carlo ray-tracing method. For the first time, both monodisperse and polydisperse droplets were considered, with contact angle between 0 and 180°, arranged either in an ordered hexagonal pattern or randomly distributed on the window backside with projected surface area coverage between 0 and 90%. The directional-hemispherical transmittance was found to be independent of the size and spatial distributions of the droplets. Instead, it depended on (i) the incident angle, (ii) the optical properties of the window and droplets, and on (iii) the droplet contact angle and (iv) projected surface area coverage. In fact, the directional-hemispherical transmittance decreased with increasing incident angle. Four optical regimes were identified in the normal-hemispherical transmittance. It was nearly constant for droplet contact angles either smaller than the critical angle θcr (predicted by Snell's law) for total internal reflection at the droplet/air interface or larger than 180°-θcr. However, between these critical contact angles, the normal-hemispherical transmittance decreased rapidly to reach a minimum at 90° and increased rapidly with increasing contact angles up to 180°-θcr. This was attributed to total internal reflection at the droplet/air interface which led to increasing reflectance. In addition, the normal-hemispherical transmittance increased slightly with increasing projected surface area coverage for contact angle was smaller than θcr. However, it decreased monotonously with increasing droplet projected surface area coverage for contact angle larger than θcr. These results can be used to select the material or surface coating with advantageous surface properties for applications when dropwise condensation may otherwise have a negative effect on light transmittance.

Angle-resolved reflection spectroscopy of high-quality PMMA opal crystal

NASA Astrophysics Data System (ADS)

Nemtsev, Ivan V.; Tambasov, Igor A.; Ivanenko, Alexander A.; Zyryanov, Victor Ya.

2018-02-01

PMMA opal crystal was prepared by a simple hybrid method, which includes sedimentation, meniscus formation and evaporation. We investigated three surfaces of this crystal by angle-resolved reflective light spectroscopy and SEM study. The angle-resolved reflective measurements were carried out in the 400-1100 nm range. We have determined the high-quality ordered surface of the crystal region. Narrow particle size distribution of the surface has been revealed. The average particle diameter obtained with SEM was nearly 361 nm. The most interesting result was that reflectivity of the surface turned out up to 98% at normal light incidence. Using a fit of dependences of the maximum reflectivity wavelength from an angle based on the Bragg-Snell law, the wavelength of maximum 0° reflectivity, the particle diameter and the fill factor have been determined. For the best surface maximum reflectivity wavelength of a 0° angle was estimated to be 869 nm. The particle diameter and fill factor were calculated as 372 nm and 0.8715, respectively. The diameter obtained by fitting is in excellent agreement with the particle diameter obtained with SEM. The reflectivity maximum is assumed to increase significantly when increasing the fill factor. We believe that using our simple approach to manufacture PMMA opal crystals will significantly increase the fabrication of high-quality photonic crystal templates and thin films.

The preparation of polytrifluorochloroethylene (PCTFE) micro-particles and application on treating bearing steel surfaces to improve the lubrication effect for copper-graphite (Cu/C)

NASA Astrophysics Data System (ADS)

Lu, Hailin; Zhang, Pengpeng; Ren, Shanshan; Guo, Junde; Li, Xing; Dong, Guangneng

2018-01-01

Contact mechanical seal is a normal technology applied on middle axis of liquid rocket turbo pump, and the kinetic and static seal rings contact low temperature rocket propellant. Copper-graphite (Cu/C) composite as an excellent self-lubrication material was widely used in aerospace industry, this study took Cu/C as ball and bearing steel as disk to investigate the tribology properties, and distilled water were used to simulate the lox tribology performances. This study prepared polytrifluorochloroethylene (PCTFE) micro-particles which were coated on the oxide surfaces of bearing steel disk at temperature of 150 °C. The tribology results showed that the oxide surfaces treated with micro PCTFE particles have lower fiction coefficient and lower wear rate than original disk in water, and the wear morphology revealed that the treated surfaces obviously had less Cu/C composite transfer film than original disk. Meanwhile SEM, EDS, XRD, XPS and light microscope etc revealed that PCTFE micro-particles could associate with the oxide surfaces and caused higher water contact angle, due to the properties of the fluorine-containing composite may cause the good lubrication effect in water. Thus this technology shows great potential to enhance tribological performances for aerospace industry on a large scale.

The influence of surface chemistry and topography on the contact guidance of MG63 osteoblast cells.

PubMed

Ismail, F S Magdon; Rohanizadeh, R; Atwa, S; Mason, R S; Ruys, A J; Martin, P J; Bendavid, A

2007-05-01

The purpose of the present study was to determine in vitro the effects of different surface topographies and chemistries of commercially pure titanium (cpTi) and diamond-like carbon (DLC) surfaces on osteoblast growth and attachment. Microgrooves (widths of 2, 4, 8 and 10 microm and a depth of 1.5-2 microm) were patterned onto silicon (Si) substrates using microlithography and reactive ion etching. The Si substrates were subsequently vapor coated with either cpTi or DLC coatings. All surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Using the MG63 Osteoblast-Like cell line, we determined cell viability, adhesion, and morphology on different substrates over a 3 day culture period. The results showed cpTi surfaces to be significantly more hydrophilic than DLC for groove sizes larger than 2 microm. Cell contact guidance was observed for all grooved samples in comparison to the unpatterned controls. The cell viability tests indicated a significantly greater cell number for 8 and 10 microm grooves on cpTi surfaces compared to other groove sizes. The cell adhesion study showed that the smaller groove sizes, as well as the unpatterned control groups, displayed better cell adhesion to the substrate.

[Experimental study on tissue engineered cartilage complex three-dimensional nano-scaffold with collagen type II and hyaluronic acid in vitro].

PubMed

Yang, Zelong; Chen, Zhu; Liu, Kang; Bai, Yiguang; Jiang, Ting; Feng, Daxiong; Feng, Gang

2013-10-01

To explore the possibility of constructing tissue engineered cartilage complex three-dimensional nano-scaffold with collagen type II and hyaluronic acid (HA) by electrospinning. The three-dimensional porous nano-scaffolds were prepared by electrospinning techniques with collagen type II and HA (8 : 1, W : W), which was dissolved in mixed solvent of 3-trifluoroethanol and water (1 : 1, V : V). The morphology were observed by light microscope and scanning electron microscope (SEM). And the porosity, water absorption rate, contact angle, and degradation rate were detected. Chondrocytes were harvested from 1-week-old Japanese white rabbit, which was disgested by 0.25% trypsin 30 minutes and 1% collagenase overlight. The passage 2 chondrocytes were seeded on the nano-scaffold. The cell adhesion and proliferation were evaluated by cell counting kit 8 (CCK-8). The cell-scaffold composites were cultured for 2 weeks in vitro, and the biological morphology and extracelluar matrix (ECM) secretion were observed by histological analysis. The optimal electrospinning condition of nano-scaffold was 10% electrospinning solution concentration, 10 cm receiver distance, 5 mL/h spinning injection speed. The scaffold had uniform diameter and good porosity through the light microscope and SEM. The diameter was 300-600 nm, and the porosity was 89.5% +/- 25.0%. The contact angle was (35.6 +/- 3.4) degrees, and the water absorption was 1 120% +/- 34% at 24 hours, which indicated excellent hydrophilicity. The degradation rate was 42.24% +/- 1.51% at 48 days. CCK-8 results showed that the adhesive rate of cells with scaffold was 169.14% +/- 11.26% at 12 hours, and the cell survival rate was 126.03% +/- 4.54% at 7 days. The histological and immunohistochemical staining results showed that the chondrocytes could grow well on the scaffold and secreted ECM. And the similar cartilage lacuma structure could be found at 2 weeks after co-culture, which suggested that hyaline cartilage formed. The collage type II and HA complex three-dimensional nano-scaffold has good physicochemical properties and excellent biocompatibility, so it can be used as a tissue engineered cartilage

Characterization of Tape Adhesion to Chemical Agent Resistant Coatings

DTIC Science & Technology

2015-01-01

use by OEM’s and depots. More specifically, each tape was tested on water dispersible and solvent borne polyurethane topcoats in the two most common...andGenerally, systems formulated to be water dispersible produced films that were slightly hydrophilic (water contact angle < 90°) whereas systems...8). Table 8: Average water contact angle of various CARC systems. advancing contact angle of water (degrees) waterborne polyurethane

The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint

PubMed Central

Sopher, Ran S; Amis, Andrew A; Davies, D Ceri; Jeffers, Jonathan RT

2016-01-01

Data about a muscle’s fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep pennation angles. Inter-subject variability in muscle architecture affected ankle muscle and contact loads only slightly. The link between muscle architecture and function contributes to the understanding of the relationship between muscle structure and function. PMID:29805194

Investigation of pH response and photo-control of wettability on spiropyran-derivatized surfaces

NASA Astrophysics Data System (ADS)

Park, Choong-Do

2009-12-01

One promising method to control a liquid drop on a surface for microfluidic devices is to use the surface tension gradient on a photo-responsive surface by light irradiation. A photo-switchable spiropyran monolayer was prepared on smooth glass or silicon wafers via 3-aminopropylmethyldiethoxysilane linkages. The pH response of the surface-bound spiropyran was investigated by measuring contact angle as a function of pH, since the pH value of the liquids applied to a microfluidic system can vary widely. Based on the contact angle titration and UV-Vis spectroscopic data, a protonation and deprotonation mechanism of the surface-bound spiropyran was proposed. The advancing contact angles under UV and under visible light irradiation at high pH values were about 100 smaller than those at low pH values. The decrease in contact angle under UV light with decreasing pH value was assigned to the protonation of open merocyanine (MC) to MC-OH+. Meanwhile, the decrease in contact angle under visible light was attributed to the protonation of the closed spiropryan (SP), generating a mixed state of MC-OH+ in equilibrium with N-protonated SP-NH+. In order to examine the possibility of light-induced liquid drop motion on the spiropyran-derivatized smooth surfaces, the light-induced surface tension change between SP and MC was estimated using the contact angle hysteresis (CAH) and the Lifshitz---van der Waals/Acid-Base (LWAB) approaches based on the contact angle data. The average light-induced surface energy change between the two isomers under UV and visible light exposure was 1.4 mJ/m 2, implying that the small change in surface tension is not sufficient to move a liquid droplet on the surface. Liquid drop motion requires that the light-induced switching angle be greater than the contact angle hysteresis. However, the light-induced switching angle of the spiropyran-derivatized surface was significantly smaller than the hysteresis. Thus, in order to achieve liquid drop motion on the spiropyran-derivatized surface, a new surface design which employs a combination of chemical modification of a hydrophobic organosilane and micropatterned rough surface morphology was suggested.

On the equilibrium contact angle of sessile liquid drops from molecular dynamics simulations.

PubMed

Ravipati, Srikanth; Aymard, Benjamin; Kalliadasis, Serafim; Galindo, Amparo

2018-04-28

We present a new methodology to estimate the contact angles of sessile drops from molecular simulations by using the Gaussian convolution method of Willard and Chandler [J. Phys. Chem. B 114, 1954-1958 (2010)] to calculate the coarse-grained density from atomic coordinates. The iso-density contour with average coarse-grained density value equal to half of the bulk liquid density is identified as the average liquid-vapor (LV) interface. Angles between the unit normal vectors to the average LV interface and unit normal vector to the solid surface, as a function of the distance normal to the solid surface, are calculated. The cosines of these angles are extrapolated to the three-phase contact line to estimate the sessile drop contact angle. The proposed methodology, which is relatively easy to implement, is systematically applied to three systems: (i) a Lennard-Jones (LJ) drop on a featureless LJ 9-3 surface; (ii) an SPC/E water drop on a featureless LJ 9-3 surface; and (iii) an SPC/E water drop on a graphite surface. The sessile drop contact angles estimated with our methodology for the first two systems are shown to be in good agreement with the angles predicted from Young's equation. The interfacial tensions required for this equation are computed by employing the test-area perturbation method for the corresponding planar interfaces. Our findings suggest that the widely adopted spherical-cap approximation should be used with caution, as it could take a long time for a sessile drop to relax to a spherical shape, of the order of 100 ns, especially for water molecules initiated in a lattice configuration on a solid surface. But even though a water drop can take a long time to reach the spherical shape, we find that the contact angle is well established much faster and the drop evolves toward the spherical shape following a constant-contact-angle relaxation dynamics. Making use of this observation, our methodology allows a good estimation of the sessile drop contact angle values even for moderate system sizes (with, e.g., 4000 molecules), without the need for long simulation times to reach the spherical shape.

On the equilibrium contact angle of sessile liquid drops from molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Ravipati, Srikanth; Aymard, Benjamin; Kalliadasis, Serafim; Galindo, Amparo

2018-04-01

We present a new methodology to estimate the contact angles of sessile drops from molecular simulations by using the Gaussian convolution method of Willard and Chandler [J. Phys. Chem. B 114, 1954-1958 (2010)] to calculate the coarse-grained density from atomic coordinates. The iso-density contour with average coarse-grained density value equal to half of the bulk liquid density is identified as the average liquid-vapor (LV) interface. Angles between the unit normal vectors to the average LV interface and unit normal vector to the solid surface, as a function of the distance normal to the solid surface, are calculated. The cosines of these angles are extrapolated to the three-phase contact line to estimate the sessile drop contact angle. The proposed methodology, which is relatively easy to implement, is systematically applied to three systems: (i) a Lennard-Jones (LJ) drop on a featureless LJ 9-3 surface; (ii) an SPC/E water drop on a featureless LJ 9-3 surface; and (iii) an SPC/E water drop on a graphite surface. The sessile drop contact angles estimated with our methodology for the first two systems are shown to be in good agreement with the angles predicted from Young's equation. The interfacial tensions required for this equation are computed by employing the test-area perturbation method for the corresponding planar interfaces. Our findings suggest that the widely adopted spherical-cap approximation should be used with caution, as it could take a long time for a sessile drop to relax to a spherical shape, of the order of 100 ns, especially for water molecules initiated in a lattice configuration on a solid surface. But even though a water drop can take a long time to reach the spherical shape, we find that the contact angle is well established much faster and the drop evolves toward the spherical shape following a constant-contact-angle relaxation dynamics. Making use of this observation, our methodology allows a good estimation of the sessile drop contact angle values even for moderate system sizes (with, e.g., 4000 molecules), without the need for long simulation times to reach the spherical shape.

Determination of the Contact Angle Based on the Casimir Effect

NASA Technical Reports Server (NTRS)

Mazuruk, K.; Volz, M. P.

2015-01-01

In several crystal growth processed based on capillarity, a melt comes into contact with a crucible wall at an angle defined as the contact angle. For molten metals and semiconductors, this contact angle is dependent upon both the crucible and melt material and typical values fall in the range 80-170deg. However, on a microscopic scale, there does not exist a precise and sharp contact angle but rather the melt and solid surfaces merge smoothly and continuously over a distance of up to several micrometers. Accurate modeling requires a more advanced treatment of this interaction. The interaction between the melt and solid surfaces can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir force. The Casimir force between the two bodies of complex geometry is calculated using a retarded temperature Green's function (Matsubara type) for the photon in the medium. The governing equations are cast in the form of a set of boundary integral equations which are then solved numerically for the case of molten Ge on SiO2. The shape of the molten surface approaching the flat solid body is determined, and the contact angle is defined as the angle between the two surfaces at the microscopically asymptotic distance of 1-2 micrometers. The formulation of this model and the results of the numerical calculations will be presented and discussed.

Contact Hamiltonian systems and complete integrability

NASA Astrophysics Data System (ADS)

Visinescu, Mihai

2017-12-01

We summarize recent results on the integrability of Hamiltonian systems on contact manifolds. We explain how to extend the classical formulation of action-angle variables to contact integrable systems. Using the Jacobi brackets defined on contact manifolds, we discuss the commutativity of first integrals for contact Hamiltonian systems and present the construction of generalized contact action-angle variables. We illustrate the integrability in the contact geometry on the five-dimensional Sasaki-Einstein spaces T1,1 and Yp,q.

Proper Brushing

MedlinePlus

... bristles along the gumline at a 45-degree angle. Bristles should contact both the tooth surface and the gumline. Gently ... A rolling motion is when the brush makes contact with the gumline and ... a 45-degree angle with bristles contacting the tooth surface and gumline. ...

Effects of Evaporation/Condensation on Spreading and Contact Angle of a Volatile Liquid Drop

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chao, David F.; Singh, Bhim S. (Technical Monitor)

2000-01-01

Effects of evaporation/condensation on spreading and contact angle were experimentally studied. A sessile drop of R-113 was tested at different vapor environments to determine the effects of evaporation/condensation on the evolution of contact diameter and contact angle of the drop. Condensation on the drop surface occurs at both the saturated and a nonsaturated vapor environments and promotes the spreading. When the drop is placed in the saturated vapor environment it tends to completely wetting and spreads rapidly. In a nonsaturated vapor environment, the evolution of the sessile drop is divided three stages: condensation-spreading stage, evaporation-retracting stage and rapid contracting stage. In the first stage the drop behaves as in the saturated environment. In the evaporation -retracting stage, the competition between spreading and evaporation of the drop determines the evolution characteristics of the contact diameter and the contact angle. A lower evaporation rate struggles against the spreading power to turn the drop from spreading to retracting with a continuous increase of the contact angle. The drop placed in open air has a much higher evaporation rate. The strong evaporation suppresses the spreading and accelerates the retraction of the drop with a linear decrease of the contact diameter. The contraction of the evaporating drops is gradually accelerated when the contact diameter decreases to 3 min and less till drying up, though the evaporation rate is gradually slowing down.

Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.

PubMed

Iliev, Stanimir; Pesheva, Nina

2016-06-01

We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1-0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012)LANGD50743-746310.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

Growth of GaN- and ZnO-Based Nanorod Compound Structures

DTIC Science & Technology

2013-08-16

parallel with or forming a 60o tilted angle with respect to the two parallel lateral sides of individual NRs. In the edge-to-edge pattern, the shortest...kV and a probe forming lens of Cs = 1.2 mm. 3. SEM and TEM Observations Figures 2(a)-2(f) show the plan-view SEM images of samples I-VI... angle annular dark field (HAADF) image in TEM observation of an InGaN/GaN QW NR of sample I. In this image, the three almost vertical bright lines

Three-dimensional lattice Boltzmann simulations of microdroplets including contact angle hysteresis on topologically structured surfaces

DOE PAGES

Ba, Yan; Kang, Qinjun; Liu, Haihu; ...

2016-04-14

In this study, the dynamical behavior of a droplet on topologically structured surface is investigated by using a three-dimensional color-gradient lattice Boltzmann model. A wetting boundary condition is proposed to model fluid-surface interactions, which is advantageous to improve the accuracy of the simulation and suppress spurious velocities at the contact line. The model is validated by the droplet partial wetting test and reproduction of the Cassie and Wenzel states. A series of simulations are conducted to investigate the behavior of a droplet when subjected to a shear flow. It is found that in Cassie state, the droplet undergoes a transitionmore » from stationary, to slipping and finally to detachment states as the capillary number increases, while in Wenzel state, the last state changes to the breakup state. The critical capillary number, above which the droplet slipping occurs, is small for the Cassie droplet, but is significantly enhanced for the Wenzel droplet due to the increased contact angle hysteresis. In Cassie state, the receding contact angle nearly equals the prediction by the Cassie relation, and the advancing contact angle is close to 180°, leading to a small contact angle hysteresis. In Wenzel state, however, the contact angle hysteresis is extremely large (around 100°). Finally, high droplet mobility can be easily achieved for Cassie droplets, whereas in Wenzel state, extremely low droplet mobility is identified.« less

Creation of hydrophobic surfaces using a paint containing functionalized oxide particles

NASA Astrophysics Data System (ADS)

Sino, Paul Albert L.; Herrera, Marvin U.; Balela, Mary Donnabelle L.

2017-05-01

Hydrophobic surfaces were created by coating various substrates (aluminum sheet, soda-lime glass, silicon carbide polishing paper, glass with double-sided adhesive) with paint containing functionalized oxide particles. The paint was created by functionalizing oxide particles (ground ZnO, TiO2 nanoparticles, or TiO2 microparticles) with fluorosilane molecules in absolute ethanol. Water contact angle of samples shows that the coated substrate becomes hydrophobic (water contact angle ≥ 90°). Among the oxides that were used, ground ZnO yielded contact angle exemplifying superhydrophobicity (water contact angle ≥ 150°). Scanning electron micrograph of paint-containing TiO2 nanoparticles shows rough functionalized oxides structures which probably increase the hydrophobicity of the surface.

Smoothed particle hydrodynamics study of the roughness effect on contact angle and droplet flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shigorina, Elena; Kordilla, Jannes; Tartakovsky, Alexandre M.

We employ a pairwise force Smoothed Particle Hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows for modeling of free surface flow without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on rough surfaces in a shape of a sinusoidal functionmore » and made of rectangular bars placed on top of a flat surface. We find that the effective static contact angles of Cassie and Wenzel droplets on a rough surface are greater than the corresponding microscale static contact angles. As a result, microscale hydrophobic rough surfaces also show effective hydrophobic behavior. On the other hand, microscale hydrophilic surfaces may be macroscopically hydrophilic or hydrophobic, depending on the type of roughness. Next, we study the impact of the roughness orientation (i.e., an anisotropic roughness) and surface inclination on droplet flow velocities. Simulations show that droplet flow velocities are lower if the surface roughness is oriented perpendicular to the flow direction. If the predominant elements of surface roughness are in alignment with the flow direction, the flow velocities increase compared to smooth surfaces, which can be attributed to the decrease in fluid-solid contact area similar to the classical lotus effect. We demonstrate that linear scaling relationships between Bond and capillary number for droplet flow on flat surfaces also hold for flow on rough surfaces.« less

Contact angle determination procedure and detection of an invisible surface film

NASA Technical Reports Server (NTRS)

Meyer, G.; Grat, R.

1990-01-01

The contact angle value, i.e., the tangent angle of liquid resting on a planar solid surface, is a basic parameter which can be applied to a wide range of applications. The goal is to provide a basic understanding of the contact angle measurement technique and to present a simple illustration that can be applied as a quality control method; namely, detection of a surface contaminant which exists on a surface that appears clean to the unaided eye. The equipment and experimental procedures are detailed.

Controlling the Transient Interface Shape and Deposition Profile Left by Desiccation of Colloidal Droplets on Multiple Polymer Surfaces

NASA Astrophysics Data System (ADS)

Dunning, Peter David

A colloidal suspension is a small constituent of insoluble solid particles suspended in a liquid medium. Control over the wetting, evaporation, and deposition patterns left by colloidal suspensions is valuable in many biological, medical, industrial, and agricultural applications. Understanding the governing principles of wetting and evaporative phenomena of these colloidal suspensions may lead to greater control over resultant deposition patterns. Perhaps the most familiar pattern forms when an initially heterogeneous colloidal suspension leaves a dark ring pattern at the edge of a drop. This pattern is referred to as a coffee-stain and it can be seen from dried droplets of spilled coffee. This coffee-stain effect was first investigated by Deegan et. al. who discovered that these patterns occur when outward radial flows driven by evaporation at the triple contact line dominate over other effects. While the presence of coffee-stain patterns is undesirable in many printing and medical diagnostic processes, it can also be advantageous in the production of low cost transparent conductive films, the deposition of metal vapor, and the manipulation of biological structures. Controlling the interactions between the substrate, liquid, vapor, and particles can lead to control over the size and morphology of evaporative deposition patterns left by aqueous colloidal suspensions. Several methods have been developed to control the evaporation of colloidal suspensions to either suppress or enhance the coffee stain effect. Electrowetting on Dielectric (EWOD) is one promising method that has been used to control colloidal depositions by applying either an AC or DC electric field. EWOD actuation has the potential to dynamically control colloidal deposition left by desiccated droplets to either suppress or enhance the coffee stain effect. It may also allow for independent control of the fluidic interface and deposition of particles via electrowetting and electrokinetic forces. Implementation of this technique requires that the colloidal droplet be separated from the active electrode by a dielectric layer to prevent electrolysis. A variety of polymer layers have been used in EWOD devices for a variety of applications. In applications that involve desiccation of colloidal suspensions, the material for this layer should be chosen carefully as it can play an important role in the resulting deposition pattern. An experimental method to monitor the transient evolution of the shape of an evaporating colloidal droplet and optically quantify the resultant deposition pattern is presented. Unactuated colloidal suspensions will be desiccated on a variety of substrates commonly used in EWOD applications. Transient image profiles and particle deposition patterns are examined for droplets containing fluorescent micro-particles. Qualitative and quantitative comparisons of these results will be used to compare multiple different cases in an effort to provide insight into the effects of polymer selection on the drying dynamics and resultant deposition patterns of desiccated colloidal materials. It was found that the equilibrium and receding contact angles between the surface and the droplet play a key role in the evaporation dynamics and the resulting deposition patterns left by a desiccated colloidal suspension. The equilibrium contact angle controls the initial contact diameter for a droplet of a given volume. As a droplet on a surface evaporates, the evolution of the interface shape and the contact diameter can generally be described by three different regimes. The Constant Contact Radius (CCR) regime occurs when the contact line is pinned while the contact angle decreases. The Constant Contact Angle (CCA) regime occurs when the contact line recedes while the contact angle remains constant. The Mixed regime occurs when the contact radius and angle both reduce over time. The presence of the CCA regime allows the contact line to recede creating a more uniform deposition. However, not all droplets move into the CCA regime. Some remain in the CCR regime creating a coffee-stain pattern. In order to transition into the CCA regime, the dynamic contact angle of the droplet must be reduced to an angle close to the receding contact angle. Transient interface shapes and deposition patterns were examined on four surfaces: (i) Glass, (ii) Kapton HN polyimide tape, (iii) SU-8 3005, and (iv) Teflon AF. Glass has a low equilibrium contact angle and a very low receding contact angle resulting in a large uniform coffee-stain deposition. Kapton HN and SU-8 3005 have similar equilibrium contact angles that result in similar initial contact diameters. However, Kapton HN pins at that initial diameter due to a low receding contact angle producing a smaller more intense coffee-stain. SU-8 3005 has a large receding contact angle that allows for the transition into the CCA regime which results in a smaller, more uniform, and more intense spot. Teflon AF has the largest equilibrium and receding contact angle producing the smallest, most uniform, and most intense spot. Results presented here suggest that a lower receding contact angle is beneficial in areas where the coffee-stain effect needs to be enhanced while a larger receding contact angle is beneficial in areas where the coffee-stain needs to be suppressed. Preliminary results are also presented examining droplets actuated via AC electrowetting to examine the effect of electrode geometry and applied voltage on electrowetting behavior and colloidal depositions in these cases. It was found that the Young-Lippmann equation needs to be modified to satisfy the modified capacitance per unit area of a system with different electrode geometries.

Low Voltage Electrowetting on Ferroelectric PVDF-HFP Insulator with Highly Tunable Contact Angle Range.

PubMed

Sawane, Yogesh B; Ogale, Satishchandra B; Banpurkar, Arun G

2016-09-14

We demonstrate a consistent electrowetting response on ferroelectric poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) insulator covered with a thin Teflon AF layer. This bilayer exhibits a factor of 3 enhancement in the contact angle modulation compared to that of conventional single-layered Teflon AF dielectric. On the basis of the proposed model the enhancement is attributed to the high value of effective dielectric constant (εeff ≈ 6) of the bilayer. Furthermore, the bilayer dielectric exhibits a hysteresis-free contact angle modulation over many AC voltage cycles. But the contact angle modulation for DC voltage shows a hysteresis because of the field-induced residual polarization in the ferroelectric layer. Finally, we show that a thin bilayer exhibits contact angle modulation of Δθ (U) ≈ 60° at merely 15 V amplitude of AC voltage indicating a potential dielectric for practical low voltage electrowetting applications. A proof of concept confirms electrowetting based rapid mixing of a fluorescent dye in aqueous glycerol solution for 15 V AC signal.

Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb

NASA Technical Reports Server (NTRS)

Wang, Yazhen; Regel, Liya L.; Wilcox, William R.

2000-01-01

We extended the previous analysis of detached solidification of InSb based on the moving meniscus model. We found that for steady detached solidification to occur in a sealed ampoule in zero gravity, it is necessary for the growth angle to exceed a critical value, the contact angle for the melt on the ampoule wall to exceed a critical value, and the melt-gas surface tension to be below a critical value. These critical values would depend on the material properties and the growth parameters. For the conditions examined here, the sum of the growth angle and the contact angle must exceed approximately 130, which is significantly less than required if both ends of the ampoule are open.

Dynamics of contact line depinning during droplet evaporation based on thermodynamics.

PubMed

Yu, Dong In; Kwak, Ho Jae; Doh, Seung Woo; Ahn, Ho Seon; Park, Hyun Sun; Kiyofumi, Moriyama; Kim, Moo Hwan

2015-02-17

For several decades, evaporation phenomena have been intensively investigated for a broad range of applications. However, the dynamics of contact line depinning during droplet evaporation has only been inductively inferred on the basis of experimental data and remains unclear. This study focuses on the dynamics of contact line depinning during droplet evaporation based on thermodynamics. Considering the decrease in the Gibbs free energy of a system with different evaporation modes, a theoretical model was developed to estimate the receding contact angle during contact line depinning as a function of surface conditions. Comparison of experimentally measured and theoretically modeled receding contact angles indicated that the dynamics of contact line depinning during droplet evaporation was caused by the most favorable thermodynamic process encountered during constant contact radius (CCR mode) and constant contact angle (CCA mode) evaporation to rapidly reach an equilibrium state during droplet evaporation.

Wettability of graphitic-carbon and silicon surfaces: MD modeling and theoretical analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

2015-07-28

The wettability of graphitic carbon and silicon surfaces was numerically and theoretically investigated. A multi-response method has been developed for the analysis of conventional molecular dynamics (MD) simulations of droplets wettability. The contact angle and indicators of the quality of the computations are tracked as a function of the data sets analyzed over time. This method of analysis allows accurate calculations of the contact angle obtained from the MD simulations. Analytical models were also developed for the calculation of the work of adhesion using the mean-field theory, accounting for the interfacial entropy changes. A calibration method is proposed to providemore » better predictions of the respective contact angles under different solid-liquid interaction potentials. Estimations of the binding energy between a water monomer and graphite match those previously reported. In addition, a breakdown in the relationship between the binding energy and the contact angle was observed. The macroscopic contact angles obtained from the MD simulations were found to match those predicted by the mean-field model for graphite under different wettability conditions, as well as the contact angles of Si(100) and Si(111) surfaces. Finally, an assessment of the effect of the Lennard-Jones cutoff radius was conducted to provide guidelines for future comparisons between numerical simulations and analytical models of wettability.« less

Spontaneous imbibition in fractal tortuous micro-nano pores considering dynamic contact angle and slip effect: phase portrait analysis and analytical solutions.

PubMed

Li, Caoxiong; Shen, Yinghao; Ge, Hongkui; Zhang, Yanjun; Liu, Tao

2018-03-02

Shales have abundant micro-nano pores. Meanwhile, a considerable amount of fracturing liquid is imbibed spontaneously in the hydraulic fracturing process. The spontaneous imbibition in tortuous micro-nano pores is special to shale, and dynamic contact angle and slippage are two important characteristics. In this work, we mainly investigate spontaneous imbibition considering dynamic contact angle and slip effect in fractal tortuous capillaries. We introduce phase portrait analysis to analyse the dynamic state and stability of imbibition. Moreover, analytical solutions to the imbibition equation are derived under special situations, and the solutions are verified by published data. Finally, we discuss the influences of slip length, dynamic contact angle and gravity on spontaneous imbibition. The analysis shows that phase portrait is an ideal tool for analysing spontaneous imbibition because it can evaluate the process without solving the complex governing ordinary differential equations. Moreover, dynamic contact angle and slip effect play an important role in fluid imbibition in fractal tortuous capillaries. Neglecting slip effect in micro-nano pores apparently underestimates imbibition capability, and ignoring variations in contact angle causes inaccuracy in predicting imbibition speed at the initial stage of the process. Finally, gravity is one of the factors that control the stabilisation of the imbibition process.

An effective medium approach to predict the apparent contact angle of drops on super-hydrophobic randomly rough surfaces.

PubMed

Bottiglione, F; Carbone, G

2015-01-14

The apparent contact angle of large 2D drops with randomly rough self-affine profiles is numerically investigated. The numerical approach is based upon the assumption of large separation of length scales, i.e. it is assumed that the roughness length scales are much smaller than the drop size, thus making it possible to treat the problem through a mean-field like approach relying on the large-separation of scales. The apparent contact angle at equilibrium is calculated in all wetting regimes from full wetting (Wenzel state) to partial wetting (Cassie state). It was found that for very large values of the roughness Wenzel parameter (r(W) > -1/ cos θ(Y), where θ(Y) is the Young's contact angle), the interface approaches the perfect non-wetting condition and the apparent contact angle is almost equal to 180°. The results are compared with the case of roughness on one single scale (sinusoidal surface) and it is found that, given the same value of the Wenzel roughness parameter rW, the apparent contact angle is much larger for the case of a randomly rough surface, proving that the multi-scale character of randomly rough surfaces is a key factor to enhance superhydrophobicity. Moreover, it is shown that for millimetre-sized drops, the actual drop pressure at static equilibrium weakly affects the wetting regime, which instead seems to be dominated by the roughness parameter. For this reason a methodology to estimate the apparent contact angle is proposed, which relies only upon the micro-scale properties of the rough surface.

Novel characteristics of traction force in biliary self-expandable metallic stents.

PubMed

Hori, Yasuki; Hayashi, Kazuki; Yoshida, Michihiro; Naitoh, Itaru; Ban, Tesshin; Miyabe, Katsuyuki; Kondo, Hiromu; Nishi, Yuji; Umemura, Shuichiro; Fujita, Yasuaki; Natsume, Makoto; Kato, Akihisa; Ohara, Hirotaka; Joh, Takashi

2017-05-01

In recent years, knowledge concerning the mechanical properties of self-expandable metallic stents (SEMS) has increased. In a previous study, we defined traction force and traction momentum and reported that these characteristics are important for optimal stent deployment. However, traction force and traction momentum were represented as relative values and were not evaluated in various conditions. The purpose of the present study was to measure traction force in various situations assumed during SEMS placement. Traction force and traction momentum were measured in non-stricture, stricture, and angled stricture models using in-house equipment. Stricture and angled stricture models had significantly higher traction force and traction momentum than those of the non-stricture model (stricture vs non-stricture: traction force, 7.2 N vs 1.4 N, P < 0.001; traction momentum, 237.8 Ns vs 62.3 Ns, P = 0.001; angled stricture vs non-stricture: traction force, 7.4 N vs 1.4 N, P < 0.001; traction momentum, 307.2 Ns vs 62.3 Ns, P < 0.001). Traction force was variable during SEMS placement and was categorized into five different stages, which were similar in both the stricture and angled stricture models. We measured traction force and traction momentum under simulated clinical conditions and demonstrated that strictures and the angular positioning of the stent influenced the traction force. Clinicians should be aware of the transition of the traction force and should schedule X-ray imaging during SEMS placement. © 2017 Japan Gastroenterological Endoscopy Society.

Superhydrophobic alumina surface based on stearic acid modification

NASA Astrophysics Data System (ADS)

Feng, Libang; Zhang, Hongxia; Mao, Pengzhi; Wang, Yanping; Ge, Yang

2011-02-01

A novel superhydrophobic alumina surface is fabricated by grafting stearic acid layer onto the porous and roughened aluminum film. The chemical and phase structure, morphology, and the chemical state of the atoms at the superhydrophobic surface were investigated by techniques as FTIR, XRD, FE-SEM, and XPS, respectively. Results show that a super water-repellent surface with a contact angle of 154.2° is generated. The superhydrophobic alumina surface takes on an uneven flowerlike structure with many nanometer-scale hollows distribute in the nipple-shaped protrusions, and which is composed of boehmite crystal and γ-Al2O3. Furthermore, the roughened and porous alumina surface is coated with a layer of hydrophobic alkyl chains which come from stearic acid molecules. Therefore, both the roughened structure and the hydrophobic layer endue the alumina surface with the superhydrophobic behavior.

Performance of nanocomposites for preservation of artistic stones

NASA Astrophysics Data System (ADS)

Giancristofaro, Cristina; D'Amato, Rosaria; Caneve, Luisa; Pilloni, Luciano; Rinaldi, Antonio; Persia, Franca

2014-06-01

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. The results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.

Construction of super - hydrophobic copper alloy surface by one - step mixed solution immersion method

NASA Astrophysics Data System (ADS)

Gu, Qiang; Chen, Ying; Chen, Dong; Zhang, Zeting

2018-01-01

This paper presents a method for preparing a super hydrophobic surface with a fast, simple, low-cost, one-step reaction by immersing copper alloy in an ethanol solution containing silver nitrate and myristic acid. The effects of reaction time, reaction temperature, reactant concentration and reaction time on the wettability of the material were studied. The surface wettability, appearance, chemical composition, durability and chemical stability of the prepared samples was measured by water contact angle (CA), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results show that when the reaction time is only 10min, the surface WCA of the prepared material can reach 154.9. This study provides an effective method for the rapid preparation of stable super hydrophobic surfaces.

Photocatalytic Degradation Effect of μ-Dielectric Barrier Discharge Plasma Treated Titanium Dioxide Nanoparticles on Environmental Contaminant.

PubMed

Seo, Hyeon Jin; Hwang, Ki-Hwan; Na, Young Hoon; Boo, Jin-Hyo

2018-09-01

This study focused on the photocatalytic degradation effect of the μ-dielectric barrier discharge (μ-DBD) plasma treated titanium dioxide (TiO2) nanoparticles on environmental contaminant such as formaldehyde. TiO2 nanoparticles were treated by a μ-DBD plasma source with nitrogen gas. We analyzed the degradation of formaldehyde with the plasma treated TiO2 nanoparticles by UV-visible spectrophotometer (UV-VIS), and demonstrated that the photocatalytic activity of the μ-DBD plasma-treated TiO2 nanoparticles showed significantly high catalytic efficiency rather than without plasma treated TiO2 nanoparticles. Field emission scanning electron microscopes (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and water contact angle analyzer were used to measure the effects of photocatalytic degradation for the plasma treated TiO2 nanoparticles.

CO2-Switchable Membranes Prepared by Immobilization of CO2-Breathing Microgels.

PubMed

Zhang, Qi; Wang, Zhenwu; Lei, Lei; Tang, Jun; Wang, Jianli; Zhu, Shiping

2017-12-20

Herein, we report the development of a novel CO 2 -responsive membrane system through immobilization of CO 2 -responsive microgels into commercially available microfiltration membranes using a method of dynamic adsorption. The microgels, prepared from soap-free emulsion polymerization of CO 2 -responsive monomer 2-(diethylamino)ethyl methacrylate (DEA), can be reversibly expanded and shrunken upon CO 2 /N 2 alternation. When incorporated into the membranes, this switching behavior was preserved and further led to transformation between microfiltration and ultrafiltration membranes, as indicated from the dramatic changes on water flux and BSA rejection results. This CO 2 -regulated performance switching of membranes was caused by the changes of water transportation channel, as revealed from the dynamic water contact angle tests and SEM observation. This work represents a simple yet versatile strategy for making CO 2 -responsive membranes.

Ferrocene-functionalized graphene electrode for biosensing applications.

PubMed

Rabti, Amal; Mayorga-Martinez, Carmen C; Baptista-Pires, Luis; Raouafi, Noureddine; Merkoçi, Arben

2016-07-05

A novel ferrocene-functionalized reduced graphene oxide (rGO)-based electrode is proposed. It was fabricated by the drop casting of ferrocene-functionalized graphene onto polyester substrate as the working electrode integrated within screen-printed reference and counter electrodes. The ferrocene-functionalized rGO has been fully characterized using FTIR, XPS, contact angle measurements, SEM and TEM microscopy, and cyclic voltammetry. The XPS and EDX analysis showed the presence of Fe element related to the introduced ferrocene groups, which is confirmed by a clear CV signal at ca. 0.25 V vs. Ag/AgCl (0.1 KCl). Mediated redox catalysis of H2O2 and bio-functionalization with glucose oxidase for glucose detection were achieved by the bioelectrode providing a proof for potential biosensing applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Surface characterization and adhesion of oxygen plasma-modified LARC-TPI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, J.W.; Wightman, J.P.

1992-01-01

LARC-TPI, an aromatic thermoplastic polyimide, was exposed to an oxygen plasma as a surface pretreatment of adhesive bonding. Chemical and physical changes which occurred in the polyimide surface as a result of the plasma treatment were investigated using X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IR-RAS), contact angle analysis, ellipsometry and high resolution scanning electron microscopy (HR-SEM). A 180{degree} peel test with an acrylate-based pressure sensitive adhesive as a flexible adherend was utilized to study the interactions of the plasma-treated polyimide surface with other polymeric materials. The surface characterization and adhesion testing results showed that the oxygen plasma treatment, whilemore » creating a more hydrophilic, polar surface, also caused chain scission resulting in the formation of a weak boundary layer which inhibited adhesion.« less

Surface modification of polyester synthetic leather with tetramethylsilane by atmospheric pressure plasma

NASA Astrophysics Data System (ADS)

Kan, C. W.; Kwong, C. H.; Ng, S. P.

2015-08-01

Much works have been done on synthetic materials but scarcely on synthetic leather owing to its surface structures in terms of porosity and roughness. This paper examines the use of atmospheric pressure plasma (APP) treatment for improving the surface performance of polyester synthetic leather by use of a precursor, tetramethylsilane (TMS). Plasma deposition is regarded as an effective, simple and single-step method with low pollution. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) confirm the deposition of organosilanes on the sample's surface. The results showed that under a particular combination of treatment parameters, a hydrophobic surface was achieved on the APP treated sample with sessile drop static contact angle of 138°. The hydrophobic surface is stable without hydrophilic recovery 30 days after plasma treatment.

Influence of surfactants in forced dynamic dewetting.

PubMed

Henrich, Franziska; Fell, Daniela; Truszkowska, Dorota; Weirich, Marcel; Anyfantakis, Manos; Nguyen, Thi-Huong; Wagner, Manfred; Auernhammer, Günter K; Butt, Hans-Jürgen

2016-09-20

In this work we show that the forced dynamic dewetting of surfactant solutions depends sensitively on the surfactant concentration. To measure this effect, a hydrophobic rotating cylinder was horizontally half immersed in aqueous surfactant solutions. Dynamic contact angles were measured optically by extrapolating the contour of the meniscus to the contact line. Anionic (sodium 1-decanesulfonate, S-1DeS), cationic (cetyl trimethylammonium bromide, CTAB) and nonionic surfactants (C 4 E 1 , C 8 E 3 and C 12 E 5 ) with critical micelle concentrations (CMCs) spanning four orders of magnitude were used. The receding contact angle in water decreased with increasing velocity. This decrease was strongly enhanced when adding surfactant, even at surfactant concentrations of 10% of the critical micelle concentration. Plots of the receding contact angle-versus-velocity almost superimpose when being plotted at the same relative concentration (concentration/CMC). Thus the rescaled concentration is the dominating property for dynamic dewetting. The charge of the surfactants did not play a role, thus excluding electrostatic effects. The change in contact angle can be interpreted by local surface tension gradients, i.e. Marangoni stresses, close to the three-phase contact line. The decrease of dynamic contact angles with velocity follows two regimes. Despite the existence of Marangoni stresses close to the contact line, for a dewetting velocity above 1-10 mm s -1 the hydrodynamic theory is able to describe the experimental results for all surfactant concentrations. At slower velocities an additional steep decrease of the contact angle with velocity was observed. Particle tracking velocimetry showed that the flow profiles do not differ with and without surfactant on a scales >100 μm.

Comparison of pre-contact joint kinematics and vertical impulse between vertical jump landings and step-off landings from equal heights.

PubMed

Harry, John R; Freedman Silvernail, Julia; Mercer, John A; Dufek, Janet S

2017-12-01

Although impact phase differences between vertical jump landings (VJL) and step-off landings (STL) may be related to task-specific pre-contact strategies, pre-contact mechanics are rarely examined. Thus, pre-contact kinematics and vertical ground reaction force (vGRF) impulse were examined between VJL and STL. Ten health adults (20.9 ± 1.6 yrs; 167.8 ± 4.2 cm; 68.5 ± 7.15 kg) performed 15 VJL and 15 STL from equal heights. Limb (lead; trail) by task (VJL; STL) ANOVAs (α = 0.05) compared hip, knee, and ankle joint angles 150 ms pre-contact, 100 ms pre-contact, 50 ms pre-contact, and at ground contact. Joint angular displacement was also evaluated between 150 ms pre-contact and ground contact. vGRF impulse was compared during the loading (ground contact to peak vGRF) and attenuation (peak vGRF to end of impact) phases. Greater hip flexion angles occurred during STL versus VJL at each event except 150 ms pre-contact (p ≤ .004). Trail limb knee flexion angles were greater at each event when compared to the lead limb during STL (p ≤ .019). Greater trail limb knee flexion angles occurred during STL versus VJL at all four events (p ≤ .018), while greater plantarflexion angles occurred at all four events during VJL versus STL (p ≤ .034). During STL, greater trail limb plantarflexion angles were detected at each event versus the lead limb (p < .001). Lesser hip, lead and trail limb knee displacement occurred during STL versus VJL (p < .05). Greater vGRF impulse was detected during the loading phase of VJL (<.001), while greater vGRF impulse occurred during the attenuation phase of STL (p = .025). These tasks are characterized by distinct pre-contact kinematic strategies and post-contact kinetics. The task utilized in practice should reflect the requirements of the population of interest. Copyright © 2017 Elsevier B.V. All rights reserved.

Dynamics of Contact Line Pinning and Depinning of Droplets Evaporating on Microribs.

PubMed

Mazloomi Moqaddam, Ali; Derome, Dominique; Carmeliet, Jan

2018-05-15

The contact line dynamics of evaporating droplets deposited on a set of parallel microribs is analyzed with the use of a recently developed entropic lattice Boltzmann model for two-phase flow. Upon deposition, part of the droplet penetrates into the space between ribs because of capillary action, whereas the remaining liquid of the droplet remains pinned on top of the microribs. In the first stage, evaporation continues until the droplet undergoes a series of pinning-depinning events, showing alternatively the constant contact radius and constant contact angle modes. While the droplet is pinned, evaporation results in a contact angle reduction, whereas the contact radius remains constant. At a critical contact angle, the contact line depins, the contact radius reduces, and the droplet rearranges to a larger apparent contact angle. This pinning-depinning behavior goes on until the liquid above the microribs is evaporated. By computing the Gibbs free energy taking into account the interfacial energy, pressure terms, and viscous dissipation due to drop internal flow, we found that the mechanism that causes the unpinning of the contact line results from an excess in Gibbs free energy. The spacing distance and the rib height play an important role in controlling the pinning-depinning cycling, the critical contact angle, and the excess Gibbs free energy. However, we found that neither the critical contact angle nor the maximum excess Gibbs free energy depends on the rib width. We show that the different terms, that is, pressure term, viscous dissipation, and interfacial energy, contributing to the excess Gibbs free energy, can be varied differently by varying different geometrical properties of the microribs. It is demonstrated that, by varying the spacing distance between the ribs, the energy barrier is controlled by the interfacial energy while the contribution of the viscous dissipation is dominant if either rib height or width is changed. Main finding of this is study is that, for microrib patterned surfaces, the energy barrier required for the contact line to depin can be enlarged by increasing the spacing or the rib height, which can be important for practical applications.

Evaporation of liquid droplets on solid substrates. II. Periodic substrates with moving contact lines

NASA Astrophysics Data System (ADS)

Amini, Amirhossein; Homsy, G. M.

2017-04-01

Experiments on evaporating droplets on structured surfaces have shown that the contact line does not move with constant speed, but rather in a steplike "stick-slip" fashion. As a first step in understanding such behavior, we study the evaporation of a two-dimensional volatile liquid droplet on a nonplanar heated solid substrate with a moving contact line and fixed contact angle. The model for the flat case is adapted to include curved substrates, numerical solutions are achieved for various periodic and quasiperiodic substrate profiles, and the dynamics of the contact line and the apparent contact angle are studied. In contrast with our results for a flat substrate, for which the contact line recedes in a nearly constant speed, we observe that the contact line speed and position show significant time variation and that the contact line moves in an approximate steplike fashion on relatively steep substrates. For the simplest case of a periodic substrate, we find that the apparent contact angle is periodic in time. For doubly periodic substrates, we find that the apparent contact angle is periodic and that the problem exhibits a phase-locking behavior. For multimode quasiperiodic substrates, we find the contact line behavior to be temporally complex and not only limited to a stick-slip motion. In all cases, we find that the overall evaporation is increased relative to the flat substrate.

Investigation of porous silicon obtained under different conditions by the contact angle method

NASA Astrophysics Data System (ADS)

Belorus, A. O.; Bukina, Y. V.; Pastukhov, A. I.; Stebko, D. S.; Spivak, Yu M.; Moshnikov, V. A.

2017-11-01

This paper investigates a hydrophobicity/hydrophilicity of porous silicon by the contact angle method. Porous silicon series were obtained by electrochemical anodic etching of n-Si (100) and (111) under the current anodization density range of 5-120 mA/cm2. For this purpose the original laboratory installation and the software «Measurement of contact angle» were developed. It is shown that, the contact angle can vary significantly (up to 80 degrees for (100)) depending on the current anodization Discussion of the results is carried out taking in account the composition of the functional groups and of surface morphology of the porous silicon. These results are important for developing porous silicon particles as nanocontainers in the targeted drug delivery.

The effect of temperature, matrix alloying and substrate coatings on wettability and shear strength of Al/Al2O3 couples

NASA Astrophysics Data System (ADS)

Sobczak, N.; Ksiazek, M.; Radziwill, W.; Asthana, R.; Mikulowski, B.

2004-03-01

A fresh approach has been advanced to examine in the Al/Al2O3 system the effects of temperature, alloying of Al with Ti or Sn, and Ti and Sn coatings on the substrate, on contact angles measured using a sessile-drop test, and on interface strength measured using a modified push-off test that allows shearing of solidified droplets with less than 90 deg contact angle. In the modified test, the solidified sessile-drop samples are bisected perpendicular to the drop/Al2O3 interface at the midplane of the contact circle to obtain samples that permit bond strength measurement by stress application to the flat surface of the bisected couple. The test results show that interface strength is strongly influenced by the wetting properties; low contact angles correspond to high interface strength, which also exhibits a strong temperature dependence. An increase in the wettability test temperature led to an increase in the interface strength in the low-temperature range where contact angles were large and wettability was poor. The room-temperature shear tests conducted on thermally cycled sessile-drop test specimens revealed the effect of chemically formed interfacial oxides; a weakening of the thermally cycled Al/Al2O3 interface was caused under the following conditions: (1) slow contact heating and short contact times in the wettability test, and (2) fast contact heating and longer contact times. The addition of 6 wt pct Ti or 7 wt pct Sn to Al only marginally influenced the contact angle and interfacial shear strength. However, Al2O3 substrates having thin (<1 µm) Ti coatings yielded relatively low contact angles and high bond strength, which appears to be related to the dissolution of the coating in Al and formation of a favorable interface structure.

Determination of the Contact Angle Based on the Casimir Effect

NASA Technical Reports Server (NTRS)

Mazuruk, Konstantin; Volz, Martin P.

2015-01-01

On a macroscopic scale, a nonreactive liquid partially covering a homogeneous solid surface will intersect the solid at an angle called the contact angle. For molten metals and semiconductors, the contact angle is materially dependent upon both the solid and liquid and typical values fall in the range 80-170 deg, depending on the crucible material. On a microscopic scale, there does not exist a precise and sharp contact angle but rather the liquid and solid surfaces merge smoothly and continuously. Consider the example of the so called detached Bridgman crystal growth process. In this technique, a small gap is formed between the growing crystal and the crucible. At the crystal/melt interface, a meniscus ring is formed. Its width can be in the range of a few micrometers, approaching a microscopic scale. It then becomes questionable to describe the shape of this meniscus by the contact angle. A more advanced treatment of the interface is needed and here we propose such a refined model. The interaction of the liquid surface with the solid can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir or van der Waals force.

Measurements of advancing and receding contact angles of water on PMMA and CR-39 at various g-levels

NASA Astrophysics Data System (ADS)

Mireault, Nicolas; Abel, Gilles; Andrzejewski, Lukasz; Ross, Guy

2005-03-01

The main purpose of this work is to clarify the controversy that has been widely discussed after the publication of Ward et al. [1, 2, 3] about whether varying g-levels should have an influence on contact angles of liquids on solid surfaces. Surface modification using PBII has been used to vary the contact angles of water on PMMA and CR-39 samples by implantation of O2 and Ar ions. Advancing and receding contact angles (θa and θr) have been measured using the injection and the withdrawn of a 3 μL water drop at a 2 μL/min rate on these PMMA and CR-39 samples, implanted or not. Analysis of the recorded frames of the whole parabola yielded the θa and θr vs g plots that are shown and discussed, while g-level vary from g˜0.03 up to g˜2.5. Comparison of the variable g hystereses with those measured in constant 1 g using the same samples is also made. Angle variations being lower than the measurement precision, the results indicate that the contact angles do not vary with g-level.

Comparative Biomechanical Study on Contact Alterations After Lateral Meniscus Posterior Root Avulsion, Transosseous Reinsertion, and Total Meniscectomy.

PubMed

Perez-Blanca, Ana; Espejo-Baena, Alejandro; Amat Trujillo, Daniel; Prado Nóvoa, María; Espejo-Reina, Alejandro; Quintero López, Clara; Ezquerro Juanco, Francisco

2016-04-01

To compare the effects of lateral meniscus posterior root avulsion left in situ, its repair, and meniscectomy on contact pressure distribution in both tibiofemoral compartments at different flexion angles. Eight cadaveric knees were tested under compressive 1000 N load for 4 lateral meniscus conditions (intact, posterior root avulsion, transosseous root repair, and total meniscectomy) at flexion angles 0°, 30°, 60°, and 90°. Contact area and pressure distribution were registered using K-scan pressure sensors inserted between menisci and tibial plateau. In the lateral compartment, root detachment decreased contact area (P = .017, 0° and 30°; P = .012, 60° and 90°) and increased mean (P = .012, all angles) and maximum (P = .025, 0° and 30°; P = .017, 60°; P = .012, 90°) pressures relative to intact condition. Repair restored all measured parameters close to intact at 0°, but effectiveness decreased with flexion angle, yielding no significant effect at 90°. Meniscectomy produced higher decreases than root avulsion in contact area (P = .012, 0° and 90°; P = .05, 30° and 60°) and increases in mean (P = .017, 0° and 30°; P = .018, 90°) and maximum pressure (P = .012, 0°; P = .036, 30°). In the medial compartment, lesion changed the contact area at high flexion angles only, while meniscectomy induced greater changes at all angles. Lateral meniscus posterior root avulsion generates significant alterations in contact area and pressures at lateral knee compartment for flexion angles between full extension and 90°. Meniscectomy causes greater disorders than the avulsion left in situ. Transosseous repair with a single suture restores these alterations to conditions close to intact at 0° and 30° but not at 60° and 90°. Altered contact mechanics after lateral meniscus posterior root avulsion might have degenerative consequences. Transosseous repair with one suture should be revised to effectively restore contact mechanics at high flexion angles. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Contact Angle and Adhesion Dynamics and Hysteresis on Molecularly Smooth Chemically Homogeneous Surfaces.

PubMed

Chen, Szu-Ying; Kaufman, Yair; Schrader, Alex M; Seo, Dongjin; Lee, Dong Woog; Page, Steven H; Koenig, Peter H; Isaacs, Sandra; Gizaw, Yonas; Israelachvili, Jacob N

2017-09-26

Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values is experimentally difficult because it requires loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading adhesion energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of "contact mechanics" and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for systems that exhibited both steady and varying velocities from V ≈ 10 mm/s to 1 nm/s, where in all cases but one, the advancing (V > 0) and receding (V < 0) adhesion energies and/or contact angles converged toward the same theoretical (thermodynamic) values as V → 0. Our equations for the dynamic contact angles are similar to the classic equations of Blake & Haynes (1969) and fitted the experimental adhesion data equally well over the range of velocities studied, although with somewhat different fitting parameters for the characteristic molecular length/dimension or area and characteristic bond formation/rupture lifetime or velocity. Our theoretical and experimental methods and results unify previous kinetic theories of adhesion and contact angle hysteresis and offer new experimental methods for testing kinetic models in the thermodynamic, quasi-static, limit. Our analyses are limited to kinetic effects only, and we conclude that hydrodynamic, i.e., viscous, and inertial effects do not play a role at the interfacial velocities of our experiments, i.e., V < (1-10) mm/s (for water and hexadecane, but for viscous polymers it may be different), consistent with previously reported studies.

Wetting and interfacial properties of water nanodroplets in contact with graphene and monolayer boron-nitride sheets.

PubMed

Li, Hui; Zeng, Xiao Cheng

2012-03-27

Born-Oppenheim quantum molecular dynamics (QMD) simulations are performed to investigate wetting, diffusive, and interfacial properties of water nanodroplets in contact with a graphene sheet or a monolayer boron-nitride (BN) sheet. Contact angles of the water nanodroplets on the two sheets are computed for the first time using QMD simulations. Structural and dynamic properties of the water droplets near the graphene or BN sheet are also studied to gain insights into the interfacial interaction between the water droplet and the substrate. QMD simulation results are compared with those from previous classic MD simulations and with the experimental measurements. The QMD simulations show that the graphene sheet yields a contact angle of 87°, while the monolayer BN sheet gives rise to a contact angle of 86°. Hence, like graphene, the monolayer BN sheet is also weakly hydrophobic, even though the BN bonds entail a large local dipole moment. QMD simulations also show that the interfacial water can induce net positive charges on the contacting surface of the graphene and monolayer BN sheets, and such charge induction may affect electronic structure of the contacting graphene in view that graphene is a semimetal. Contact angles of nanodroplets of water in a supercooled state on the graphene are also computed. It is found that under the supercooled condition, water nanodroplets exhibit an appreciably larger contact angle than under the ambient condition. © 2012 American Chemical Society

Role of Viscous Dissipative Processes on the Wetting of Textured Surfaces

PubMed Central

Grewal, H. S.; Nam Kim, Hong; Cho, Il-Joo; Yoon, Eui-Sung

2015-01-01

We investigate the role of viscous forces on the wetting of hydrophobic, semi-hydrophobic, and hydrophilic textured surfaces as second-order effects. We show that during the initial contact, the transition from inertia- to viscous-dominant regime occurs regardless of their surface topography and chemistry. Furthermore, we demonstrate the effect of viscosity on the apparent contact angle under quasi-static conditions by modulating the ratio of a water/glycerol mixture and show the effect of viscosity, especially on the semi-hydrophobic and hydrophobic textured substrates. The reason why the viscous force does not affect the apparent contact angle of the hydrophilic surface is explained based on the relationship between the disjoining pressure and surface chemistry. We further propose a wetting model that can predict the apparent contact angle of a liquid drop on a textured substrate by incorporating a viscous force component in the force balance equation. This model can predict apparent contact angles on semi-hydrophobic and hydrophobic textured surfaces exhibiting Wenzel state more accurately than the Wenzel model, indicating the importance of viscous forces in determining the apparent contact angle. The modified model can be applied for estimating the wetting properties of arbitrary engineered surfaces. PMID:26390958

Articular contact pressures of meniscal repair techniques at various knee flexion angles.

PubMed

Flanigan, David C; Lin, Fang; Koh, Jason L; Zhang, Li-Qun

2010-07-13

Articular cartilage injury can occur after meniscal repair with biodegradable implants. Previous contact pressure analyses of the knee have been based on the tibial side of the meniscus at limited knee flexion angles. We investigated articular contact pressures on the posterior femoral condyle with different knee flexion angles and surgical repair techniques. Medial meniscus tears were repaired in 30 fresh bovine knees. Knees were mounted on a 6-degrees-of-freedom jig and statically loaded to 200 N at 45 degrees, 70 degrees, 90 degrees, and 110 degrees of knee flexion under 3 conditions: intact meniscus, torn meniscus, and meniscus after repair. For each repair, 3 sutures or biodegradable implants were used. A pressure sensor was used to determine the contact area and peak pressure. Peak pressures over each implant position were measured. Peak pressure increased significantly as knee flexion increased in normal, injured, and repaired knees. The change in peak pressure in knees with implant repairs was significantly higher than suture repairs at all knee flexion angles. Articular contact pressure on the posterior femoral condyle increased with knee flexion. Avoidance of deep knee flexion angles postoperatively may limit increases in articular contact pressures and potential chondral injury. Copyright 2010, SLACK Incorporated.

Thermodynamics of Surface Nanobubbles.

PubMed

Zargarzadeh, Leila; Elliott, Janet A W

2016-11-01

In this paper, we examine the thermodynamic stability of surface nanobubbles. The appropriate free energy is defined for the system of nanobubbles on a solid surface submerged in a supersaturated liquid solution at constant pressure and temperature, under conditions where an individual nanobubble is not in diffusive contact with a gas phase outside of the system or with other nanobubbles on the time scale of the experiment. The conditions under which plots of free energy versus the radius of curvature of the nanobubbles show a global minimum, which denotes the stable equilibrium state, are explored. Our investigation shows that supersaturation and an anomalously high contact angle (measured through the liquid) are required to have stable surface nanobubbles. In addition, the anomalously high contact angle of surface nanobubbles is discussed from the standpoint of a framework recently proposed by Koch, Amirfazli, and Elliott that relates advancing and receding contact angles to thermodynamic equilibrium contact angles, combined with the existence of a gas enrichment layer.

Transition from stripe-like patterns to a particulate film using driven evaporating menisci.

PubMed

Noguera-Marín, Diego; Moraila-Martínez, Carmen L; Cabrerizo-Vílchez, Miguel A; Rodríguez-Valverde, Miguel A

2014-07-01

Better control of colloidal assembly by convective deposition is particularly helpful in particle templating. However, knowledge of the different factors that can alter colloidal patterning mechanisms is still insufficient. Deposit morphology is strongly ruled by contact line dynamics, but the wettability properties of the substrate can alter it drastically. In this work, we experimentally examined the roles of substrate contact angle hysteresis and receding contact angle using driven evaporating menisci similar to the dip-coating technique but at a low capillary number. We used smooth substrates with very different wettability properties and nanoparticles of different sizes. For fixed withdrawal velocity, evaporation conditions, and nanoparticle concentration, we analyzed the morphology of the deposits formed on each substrate. A gradual transition from stripe-like patterns to a film was observed as the contact angle hysteresis and receding contact angle were lowered.

Numerical Simulation of Dynamic Contact Angles and Contact Lines in Multiphase Flows using Level Set Method

NASA Astrophysics Data System (ADS)

Pendota, Premchand

Many physical phenomena and industrial applications involve multiphase fluid flows and hence it is of high importance to be able to simulate various aspects of these flows accurately. The Dynamic Contact Angles (DCA) and the contact lines at the wall boundaries are a couple of such important aspects. In the past few decades, many mathematical models were developed for predicting the contact angles of the inter-face with the wall boundary under various flow conditions. These models are used to incorporate the physics of DCA and contact line motion in numerical simulations using various interface capturing/tracking techniques. In the current thesis, a simple approach to incorporate the static and dynamic contact angle boundary conditions using the level set method is developed and implemented in multiphase CFD codes, LIT (Level set Interface Tracking) (Herrmann (2008)) and NGA (flow solver) (Desjardins et al (2008)). Various DCA models and associated boundary conditions are reviewed. In addition, numerical aspects such as the occurrence of a stress singularity at the contact lines and grid convergence of macroscopic interface shape are dealt with in the context of the level set approach.

Contact angles and wettability of ionic liquids on polar and non-polar surfaces†

PubMed Central

Sousa, Filipa L.; Silva, Nuno J. O.; Lopes-da-Silva, José A.; Coutinho, João A. P.; Freire, Mara G.

2016-01-01

Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation–anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation–anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application. PMID:26554705

Contact angles and wettability of ionic liquids on polar and non-polar surfaces.

PubMed

Pereira, Matheus M; Kurnia, Kiki A; Sousa, Filipa L; Silva, Nuno J O; Lopes-da-Silva, José A; Coutinho, João A P; Freire, Mara G

2015-12-21

Many applications involving ionic liquids (ILs) require the knowledge of their interfacial behaviour, such as wettability and adhesion. In this context, herein, two approaches were combined aiming at understanding the impact of the IL chemical structures on their wettability on both polar and non-polar surfaces, namely: (i) the experimental determination of the contact angles of a broad range of ILs (covering a wide number of anions of variable polarity, cations, and cation alkyl side chain lengths) on polar and non-polar solid substrates (glass, Al-plate, and poly-(tetrafluoroethylene) (PTFE)); and (ii) the correlation of the experimental contact angles with the cation-anion pair interaction energies generated by the Conductor-like Screening Model for Real Solvents (COSMO-RS). The combined results reveal that the hydrogen-bond basicity of ILs, and thus the IL anion, plays a major role through their wettability on both polar and non-polar surfaces. The increase of the IL hydrogen-bond accepting ability leads to an improved wettability of more polar surfaces (lower contact angles) while the opposite trend is observed on non-polar surfaces. The cation nature and alkyl side chain lengths have however a smaller impact on the wetting ability of ILs. Linear correlations were found between the experimental contact angles and the cation-anion hydrogen-bonding and cation ring energies, estimated using COSMO-RS, suggesting that these features primarily control the wetting ability of ILs. Furthermore, two-descriptor correlations are proposed here to predict the contact angles of a wide variety of ILs on glass, Al-plate, and PTFE surfaces. A new extended list is provided for the contact angles of ILs on three surfaces, which can be used as a priori information to choose appropriate ILs before a given application.

Capillary spreading of contact line over a sinking sphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Seong Jin; Fezzaa, Kamel; An, Jim

The contact line dynamics over a sinking solid sphere are investigated in comparison with classical spreading theories. Experimentally, high-speed imaging systems with optical light or x-ray illumination are employed to accurately measure the spreading motion and dynamic contact angle of the contact line. Millimetric spheres are controlled to descend with a constant speed ranging from 7.3 × 10-5 to 0.79 m/s. We observed three different spreading stages over a sinking sphere, which depends on the contact line velocity and contact angle. These stages consistently showed the characteristics of capillarity-driven spreading as the contact line spreads faster with a higher contactmore » angle. The contact line velocity is observed to follow a classical capillary-viscous model at a high Ohnesorge number (> 0.02). For the cases with a relatively low Ohnesorge number (< 0.02), the contact line velocity is significantly lower than the speed predicted by the capillary-viscous balance. This indicates the existence of an additional opposing force (inertia) for a decreasing Ohnesorge number. The capillary-inertial balance is only observed at the very beginning of the capillary rise, in which the maximum velocity is independent of the sphere’s sinking speed. Additionally, we observed the linear relation between the contact line velocity and the sphere sinking speed during the second stage, which represents capillary adjustment by dynamic contact angle.« less

Characterization of the Intrinsic Water Wettability of Graphite Using Contact Angle Measurements: Effect of Defects on Static and Dynamic Contact Angles.

PubMed

Kozbial, Andrew; Trouba, Charlie; Liu, Haitao; Li, Lei

2017-01-31

Elucidating the intrinsic water wettability of the graphitic surface has increasingly attracted research interests, triggered by the recent finding that the well-established hydrophobicity of graphitic surfaces actually results from airborne hydrocarbon contamination. Currently, static water contact angle (WCA) is often used to characterize the intrinsic water wettability of graphitic surfaces. In the current paper, we show that because of the existence of defects, static WCA does not necessarily characterize the intrinsic water wettability. Freshly exfoliated graphite of varying qualities, characterized using atomic force microscopy and Raman spectroscopy, was studied using static, advancing, and receding WCA measurements. The results showed that graphite of different qualities (i.e., defect density) always has a similar advancing WCA, but it could have very different static and receding WCAs. This finding indicates that defects play an important role in contact angle measurements, and the static contact angle does not always represent the intrinsic water wettability of pristine graphite. On the basis of the experimental results, a qualitative model is proposed to explain the effect of defects on static, advancing, and receding contact angles. The model suggests that the advancing WCA reflects the intrinsic water wettability of pristine (defect-free) graphite. Our results showed that the advancing WCA for pristine graphite is 68.6°, which indicates that graphitic carbon is intrinsically mildly hydrophilic.

The Influence of Dynamic Contact Angle on Wetting Dynamics

NASA Technical Reports Server (NTRS)

Rame, Enrique; Garoff, Steven

2005-01-01

When surface tension forces dominate, and regardless of whether the situation is static or dynamic, the contact angle (the angle the interface between two immiscible fluids makes when it contacts a solid) is the key parameter that determines the shape of a fluid-fluid interface. The static contact angle is easy to measure and implement in models predicting static capillary surface shapes and such associated quantities as pressure drops. By contrast, when the interface moves relative to the solid (as in dynamic wetting processes) the dynamic contact angle is not identified unambiguously because it depends on the geometry of the system Consequently, its determination becomes problematic and measurements in one geometry cannot be applied in another for prediction purposes. However, knowing how to measure and use the dynamic contact angle is crucial to determine such dynamics as a microsystem throughput reliably. In this talk we will present experimental and analytical efforts aimed at resolving modeling issues present in dynamic wetting. We will review experiments that show the inadequacy of the usual hydrodynamic model when a fluid-fluid meniscus moves over a solid surface such as the wall of a small tube or duct. We will then present analytical results that show how to parametrize these problems in a predictive manner. We will illustrate these ideas by showing how to implement the method in numerical fluid mechanical calculations.

Investigation of surface porosity measurements and compaction pressure as means to ensure consistent contact angle determinations.

PubMed

Holm, René; Borkenfelt, Simon; Allesø, Morten; Andersen, Jens Enevold Thaulov; Beato, Stefania; Holm, Per

2016-02-10

Compounds wettability is critical for a number of central processes including disintegration, dispersion, solubilisation and dissolution. It is therefore an important optimisation parameter both in drug discovery but also as guidance for formulation selection and optimisation. Wettability for a compound is determined by its contact angle to a liquid, which in the present study was measured using the sessile drop method applied to a disc compact of the compound. Precise determination of the contact angle is important should it be used to either rank compounds or selected excipients to e.g. increase the wetting from a solid dosage form. Since surface roughness of the compact has been suggested to influence the measurement this study investigated if the surface quality, in terms of surface porosity, had an influence on the measured contact angle. A correlation to surface porosity was observed, however for six out of seven compounds similar results were obtained by applying a standard pressure (866 MPa) to the discs in their preparation. The data presented in the present work therefore suggest that a constant high pressure should be sufficient for most compounds when determining the contact angle. Only for special cases where compounds have poor compressibility would there be a need for a surface-quality-control step before the contact angle determination. Copyright © 2015 Elsevier B.V. All rights reserved.

Wettability measurement under high P-T conditions using X-ray imaging with application to the brine-supercritical CO2 system

NASA Astrophysics Data System (ADS)

Chaudhary, Kuldeep; Guiltinan, Eric J.; Cardenas, M. Bayani; Maisano, Jessica A.; Ketcham, Richard A.; Bennett, Philip C.

2015-09-01

We present a new method for measuring wettability or contact angle of minerals at reservoir pressure-temperature conditions using high-resolution X-ray computed tomography (HRXCT) and radiography. In this method, a capillary or a narrow slot is constructed from a mineral or a rock sample of interest wherein two fluids are allowed to form an interface that is imaged using X-rays. After some validation measurements at room pressure-temperature conditions, we illustrate this method by measuring the contact angle of CO2-brine on quartz, muscovite, shale, borosilicate glass, polytetrafluoroethylene (PTFE or Teflon), and polyether ether ketone (PEEK) surfaces at 60-71°C and 13.8-22.8 MPa. At reservoir conditions, PTFE and PEEK surfaces were found to be CO2-wet with contact angles of 140° and 127°, respectively. Quartz and muscovite were found to be water-wet with contact angles of 26° and 58°, respectively, under similar conditions. Borosilicate glass-air-brine at room conditions showed strong water-wet characteristics with a contact angle of 9°, whereas borosilicate glass-CO2-brine at 13.8 MPa and 60°C showed a decrease in its water-wetness with contact angle of 54°. This method provides a new application for X-ray imaging and an alternative to other methods.

Wettability of MnxSiyOz by Liquid Zn-Al Alloys

NASA Astrophysics Data System (ADS)

Kim, Yunkyum; Shin, Minsoo; Tang, Chengying; Lee, Joonho

2010-08-01

The wettability of MnxSiyOz by liquid Zn-Al alloys was investigated to obtain basic information on the coating properties of high-strength steels with surface oxides in the hot-dip galvanizing process. In this study, the contact angles of liquid Zn-Al alloys (Al concentrations were 0.12 and 0.23 wt pct) on four different MnxSiyOz oxides, namely MnO, MnSiO3, Mn2SiO4, and SiO2, were measured with the dispensed drop method. The contact angle did not change across time. With an increasing Al concentration, the contact angle was slightly decreased for MnO and Mn2SiO4, but there was no change for MnSiO3 and SiO2. With an increasing SiO2 content, the contact angle gradually increased by 54 wt pct to form MnSiO3, and for pure SiO2 substrate, the contact angle decreased again. Consequently, the MnSiO3 substrate showed the worst wettability among the four tested oxide substrates.

Wetting of nanophases: Nanobubbles, nanodroplets and micropancakes on hydrophobic surfaces.

PubMed

An, Hongjie; Liu, Guangming; Craig, Vincent S J

2015-08-01

The observation by Atomic Force Microscopy of a range of nanophases on hydrophobic surfaces poses some challenging questions, not only related to the stability of these objects but also regarding their wetting properties. Spherical capped nanobubbles are observed to exhibit contact angles that far exceed the macroscopic contact angle measured for the same materials, whereas nanodroplets exhibit contact angles that are much the same as the macroscopic contact angle. Micropancakes are reported to consist of gas, in which case their wetting properties are mysterious. They should only be stable when the van der Waals forces act to thicken the film whereas for a gas, the van der Waals forces will always act to thin the film. Here we examine the available evidence and contribute some additional experiments in order to review our understanding of the wetting properties of these nanophases. We demonstrate that if in fact micropancakes consist of a contaminant their wetting properties can be explained, though the very high contact angles of nanobubbles remain unexplained. Copyright © 2014 Elsevier B.V. All rights reserved.

Dependency of the apparent contact angle on nonisothermal conditions

NASA Astrophysics Data System (ADS)

Krahl, Rolf; Gerstmann, Jens; Behruzi, Philipp; Bänsch, Eberhard; Dreyer, Michael E.

2008-04-01

The dynamic behavior of liquids in partly filled containers is influenced to a large extend by the angle between the gas-liquid phase boundary and the solid container wall at the contact line. This contact angle in turn is influenced by nonisothermal conditions. In the case of a cold liquid meniscus spreading over a hot solid wall, the contact angle apparently becomes significantly larger. In this paper we want to establish a quantitative equation for this enlargement, both from experimental and numerical data. Our findings can be used to build a subgrid model for computations, where the resolution is not sufficient to resolve the boundary layers. This might be the case for large containers which are exposed to low accelerations and where the contact angle boundary condition determines the position of the free surface. These types of computation are performed, for example, to solve propellant management problems in launcher and satellite tanks. In this application, the knowledge of the position of the free surface is very important for the withdrawal of liquid and the calculation of heat and mass transfer.

Drop shape visualization and contact angle measurement on curved surfaces.

PubMed

Guilizzoni, Manfredo

2011-12-01

The shape and contact angles of drops on curved surfaces is experimentally investigated. Image processing, spline fitting and numerical integration are used to extract the drop contour in a number of cross-sections. The three-dimensional surfaces which describe the surface-air and drop-air interfaces can be visualized and a simple procedure to determine the equilibrium contact angle starting from measurements on curved surfaces is proposed. Contact angles on flat surfaces serve as a reference term and a procedure to measure them is proposed. Such procedure is not as accurate as the axisymmetric drop shape analysis algorithms, but it has the advantage of requiring only a side view of the drop-surface couple and no further information. It can therefore be used also for fluids with unknown surface tension and there is no need to measure the drop volume. Examples of application of the proposed techniques for distilled water drops on gemstones confirm that they can be useful for drop shape analysis and contact angle measurement on three-dimensional sculptured surfaces. Copyright © 2011 Elsevier Inc. All rights reserved.

Relaxation of contact-line singularities solely by the Kelvin effect and apparent contact angles for isothermal volatile liquids in contact with air

NASA Astrophysics Data System (ADS)

Rednikov, Alexey; Colinet, Pierre

2013-11-01

The contact (triple) line of a volatile liquid on a flat solid is studied theoretically. Like with a pure-vapor atmosphere [Phys. Rev. E 87, 010401, 2013], but here for isothermal diffusion-limited evaporation/condensation in the presence of an inert gas, we rigorously show that the notorious contact-line singularities (related to motion or phase change itself) can be regularized solely on account of the Kelvin effect (curvature dependence of the saturation conditions). No disjoining pressure, precursor films or Navier slip are in fact needed to this purpose, and nor are they taken into consideration here (``minimalist'' approach). The model applies to both perfect (zero Young's angle) and partial wetting, and is in particular used to study the related issue of evaporation-induced contact angles. Their modification by the contact-line motion (either advancing or receding) is assessed. The formulation is posed for a distinguished immediate vicinity of the contact line (the ``microregion''), the corresponding problem decoupling to leading order, here up to one unknown coefficient, from what actually happens at the macroscale. The lubrication approximation (implying sufficiently small contact angles) is used in the liquid, coupled with the diffusion equation in the gaz phase. Supported by ESA and BELSPO PRODEX and F.R.S.-FNRS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rajkumar, K.; Rajavel, K.; Cameron, D. C.

This paper reports the electrowetting properties of liquid droplet on superhydrophobic silicon nanowires with Atomic layer deposited (ALD) Al{sub 2}O{sub 3} as dielectric layer. Silicon wafer were etched by metal assisted wet chemical etching with silver as catalyst. ALD Al{sub 2}O{sub 3} films of 10nm thickness were conformally deposited over silicon nanowires. Al{sub 2}O{sub 3} dielectric film coated silicon nanowires was chemically modified with Trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane to make it superhydrophobic(SHP). The contact angle was measured and all the samples exhibited superhydrophobic nature with maximum contact angles of 163° and a minimum contact angle hysteresis of 6°.more » Electrowetting induced a maximum reversible decrease of the contact angle of 20°at 150V in air.« less

The physics of water droplets on surfaces: exploring the effects of roughness and surface chemistry

NASA Astrophysics Data System (ADS)

Eid, K. F.; Panth, M.; Sommers, A. D.

2018-03-01

This paper explores the fluid property commonly called surface tension, its effect on droplet shape and contact angle, and the major influences of contact angle behaviour (i.e. surface roughness and surface chemistry). Images of water droplets placed on treated copper surfaces are used to measure the contact angles between the droplets and the surface. The surface wettability is manipulated either by growing a self-assembled monolayer on the surface to make it hydrophobic or by changing the surface roughness. The main activities in this experiment, then, are (1) preparing and studying surfaces with different surface wettability and roughness; (2) determining the shape and contact angles of water droplets on these surfaces; and (3) demonstrating the spontaneous motion of water droplets using surface tension gradients.

Improving contact layer patterning using SEM contour based etch model

NASA Astrophysics Data System (ADS)

Weisbuch, François; Lutich, Andrey; Schatz, Jirka; Hertzsch, Tino; Moll, Hans-Peter

2016-10-01

The patterning of the contact layer is modulated by strong etch effects that are highly dependent on the geometry of the contacts. Such litho-etch biases need to be corrected to ensure a good pattern fidelity. But aggressive designs contain complex shapes that can hardly be compensated with etch bias table and are difficult to characterize with standard CD metrology. In this work we propose to implement a model based etch compensation method able to deal with any contact configuration. With the help of SEM contours, it was possible to get reliable 2D measurements particularly helpful to calibrate the etch model. The selections of calibration structures was optimized in combination with model form to achieve an overall errRMS of 3nm allowing the implementation of the model in production.

Experimental methodology of contact edge roughness on sub-100-nm pattern

NASA Astrophysics Data System (ADS)

Lee, Tae Yong; Ihm, Dongchul; Kang, Hyo Chun; Lee, Jun Bum; Lee, Byoung-Ho; Chin, Soo-Bok; Cho, Do-Hyun; Kim, Yang Hyong; Yang, Ho Dong; Yang, Kyoung Mo

2004-05-01

The measurement of edge roughness has become a hot issue in the semiconductor industry. Major vendors offer a variety of features to measure the edge roughness in their CD-SEMs. However, most of the features are limited by the applicable pattern types. For the line and space patterns, features such as Line Edge Roughness (LER) and Line Width Roughness (LWR) are available in current CD-SEMs. The edge roughness is more critical in contact process. However the measurement of contact edge roughness (CER) or contact space roughness (CSR) is more complicated than that of LER or LWR. So far, no formal standard measurement algorithm or definition of contact roughness measurement exists. In this article, currently available features are investigated to assess their representability for CER or CSR. Some new ideas to quantify CER and CSR were also suggested with preliminary experimental results.

Smoothed particle hydrodynamics study of the roughness effect on contact angle and droplet flow.

PubMed

Shigorina, Elena; Kordilla, Jannes; Tartakovsky, Alexandre M

2017-09-01

We employ a pairwise force smoothed particle hydrodynamics (PF-SPH) model to simulate sessile and transient droplets on rough hydrophobic and hydrophilic surfaces. PF-SPH allows modeling of free-surface flows without discretizing the air phase, which is achieved by imposing the surface tension and dynamic contact angles with pairwise interaction forces. We use the PF-SPH model to study the effect of surface roughness and microscopic contact angle on the effective contact angle and droplet dynamics. In the first part of this work, we investigate static contact angles of sessile droplets on different types of rough surfaces. We find that the effective static contact angles of Cassie and Wenzel droplets on a rough surface are greater than the corresponding microscale static contact angles. As a result, microscale hydrophobic rough surfaces also show effective hydrophobic behavior. On the other hand, microscale hydrophilic surfaces may be macroscopically hydrophilic or hydrophobic, depending on the type of roughness. We study the dependence of the transition between Cassie and Wenzel states on roughness and droplet size, which can be linked to the critical pressure for the given fluid-substrate combination. We observe good agreement between simulations and theoretical predictions. Finally, we study the impact of the roughness orientation (i.e., an anisotropic roughness) and surface inclination on droplet flow velocities. Simulations show that droplet flow velocities are lower if the surface roughness is oriented perpendicular to the flow direction. If the predominant elements of surface roughness are in alignment with the flow direction, the flow velocities increase compared to smooth surfaces, which can be attributed to the decrease in fluid-solid contact area similar to the lotus effect. We demonstrate that classical linear scaling relationships between Bond and capillary numbers for droplet flow on flat surfaces also hold for flow on rough surfaces.

Capillary surfaces in a wedge: Differing contact angles

NASA Technical Reports Server (NTRS)

Concus, Paul; Finn, Robert

1994-01-01

The possible zero-gravity equilibrium configurations of capillary surfaces u(x, y) in cylindrical containers whose sections are (wedge) domains with corners are investigated mathematically, for the case in which the contact angles on the two sides of the wedge may differ. In such a situation the behavior can depart in significant qualitative ways from that for which the contact angles on the two sides are the same. Conditions are described under which such qualitative changes must occur. Numerically computed surfaces are depicted to indicate the behavior.

Wettability of Pyrolytic Boron Nitride by Aluminum

NASA Technical Reports Server (NTRS)

Chiaramonte, Francis P.; Rosenthal, Bruce N.

1991-01-01

The wetting of pyrolytic boron nitride by molten 99.9999 percent pure aluminum was investigated by using the sessile drop method in a vacuum operating at approximately 660 micro-Pa at temperatures ranging from 700 to 1000 C. The equilibrium contact angle decreased with an increase in temperature. For temperatures at 900 C or less, the equilibrium contact angle was greater than 90 deg. At 1000 C a nonwetting-to-wetting transition occurred and the contact angle stabilized at 49 deg.

Contact angles of wetting and water stability of soil structure

NASA Astrophysics Data System (ADS)

Kholodov, V. A.; Yaroslavtseva, N. V.; Yashin, M. A.; Frid, A. S.; Lazarev, V. I.; Tyugai, Z. N.; Milanovskiy, E. Yu.

2015-06-01

From the soddy-podzolic soils and typical chernozems of different texture and land use, dry 3-1 mm aggregates were isolated and sieved in water. As a result, water-stable aggregates and water-unstable particles composing dry 3-1 mm aggregates were obtained. These preparations were ground, and contact angles of wetting were determined by the static sessile drop method. The angles varied from 11° to 85°. In most cases, the values of the angles for the water-stable aggregates significantly exceeded those for the water-unstable components. In terms of carbon content in structural units, there was no correlation between these parameters. When analyzing the soil varieties separately, the significant positive correlation between the carbon content and contact angle of aggregates was revealed only for the loamy-clayey typical chernozem. Based on the multivariate analysis of variance, the value of contact wetting angle was shown to be determined by the structural units belonging to water-stable or water-unstable components of macroaggregates and by the land use type. In addition, along with these parameters, the texture has an indirect effect.

Characterization of polydimethylsiloxane (PDMS) properties for biomedical micro/nanosystems.

PubMed

Mata, Alvaro; Fleischman, Aaron J; Roy, Shuvo

2005-12-01

Polydimethylsiloxane (PDMS Sylgard 184, Dow Corning Corporation) pre-polymer was combined with increasing amounts of cross-linker (5.7, 10.0, 14.3, 21.4, and 42.9 wt.%) and designated PDMS1, PDMS2, PDMS3, PDMS4, and PDMS5, respectively. These materials were processed by spin coating and subjected to common micro-fabrication, micro-machining, and biomedical processes: chemical immersion, oxygen plasma treatment, sterilization, and exposure to tissue culture media. The PDMS formulations were analyzed by gravimetry, goniometry, tensile testing, nano-indentation, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Spin coating of PDMS was formulation dependent with film thickness ranging from 308 microm on PDMS1 to 171 microm on PDMS5 at 200 revolutions per minute (rpm). Ultimate tensile stress (UTS) increased from 3.9 MPa (PDMS1) to 10.8 MPa (PDMS3), and then decreased down to 4.0 MPa (PDMS5). Autoclave sterilization (AS) increased the storage modulus (sigma) and UTS in all formulations, with the highest increase in UTS exhibited by PDMS5 (218%). PDMS surface hydrophilicity and micro-textures were generally unaffected when exposed to the different chemicals, except for micro-texture changes after immersion in potassium hydroxide and buffered hydrofluoric, nitric, sulfuric, and hydrofluoric acids; and minimal changes in contact angle after immersion in hexane, hydrochloric acid, photoresist developer, and toluene. Oxygen plasma treatment decreased the contact angle of PDMS2 from 109 degrees to 60 degrees. Exposure to tissue culture media resulted in increased PDMS surface element concentrations of nitrogen and oxygen.

Production of hybrid macro/micro/nano surface structures on Ti6Al4V surfaces by picosecond laser surface texturing and their antifouling characteristics.

PubMed

Rajab, Fatema H; Liauw, Christopher M; Benson, Paul S; Li, Lin; Whitehead, Kathryn A

2017-12-01

The development of surfaces which reduce biofouling has attracted much interest in practical applications. Three picosecond laser generated surface topographies (Ti1, Ti2, Ti3) on titanium were produced, treated with fluoroalkylsilane (FAS), then characterised using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Raman Spectroscopy, Fourier Transform Infra-Red (FTIR) spectroscopy, contact angle measurements and white light interference microscopy. The surfaces had a range of different macro/micro/nano topographies. Ti2 had a unique, surface topography with large blunt conical peaks and was predominantly a rutile surface with closely packed, self-assembled FAS; this was the most hydrophobic sample (water contact angle 160°; ΔG iwi was -135.29mJm -2 ). Bacterial attachment, adhesion and retention to the surfaces demonstrated that all the laser generated surfaces retained less bacteria than the control surface. This also occurred following the adhesion and retention assays when the bacteria were either not rinsed from the surfaces or were retained in static conditions for one hour. This work demonstrated that picosecond laser generated surfaces may be used to produce antiadhesive surfaces that significantly reduced surface fouling. It was determined that a tri-modally dimensioned surface roughness, with a blunt conical macro-topography, combined with a close-packed fluoroalkyl monolayer was required for an optimised superhydrophobic surface. These surfaces were effective even following surface immersion and static conditions for one hour, and thus may have applications in a number of food or medical industries. Copyright © 2017 Elsevier B.V. All rights reserved.

Application of hybrid organic/inorganic polymers as coatings on metallic substrates

NASA Astrophysics Data System (ADS)

Augustinho, T. R.; Motz, G.; Ihlow, S.; Machado, R. A. F.

2016-09-01

Acrylic polymers, particularly poly (methyl methacrylate) (PMMA), have certain specific properties, such as good film formation, transparency, and good mechanical properties, which have been widely used in paints, coatings and adhesives. However, the limited chemical and physical stability of these pure polymers limits their applications when exposed to hostile conditions, as in ship hulls, for example. A suitable way to enhance PMMA properties is the addition of silicon polymers with very good protective characteristics. In this study, a PMMA and HTT 1800 (commercial silazane) copolymer were applied on metallic substrate and compared to pure PMMA and HTT 1800. All the materials were applied as coatings. They were applied on stainless steel via dip-coating to investigate the coating properties. Thermal cycling was employed to analyze coating durability at high temperatures (50 °C to 600 °C). Optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the coated surfaces, and the adhesion of pure PMMA, pure HTT 1800 and PMMA/HTT 1800 coatings on metallic substrate was investigated by Cross-Cut-Test (ASTM D 3359). The sessile drop method was used to determine the contact angle. PMMA coatings presented complete degradation from 250 °C, while hybrid coatings of PMMA and HTT 1800 have good protection until 400 °C. The adherence of the coating on metallic substrate showed improvement in all synthesized materials when compared to pure PMMA, obtaining the best adherence possible. The contact angle test showed that the hydrophobicity of the hybrid coatings is higher than that of the pure coatings.

Wetting Behavior of Mold Flux Droplet on Steel Substrate With or Without Interfacial Reaction

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Li, Jingwen; Wang, Wanlin; Sohn, Il

2017-08-01

The slag entrapment in mold tends to cause severe defects on the slab surface, especially for casting steels containing active alloy elements such as Al, Ti, and Mn. The wetting behavior of molten mold flux on the initial solidified shell is considered to be a key factor to determine the entrapment of mold slag on the shell surface. Therefore, the wetting behavior of mold flux droplet on the steel substrate with or without interfacial reaction was investigated by the sessile drop method. The results indicated that the melting process of mold flux has a significant influence on the variation of contact angle, and the final contact angle for Flux1 droplet on 20Mn23AlV is only 15 deg, which is lower than the other two cases due to the intensive interracial reactions occurring in this case. In addition, the thickness of the interaction layer for the case of Flux1 on 20Mn23AlV is 10- μm greater than the other two cases, which confirms that the most intensive reactions occurred at the interface area. The microstructure and element distribution at the interface analyzed by a scanning electron microscope (SEM) and energy dispersive spectrum (EDS) suggested that the increase of wettability of mold flux droplet on the steel substrate is caused by the migration of Al, Mn, and Si elements occurring in the vicinity of the interface. The results obtained in this article can reveal the mechanism of flux entrapment by hook or shell and provide theoretic guidance for mold flux design and optimization.

RTV silicone rubber surface modification for cell biocompatibility by negative-ion implantation

NASA Astrophysics Data System (ADS)

Zheng, Chenlong; Wang, Guangfu; Chu, Yingjie; Xu, Ya; Qiu, Menglin; Xu, Mi

2016-03-01

A negative cluster ion implantation system was built on the injector of a GIC4117 tandem accelerator. Next, the system was used to study the surface modification of room temperature vulcanization silicone rubber (RTV SR) for cell biocompatibility. The water contact angle was observed to decrease from 117.6° to 99.3° as the C1- implantation dose was increased to 1 × 1016 ions/cm2, and the effects of C1-, C2- and O1- implantation result in only small differences in the water contact angle at 3 × 1015 ions/cm2. These findings indicate that the hydrophilicity of RTV SR improves as the dose is increased and that the radiation effect has a greater influence than the doping effect on the hydrophilicity. There are two factors influence hydrophilicity of RTV: (1) based on the XPS and ATR-FTIR results, it can be inferred that ion implantation breaks the hydrophobic functional groups (Sisbnd CH3, Sisbnd Osbnd Si, Csbnd H) of RTV SR and generates hydrophilic functional groups (sbnd COOH, sbnd OH, Sisbnd (O)x (x = 3,4)). (2) SEM reveals that the implanted surface of RTV SR appears the micro roughness such as cracks and wrinkles. The hydrophilicity should be reduced due to the lotus effect (Zhou Rui et al., 2009). These two factors cancel each other out and make the C-implantation sample becomes more hydrophilic in general terms. Finally, cell culture demonstrates that negative ion-implantation is an effective method to improve the cell biocompatibility of RTV SR.

Development of High-Antifouling PPSU Ultrafiltration Membrane by Using Compound Additives: Preparation, Morphologies, and Filtration Resistant Properties

PubMed Central

Liu, Jie; Zhong, Zhencheng; Ma, Rui; Zhang, Weichen; Li, Jiding

2016-01-01

In this study, flat sheet asymmetric polyphenylsulfone (PPSU) ultrafiltration membranes with enhanced antifouling properties were prepared with a non-solvent induced phase separation (NIPS) method through compound additives containing a polymeric pore-forming agent, a small molecular non-solvent and a surfactant. The formation processes of the porous asymmetric membranes with different kinds of additives were studied in detail, and the microstructure controllable preparation of membrane was achieved by establishing a bridge between the membrane preparation parameters and separation performances. All prepared membranes were characterized by using a scanning electron microscope (SEM), contact angle analysis, porosity, maximum pore size, water and BSA solution permeability studies. The performance efficiency of the membrane was evaluated by using BSA as a model foulant in terms of permeability, solute rejection (R), Rm (membrane inherent resistance), Rc (cake layer resistance), and Rp (pore plugging resistance). The results showed that when the compound additives were used, the inter-connected pores were observed, maximum pore size, contact angle and membrane filtration resistance decreased, while the porosity increased. When PVP compound additives were added, the water flux increased from 80.4 to 148.1 L/(m2·h), the BSA rejection increased from 53.2% to 81.5%. A similar trend was observed for membranes with added PEG compound additives; the water flux and BSA rejection simultaneously increased. The filtration resistance decreased as a result of compound additives. The uniformity of membrane and the number of effective pores could be enhanced by adding compound additives through the cooperation of different additives. PMID:27338487

Development of High-Antifouling PPSU Ultrafiltration Membrane by Using Compound Additives: Preparation, Morphologies, and Filtration Resistant Properties.

PubMed

Liu, Jie; Zhong, Zhencheng; Ma, Rui; Zhang, Weichen; Li, Jiding

2016-06-21

In this study, flat sheet asymmetric polyphenylsulfone (PPSU) ultrafiltration membranes with enhanced antifouling properties were prepared with a non-solvent induced phase separation (NIPS) method through compound additives containing a polymeric pore-forming agent, a small molecular non-solvent and a surfactant. The formation processes of the porous asymmetric membranes with different kinds of additives were studied in detail, and the microstructure controllable preparation of membrane was achieved by establishing a bridge between the membrane preparation parameters and separation performances. All prepared membranes were characterized by using a scanning electron microscope (SEM), contact angle analysis, porosity, maximum pore size, water and BSA solution permeability studies. The performance efficiency of the membrane was evaluated by using BSA as a model foulant in terms of permeability, solute rejection (R), Rm (membrane inherent resistance), Rc (cake layer resistance), and Rp (pore plugging resistance). The results showed that when the compound additives were used, the inter-connected pores were observed, maximum pore size, contact angle and membrane filtration resistance decreased, while the porosity increased. When PVP compound additives were added, the water flux increased from 80.4 to 148.1 L/(m²·h), the BSA rejection increased from 53.2% to 81.5%. A similar trend was observed for membranes with added PEG compound additives; the water flux and BSA rejection simultaneously increased. The filtration resistance decreased as a result of compound additives. The uniformity of membrane and the number of effective pores could be enhanced by adding compound additives through the cooperation of different additives.

Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

NASA Astrophysics Data System (ADS)

Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

2013-09-01

As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

Characterization of a novel ultra low refractive index material for biosensor application

PubMed Central

Memisevic, Jasenka; Korampally, Venumadhav; Gangopadhyay, Shubhra; Grant, Sheila A.

2009-01-01

Nanoporous materials can provide significant benefits to the field of biosensors. Their size and porous structure makes them an ideal tool for improving sensor performance. This study characterized a novel ultra low index of refraction nanoporous organosilicate (NPO) material for use as an optical platform for fluorescence-based optical biosensors. While serving as the low index cladding material, the novel coating based on organosilicate nanoparticles also provides an opportunity for a high surface area coating that can be utilized for immobilizing biological probes. Biological molecules were immobilized onto NPO, which was spin-coated on silicon and glass substrates. The biological molecule was composed of Protein A conjugated to AlexaFluor 546 fluorophore and then immobilized onto the NPO substrate via silanization. Sample analysis consisted of spectrofluorometry, FT-IR spectroscopy, scanning electron microscopy, contact angle measurement and ellipsometry. The results showed the presence of emission peaks at 574 nm, indicating that the immobilization of Protein A to the NPO material is possible. When compared to Si and glass substrates not coated with NPO, the results showed a 100X and 10X increase in packing density with the NPO coated films respectively. Ellipsometric analysis, FT-IR, contact angle, and SEM imaging of the surface immobilized NPO films suggested that while the surface modifications did induce some damage, it did not incur significant changes to its unique characteristics, i.e., pore structure, wettability and index of refraction. It was concluded that NPO films would be a viable sensor substrate to enhance sensitivity and improve sensor performance. PMID:20161155

Discrete Element Method Simulations of the Inter-Particle Contact Parameters for the Mono-Sized Iron Ore Particles.

PubMed

Li, Tongqing; Peng, Yuxing; Zhu, Zhencai; Zou, Shengyong; Yin, Zixin

2017-05-11

Aiming at predicting what happens in reality inside mills, the contact parameters of iron ore particles for discrete element method (DEM) simulations should be determined accurately. To allow the irregular shape to be accurately determined, the sphere clump method was employed in modelling the particle shape. The inter-particle contact parameters were systematically altered whilst the contact parameters between the particle and wall were arbitrarily assumed, in order to purely assess its impact on the angle of repose for the mono-sized iron ore particles. Results show that varying the restitution coefficient over the range considered does not lead to any obvious difference in the angle of repose, but the angle of repose has strong sensitivity to the rolling/static friction coefficient. The impacts of the rolling/static friction coefficient on the angle of repose are interrelated, and increasing the inter-particle rolling/static friction coefficient can evidently increase the angle of repose. However, the impact of the static friction coefficient is more profound than that of the rolling friction coefficient. Finally, a predictive equation is established and a very close agreement between the predicted and simulated angle of repose is attained. This predictive equation can enormously shorten the inter-particle contact parameters calibration time that can help in the implementation of DEM simulations.

Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge

NASA Astrophysics Data System (ADS)

Xu, Shijing; Wang, Jingyao; Wu, Jiazhong; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng

2018-04-01

Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0.992 e/nm2, the contact angle reaches up to 78.8° and the water-wet state is very apparent. The variation of contact angles can be confirmed from the number density distributions of oil molecules. With increasing the surface charge density, the adsorption of oil molecules weakens and the contact areas between nano-droplets and silicon dioxide surface are reduced. In addition, the number density distributions, RDF distributions, and molecular orientations indicate that the oil molecules are adsorbed on the silicon dioxide surface layer-by-layer with an orientation parallel to the surface. However, the layered structure of oil molecules near the silicon dioxide surface becomes more and more obscure at higher surface charge densities.

Oil Contact Angles in a Water-Decane-Silicon Dioxide System: Effects of Surface Charge.

PubMed

Xu, Shijing; Wang, Jingyao; Wu, Jiazhong; Liu, Qingjie; Sun, Chengzhen; Bai, Bofeng

2018-04-19

Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0.992 e/nm 2 , the contact angle reaches up to 78.8° and the water-wet state is very apparent. The variation of contact angles can be confirmed from the number density distributions of oil molecules. With increasing the surface charge density, the adsorption of oil molecules weakens and the contact areas between nano-droplets and silicon dioxide surface are reduced. In addition, the number density distributions, RDF distributions, and molecular orientations indicate that the oil molecules are adsorbed on the silicon dioxide surface layer-by-layer with an orientation parallel to the surface. However, the layered structure of oil molecules near the silicon dioxide surface becomes more and more obscure at higher surface charge densities.

Evaporation of liquid droplets on solid substrates. I. Flat substrate with pinned or moving contact line

NASA Astrophysics Data System (ADS)

Amini, Amirhossein; Homsy, G. M.

2017-04-01

We study the evolution of the profile of a two-dimensional volatile liquid droplet that is evaporating on a flat heated substrate. We adopt a one-sided model with thermal control that, together with the lubrication approximation, results in an evolution equation for the local height of the droplet. Without requiring any presumption for the shape of the drop, the problem is formulated for the two modes of evaporation: a pinned contact line and a moving contact line with fixed contact angle. Numerical solutions are provided for each case. For the pinned contact line case, we observe that after a time interval the contact angle dynamics become nonlinear and, interestingly, the local contact angle goes to zero in advance of total evaporation of the drop. For the case of a moving contact line, in which the singularity at the contact line is treated by a numerical slip model, we find that the droplet nearly keeps its initial circular shape and that the contact line recedes with constant speed.

Correlating contact line capillarity and dynamic contact angle hysteresis in surfactant-nanoparticle based complex fluids

NASA Astrophysics Data System (ADS)

Harikrishnan, A. R.; Dhar, Purbarun; Agnihotri, Prabhat K.; Gedupudi, Sateesh; Das, Sarit K.

2018-04-01

Dynamic wettability and contact angle hysteresis can be correlated to shed insight onto any solid-liquid interaction. Complex fluids are capable of altering the expected hysteresis and dynamic wetting behavior due to interfacial interactions. We report the effect of capillary number on the dynamic advancing and receding contact angles of surfactant-based nanocolloidal solutions on hydrophilic, near hydrophobic, and superhydrophobic surfaces by performing forced wetting and de-wetting experiments by employing the embedded needle method. A segregated study is performed to infer the contributing effects of the constituents and effects of particle morphology. The static contact angle hysteresis is found to be a function of particle and surfactant concentrations and greatly depends on the nature of the morphology of the particles. An order of estimate of line energy and a dynamic flow parameter called spreading factor and the transient variations of these parameters are explored which sheds light on the dynamics of contact line movement and response to perturbation of three-phase contact. The Cox-Voinov-Tanner law was found to hold for hydrophilic and a weak dependency on superhydrophobic surfaces with capillary number, and even for the complex fluids, with a varying degree of dependency for different fluids.

The synergistic effect of TiO2 nanoporous modification and platelet-rich plasma treatment on titanium-implant stability in ovariectomized rats.

PubMed

Jiang, Nan; Du, Pinggong; Qu, Weidong; Li, Lin; Liu, Zhonghao; Zhu, Songsong

For several decades, titanium and its alloys have been commonly utilized for endosseous implantable materials, because of their good mechanical properties, chemical resistance, and biocompatibility. But associated low bone mass, wear and loss characteristics, and high coefficients of friction have limited their long-term stable performance, especially in certain abnormal bone-metabolism conditions, such as postmenopausal osteoporosis. In this study, we investigated the effects of platelet-rich plasma (PRP) treatment and TiO 2 nanoporous modification on the stability of titanium implants in osteoporotic bone. After surface morphology, topographical structure, and chemical changes of implant surface had been detected by scanning electron microscopy (SEM), atomic force microscopy, contact-angle measurement, and X-ray diffraction, we firstly assessed in vivo the effect of PRP treatment on osseointegration of TiO 2 -modified implants in ovariectomized rats by microcomputed tomography examinations, histology, biomechanical testing, and SEM observation. Meanwhile, the potential molecular mechanism involved in peri-implant osseous enhancement was also determined by quantitative real-time polymerase chain reaction. The results showed that this TiO 2 -modified surface was able to lead to improve bone implant contact, while PRP treatment was able to increase the implant surrounding bone mass. The synergistic effect of both was able to enhance the terminal force of implants drastically in biomechanical testing. Compared with surface modification, PRP treatment promoted earlier osteogenesis with increased expression of the RUNX2 and COL1 genes and suppressed osteoclastogenesis with increased expression of OPG and decreased levels of RANKL. These promising results show that PRP treatment combined with a TiO 2 -nanomodified surface can improve titanium-implant biomechanical stability in ovariectomized rats, suggesting a beneficial effect to support the success of implants in osteoporotic bone.

The synergistic effect of TiO2 nanoporous modification and platelet-rich plasma treatment on titanium-implant stability in ovariectomized rats

PubMed Central

Jiang, Nan; Du, Pinggong; Qu, Weidong; Li, Lin; Liu, Zhonghao; Zhu, Songsong

2016-01-01

For several decades, titanium and its alloys have been commonly utilized for endosseous implantable materials, because of their good mechanical properties, chemical resistance, and biocompatibility. But associated low bone mass, wear and loss characteristics, and high coefficients of friction have limited their long-term stable performance, especially in certain abnormal bone-metabolism conditions, such as postmenopausal osteoporosis. In this study, we investigated the effects of platelet-rich plasma (PRP) treatment and TiO2 nanoporous modification on the stability of titanium implants in osteoporotic bone. After surface morphology, topographical structure, and chemical changes of implant surface had been detected by scanning electron microscopy (SEM), atomic force microscopy, contact-angle measurement, and X-ray diffraction, we firstly assessed in vivo the effect of PRP treatment on osseointegration of TiO2-modified implants in ovariectomized rats by microcomputed tomography examinations, histology, biomechanical testing, and SEM observation. Meanwhile, the potential molecular mechanism involved in peri-implant osseous enhancement was also determined by quantitative real-time polymerase chain reaction. The results showed that this TiO2-modified surface was able to lead to improve bone implant contact, while PRP treatment was able to increase the implant surrounding bone mass. The synergistic effect of both was able to enhance the terminal force of implants drastically in biomechanical testing. Compared with surface modification, PRP treatment promoted earlier osteogenesis with increased expression of the RUNX2 and COL1 genes and suppressed osteoclastogenesis with increased expression of OPG and decreased levels of RANKL. These promising results show that PRP treatment combined with a TiO2-nanomodified surface can improve titanium-implant biomechanical stability in ovariectomized rats, suggesting a beneficial effect to support the success of implants in osteoporotic bone. PMID:27695328

Surface roughness effects on contact line motion with small capillary number

NASA Astrophysics Data System (ADS)

Yang, Feng-Chao; Chen, Xiao-Peng; Yue, Pengtao

2018-01-01

In this work, we investigate how surface roughness influences contact line dynamics by simulating forced wetting in a capillary tube. The tube wall is decorated with microgrooves and is intrinsically hydrophilic. A phase-field method is used to capture the fluid interface and the moving contact line. According to the numerical results, a criterion is proposed to judge whether the grooves are entirely wetted or not at vanishing capillary numbers. When the contact line moves over a train of grooves, the apparent contact angle exhibits a periodic nature, no matter whether the Cassie-Baxter or the Wenzel state is achieved. The oscillation amplitude of apparent contact angle is analyzed and found to be inversely proportional to the interface area. The contact line motion can be characterized as stick-jump-slip in the Cassie-Baxter state and stick-slip in the Wenzel state. By comparing to the contact line dynamics on smooth surfaces, equivalent microscopic contact angles and slip lengths are obtained. The equivalent slip length in the Cassie-Baxter state agrees well with the theoretical model in the literature. The equivalent contact angles are, however, much greater than the predictions of the Cassie-Baxter model and the Wenzel model for equilibrium stable states. Our results reveal that the pinning of the contact line at surface defects effectively enhances the hydrophobicity of rough surfaces, even when the surface material is intrinsically hydrophilic and the flow is under the Wenzel state.

In vitro cell response to differences in poly-L-lactide crystallinity.

PubMed

Park, A; Cima, L G

1996-05-01

Many different processing techniques are currently being used to produce tissue regeneration devices from polyesters in the polylactide/polyglycolide family. While it is generally well recognized that processing techniques influence bulk mechanical and degradation properties of these materials, the effects on surface properties are relatively less well studied. We thus investigated the effects of processing conditions that are known to change bulk properties, but not composition, on the surface properties of poly-L-lactide (PLLA). Specifically, we investigated the role of bulk crystallinity of PLLA substrates on several physiochemical aspects of the surface and on the attachment, morphology, and differentiated function of cultured primary hepatocytes and growth of 3T3 fibroblasts. We fabricated smooth, clear PLLA films of 13-37% crystallinity. Glancing angle X-ray diffraction indicated that low crystallinity films lacked order in the first 50 A of the surface while relatively high crystallinity films had detectable order in this range. In other aspects, the surfaces of all PLLA substrates appeared identical with XPS, SEM, and advancing contact angle analysis, but contact angle hysteresis was slightly greater for more crystalline films. Although the physicochemical properties of the surfaces appeared almost identical, we observed differences in cell behavior on less crystalline versus more crystalline films. Hepatocytes formed spheroids on all PLLA substrates, but spheroid formation was faster (24-48 H) on crystalline substrates. quantitative image analysis was used to assess the average cell area as a function of time in culture, and our data confirm previous reports that retention of differentiated function is inversely related to cell spreading where function was assessed by P-450 enzyme activity. In addition, the growth rate of 3T3 fibroblasts was lower on crystalline substrates than on amorphous substrates. An important conclusion from this work is that processing techniques that lead to seemingly inconsequential changes in bulk and surface properties of these polymers may influence biological response.

Wettability measurement under high P-T conditions using X-ray imaging with application to the brine-supercritical CO 2 system: WETTABILITY MEASUREMENT USING X-RAY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhary, Kuldeep; Guiltinan, Eric J.; Cardenas, M. Bayani

2015-08-30

We present a new method for measuring wettability or contact angle of minerals at reservoir pressure-temperature conditions using high-resolution X-ray computed tomography (HRXCT) and radiography. In this method, a capillary or a narrow slot is constructed from a mineral or a rock sample of interest wherein two fluids are allowed to form an interface that is imaged using X-rays. After some validation measurements at room pressure-temperature conditions, we illustrate this method by measuring the contact angle of CO 2-brine on quartz, muscovite, shale, borosilicate glass, polytetrafluoroethylene (PTFE or Teflon), and polyether ether ketone (PEEK) surfaces at 60–71°C and 13.8–22.8 MPa.more » At reservoir conditions, PTFE and PEEK surfaces were found to be CO 2-wet with contact angles of 140° and 127°, respectively. Quartz and muscovite were found to be water-wet with contact angles of 26° and 58°, respectively, under similar conditions. Borosilicate glass-air-brine at room conditions showed strong water-wet characteristics with a contact angle of 9°, whereas borosilicate glass-CO 2-brine at 13.8 MPa and 60°C showed a decrease in its water-wetness with contact angle of 54°. This method provides a new application for X-ray imaging and an alternative to other methods.« less

Poly(styrene-co-butadiene) random copolymer thin films and nanostructures on a mica surface: morphology and contact angles of nanodroplets.

PubMed

McClements, Jake; Buffone, Cosimo; Shaver, Michael P; Sefiane, Khellil; Koutsos, Vasileios

2017-09-20

The self-assembly of poly(styrene-co-butadiene) random copolymers on mica surfaces was studied by varying solution concentrations and polymer molecular weights. Toluene solutions of the poly(styrene-co-butadiene) samples were spin coated onto a mica surface and the resulting polymer morphology was investigated by atomic force microscopy. At higher concentrations, thin films formed with varying thicknesses; some dewetting was observed which depended on the molecular weight. Total dewetting did not occur despite the polymer's low glass transition temperature. Instead, partial dewetting was observed suggesting that the polymer was in a metastable equilibrium state. At lower concentrations, spherical cap shaped nanodroplets formed with varying sizes from single polymer chains to aggregates containing millions of chains. As the molecular weight was increased, fewer aggregates were observed on the surface, albeit with larger sizes resulting from increased solution viscosities and more chain entanglements at higher molecular weights. The contact angles of the nanodroplets were shown to be size dependent. A minimum contact angle occurs for droplets with radii of 100-250 nm at each molecular weight. Droplets smaller than 100 nm showed a sharp increase in contact angle; attributed to an increase in the elastic modulus of the droplets, in addition, to a positive line tension value. Droplets larger than 250 nm also showed an increased contact angle due to surface heterogeneities which cannot be avoided for larger droplets. This increase in contact angle plateaus as the droplet size reaches the macroscopic scale.

Complex Contact Angles Calculated from Capillary Rise Measurements on Rock Fracture Faces

NASA Astrophysics Data System (ADS)

Perfect, E.; Gates, C. H.; Brabazon, J. W.; Santodonato, L. J.; Dhiman, I.; Bilheux, H.; Bilheux, J. C.; Lokitz, B. S.

2017-12-01

Contact angles for fluids in unconventional reservoir rocks are needed for modeling hydraulic fracturing leakoff and subsequent oil and gas extraction. Contact angle measurements for wetting fluids on rocks are normally performed using polished flat surfaces. However, such prepared surfaces are not representative of natural rock fracture faces, which have been shown to be rough over multiple scales. We applied a variant of the Wilhelmy plate method for determining contact angle from the height of capillary rise on a vertical surface to the wetting of rock fracture faces by water in the presence of air. Cylindrical core samples (5.05 cm long x 2.54 cm diameter) of Mancos shale and 6 other rock types were investigated. Mode I fractures were created within the cores using the Brazilian method. Each fractured core was then separated into halves exposing the fracture faces. One fracture face from each rock type was oriented parallel to a collimated neutron beam in the CG-1D imaging instrument at ORNL's High Flux Isotope Reactor. Neutron radiography was performed using the multi-channel plate detector with a spatial resolution of 50 μm. Images were acquired every 60 s after a water reservoir contacted the base of the fracture face. The images were normalized to the initial dry condition so that the upward movement of water on the fracture face was clearly visible. The height of wetting at equilibrium was measured on the normalized images using ImageJ. Contact angles were also measured on polished flat surfaces using the conventional sessile drop method. Equilibrium capillary rise on the exposed fracture faces was up to 8.5 times greater than that predicted for polished flat surfaces from the sessile drop measurements. These results indicate that rock fracture faces are hyperhydrophilic (i.e., the height of capillary rise is greater than that predicted for a contact angle of zero degrees). The use of complex numbers permitted calculation of imaginary contact angles for such surfaces. This analysis yielded a continuum of contact angles (real above, and imaginary below, zero degrees) that can be used to investigate relationships with properties such surface roughness and porosity. It should be noted these are preliminary, unreplicated results and further research will be needed to verify them and refine the approach.

Pulse electrodeposition of self-lubricating Ni-W/PTFE nanocomposite coatings on mild steel surface

NASA Astrophysics Data System (ADS)

Sangeetha, S.; Kalaignan, G. Paruthimal; Anthuvan, J. Tennis

2015-12-01

Ni-W/PTFE nanocomposite coatings with various contents of PTFE (polytetafluoroethylene) particles were prepared by pulse current (PC) electrodeposition from the Ni-W plating bath containing self lubricant PTFE particles to be co-deposited. Co-deposited PTFE particulates were uniformly distributed in the Ni-W alloy matrix. The coatings were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX), X-ray Diffractometry (XRD) and Vicker's micro hardness tester. Tafel Polarization and electrochemical Impedance methods were used to evaluate the corrosion resistance behaviour of the nanocomposite coatings in 3.5% NaCl solution. It was found that, the Ni-W/PTFE nanocomposite coating has better corrosion resistance than the Ni-W alloy coating. Surface roughness and friction coefficient of the coated samples were assessed by Mitutoyo Surftest SJ-310 (ISO1997) and Scratch tester TR-101-M4 respectively. The contact angle (CA) of a water droplet on the surface of nanocomposite coating was measured by Optical Contact Goniometry (OCA 35). These results indicated that, the addition of PTFE in the Ni-W alloy matrix has resulted moderate microhardness, smooth surface, less friction coefficient, excellent water repellency and enhanced corrosion resistance of the nanocomposite coatings.

A flexible thermoresponsive cell culture substrate for direct transfer of keratinocyte cell sheets.

PubMed

Praveen, Wulligundam; Madathil, Bernadette K; Sajin Raj, R S; Kumary, T V; Anil Kumar, P R

2017-10-25

Most cell sheet engineering systems require a support or carrier to handle the harvested cell sheets. In this study, polyethylene terephthalate-based overhead projection transparency sheets (OHPS) were subjected to surface hydrolysis by alkali treatment to increase pliability and hydrophilicity and enable poly(N-isopropylacrylamide-co-glycidylmethacrylate) copolymer (NGMA) coating to impart thermoresponsiveness. NGMA was applied on the modified OHPS by the technique of spin coating using an indigenously designed spin coater. The spin coating had the advantage of using low volumes of the polymer and a reduced coating time. The surface chemistry and thermoresponsive coating was analyzed by Fourier transform infrared spectroscopy and water contact angle. Human keratinocyte cells were cultured on the spin coated surface and scaffold-free cell sheets were successfully harvested by simple variation of temperature. These cell sheets were found to be viable, exhibited epithelial characteristic and cell-cell contact as confirmed by positive immunostaining for ZO-1. The integrity and morphology of the cell sheet was confirmed by stereomicroscopy and E-SEM. These results highlight the potential of the NGMA spin coated modified OHPS to serve as a thermoresponsive culture surface-cum-flexible transfer tool.

Statistical contact angle analyses; "slow moving" drops on a horizontal silicon-oxide surface.

PubMed

Schmitt, M; Grub, J; Heib, F

2015-06-01

Sessile drop experiments on horizontal surfaces are commonly used to characterise surface properties in science and in industry. The advancing angle and the receding angle are measurable on every solid. Specially on horizontal surfaces even the notions themselves are critically questioned by some authors. Building a standard, reproducible and valid method of measuring and defining specific (advancing/receding) contact angles is an important challenge of surface science. Recently we have developed two/three approaches, by sigmoid fitting, by independent and by dependent statistical analyses, which are practicable for the determination of specific angles/slopes if inclining the sample surface. These approaches lead to contact angle data which are independent on "user-skills" and subjectivity of the operator which is also of urgent need to evaluate dynamic measurements of contact angles. We will show in this contribution that the slightly modified procedures are also applicable to find specific angles for experiments on horizontal surfaces. As an example droplets on a flat freshly cleaned silicon-oxide surface (wafer) are dynamically measured by sessile drop technique while the volume of the liquid is increased/decreased. The triple points, the time, the contact angles during the advancing and the receding of the drop obtained by high-precision drop shape analysis are statistically analysed. As stated in the previous contribution the procedure is called "slow movement" analysis due to the small covered distance and the dominance of data points with low velocity. Even smallest variations in velocity such as the minimal advancing motion during the withdrawing of the liquid are identifiable which confirms the flatness and the chemical homogeneity of the sample surface and the high sensitivity of the presented approaches. Copyright © 2014 Elsevier Inc. All rights reserved.

Wetting, meniscus structure, and capillary interactions of microspheres bound to a cylindrical liquid interface.

PubMed

Kim, Paul Y; Dinsmore, Anthony D; Hoagland, David A; Russell, Thomas P

2018-03-14

Wetting, meniscus structure, and capillary interactions for polystyrene microspheres deposited on constant curvature cylindrical liquid interfaces, constructed from nonvolatile ionic or oligomeric liquids, were studied by optical interferometry and optical microscopy. The liquid interface curvature resulted from the preferential wetting of finite width lines patterned onto planar silicon substrates. Key variables included sphere diameter, nominal (or average) contact angle, and deviatoric interfacial curvature. Menisci adopted the quadrupolar symmetry anticipated by theory, with interfacial deformation closely following predicted dependences on sphere diameter and nominal contact angle. Unexpectedly, the contact angle was not constant locally around the contact line, the nominal contact angle varied among seemingly identical spheres, and the maximum interface deviation did not follow the predicted dependence on deviatoric interfacial curvature. Instead, this deviation was up to an order-of-magnitude larger than predicted. Trajectories of neighboring microspheres visually manifested quadrupole-quadrupole interactions, eventually producing square sphere packings that foreshadow interfacial assembly as a potential route to hierarchical 2D particle structures.

Contact angle change during evaporation of near-critical liquids

NASA Astrophysics Data System (ADS)

Nikolayev, Vadim; Hegseth, John; Beysens, Daniel

1998-03-01

An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling".

Comparative of fibroblast and osteoblast cells adhesion on surface modified nanofibrous substrates based on polycaprolactone.

PubMed

Sharifi, Fereshteh; Irani, Shiva; Zandi, Mojgan; Soleimani, Masoud; Atyabi, Seyed Mohammad

2016-12-01

One of the determinant factors for successful bioengineering is to achieve appropriate nano-topography and three-dimensional substrate. In this research, polycaprolactone (PCL) nano-fibrous mat with different roughness modified with O 2 plasma was fabricated via electrospinning. The purpose of this study was to evaluate the effect of plasma modification along with surface nano-topography of mats on the quality of human fibroblast (HDFs) and osteoblast cells (OSTs)-substrate interaction. Surface properties were studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle, Fourier-transformation infrared spectroscopy. We evaluated mechanical properties of fabricated mats by tensile test. The viability and proliferation of HDFs and OSTs on the substrates were followed by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT). Mineralization of the substrate was determined by alizarin red staining method and calcium content of OSTs was determined by calcium content kit. Cells morphology was studied by SEM analysis. The results revealed that the plasma-treated electrospun nano-fibrous substrate with higher roughness was an excellent designed substrate. A bioactive topography for stimulating proliferation of HDFs and OSTs is to accelerate the latter's differentiation time. Therefore, the PCL substrate with high density and major nano-topography were considered as a bio-functional and elegant bio-substrate for tissue regeneration applications.

A novel hydroxyl epoxy phosphate monomer enhancing the anticorrosive performance of waterborne Graphene/Epoxy coatings

NASA Astrophysics Data System (ADS)

Ding, Jiheng; Rahman, Obaid ur; Peng, Wanjun; Dou, Huimin; Yu, Haibin

2018-01-01

Herein, we report the synthesis of a novel hydroxyl epoxy phosphate monomer (PGHEP) as an efficient dispersant for graphene to enhance the compatibility of the graphene in epoxy resin. Raman spectroscopy, Ultraviolet-visible spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS) studies were confirmed the π-π interactions between PGHEP and graphene. Well-dispersed states of PGHEP functionalized graphene (G) sheets in water were analyzed by transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Further, microstructure of prepared G/waterborne epoxy coatings containing 0.5-1.0 wt.% of PGHEP functionalized G sheets were also observed with the help of SEM and TEM. The PGHEP functionalized G sheets dispersed composite coatings displayed enhanced corrosion resistance compared with pure epoxy resin, these coatings have higher contact angle, lower water absorption as evident from the results of electrochemical impedance spectroscopy (EIS) and salt spray tests. The superior corrosion protection performances of G/epoxy coatings were mainly attributed to the formed passive film from uniformly dispersed PGHEP functionalized G sheets which act as physical barrier on the steel surface. Therefore, this work provides a novel bio-based efficient dispersant for G sheets and an important method for preparing G/waterborne epoxy coatings with superior corrosion resistance properties.

Chondroitin sulfate immobilization at the surface of electrospun nanofiber meshes for cartilage tissue regeneration approaches

NASA Astrophysics Data System (ADS)

Piai, Juliana Francis; da Silva, Marta Alves; Martins, Albino; Torres, Ana Bela; Faria, Susana; Reis, Rui L.; Muniz, Edvani Curti; Neves, Nuno M.

2017-05-01

Aiming at improving the biocompatibility of biomaterial scaffolds, surface modification presents a way to preserve their mechanical properties and to improve the surface bioactivity. In this work, chondroitin sulfate (CS) was immobilized at the surface of electrospun poly(caprolactone) nanofiber meshes (PCL NFMs), previously functionalized by UV/O3 exposure and aminolysis. Contact angle, SEM, optical profilometry, FTIR, X-ray photoelectron spectroscopy techniques confirmed the success of CS-immobilization in PCL NFMs. Furthermore, CS-immobilized PCL NFMs showed lower roughness and higher hydrophilicity than the samples without CS. Human articular chondrocytes (hACs) were cultured on electrospun PCL NFMs with or without CS immobilization. It was observed that hACs proliferated through the entire time course of the experiment in both types of nanofibrous scaffolds, as well as for the production of glycosaminoglycans. Quantitative-PCR results demonstrated over-expression of cartilage-related genes such as Aggrecan, Collagen type II, COMP and Sox9 on both types of nanofibrous scaffolds. Morphological observations from SEM and LSCM revealed that hACs maintained their characteristic round shape and cellular agglomeration exclusively on PCL NFMs with CS immobilization. In conclusion, CS immobilization at the surface of PCL NFMs was achieved successfully and provides a valid platform enabling further surface functionalization methods in scaffolds to be developed for cartilage tissue engineering.

The impact of diamond nanocrystallinity on osteoblast functions.

PubMed

Yang, Lei; Sheldon, Brian W; Webster, Thomas J

2009-07-01

Nanocrystalline diamond has been proposed as an anti-abrasive film on orthopedic implants. In this study, osteoblast (bone forming cells) functions including adhesion (up to 4h), proliferation (up to 5 days) and differentiation (up to 21 days) on different diamond film topographies were systematically investigated. In order to exclude interferences from changes in surface chemistry and wettability (energy), diamond films with nanometer and micron scale topographies were fabricated through microwave plasma enhanced chemical-vapor-deposition and hydrogen plasma treatment. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and water contact angle measurements verified the similar surface chemistry and wettability but varied topographies for all of the diamond films prepared on silicon in this study. Cytocompatibility assays demonstrated enhanced osteoblast functions (including adhesion, proliferation, intracellular protein synthesis, alkaline phosphatase activity and extracellular calcium deposition) on nanocrystalline diamond compared to submicron diamond grain size films for all time periods tested up to 21 days. An SEM study of osteoblast attachment helped to explain the topographical impact diamond had on osteoblast functions by showing altered filopodia extensions on the different diamond topographies. In summary, these results provided insights into understanding the role diamond nanotopography had on osteoblast interactions and more importantly, the application of diamond films to improve orthopedic implant lifetimes.

Water-repellent coatings prepared by modification of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Chakradhar, R. P. S.; Dinesh Kumar, V.

Superhydrophobic coatings with a static water contact angle (WCA) > 150° were prepared by modifying ZnO nanoparticles with stearic acid (ZnO@SA). ZnO nanoparticles of size ˜14 nm were prepared by solution combustion method. X-ray diffraction (XRD) studies reveal that as prepared ZnO has hexagonal wurtzite structure whereas the modified coatings convert to zinc stearate. Field emission scanning electron micrographs (FE-SEM) show the dual morphology of the coatings exhibiting both particles and flakes. The flakes are highly fluffy in nature with voids and nanopores. Fourier transformed infrared (FTIR) spectrum shows the stearate ion co-ordinates with Zn2+ in the bidentate form. The surface properties such as surface free energy (γp) and work of adhesion (W) of the unmodified and modified ZnO coatings have been evaluated. The electron paramagnetic resonance (EPR) spectroscopy reveals that surface defects play a major role in the wetting behavior.

Study program to develop and evaluate die and container materials for the growth of silicon ribbons. [for development of low cost solar cells

NASA Technical Reports Server (NTRS)

Addington, L. A.; Ownby, P. D.; Yu, B. B.; Barsoum, M. W.; Romero, H. V.; Zealer, B. G.

1979-01-01

The development and evaluation of proprietary coatings of pure silicon carbide, silicon nitride, and aluminum nitride on less pure hot pressed substrates of the respective ceramic materials, is described. Silicon sessile drop experiments were performed on coated test specimens under controlled oxygen partial pressure. Prior to testing, X-ray diffraction and SEM characterization was performed. The reaction interfaces were characterized after testing with optical and scanning electron microscopy and Auger electron spectroscopy. Increasing the oxygen partial pressure was found to increase the molten silicon contact angle, apparently because adsorbed oxygen lowers the solid-vapor interfacial free energy. It was also found that adsorbed oxygen increased the degree of attack of molten silicon upon the chemical vapor deposited coatings. Cost projections show that reasonably priced, coated, molten silicon resistant refractory material shapes are obtainable.

Evaluation of protein immobilization capacity on various carbon nanotube embedded hydrogel biomaterials.

PubMed

Derkus, Burak; Emregul, Kaan Cebesoy; Emregul, Emel

2015-11-01

This study investigates effective immobilization of proteins, an important procedure in many fields of bioengineering and medicine, using various biomaterials. Gelatin, alginate and chitosan were chosen as polymeric carriers, and applied in both their composites and nanocomposite forms in combination with carbon nanotubes (CNTs). The prepared nano/composite structures were characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TG) and contact angle analysis (CA). Electrochemical impedance spectroscopy analysis revealed gelatin composites in general to exhibit better immobilization performance relative to the native gelatin which can be attributed to enhanced film morphologies of the composite structures. Moreover, superior immobilization efficiencies were obtained with the addition of carbon nanotubes, due to their conducting and surface enhancement features, especially in the gelatin-chitosan structures due to the presence of structural active groups. Copyright © 2015 Elsevier B.V. All rights reserved.

Materials challenges for repeatable RF wireless device reconfiguration with microfluidic channels

NASA Astrophysics Data System (ADS)

Griffin, Anthony S.; Sottos, Nancy R.; White, Scott R.

2018-03-01

Recently, adaptive wireless devices have utilized displacement of EGaIn within microchannels as an electrical switching mechanism to enable reconfigurable electronics. Device reconfiguration using EGaIn in microchannels overcomes many challenges encountered by more traditional reconfiguration mechanisms such as diodes and microelectromechanical systems (MEMS). Reconfiguration using EGaIn is severely limited by undesired permanent shorting due to retention of the liquid in microchannels caused by wetting and rapid oxide skin formation. Here, we investigate the conditions which prevent repeatable electrical switching using EGaIn in microchannels. Initial contact angle tests of EGaIn on epoxy surfaces demonstrate the wettability of EGaIn on flat surfaces. SEM cross-sections of microchannels reveal adhesion of EGaIn residue to channel walls. Micro-computed tomography (microCT) scans of provide volumetric measurements of EGaIn remaining inside channels after flow cycling. Non-wetting coatings are proposed as materials based strategy to overcome these issues in future work.

Characterization of purified bacterial cellulose focused on its use on paper restoration.

PubMed

Santos, Sara M; Carbajo, José M; Quintana, Ester; Ibarra, David; Gomez, Nuria; Ladero, Miguel; Eugenio, M Eugenia; Villar, Juan C

2015-02-13

Bacterial cellulose (BC) synthesized by Gluconacetobacter sucrofermentans CECT 7291 seems to be a good option for the restoration of degraded paper. In this work BC layers are cultivated and purified by two different methods: an alkaline treatment when the culture media contains ethanol and a thermal treatment if the media is free from ethanol. The main goal of these tests was the characterization of BC layers measured in terms of tear and burst indexes, optical properties, SEM, X-ray diffraction, FTIR, degree of polymerization, static and dynamic contact angles, and mercury intrusion porosimetry. The BC layers were also evaluated in the same terms after an aging treatment. Results showed that BC has got high crystallinity index, low internal porosity, good mechanical properties and high stability over time, especially when purified by the alkaline treatment. These features make BC an adequate candidate for degraded paper reinforcement. Copyright © 2014 Elsevier Ltd. All rights reserved.

The fabrication of visible light responsive Ag-SiO2 co-doped TiO2 thin films by the sol-gel method

NASA Astrophysics Data System (ADS)

Dam Le, Duy; Dung Dang, Thi My; Thang Chau, Vinh; Chien Dang, Mau

2010-03-01

In this study we have successfully deposited Ag-SiO2 co-doped TiO2 thin films on glass substrates by the sol-gel method. After being coated by a dip coating method, the film was transparent, smooth and had strong adhesion on the glass surface. The deposited film was characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), a scanning electron microscope (SEM) and atomic force microscope (AFM) to investigate its crystallization, transmittance and surface structure. The antifogging ability is explained by the contact angle of water on the surface of the glass substrates under visible-light. The obtained results show that Ag-SiO2 co-doped TiO2 film has potential applications for self cleaning and anti-bacterial ceramic tiles.

Synthesis of Graphene Based Membranes: Effect of Substrate Surface Properties on Monolayer Graphene Transfer.

PubMed

Kafiah, Feras; Khan, Zafarullah; Ibrahim, Ahmed; Atieh, Muataz; Laoui, Tahar

2017-01-21

In this work, we report the transfer of graphene onto eight commercial microfiltration substrates having different pore sizes and surface characteristics. Monolayer graphene grown on copper by the chemical vapor deposition (CVD) process was transferred by the pressing method over the target substrates, followed by wet etching of copper to obtain monolayer graphene/polymer membranes. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle (CA) measurements were carried out to explore the graphene layer transferability. Three factors, namely, the substrate roughness, its pore size, and its surface wetting (degree of hydrophobicity) are found to affect the conformality and coverage of the transferred graphene monolayer on the substrate surface. A good quality graphene transfer is achieved on the substrate with the following characteristics; being hydrophobic (CA > 90°), having small pore size, and low surface roughness, with a CA to RMS (root mean square) ratio higher than 2.7°/nm.

UV light induced surface modification of HDPE films with bioactive compounds

NASA Astrophysics Data System (ADS)

Daniloska, Vesna; Blazevska-Gilev, Jadranka; Dimova, Vesna; Fajgar, Radek; Tomovska, Radmila

2010-01-01

The development of different techniques for surface modification of polymers becomes popular in a last decade. These techniques preserve useful bulk polymer properties unchanged, while the activation of the polymer surface offers more possibilities for polymer applications. In this work, a new, one-step method for bio-activation of HDPE (high density polyethylene) surface by UV irradiation is presented. HDPE films coupled with selected active compound and a photoinitiator was treated by UV lamp, emitting light at 254 nm. For surface functionalization of HDPE films, the following compounds were employed: 2-aminopyridine (AP), N 1-(2-pyridylaminomethyl)-1,2,4-triazole (TA) and benzocaine (BC). The influence of irradiation time on the extent of surface changes was investigated. The modified polymer surfaces were investigated by Fourier transformed infrared (FTIR) and Raman spectroscopy, scanning electron microscopy (SEM) and contact angle measurements, demonstrating successful functionalization of HDPE surface.

Biocompatibility of PCL/PLGA-BCP porous scaffold for bone tissue engineering applications.

PubMed

Thi Hiep, Nguyen; Chan Khon, Huynh; Dai Hai, Nguyen; Byong-Taek, Lee; Van Toi, Vo; Thanh Hung, Le

2017-06-01

In this study, biomimic porous polycaprolactone/poly (lactide-co-glycolide) loading biphasic tricalcium phosphate (PCL/PLGA-BCP) scaffolds were fabricated successfully by solvent evaporation method. The distribution of biphasic tricalcium phosphate (BCP) in polycaprolactone/poly (lactide-co-glycolide) (PCL/PLGA) scaffold was confirmed by micro-computed tomography (micro-CT) scanning, scanning electron microscope (SEM) observation and Energy-dispersive X-ray Spectroscopy (EDS) analysis. The hydrophilicity of the scaffolds was confirmed by contact angle measurement. In in vitro experiments, proliferation of human bone marrow mesenchymal stem cell (hBMSCs) and its osteoblastic differentiation on scaffold were assessed for 1, 2 and 3 weeks using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, fluorescence observation, hematoxylin & eosin (H&E) staining and real-time polymerase chain reaction (RT-PCR). In in vivo experiments, ossification was observed using micro-CT analysis and histological staining.

A fundamental approach to the sticking of insect residues to aircraft wings

NASA Technical Reports Server (NTRS)

Eiss, N. S., Jr.; Wightman, J. P.; Gilliam, D. R.; Siochi, E. J.

1984-01-01

A proposed testing scheme is described for obtaining data on the effects of surface roughness and surface energy on insect adhesion. The road test apparatus is discussed as well as surface preparation techniques. Uncoated and polymer coated metal substrates were analyzed by SEM/ESCA/IRS before and following collision with insects. Critical surface tensions of unexposed Nyebar and poly sulfone coatings were 10 and 33 dynes/cm, respectively, as determined from contact angles. A total of 95% of insect residues collected belong to order Diptera. Significantly less insect debris was detected on the coated plates as compared to the uncoated plates. Minimal contamination at the 5 nm level of both coated and uncoated plates occurs even after hours of exposure to road conditions as determined by ESCA analysis. The presence of nitrogen detected by ESCA on exposed plates is unequivocal evidence for insect residues left on plates.

Effects of (Oxy-)Fluorination on Various High-Performance Yarns.

PubMed

Kruppke, Iris; Bartusch, Matthias; Hickmann, Rico; Hund, Rolf-Dieter; Cherif, Chokri

2016-08-26

In this work, typical high-performance yarns are oxy-fluorinated, such as carbon fibers, ultra-high-molecular-weight polyethylene, poly(p-phenylene sulfide) and poly(p-phenylene terephthalamide). The focus is on the property changes of the fiber surface, especially the wetting behavior, structure and chemical composition. Therefore, contact angle, XPS and tensile strength measurements are performed on treated and untreated fibers, while SEM is utilized to evaluate the surface structure. Different results for the fiber materials are observed. While polyethylene exhibits a relevant impact on both surface and bulk properties, polyphenylene terephthalamide and polyphenylene sulfide are only affected slightly by (oxy-)fluorination. The wetting of carbon fiber needs higher treatment intensities, but in contrast to the organic fibers, even its textile-physical properties are enhanced by the treatment. Based on these findings, the capability of (oxy-)fluorination to improve the adhesion of textiles in fiber-reinforced composite materials can be derived.

Surface modification of epoxy resin using He/CF4 atmospheric pressure plasma jet for flashover withstanding characteristics improvement in vacuum

NASA Astrophysics Data System (ADS)

Chen, Sile; Wang, Shuai; Wang, Yibo; Guo, Baohong; Li, Guoqiang; Chang, Zhengshi; Zhang, Guan-Jun

2017-08-01

For enhancing the surface electric withstanding strength of insulating materials, epoxy resin (EP) samples are treated by atmospheric pressure plasma jet (APPJ) with different time interval from 0 to 300s. Helium (He) and tetrafluoromethane (CF4) mixtures are used as working gases with the concentration of CF4 ranging 0%-5%, and when CF4 is ∼3%, the APPJ exhibits an optimal steady state. The flashover withstanding characteristics of modified EP in vacuum are greatly improved under appropriate APPJ treatment conditions. The surface properties of EP samples are evaluated by surface roughness, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle. It is considered that both physical and chemical effects lead to the enhancement of flashover strength. The physical effect is reflected in the increase of surface roughness, while the chemical effect is reflected in the graft of fluorine groups.

Colorful Hydrophobic Poly(Vinyl Butyral)/Cationic Dye Fibrous Membranes via a Colored Solution Electrospinning Process

NASA Astrophysics Data System (ADS)

Yan, Xu; You, Ming-Hao; Lou, Tao; Yu, Miao; Zhang, Jun-Cheng; Gong, Mao-Gang; Lv, Fu-Yan; Huang, Yuan-Yuan; Long, Yun-Ze

2016-12-01

Colorful nanofibrous membranes have attracted much attention for their visual varieties and various functionalities. In this article, a colored solution electrospinning process was used to fabricate colorful hydrophobic poly(vinyl butyral) (PVB)/cationic dye nanofibrous membranes (NFMs) successfully. The color and morphology of these as-spun nanofibrous membranes have been analyzed by colorimetry, spectroscopy, and scanning electron microscopy (SEM). It is shown that the as-spun colorful PVB-based membranes exhibit excellent level-dyeing property and color stability. Furthermore, the doping of cationic dye and the increase of dye concentration can decrease the diameter of the as-spun colored fibers, which results in better level-dyeing property and higher water contact angle more than 140°. The stained PVB fibrous membranes with excellent level-dyeing property and hydrophobicity are promising in some applications such as textiles, wallpapers, and anticorrosive coating/painting.

Comparison of titanium soaked in 5 M NaOH or 5 M KOH solutions

PubMed Central

Kim, Christina; Kendall, Matthew R.; Miller, Matthew A.; Long, Courtney L.; Larson, Preston R.; Humphrey, Mary Beth; Madden, Andrew S.; Tas, A. Cuneyt

2012-01-01

Commercially pure titanium plates/coupons and pure titanium powders were soaked for 24 h in 5 M NaOH and 5 M KOH solutions, under identical conditions, over the temperature range of 37° to 90°C. Wettability of the surfaces of alkali-treated cpTi coupons were studied by using contact angle goniometry. cpTi coupons soaked in 5 M NaOH or 5 M KOH solutions were found to have hydrophilic surfaces. Hydrous alkali titanate nanofibers and nanotubes were identified with SEM/EDXS and grazing incidence XRD. Surface areas of Ti powders increased >50–220 times, depending on the treatment, when soaked in the above solutions. A solution was developed to coat amorphous calcium phosphate, instead of hydroxyapatite, on Ti coupon surfaces. In vitro cell culture tests were performed with osteoblast-like cells on the alkali-treated samples. PMID:23565038

Preparation of active antibacterial LDPE surface through multistep physicochemical approach: I. Allylamine grafting, attachment of antibacterial agent and antibacterial activity assessment.

PubMed

Bílek, František; Křížová, Táňa; Lehocký, Marián

2011-11-01

Low-density polyethylene (LDPE) samples were treated in air plasma discharge, coated by polyallyamine brush thought copolymeric grafting surface-from reaction and deposited four common antibacterial agents (benzalkonium chloride, bronopol, chlorhexidine and triclosan) to gain material with active antibacterial properties. Surface characteristics were evaluated by static contact angle measurement with surface energy evaluation ATR-FTIR, X-ray Photoelectron Spectroscopy (XPS) and SEM analysis. Inhibition zone on agar was used as in vitro test of antibacterial properties on two representative gram positive Staphylococcus aureus (S. aureus) and gram negative Escherichia coli (E. coli) strains. It was confirmed, that after grafting of polyallyamine, more antibacterial agent is immobilized on the surface. The highest increase of antibacterial activity was observed by the sample containing triclosan. Samples covered by bronopol did not show significant antibacterial activity. Copyright © 2011 Elsevier B.V. All rights reserved.

A facile method to fabricate a superhydrophobic surface with biomimetic structure on magnesium alloy

NASA Astrophysics Data System (ADS)

Bai, Zigang; Zhu, Jiyuan

2018-06-01

Superhydrophobic surface was obtained via a convenient two-step method in this paper on magnesium alloy. The microstructured oxide or hydroxide layers were constructed on the Mg alloy though hydrothermal process. The treated sample was modified with low-energy surface material. After modification, the contact angle of water droplet on the surface is higher than 150° which indicates superhydrophobicity. With scanning electron microscope(SEM), mammillaria-herrerae-like rough structure was obtained. The composition of the superhydrophobic film was analyzed by using x-ray Diffraction instrument and Fourier-transform infrared spectrometer. Moreover, the superhydrophobic surface has good stability. The potentiodynamic polarization test shows that the corrosion current density of superhydrophobic surface was 1–2 order of magnitudes smaller than the bare substrate, which means the anti-corrosion performance has been improved significantly. This route offers an environmentally-benign and effective way to fabricate superhydrophobic surface without using complicated equipment and dangerous chemicals.

Preparation of superhydrophobic titanium surfaces via electrochemical etching and fluorosilane modification

NASA Astrophysics Data System (ADS)

Lu, Yao; Xu, Wenji; Song, Jinlong; Liu, Xin; Xing, Yingjie; Sun, Jing

2012-12-01

The preparation of superhydrophobic surfaces on hydrophilic metal substrates depends on both surface microstructures and low surface energy modification. In this study, a simple and inexpensive electrochemical method for preparing robust superhydrophobic titanium surfaces is reported. The neutral sodium chloride solution is used as electrolyte. Fluoroalkylsilane (FAS) was used to reduce the surface energy of the electrochemically etched surface. Scanning electron microscopy (SEM) images, energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) spectra, and contact angle measurement are performed to characterize the morphological features, chemical composition, and wettability of the titanium surfaces. Stability and friction tests indicate that the prepared titanium surfaces are robust. The analysis of electrolyte, reaction process, and products demonstrates that the electrochemical processing is very inexpensive and environment-friendly. This method is believed to be easily adaptable for use in large-scale industry productions to promote the application of superhydrophobic titanium surfaces in aviation, aerospace, shipbuilding, and the military industry.

Antimicrobial agent-free hybrid cationic starch/sodium alginate polyelectrolyte films for food packaging materials.

PubMed

Şen, Ferhat; Uzunsoy, İrem; Baştürk, Emre; Kahraman, Memet Vezir

2017-08-15

This study aimed to develop polyelectrolyte structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic starch was synthesized and characterized by FT-IR spectroscopy and 1 H NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte structured antimicrobial food packaging materials were prepared using starch, cationic starch and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by TGA and DSC. Hydrophobicity of samples was determined by contact angle measurements. Surface morphology of samples was investigated by SEM. Moreover, gel contents of samples were determined. The obtained results prove that produced food packaging materials have good thermal, antimicrobial and surface properties, and they can be used as food packaging material in many industries. Copyright © 2017 Elsevier Ltd. All rights reserved.

Si NW network by Ag nanoparticle assisted etching and TiO2/Si NWs as photodetector

NASA Astrophysics Data System (ADS)

Bhowmik, Kishan; Mondal, Aniruddha

2015-03-01

Glancing angle deposited silver (Ag) nanoparticles (NPs) were employed to fabricate the silicon (Si) nanowire (NW) network on p-type Si substrate. The Si NWs were characterized by X-ray diffraction, which shows the (311) oriented single crystalline nature. The FEG-SEM images show that the nanowire diameters are in the order of 60-180 nm. The photoluminescence emission at 525 nm was recognized from the Si NWs. The Ag-TiO2 contacts exhibit Schottky behavior and higher photoconduction was observed for TiO2-Si NW detector than that of TiO2 Thin film under illumination up to 2.5 V applied potential. A threefold enhanced photodetection for the Silicon nanowire device was observed compared to the TiO2 thin film device, under applied voltages of 0.4-1.5 V. [Figure not available: see fulltext.

Reduction in static friction by deposition of a homogeneous diamond-like carbon (DLC) coating on orthodontic brackets.

PubMed

Akaike, Shun; Hayakawa, Tohru; Kobayashi, Daishiro; Aono, Yuko; Hirata, Atsushi; Hiratsuka, Masanori; Nakamura, Yoshiki

2015-01-01

In orthodontics, a reduction in static friction between the brackets and wire is important to enable easy tooth movement. The aim of this study was to examine the effects of a homogeneous diamond-like carbon (DLC) coating on the whole surfaces of slots in stainless steel orthodontic brackets on reducing the static friction between the brackets and the wire. The DLC coating was characterized using Raman spectroscopy, surface roughness and contact angle measurements, and SEM observations. Rectangular stainless steel and titanium-molybdenum alloy wires with two different sizes were employed, and the static friction between the brackets and wire was measured under dry and wet conditions. The DLC coating had a thickness of approximately 1.0 μm and an amorphous structure was identified. The results indicated that the DLC coating always led to a reduction in static friction.

The effect of polyether functional polydimethylsiloxane on surface and thermal properties of waterborne polyurethane

NASA Astrophysics Data System (ADS)

Zheng, Guikai; Lu, Ming; Rui, Xiaoping

2017-03-01

Waterborne polyurethanes (WPU) modified with polyether functional polydimethylsiloxane (PDMS) were synthesized by pre-polymerization method using isophorone diisocyanate (IPDI) and 1,4-butanediol (BDO) as hard segments and polybutylene adipate glycol (PBA) and polyether functional PDMS as soft segments. The effect of polyether functional PDMS on phase separation, thermal properties, surface properties including surface composition, morphology and wettability were investigated by FTIR, contact angle measurements, ARXPS, SEM-EDS, AFM, TG and DSC. The results showed that the compatibility between urethane hard segment and PDMS modified with polyether was good, and there was no distinct phase separation in both bulk and surface of WPU films. The degradation temperature and low temperature flexibility increased with increasing amounts of polyether functional PDMS. The enrichment of polyether functional PDMS with low surface energy on the surface imparted excellent hydrophobicity to WPU films.

Electrostatic powder spraying process for the fabrication of stable superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Gu, Guotuan; Tian, Yuping; Li, Zhantie; Lu, Dongfang

2011-03-01

Nano-sized Al2O3 particles were modified by heptadecafluorodecyl trimethoxysilane and 2,3-epoxy propoxy propyl trimethoxysilicane to make it both hydrophobic and reactive. The reactive nano-particles were mixed with polyester resin containing curing agents and electrostatic sprayed on stainless steel substrates to obtain stable superhydrophobic coatings after curing. The water contact angle (WCA) on the hybrid coating is influenced by the content of Al2O3 particles in the coating. As the Al2O3 concentration in the coating was increased from 0% to 8%, WCA increased from 68° to 165°. Surface topography of the coatings was examined using scanning electron microscopy (SEM). Nano-particles covered on the coating surface formed continuous film with greatly enhanced roughness, which was found to be responsible for the superhydrophobicity. The method is simple and cost effective and can be used for preparing self-cleaning superhydrophobic coating on large areas.

Preparation of Langmuir-Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties

NASA Astrophysics Data System (ADS)

Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat

2015-12-01

Organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure-area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.

Performance of nanocomposites for preservation of artistic stones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giancristofaro, Cristina; Pilloni, Luciano; Rinaldi, Antonio

2014-06-19

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. Themore » results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.« less

Fabrication of FDTS-modified PDMS-ZnO nanocomposite hydrophobic coating with anti-fouling capability for corrosion protection of Q235 steel.

PubMed

Arukalam, Innocent O; Oguzie, Emeka E; Li, Ying

2016-12-15

Perfluorodecyltrichlorosilane-based poly(dimethylsiloxane)-ZnO (FDTS-based PDMS-ZnO) nanocomposite coating with anti-corrosion and anti-fouling capabilities has been prepared using a one-step fabrication technique. XPS analysis and contact angle measurements showed the fluorine content to increase, while the hydrophobicity of the coatings decreased with addition of FDTS. XRD analysis revealed existence of ZnO nanoparticles of dimensions ranging from 11.45 to 93.01nm on the surface of coatings, with the mean particle size decreasing with FDTS addition, and was confirmed by SEM and TEM observations. Interestingly, the anti-corrosion performance and mechanical properties of the coatings increased remarkably on addition of FDTS. Indeed, the observed low adhesion strength, surface energies and the outstanding anti-corrosive properties imply that the obtained coating would be useful in anti-fouling applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Three dimensional profile measurement using multi-channel detector MVM-SEM

NASA Astrophysics Data System (ADS)

Yoshikawa, Makoto; Harada, Sumito; Ito, Keisuke; Murakawa, Tsutomu; Shida, Soichi; Matsumoto, Jun; Nakamura, Takayuki

2014-07-01

In next generation lithography (NGL) for the 1x nm node and beyond, the three dimensional (3D) shape measurements such as side wall angle (SWA) and height of feature on photomask become more critical for the process control. Until today, AFM (Atomic Force Microscope), X-SEM (cross-section Scanning Electron Microscope) and TEM (Transmission Electron Microscope) tools are normally used for 3D measurements, however, these techniques require time-consuming preparation and observation. And both X-SEM and TEM are destructive measurement techniques. This paper presents a technology for quick and non-destructive 3D shape analysis using multi-channel detector MVM-SEM (Multi Vision Metrology SEM), and also reports its accuracy and precision.

Carbon dioxide/brine wettability of porous sandstone versus solid quartz: An experimental and theoretical investigation.

PubMed

Alnili, Firas; Al-Yaseri, Ahmed; Roshan, Hamid; Rahman, Taufiq; Verall, Michael; Lebedev, Maxim; Sarmadivaleh, Mohammad; Iglauer, Stefan; Barifcani, Ahmed

2018-08-15

Wettability plays an important role in underground geological storage of carbon dioxide because the fluid flow and distribution mechanism within porous media is controlled by this phenomenon. CO 2 pressure, temperature, brine composition, and mineral type have significant effects on wettability. Despite past research on this subject, the factors that control the wettability variation for CO 2 /water/minerals, particularly the effects of pores in the porous substrate on the contact angle at different pressures, temperatures, and salinities, as well as the physical processes involved are not fully understood. We measured the contact angle of deionised water and brine/CO 2 /porous sandstone samples at different pressures, temperatures, and salinities. Then, we compared the results with those of pure quartz. Finally, we developed a physical model to explain the observed phenomena. The measured contact angle of sandstone was systematically greater than that of pure quartz because of the pores present in sandstone. Moreover, the effect of pressure and temperature on the contact angle of sandstone was similar to that of pure quartz. The results showed that the contact angle increases with increase in temperature and pressure and decreases with increase in salinity. Copyright © 2018 Elsevier Inc. All rights reserved.

Control of melt-crystal interface shape during sapphire crystal growth by heat exchanger method

NASA Astrophysics Data System (ADS)

Wu, Ming; Liu, Lijun; Ma, Wencheng

2017-09-01

We numerically investigate the melt-crystal interface shape during the early stage of the solidification process when the crystal diameter increases. The contact angle between the melt-crystal interface and the crucible bottom wall is found obtuse during this stage, which is unfavorable for the crystal quality. We found that the obtuse contact angle is caused by the thermal resistance difference between the sapphire crystal and melt as well as the insufficient cooling effect of the crucible bottom. Two approaches are proposed to suppress the obtuse contact angle. The first approach is to increase the emissivity of the outer surface of crucible bottom. The second approach is to install a heat shield near the crucible bottom. The reduction of the emissivity of the heat shield is also favorable for the suppression of the obtuse contact angle. Compared with the increase of the emissivity of the crucible bottom, the installation of a heat shield is a more effective approach to prevent the appearance of an obtuse contact angle for the sake of reliability since a molybdenum heat shield can be reused and will not induce other impurities.

Mathematical modeling of two phase stratified flow in a microchannel with curved interface

NASA Astrophysics Data System (ADS)

Dandekar, Rajat; Picardo, Jason R.; Pushpavanam, S.

2017-11-01

Stratified or layered two-phase flows are encountered in several applications of microchannels, such as solvent extraction. Assuming steady, unidirectional creeping flow, it is possible to solve the Stokes equations by the method of eigenfunctions, provided the interface is flat and meets the wall with a 90 degree contact angle. However, in reality the contact angle depends on the pair of liquids and the material of the channel, and differs significantly from 90 degrees in many practical cases. For unidirectional flow, this implies that the interface is a circular arc (of constant curvature). We solve this problem within the framework of eigenfunctions, using the procedure developed by Shankar. We consider two distinct cases: (a) the interface meets the wall with the equilibrium contact angle; (b) the interface is pinned by surface treatment of the walls, so that the flow rates determine the apparent contact angle. We show that the contact angle appreciably affects the velocity profile and the volume fractions of the liquids, while limiting the range of flow rates that can be sustained without the interface touching the top/bottom walls. Non-intuitively, we find that the pressure drop is reduced when the more viscous liquid wets the wall.

Novel Determination of the Orientation of Calcite on Mineral Substrates

NASA Astrophysics Data System (ADS)

Zhao, L.; Ji, X.; Teng, H.

2016-12-01

In the threat of global warming, the transformation from CO2 to stable carbonate minerals is significant to geological CO2 sequestration in the long term.Previous efforts have found that when carbonate minerals nucleate on some mineral substrates ,the time of carbon capture can be shorted .Many efforts have been focused on the dynamics when carbonate minerals nucleate on mineral substrates, but few have studied the orientation of carbonate minerals on mineral substrates. In our experiment, we mainly focused on the orientation of calcite on mineral substrates.We mixed NaHCO3 and CaCl2 to nucleate when mineral substrates were added and a multi-parameter analyzer was used to monitor in real time to determine the induction time for nucleation. On the basis of classical nucleation theory, we got a brand new formula to decide the orientation of calcite on mineral substrates. lntind=(2-cosθ+cos3θ)*16πγ3vm2(12*(kBT)3*(lnS)2)+ln(1/N0v)+ ΔEa/(kBT)where θ is the angle between the substrate and the nuclei, tind is the induction time for nucleation, γ is he average surface free energy, N0 is the total number of particles per unit volume of solution, ΔEa is the activation energy for molecular motion across the embryo-matrix interface, S is the supersaturation index ,kB is the Boltzmann constant. Using the new formula above , when biotite was used as substrate mineral ,we found that the angle between the biotite and the nuclei was 119°. Angle measured on SEM images also supported our conclusion above. Combined with SEM and Debye ring analysed by Rigaku 2D data processing software, we only found one point of (006) in Debye ring, unlike (104)(many points in one ring and it meant that the orientation of (104) is random ). That meant (001) of calcite was first formed on biotite (001). In that case we inferred that 119° was formed by (001) of botite and (012) of calcite for the intersection angle of (001) and (012) was 120°. Future research will focus on the orientation of calcite on muscovite and feldspar to find out the main influence factor of the contact relationship.

Transmittance of semitransparent windows with absorbing cap-shaped droplets condensed on their backside

NASA Astrophysics Data System (ADS)

Zhu, Keyong; Pilon, Laurent

2017-11-01

This study aims to investigate systematically light transfer through semitransparent windows with absorbing cap-shaped droplets condensed on their backside as encountered in greenhouses, solar desalination plants, photobioreactors and covered raceway ponds. The Monte Carlo ray-tracing method was used to predict the normal-hemispherical transmittance, reflectance, and normal absorptance accounting for reflection and refraction at the air/droplet, droplet/window, and window/air interfaces and absorption in both the droplets and the window. The droplets were monodisperse or polydisperse and arranged either in an ordered hexagonal pattern or randomly distributed on the backside with droplet contact angle θc ranging between 0 and 180° The normal-hemispherical transmittance was found to be independent of the spatial distribution of droplets. However, it decreased with increasing droplet diameter and polydispersity. The normal-hemispherical transmittance featured four distinct optical regimes for semitransparent window supporting nonabsorbing droplets. These optical regimes were defined based on contact angle and critical angle for internal reflection at the droplet/air interface. However, for strongly absorbing droplets, the normal-hemispherical transmittance (i) decreased monotonously with increasing contact angle for θc <90° and (ii) remained constant and independent of droplet absorption index kd, droplet mean diameter dm, and contact angle θc for θc ≥ 90° Analytical expressions for the normal-hemispherical transmittance were provided in the asymptotic cases when (1) the window was absorbing but the droplets were nonabsorbing with any contact angles θc, and (2) the droplets were strongly absorbing with contact angle θc >90° Finally, the spectral normal-hemispherical transmittance of a 3 mm-thick glass window supporting condensed water droplets for wavelength between 0.4 and 5 μm was predicted and discussed in light of the earlier parametric study and asymptotic behavior.

Wetting of flat gradient surfaces.

PubMed

Bormashenko, Edward

2018-04-01

Gradient, chemically modified, flat surfaces enable directed transport of droplets. Calculation of apparent contact angles inherent for gradient surfaces is challenging even for atomically flat ones. Wetting of gradient, flat solid surfaces is treated within the variational approach, under which the contact line is free to move along the substrate. Transversality conditions of the variational problem give rise to the generalized Young equation valid for gradient solid surfaces. The apparent (equilibrium) contact angle of a droplet, placed on a gradient surface depends on the radius of the contact line and the values of derivatives of interfacial tensions. The linear approximation of the problem is considered. It is demonstrated that the contact angle hysteresis is inevitable on gradient surfaces. Electrowetting of gradient surfaces is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

Liquid-bridge stability and breakup on surfaces with contact-angle hysteresis.

PubMed

Akbari, Amir; Hill, Reghan J

2016-08-10

We study the stability and breakup of liquid bridges with a free contact line on surfaces with contact-angle hysteresis (CAH) under zero-gravity conditions. Non-ideal surfaces exhibit CAH because of surface imperfections, by which the constraints on three-phase contact lines are influenced. Given that interfacial instabilities are constraint-sensitive, understanding how CAH affects the stability and breakup of liquid bridges is crucial for predicting the drop size in contact-drop dispensing. Unlike ideal surfaces on which contact lines are always free irrespective of surface wettability, contact lines may undergo transitions from pinned to free and vice versa during drop deposition on non-ideal surfaces. Here, we experimentally and theoretically examine how stability and breakup are affected by CAH, highlighting cases where stability is lost during a transition from a pinned-pinned (more constrained) to pinned-free (less constrained) interface-rather than a critical state. This provides a practical means of expediting or delaying stability loss. We also demonstrate how the dynamic contact angle can control the contact-line radius following stability loss.

New Method Developed to Measure Contact Angles of a Sessile Drop

NASA Technical Reports Server (NTRS)

Chao, David F.; Zhang, Nengli

2002-01-01

The spreading of an evaporating liquid on a solid surface occurs in many practical processes and is of importance in a number of practical situations such as painting, textile dyeing, coating, gluing, and thermal engineering. Typical processes involving heat transfer where the contact angle plays an important role are film cooling, boiling, and the heat transfer through heat pipes. The biological phenomenon of cell spreading also is analogous to a drop spreading (ref. 1). In the study of spreading, the dynamic contact angle describes the interfacial properties on solid substrates and, therefore, has been studied by physicists and fluid mechanics investigators. The dynamic contact angle of a spreading nonvolatile liquid drop provides a simple tool in the study of the free-boundary problem, but the study of the spreading of a volatile liquid drop is of more practical interest because the evaporation of common liquids is inevitable in practical processes. The most common method to measure the contact angle, the contact radius, and the height of a sessile drop on a solid surface is to view the drop from its edge through an optical microscope. However, this method gives only local information in the view direction. Zhang and Yang (ref. 2) developed a laser shadowgraphy method to investigate the evaporation of sessile drop on a glass plate. As described here, Zhang and Chao (refs. 3 and 4) improved the method and suggested a new optical arrangement to measure the dynamic contact angle and the instant evaporation rate of a sessile drop with much higher accuracy (less than 1 percent). With this method, any fluid motion in the evaporating drop can be visualized through shadowgraphy without using a tracer, which often affects the field under investigation.

Controlled growth of standing Ag nanorod arrays on bare Si substrate using glancing angle deposition for self-cleaning applications

NASA Astrophysics Data System (ADS)

Singh, Dhruv P.; Singh, J. P.

2014-03-01

A facile approach to manipulate the hydrophobicity of surface by controlled growth of standing Ag nanorod arrays is presented. Instead of following the complicated conventional method of the template-assisted growth, the morphology or particularly average diameter and number density (nanorods cm-2) of nanorods were controlled on bare Si substrate by simply varying the deposition rate during glancing angle deposition. The contact angle measurements showed that the evolution of Ag nanorods reduces the surface energy and makes an increment in the apparent water contact angle compared to the plain Ag thin film. The contact angle was found to increase for the Ag nanorod samples grown at lower deposition rates. Interestingly, the morphology of the nanorod arrays grown at very low deposition rate (1.2 Å sec-1) results in a self-cleaning superhydrophobic surface of contact angle about 157° and a small roll-off angle about 5°. The observed improvement in hydrophobicity with change in the morphology of nanorod arrays is explained as the effect of reduction in solid fraction within the framework of Cassie-Baxter model. These self-cleaning Ag nanorod arrays could have a significant impact in wide range of applications such as anti-icing coatings, sensors and solar panels.

Lattice Boltzmann simulation of immiscible displacement in the cavity with different channel configurations

NASA Astrophysics Data System (ADS)

Lou, Qin; Zang, Chenqiang; Yang, Mo; Xu, Hongtao

In this work, the immiscible displacement in a cavity with different channel configurations is studied using an improved pseudo-potential lattice Boltzmann equation (LBE) model. This model overcomes the drawback of the dependence of the fluid properties on the grid size, which exists in the original pseudo-potential LBE model. The approach is first validated by the Laplace law. Then, it is employed to study the immiscible displacement process. The influences of different factors, such as the surface wettability, the distance between the gas cavity and liquid cavity and the surface roughness of the channel are investigated. Numerical results show that the displacement efficiency increases and the displacement time decreases with the increase of the surface contact angle. On the other hand, the displacement efficiency increases with increasing distance between the gas cavity and the liquid cavity at first and finally reaches a constant value. As for the surface roughness, two structures (a semicircular cavity and a semicircular bulge) are studied. The comprehensive results show that although the displacement processes for both the structures depend on the surface wettability, they present quite different behaviors. Specially, for the roughness structure constituted by the semicircular cavity, the displacement efficiency decreases and displacement time increases evidently with the size of the semicircular cavity for the small contact angle. The trend slows down as the increase of the contact angle. Once the contact angle exceeds a certain value, the size of the semicircular cavity almost has no influence on the displacement process. While for the roughness structure of a semicircular bulge, the displacement efficiency increases with the size of bulge first and then it decreases for the small contact angle. The displacement efficiency increases first and finally reaches a constant for the large contact angle. The results also show that the displacement time has an extreme value in these cases for the small contact angles.

Creation of superwetting surfaces with roughness structures.

PubMed

Garg, Varun; Qiao, Lei; Sarwate, Prasha; Luo, Cheng

2014-12-09

In this work, we explored the possibility of creating superwetting surfaces, which are defined here as those with apparent contact angles of <5°, using roughness structures for the purpose of eliminating the surface tension effect on a floating small plate, which is denser than the surrounding liquid. The roughness ratio is often thought to play a critical role in generating superwetting surfaces. However, we found that the top surface ratio had more influence on apparent contact angles. When this ratio was <0.013, the resulting apparent contact angle might be less than 5°, when the intrinsic contact angle was ≥40°. Accordingly, hybrid micro- and nanostructures, which had such a small ratio, were chosen to create the superwetting surfaces. These surfaces were subsequently applied to eliminate the surface tension effect on a small plate. As a result of this elimination, the small plate sank down to the bottom of the liquid.

Increasing light coupling in a photovoltaic film by tuning nanoparticle shape with substrate surface energy

NASA Astrophysics Data System (ADS)

Kataria, Devika; Krishnamoorthy, Kothandam; Iyer, S. Sundar Kumar

2017-08-01

Tuning metal nanoparticle (MNP) contact angle on the surface it is formed can help maximise the useful optical coupling in photovoltaic films by localized surface plasmon (LSP) resonance—opening up the possibility of building improved photovoltaic cells. In this work experimental demonstration of optical absorption increase in copper phthalocyanine (CuPc) films by tuning silver MNP shape by changing its contact angles with substrate has been reported. Thin films of poly3,4 ethylenedioxythiophene: sodium dodecycl sulphate (PEDOT:SDS) with different surface energies were formed on indium tin oxide (ITO) coated glass by electro-deposition. Silver MNPs thermally evaporated directly on ozonised ITO as well as on the PEDOT:SDS films showed contact angles ranging from 60° to 125°. The CuPc layer was deposited on top of the MNPs. For the samples studied, best optical absorption in the CuPc layer was for a contact angle of 110°.

Preliminary Study of Water Repellent Properties of Red Pepper Seed Oil

NASA Astrophysics Data System (ADS)

Kurniawan, F.; Madurani, K. A.; Wahyulis, N. C.

2017-03-01

The water-repellent properties of red pepper seed oil (capsicol) have been studied. The oil was coated on the glass surface by spray technique. Water repellent properties were performed by measuring the contact angle of water droplets. The measurement was conducted by varying the drying time of the oil coating at room temperature. The optimum contact angle of the droplets on the glass with capsicol coating is 46.77°, which can be achieved in 30 min of drying time. It also obtained the smallest diameter of the droplets (0.47 cm). The longer drying time decrease the contact angles and increases the diameter. The results were compared with the bare glass and commercial water repellent. The contact angle of the droplets on the glass surface with capsicol coating is higher than bare glass, but lower than glass with commercial water repellent coating. It means that capsicol has the water-repellent properties.

Discrete Element Method Simulations of the Inter-Particle Contact Parameters for the Mono-Sized Iron Ore Particles

PubMed Central

Li, Tongqing; Peng, Yuxing; Zhu, Zhencai; Zou, Shengyong; Yin, Zixin

2017-01-01

Aiming at predicting what happens in reality inside mills, the contact parameters of iron ore particles for discrete element method (DEM) simulations should be determined accurately. To allow the irregular shape to be accurately determined, the sphere clump method was employed in modelling the particle shape. The inter-particle contact parameters were systematically altered whilst the contact parameters between the particle and wall were arbitrarily assumed, in order to purely assess its impact on the angle of repose for the mono-sized iron ore particles. Results show that varying the restitution coefficient over the range considered does not lead to any obvious difference in the angle of repose, but the angle of repose has strong sensitivity to the rolling/static friction coefficient. The impacts of the rolling/static friction coefficient on the angle of repose are interrelated, and increasing the inter-particle rolling/static friction coefficient can evidently increase the angle of repose. However, the impact of the static friction coefficient is more profound than that of the rolling friction coefficient. Finally, a predictive equation is established and a very close agreement between the predicted and simulated angle of repose is attained. This predictive equation can enormously shorten the inter-particle contact parameters calibration time that can help in the implementation of DEM simulations. PMID:28772880

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ba, Yan; Kang, Qinjun; Liu, Haihu

In this study, the dynamical behavior of a droplet on topologically structured surface is investigated by using a three-dimensional color-gradient lattice Boltzmann model. A wetting boundary condition is proposed to model fluid-surface interactions, which is advantageous to improve the accuracy of the simulation and suppress spurious velocities at the contact line. The model is validated by the droplet partial wetting test and reproduction of the Cassie and Wenzel states. A series of simulations are conducted to investigate the behavior of a droplet when subjected to a shear flow. It is found that in Cassie state, the droplet undergoes a transitionmore » from stationary, to slipping and finally to detachment states as the capillary number increases, while in Wenzel state, the last state changes to the breakup state. The critical capillary number, above which the droplet slipping occurs, is small for the Cassie droplet, but is significantly enhanced for the Wenzel droplet due to the increased contact angle hysteresis. In Cassie state, the receding contact angle nearly equals the prediction by the Cassie relation, and the advancing contact angle is close to 180°, leading to a small contact angle hysteresis. In Wenzel state, however, the contact angle hysteresis is extremely large (around 100°). Finally, high droplet mobility can be easily achieved for Cassie droplets, whereas in Wenzel state, extremely low droplet mobility is identified.« less

Modeling, investigation and formulation of hydrophobic coatings for potential self-cleaning applications

NASA Astrophysics Data System (ADS)

Rios, Pablo Fabian

Self-cleaning surfaces have received a great deal of attention, both in research and commercial applications. Transparent and non-transparent self-cleaning surfaces are highly desired. The Lotus flower is a symbol of purity in Asian cultures, even when rising from muddy waters it stays clean and untouched by dirt. The Lotus leaf "self-cleaning" surface is hydrophobic and rough, showing a two-layer morphology. While hydrophobicity produces a high contact angle, surface morphology reduces the adhesion of dirt and water to the surface, thus water drops slide easily across the leaf carrying the dirt particles with them. Nature example in the Lotus-effect and extensive scientific research on related fields have rooted wide acceptance that high hydrophobicity can be obtained only by a proper combination of surface chemistry and roughness. Most researchers relate hydrophobicity to a high contact angle. However, the contact angle is not the only parameter that defines liquid-solid interactions. An additional parameter, the sliding angle, related to the adhesion between the liquid drop and the solid surface is also important in cases where liquid sliding is involved, such as self-cleaning applications. In this work, it is postulated that wetting which is related to the contact angle, and interfacial adhesion, which is related to the sliding angle, are interdependent phenomena and have to be considered simultaneously. A variety of models that relate the sliding angle to forces developed along the contact line between a liquid drop and a solid surface have been proposed in the literature. A new model is proposed here that quantifies the drop sliding phenomenon, based also on the interfacial adhesion across the contact area of the liquid/solid interface. The effects of roughness and chemical composition on the contact and sliding angles of hydrophobic smooth and rough surfaces were studied theoretically and experimentally. The validity of the proposed model was investigated and compared with the existing models. Ultra-hydrophobic non-transparent and transparent coatings for potential self-cleaning applications were produced using hydrophobic chemistry and different configurations of roughening micro and nano-particles, however they present low adhesion and durability. Durability and stability enhancement of such coatings was attempted and improved by different methods.

A new water retention and hydraulic conductivity model accounting for contact angle

NASA Astrophysics Data System (ADS)

Diamantopoulos, Efstathios; Durner, Wolfgang

2013-04-01

The description of soil water transport in the unsaturated zone requires the knowledge of the soil hydraulic properties, i.e. the water retention and the hydraulic conductivity function. A great amount of parameterizations for this can be found in the literature, the majority of which represent the complex pore space of soils as a bundle of cylindrical capillary tubes of various sizes. The assumption of zero contact angles between water and surface of the grains is also made. However, these assumptions limit the predictive capabilities of these models, leading often to enormous errors in the prediction of water dynamics in soils. We present a pore scale analysis for equilibrium liquid configurations (retention) in angular pores taking the effect of contact angle into account. Furthermore, we propose an alternative derivation of the hydraulic conductivity function, again as a function of the contact angle, assuming flow perpendicular to pore cross sections. Finally, we upscale our model from the pore to the sample scale by assuming a gamma statistical distribution of the pore sizes. Closed form expressions are derived for both sample water retention and conductivity functions. The new model was tested against experimental data from multistep inflow/outflow (MSI/MSO) experiments for a sandy material. They were conducted using ethanol and water as the wetting liquid. Ethanol was assumed to form a zero contact angle with the soil grains. The proposed model described both imbibition and drainage of water and ethanol very well. Lastly, the consideration of the contact angle allowed the description of the observed hysteresis.

Measurement of Capillary Radius and Contact Angle within Porous Media.

PubMed

Ravi, Saitej; Dharmarajan, Ramanathan; Moghaddam, Saeed

2015-12-01

The pore radius (i.e., capillary radius) and contact angle determine the capillary pressure generated in a porous medium. The most common method to determine these two parameters is through measurement of the capillary pressure generated by a reference liquid (i.e., a liquid with near-zero contact angle) and a test liquid. The rate of rise technique, commonly used to determine the capillary pressure, results in significant uncertainties. In this study, we utilize a recently developed technique for independently measuring the capillary pressure and permeability to determine the equivalent minimum capillary radii and contact angle of water within micropillar wick structures. In this method, the experimentally measured dryout threshold of a wick structure at different wicking lengths is fit to Darcy's law to extract the maximum capillary pressure generated by the test liquid. The equivalent minimum capillary radii of different wick geometries are determined by measuring the maximum capillary pressures generated using n-hexane as the working fluid. It is found that the equivalent minimum capillary radius is dependent on the diameter of pillars and the spacing between pillars. The equivalent capillary radii of micropillar wicks determined using the new method are found to be up to 7 times greater than the current geometry-based first-order estimates. The contact angle subtended by water at the walls of the micropillars is determined by measuring the capillary pressure generated by water within the arrays and the measured capillary radii for the different geometries. This mean contact angle of water is determined to be 54.7°.

Capillary Rise: Validity of the Dynamic Contact Angle Models.

PubMed

Wu, Pingkeng; Nikolov, Alex D; Wasan, Darsh T

2017-08-15

The classical Lucas-Washburn-Rideal (LWR) equation, using the equilibrium contact angle, predicts a faster capillary rise process than experiments in many cases. The major contributor to the faster prediction is believed to be the velocity dependent dynamic contact angle. In this work, we investigated the dynamic contact angle models for their ability to correct the dynamic contact angle effect in the capillary rise process. We conducted capillary rise experiments of various wetting liquids in borosilicate glass capillaries and compared the model predictions with our experimental data. The results show that the LWR equations modified by the molecular kinetic theory and hydrodynamic model provide good predictions on the capillary rise of all the testing liquids with fitting parameters, while the one modified by Joos' empirical equation works for specific liquids, such as silicone oils. The LWR equation modified by molecular self-layering model predicts well the capillary rise of carbon tetrachloride, octamethylcyclotetrasiloxane, and n-alkanes with the molecular diameter or measured solvation force data. The molecular self-layering model modified LWR equation also has good predictions on the capillary rise of silicone oils covering a wide range of bulk viscosities with the same key parameter W(0), which results from the molecular self-layering. The advantage of the molecular self-layering model over the other models reveals the importance of the layered molecularly thin wetting film ahead of the main meniscus in the energy dissipation associated with dynamic contact angle. The analysis of the capillary rise of silicone oils with a wide range of bulk viscosities provides new insights into the capillary dynamics of polymer melts.

Effects of bolt-hole contact on bearing-bypass damage-onset strength

NASA Technical Reports Server (NTRS)

Crews, John H., Jr.; Naik, Rajiv A.

1991-01-01

A combined experimental and analytical study was conducted to investigate the effects of bolt-hole contact on the bearing bypass strength of a graphite-epoxy laminate. Tests were conducted on specimens consisting of 16-ply quasi-isotropic T300/5208 laminates with a centrally located hole. Bearing loads were applied through a clearance-fit steel bolt. Damage onset strength and damage mode were determined for each test case. A finite element procedure was used to calculate the bolt-hole stresses and bolt contact for each test case. A finite element procedure was used to calculate the bolt-hole stresses and bolt contact for each measured damage-onset strength. For the tension bearing-bypass cases tested, the bolt contact half-angle was approximately 60 degrees at damage onset. For compression, the contact angle was 20 degrees as the bypass load increased. A corresponding decrease in the bearing damage onset strength was attributed to the decrease in contact angle which made the bearing loads more severe. Hole boundary stresses were also computed by superimposing stresses for separate bearing and bypass loading. Stresses at the specimen net section were accurately approximated by the superposition procedure. However, the peak bearing stresses had large errors because the bolt contact angles were not represented correctly. For compression, peak bearing stress errors of nearly 50 percent were calculated.

Modifying the mechanical properties of silk nanofiber scaffold by knitted orientation for regenerative medicine applications.

PubMed

Dodel, M; Hemmati Nejad, N; Bahrami, S H; Soleimani, M; Hanaee-Ahvaz, H

2016-08-31

Tissue reconstruction is among the increasing applications of polymer nanofibers. Fibrous scaffolds (mats) can be easily produced using the electrospinning method with structure and biomechanical properties similar to those of a cellular matrix. Electrospinning is widely used in the production of nanofibers and the GAP-method electrospinning is one of the means of producing fully aligned nanofibers. In this research, using the GAP-method, knitted fibrous scaffolds were made of silk fibroin, which is a biocompatible and biodegradable polymer. To extract fibroin from cocoons, the sodium chloride solution as well as dialysis and freeze-drying techniques were employed. The molecular weight of the extracted fibroin was measured with the SDS-Page electrophoresis technique. Moreover, the pure fibroin structure was examined using the ATR-FTIR method, and the viscosity of the solution used for electrospinning was measured with the Brookfield rotational viscometer. The scaffolds were prepared through electrospinning of the silk fibroin in pure formic acid solution. The following three structures were electrospun: 1) a random structure; 2) a knitted structure with an interstitial angle of 60 degrees; 3) a knitted structure with an interstitial angle of 90 degrees. Morphology of the resulting fibers was studied with a SEM (scanning electron microscope). Fibroin scaffolds are degradable in water. Therefore, they were fixated through immersion in methanol to be prepared for assays. The mechanical properties of the scaffolds were also studied using a tensile strength test device. The effect of methanol on the strength properties of the samples was also assessed. The hydrophilic potential of the samples was measured via a contact angle test. To increase the hydrophilicity of the scaffold surfaces, the cold oxygen plasma technique was employed. Finally, the biocompatibility and cell adhesion of the resulting scaffolds were examined through a HEK 293 cell culture, and the results were analyzed through the MTT, DAPI staining, and SEM imaging techniques. Results revealed that the oriented knitted structure contributed to the increase in Young's modulus and the maximum strength of scaffolds as compared to the random samples. Moreover, this structure can also be a suitable alternative to the typical chemical means of increasing strength.

Contact Angle Measurements Using a Simplified Experimental Setup

ERIC Educational Resources Information Center

Lamour, Guillaume; Hamraoui, Ahmed; Buvailo, Andrii; Xing, Yangjun; Keuleyan, Sean; Prakash, Vivek; Eftekhari-Bafrooei, Ali; Borguet, Eric

2010-01-01

A basic and affordable experimental apparatus is described that measures the static contact angle of a liquid drop in contact with a solid. The image of the drop is made with a simple digital camera by taking a picture that is magnified by an optical lens. The profile of the drop is then processed with ImageJ free software. The ImageJ contact…

Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

NASA Astrophysics Data System (ADS)

Owkes, Mark

2017-11-01

In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

Free-surface phenomena under low- and zero-gravity conditions

NASA Technical Reports Server (NTRS)

Coles, D.

1985-01-01

An apparatus to measure contact angle was constructed to exploit the proposed internal-corner criterion. If 2 alfa is the internal angle between two intersecting vertical planes and gamma is the contact angle, a meniscus at the corner rises to a finite height if alfa + gamma pi/2 and to an infinite height if alfa + gamma pi/2. The apparatus operates by decreasing the angle alfa from pi/2 until the meniscus height changes abruptly. A number of liquids are tested on glass and plexiglas.

Simultaneous spreading and evaporation: recent developments.

PubMed

Semenov, Sergey; Trybala, Anna; Rubio, Ramon G; Kovalchuk, Nina; Starov, Victor; Velarde, Manuel G

2014-04-01

The recent progress in theoretical and experimental studies of simultaneous spreading and evaporation of liquid droplets on solid substrates is discussed for pure liquids including nanodroplets, nanosuspensions of inorganic particles (nanofluids) and surfactant solutions. Evaporation of both complete wetting and partial wetting liquids into a nonsaturated vapour atmosphere are considered. However, the main attention is paid to the case of partial wetting when the hysteresis of static contact angle takes place. In the case of complete wetting the spreading/evaporation process proceeds in two stages. A theory was suggested for this case and a good agreement with available experimental data was achieved. In the case of partial wetting the spreading/evaporation of a sessile droplet of pure liquid goes through four subsequent stages: (i) the initial stage, spreading, is relatively short (1-2 min) and therefore evaporation can be neglected during this stage; during the initial stage the contact angle reaches the value of advancing contact angle and the radius of the droplet base reaches its maximum value, (ii) the first stage of evaporation is characterised by the constant value of the radius of the droplet base; the value of the contact angle during the first stage decreases from static advancing to static receding contact angle; (iii) during the second stage of evaporation the contact angle remains constant and equal to its receding value, while the radius of the droplet base decreases; and (iv) at the third stage of evaporation both the contact angle and the radius of the droplet base decrease until the drop completely disappears. It has been shown theoretically and confirmed experimentally that during the first and second stages of evaporation the volume of droplet to power 2/3 decreases linearly with time. The universal dependence of the contact angle during the first stage and of the radius of the droplet base during the second stage on the reduced time has been derived theoretically and confirmed experimentally. The theory developed for pure liquids is applicable also to nanofluids, where a good agreement with the available experimental data has been found. However, in the case of evaporation of surfactant solutions the process deviates from the theoretical predictions for pure liquids at concentration below critical wetting concentration and is in agreement with the theoretical predictions at concentrations above it. Crown Copyright © 2013. All rights reserved.

Wetting and adhesion evaluation of cosmetic ingredients and products: correlation of in vitro-in vivo contact angle measurements.

PubMed

Capra, P; Musitelli, G; Perugini, P

2017-08-01

The aim of this work was to use the contact angle measurement in order to predict the behaviour of ingredients and finished cosmetic products on skin to improve skin feel and product texture. Different classes of cosmetic ingredients and formulations were evaluated. The contact angle measurements were carried out by the sessile drop method using an apparatus, designed and set up in laboratory. Glass, Teflon and human skin were the reference substrates. In a preliminary phase, TEWL parameter, sebum content and hydration of human skin were measured to set up method. Data demonstrated that glass substrate may be used as replacement of the skin:critical surface tension of skin and glass were about of 27 and 31 dyne cm -1 , respectively. Non-ionic surfactant with increasing HLB was evaluated: a correlation between contact angle measured and HLB was not observed because of different and complex molecular structure. In detail, ethylhexyl hydroxystearate (θ glass = 17.1°) showed lower contact angle value with respect to Polysorbate 20 (θ glass = 28.1°). Sodium laureth sulphate and stearalkonium chloride were also evaluated: anionic molecule showed more affinity for glass with respect to Teflon (θ glass = 21.7° and θ Teflon = 52.3°). Lipids and silicones showed different affinity for substrate according to hydrophilic groups and hydrocarbon chain: contact angles of silicones remained unchanged independently from substrate. Finished cosmetic products (O/W, W/O emulsions, cleansing oil, dry skin oil) showed different profiles according to surfactant and its affinity for continuous phase of the formulation. Comparing the values of the contact angle on skin of non-ionic surfactants, as ethylhexyl hydroxystearate and Polysorbate 20, they showed values lower (near to zero) than ones of sodium laureth sulphate and Stearalkonium Chloride (21.7° and 66.8°, respectively). Finally, finished cosmetic products tested on human skin showed different profile: corresponded contact angle values were less than 20°. The product tended to be quickly adsorbed on human skin. Systematic study carried out by evaluating the wettability of single cosmetic ingredients on different substrates allowed to find correlations between the use of certain ingredients and the final performance of a cosmetic product. © 2017 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Conductive contact area estimation for carbon nanotube via interconnects using secondary-electron imaging

NASA Astrophysics Data System (ADS)

Abe, Yusuke; Suzuki, Makoto; Vyas, Anshul; Yang, Cary Y.

2018-01-01

A major challenge for carbon nanotube (CNT) to become a viable replacement of copper and tungsten in the next-generation on-chip via interconnects is the high contact resistance between CNT and metal electrodes. A first step in meeting this challenge is an accurate characterization of via contact resistance. In this paper, the scanning electron microscope (SEM) image contrast at low landing energy is employed to estimate the conductive CNT area inside vias. The total conductive CNT area inside each via is deduced using SEM image with 0.1 keV landing energy and a specified threshold brightness, yielding via resistance versus CNT area behavior, which correlates well with electrical nanoprobing measurements of via resistance. Monte Carlo simulation of secondary electron generation lends further support for our analysis and suggests that the residue covering the CNT does not affect the conduction across the contact for residue thickness below 1 nm. This imaging and analysis technique can add much value to CNT via interconnect contact characterization.

Measurement of the Position Angle and Separation of HJ 1924

NASA Astrophysics Data System (ADS)

Badami, Umar Ahmed; Tock, Kalée.; Carpenter, Steve; Kruger, Kurt; Freed, Rachel; Genet, Russell

2018-01-01

The position angle and separation of the binary HJ 1924 have been measured and noted in 10 publications since John Herschel's initial observation in 1828. Measurement techniques have improved in both precision and accuracy since that time. Although Herschel's initial measurement was slightly different, the position angle and separation of these stars have remained relatively constant for the past 122 years. The system was observed using the Skynet Robotic Telescope Network. AstroImageJ software was used to contribute a new data point. Our measurement of 8.12" ± 0.0127 (1 ± SEM), 225.1o ± 0.0298 (1 ± SEM),was in agreement with the 10 most recent published measurements, but not the initial one, implying that Herschel's measurement may have been inaccurate. While these stars appear to exhibit similar proper motion, and may therefore share a common origin, they are unlikely to be gravitationally bound.

[Effect of TiO2-SiO2-SnOx film with different firing temperatures on bond strength of low-fusing dental porcelain to pure titanium].

PubMed

Zhang, Zichuan; Zhang, Pei

2015-07-01

To evaluate the influence of TiO(2)-SiO(2)-SnOx nano-coatings with different firing temperatures on the bond strength of low-fusing dental porcelain to pure titanium. The surface of pure titanium was coated uniformly with TiO(2)-SiO(2)-SnOx nano-coatings by solution-gelatin (Sol-Gel) technology and then fired at 300 °C (group A) or 750 °C (group B) for 1 h. The specimens without any coatings were the control group (group C). There were 10 specimens in each group. Dental porcelain was sintered on the surface of titanium specimens. Surface roughness and contact angle of the coatings were also detected. The titanium-porcelain bond strength was investigated according to YY 0621-2008 standards using three-point flexure bond test. The phase composition of the TiO(2)-SiO(2)-SnOx nano-coatings was characterized by X-ray diffraction(XRD). The interface of titanium-porcelain and TiO(2)-SiO(2)-SnOx nano-coatings were observed using scanning electron microscope (SEM). No rutile phase was found in these specimens of group A and group B. The surface roughness of group A, B, C was (0.97 ± 0.06), (0.99 ± 0.03), (0.96 ± 0.07) µm, respectively. No significant difference was found among the three groups. Compared with that of group C (64.37° ± 3.01°), contact angles detected in group A (52.04° ± 3.15°) and group B (85.27° ± 4.17°) were significantly different (P < 0.05). The bond strength of titanium-porcelain in group A [(35.66 ± 2.65) MPa] was significantly increased compared with those in group B [(26.18 ± 2.22) MPa] and group C [(31.66 ± 3.52) MPa]. SEM photomicrographs of titanium-porcelain interface morphology of the specimens before porcelain sintering showed that TiO(2)-SiO(2)-SnOx nano-coatings in group A were compact and homogeneous with petty cracks and those in group B was loose and arranged disorderly. TiO(2)-SiO(2)-SnOx nano-coating fired at 300 °C is significantly effective in improving the titanium-porcelain bond strength.

Preparation of crosslinked polysiloxane/SiO2 nanocomposite via in-situ condensation and its surface modification on cotton fabrics

NASA Astrophysics Data System (ADS)

Hao, Lifen; Gao, Tingting; Xu, Wei; Wang, Xuechuan; Yang, Shuqin; Liu, Xiangguo

2016-05-01

Novel crosslinked polysiloxane/SiO2 nanocomposite (CLPS-SiO2) was successfully prepared via the in-situ condensation reaction of silica sols and crosslinked polysiloxane with end-capped triethoxysilane in solvent, which was firstly fabricated through the modification of our previously developed crosslinked polysiloxane with end-capped epoxy groups using aminopropyltriethoxysilane (APTES) and noted as APTES-CLPS. Chemical structures and thermal properties of the as-prepared resultants were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectra (1H/13C NMR) and thermogravimetric analysis (TGA). CLPS-SiO2 was applied as surface modification agent to treat cotton fabrics. Film morphologies and surface properties were examined with scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), contact angle measurements, and other instruments. FTIR and NMR confirmed structure of the products. CLPS-SiO2 showed better thermal stability than APTES-CLPS due to anchor of the nanosilica. APTES-CLPS could deposit a smooth film on cotton fiber surface. Besides, CLPS-SiO2 also coated the fibers with many nano-scaled tubercles beneath this smooth film by SEM. However, the APTES-CLPS film and the CLPS-SiO2 film on silicon-wafer were never homogeneous and had a few low or high peaks. The root mean square roughness (Rq) of APTES-CLPS film reached to 0.441 nm in 2 × 2 μm2 scanning field and at 5 nm data scale. Owing to the incorporation of nanosilica, that of CLPS-SiO2 film continuously increased and could attain 4.528 nm in 2 × 2 μm2 scanning field and at 20 nm data scale. XPS analysis further demonstrates that there was a CLPS-SiO2 film covered on the cotton surface and the silyl groups had the tendency to enrich at the film-air interface. In addition, hydrophobicity of the CLPS-SiO2 treated fabric would be enhanced with augment of the amount of nanocomposite. Water contact angle of this fabric could finally attain 158.0°. But most of all, its color and softness would not be influenced instead. The CLPS-SiO2 treated fabric possessed good washing durability.

Fast Transport of Water Droplets over a Thermo-Switchable Surface Using Rewritable Wettability Gradient.

PubMed

Banuprasad, Theneyur Narayanaswamy; Vinay, Thamarasseril Vijayan; Subash, Cherumannil Karumuthil; Varghese, Soney; George, Sajan D; Varanakkottu, Subramanyan Namboodiri

2017-08-23

In spite of the reported temperature dependent tunability in wettability of poly(N-isopropylacrylamide) (PNIPAAm) surfaces for below and above lower critical solution temperature (32 °C), the transport of water droplets is inhibited by the large contact angle hysteresis. Herein, for the first time, we report on-demand, fast, and reconfigurable droplet manipulation over a PNIPAAm grafted structured polymer surface using temperature-induced wettability gradient. Our study reveals that the PNIPAAm grafted on intrinsically superhydrophobic surfaces exhibit hydrophilic nature with high contact angle hysteresis below 30 °C and superhydrophobic nature with ultralow contact angle hysteresis above 36 °C. The transition region between 30 and 36 °C is characterized by a large change in water contact angle (∼100°) with a concomitant change in contact angle hysteresis. By utilizing this "transport zone" wherein driving forces overcome the frictional forces, we demonstrate macroscopic transport of water drops with a maximum transport velocity of approximately 40 cm/s. The theoretical calculations on the force measurements concur with dominating behavior of driving forces across the transport zone. The tunability in transport velocity by varying the temperature gradient along the surface or the inclination angle of the surface (maximum angle of 15° with a reduced velocity 0.4 mm/s) is also elucidated. In addition, as a practical application, coalescence of water droplets is demonstrated by using the temperature controlled wettability gradient. The presented results are expected to provide new insights on the design and fabrication of smart multifunctional surfaces for applications such as biochemical analysis, self-cleaning, and microfluidics.

Scanning Electron Microscopy (SEM) Procedure for HE Powders on a Zeiss Sigma HD VP SEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaka, F.

This method describes the characterization of inert and HE materials by the Zeiss Sigma HD VP field emission Scanning Electron Microscope (SEM). The SEM uses an accelerated electron beam to generate high-magnification images of explosives and other materials. It is fitted with five detectors (SE, Inlens, STEM, VPSE, HDBSD) to enable imaging of the sample via different secondary electron signatures, angles, and energies. In addition to imaging through electron detection, the microscope is also fitted with two Oxford Instrument Energy Dispersive Spectrometer (EDS) 80 mm detectors to generate elemental constituent spectra and two-dimensional maps of the material being scanned.

Evaporation kinetics of sessile water droplets on micropillared superhydrophobic surfaces.

PubMed

Xu, Wei; Leeladhar, Rajesh; Kang, Yong Tae; Choi, Chang-Hwan

2013-05-21

Evaporation modes and kinetics of sessile droplets of water on micropillared superhydrophobic surfaces are experimentally investigated. The results show that a constant contact radius (CCR) mode and a constant contact angle (CCA) mode are two dominating evaporation modes during droplet evaporation on the superhydrophobic surfaces. With the decrease in the solid fraction of the superhydrophobic surfaces, the duration of a CCR mode is reduced and that of a CCA mode is increased. Compared to Rowan's kinetic model, which is based on the vapor diffusion across the droplet boundary, the change in a contact angle in a CCR (pinned) mode shows a remarkable deviation, decreasing at a slower rate on the superhydrophobic surfaces with less-solid fractions. In a CCA (receding) mode, the change in a contact radius agrees well with the theoretical expectation, and the receding speed is slower on the superhydrophobic surfaces with lower solid fractions. The discrepancy between experimental results and Rowan's model is attributed to the initial large contact angle of a droplet on superhydrophobic surfaces. The droplet geometry with a large contact angle results in a narrow wedge region of air along the contact boundary, where the liquid-vapor diffusion is significantly restricted. Such an effect becomes minor as the evaporation proceeds with the decrease in a contact angle. In both the CCR and CCA modes, the evaporative mass transfer shows the linear relationship between mass(2/3) and evaporation time. However, the evaporation rate is slower on the superhydrophobic surfaces, which is more significant on the surfaces with lower solid fractions. As a result, the superhydrophobic surfaces slow down the drying process of a sessile droplet on them.

Design and Operating Characteristics of High-Speed, Small-Bore, Angular-Contact Ball Bearings

NASA Technical Reports Server (NTRS)

Pinel, Stanley I.; Signer, Hans R.; Zaretsky, Erwin V.

1998-01-01

The computer program SHABERTH was used to analyze 35-mm-bore, angular-contact ball bearings designed and manufactured for high-speed turbomachinery applications. Parametric tests of the bearings were conducted on a high-speed, high-temperature bearing tester and were compared with the computer predictions. Four bearing and cage designs were studied. The bearings were lubricated either by jet lubrication or through the split inner ring with and without outer-ring cooling. The predicted bearing life decreased with increasing speed because of increased operating contact stresses caused by changes in contact angle and centrifugal load. For thrust loads only, the difference in calculated life for the 24 deg. and 30 deg. contact-angle bearings was insignificant. However, for combined loading, the 24 deg. contact-angle bearing gave longer life. For split-inner-ring bearings, optimal operating conditions were obtained with a 24 deg. contact angle and an inner-ring, land-guided cage, using outer-ring cooling in conjunction with low lubricant flow rates. Lower temperature and power losses were obtained with a single-outer-ring, land-guided cage for the 24 deg. contact-angle bearing having a relieved inner ring and partially relieved outer ring. Inner-ring temperatures were independent of lubrication mode and cage design. In comparison with measured values, reasonably good engineering correlation was obtained using the computer program SHABERTH for predicted bearing power loss and for inner- and outer-ring temperatures. The Parker formula for XCAV (used in SHABERTH, a measure of oil volume in the bearing cavity) may need to be refined to reflect bearing lubrication mode, cage design, and location of cage-controlling land.

Thigh-calf contact parameters for six high knee flexion postures: Onset, maximum angle, total force, contact area, and center of force.

PubMed

Kingston, David C; Acker, Stacey M

2018-01-23

In high knee flexion, contact between the posterior thigh and calf is expected to decrease forces on tibiofemoral contact surfaces, therefore, thigh-calf contact needs to be thoroughly characterized to model its effect. This study measured knee angles and intersegmental contact parameters in fifty-eight young healthy participants for six common high flexion postures using motion tracking and a pressure sensor attached to the right thigh. Additionally, we introduced and assessed the reliability of a method for reducing noise in pressure sensor output. Five repetitions of two squatting, two kneeling, and two unilateral kneeling movements were completed. Interactions of posture by sex occurred for thigh-calf and heel-gluteal center of force, and thigh-calf contact area. Center of force in thigh-calf regions was farther from the knee joint center in females, compared to males, during unilateral kneeling (82 and 67 mm respectively) with an inverted relationship in the heel-gluteal region (331 and 345 mm respectively), although caution is advised when generalizing these findings from a young, relatively fit sample to a population level. Contact area was larger in females when compared to males (mean of 155.61 and 137.33 cm 2 across postures). A posture main effect was observed in contact force and sex main effects were present in onset and max angle. Males had earlier onset (121.0°) and lower max angle (147.4°) with onset and max angles having a range between movements of 8° and 3° respectively. There was a substantial total force difference of 139 N between the largest and smallest activity means. Force parameters measured in this study suggest that knee joint contact models need to incorporate activity-specific parameters when estimating loading. Copyright © 2017 Elsevier Ltd. All rights reserved.

Eliminating Deadbands In Resistive Angle Sensors

NASA Technical Reports Server (NTRS)

Salomon, Phil M.; Allen, Russell O.; Marchetto, Carl A.

1992-01-01

Proposed shaft-angle-measuring circuit provides continuous indication of angle of rotation from 0 degree to 360 degrees. Sensing elements are two continuous-rotation potentiometers, and associated circuitry eliminates deadband that occurs when wiper contact of potentiometer crosses end contacts near 0 degree position of circular resistive element. Used in valve-position indicator or similar device in which long operating life and high angular precision not required.

Temperature Dependence in Homogeneous and Heterogeneous Nucleation

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGraw R. L.; Winkler, P. M.; Wagner, P. E.

2017-08-01

Heterogeneous nucleation on stable (sub-2 nm) nuclei aids the formation of atmospheric cloud condensation nuclei (CCN) by circumventing or reducing vapor pressure barriers that would otherwise limit condensation and new particle growth. Aerosol and cloud formation depend largely on the interaction between a condensing liquid and the nucleating site. A new paper published this year reports the first direct experimental determination of contact angles as well as contact line curvature and other geometric properties of a spherical cap nucleus at nanometer scale using measurements from the Vienna Size Analyzing Nucleus Counter (SANC) (Winkler et al., 2016). For water nucleating heterogeneouslymore » on silver oxide nanoparticles we find contact angles around 15 degrees compared to around 90 degrees for the macroscopically measured equilibrium angle for water on bulk silver. The small microscopic contact angles can be attributed via the generalized Young equation to a negative line tension that becomes increasingly dominant with increasing curvature of the contact line. These results enable a consistent theoretical description of heterogeneous nucleation and provide firm insight to the wetting of nanosized objects.« less

Contact angle change during evaporation of near-critical liquids

NASA Astrophysics Data System (ADS)

Nikolayev, Vadim; Hegseth, John; Beysens, Daniel

1998-11-01

An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling". We report the preliminary results of the numerical simulation of the liquid evaporation by the Boundary Element method.

Contact angle studies on anodic porous alumina.

PubMed

Redón, Rocío; Vázquez-Olmos, A; Mata-Zamora, M E; Ordóñez-Medrano, A; Rivera-Torres, F; Saniger, J M

2005-07-15

The preparation of nanostructures using porous anodic aluminum oxide (AAO) as templates involves the introduction of dissolved materials into the pores of the membranes; one way to determine which materials are preferred to fill the pores involves the measurement of the contact angles (theta) of different solvents or test liquids on the AAOs. Thus, we present measurements of contact angles of nine solvents on four different AAO sheets by tensiometric and goniometric methods. From the solvents tested, we found dimethyl sulfoxide (DMSO) and N,N(')-dimethylformamide (DMF) to interact with the AAOs, the polarity of the solvents and the surfaces being the driving force.

High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects

NASA Astrophysics Data System (ADS)

Chang, Feng-Ming; Hong, Siang-Jie; Sheng, Yu-Jane; Tsao, Heng-Kwong

2009-08-01

A typical superhydrophobic surface is essentially nonadhesive and exhibits very low water contact angle (CA) hysteresis, so-called Lotus effect. However, leaves of some plants such as scallion and garlic with an advancing angle exceeding 150° show very serious CA hysteresis. Although surface roughness and epicuticular wax can explain the very high advancing CA, our analysis indicates that the unusual hydrophobic defect, diallyl disulfide, is the key element responsible for contact line pinning on allium leaves. After smearing diallyl disulfide on an extended polytetrafluoroethylene (PTFE) film, which is originally absent of CA hysteresis, the surface remains superhydrophobic but becomes highly adhesive.

Drop impact and wettability: From hydrophilic to superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Antonini, Carlo; Amirfazli, Alidad; Marengo, Marco

2012-10-01

Experiments to understand the effect of surface wettability on impact characteristics of water drops onto solid dry surfaces were conducted. Various surfaces were used to cover a wide range of contact angles (advancing contact angle from 48° to 166°, and contact angle hysteresis from 5° to 56°). Several different impact conditions were analyzed (12 impact velocities on 9 different surfaces, among which 2 were superhydrophobic). Results from impact tests with millimetric drops show that two different regimes can be identified: a moderate Weber number regime (30 < We < 200), in which wettability affects both drop maximum spreading and spreading characteristic time; and a high Weber number regime (We > 200), in which wettability effect is secondary, because capillary forces are overcome by inertial effects. In particular, results show the role of advancing contact angle and contact angle hysteresis as fundamental wetting parameters to allow understanding of different phases of drop spreading and beginning of recoiling. It is also shown that drop spreading on hydrophilic and superhydrophobic surfaces occurs with different time scales. Finally, if the surface is superhydrophobic, eventual impalement, i.e., transition from Cassie to Wenzel wetting state, which might occur in the vicinity of the drop impact area, does not influence drop maximum spreading.

Contact angle and detachment energy of shape anisotropic particles at fluid-fluid interfaces.

PubMed

Anjali, Thriveni G; Basavaraj, Madivala G

2016-09-15

The three phase contact angle of particles, a measure of its wettability, is an important factor that greatly influences their behaviour at interfaces. It is one of the principal design parameters for potential applications of particles as emulsion/foam stabilizers, functional coatings and other novel materials. In the present work, the effect of size, shape and surface chemistry of particles on their contact angle is investigated using the gel trapping technique, which facilitates the direct visualization of the equilibrium position of particles at interfaces. The contact angle of hematite particles of spherocylindrical, peanut and cuboidal shapes, hematite-silica core-shell and silica shells is reported at a single particle level. The spherocylindrical and peanut shaped particles are always positioned with their major axis parallel to the interface. However, for cuboidal particles at air-water as well as decane-water interfaces, different orientations namely - face-up, edge-up and the vertex-up - are observed. The influence of gravity on the equilibrium position of the colloidal particles at the interface is studied using the hematite-silica core-shell particles and the silica shells. The measured contact angle values are utilized in the calculations of the detachment and surface energies of the hematite particles adsorbed at the interface. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of the meniscus contact angle during early regimes of spontaneous imbibition in nanochannels.

PubMed

Karna, Nabin Kumar; Oyarzua, Elton; Walther, Jens H; Zambrano, Harvey A

2016-11-30

Nanoscale capillarity has been extensively investigated; nevertheless, many fundamental questions remain open. In spontaneous imbibition, the classical Lucas-Washburn equation predicts a singularity as the fluid enters the channel consisting of an anomalous infinite velocity of the capillary meniscus. Bosanquet's equation overcomes this problem by taking into account fluid inertia predicting an initial imbibition regime with constant velocity. Nevertheless, the initial constant velocity as predicted by Bosanquet's equation is much greater than those observed experimentally. In the present study, large scale atomistic simulations are conducted to investigate capillary imbibition of water in slit silica nanochannels with heights between 4 and 18 nm. We find that the meniscus contact angle remains constant during the inertial regime and its value depends on the height of the channel. We also find that the meniscus velocity computed at the channel entrance is related to the particular value of the meniscus contact angle. Moreover, during the subsequent visco-inertial regime, as the influence of viscosity increases, the meniscus contact angle is found to be time dependent for all the channels under study. Furthermore, we propose an expression for the time evolution of the dynamic contact angle in nanochannels which, when incorporated into Bosanquet's equation, satisfactorily explains the initial capillary rise.

Study of role of meniscus and viscous forces during liquid-mediated contacts separation

NASA Astrophysics Data System (ADS)

Dhital, Prabin

Menisci may form between two solid surfaces with the presence of an ultra-thin liquid film. When the separation operation is needed, meniscus and viscous forces contribute to an adhesion leading stiction, high friction, possibly high wear and potential failure of the contact systems, for instance microdevices, magnetic head disks and diesel fuel injectors. The situation may become more pronounced when the contacting surfaces are ultra-smooth and the normal load is small. Various design parameters, such as contact angle, initial separation height, surface tension and liquid viscosity, have been investigated during liquid-mediated contact separation. However, how the involved forces will change roles for various liquid is of interest and is necessary to be studied. In this study, meniscus and viscous forces due to water and liquid lubricants during separation of two flat surfaces are studied. Previously established mathematical model for meniscus and viscous forces during flat on flat contact separation is simulated. The effect of meniscus and viscous force on critical meniscus area at which those forces change role is studied with different liquid properties for flat on flat contact surfaces. The roles of the involved forces at various meniscus areas are analyzed. Experiments are done in concerns to studying the effect of surface roughness on contact angle. The impact of liquid properties, initial separation heights and contact angle on critical meniscus area for different liquid properties are analyzed. The study provides a fundamental understanding of the forces of the separation process and its value for the design of interfaces. The effect of surface roughness and liquid properties on contact angle are studied.

Biomechanical consequences of a nonanatomic posterior medial meniscal root repair.

PubMed

LaPrade, Christopher M; Foad, Abdullah; Smith, Sean D; Turnbull, Travis Lee; Dornan, Grant J; Engebretsen, Lars; Wijdicks, Coen A; LaPrade, Robert F

2015-04-01

Posterior medial meniscal root tears have been reported to extrude with the meniscus becoming adhered posteromedially along the posterior capsule. While anatomic repair has been reported to restore tibiofemoral contact mechanics, it is unknown whether nonanatomic positioning of a meniscal root repair to a posteromedial location would restore the loading profile of the knee joint. The purpose of this study was to compare the tibiofemoral contact mechanics of a nonanatomic posterior medial meniscal tear with that of the intact knee or anatomic repair. It was hypothesized that a nonanatomic root repair would not restore the tibiofemoral contact pressures and areas to that of the intact or anatomic repair state. Controlled laboratory study. Tibiofemoral contact mechanics were recorded in 6 male human cadaveric knee specimens (average age, 45.8 years) using pressure sensors. Each knee underwent 5 testing conditions for the posterior medial meniscal root: (1) intact knee; (2) root tear; (3) anatomic transtibial pull-out repair; (4) nonanatomic transtibial pull-out repair, placed 5 mm posteromedially along the edge of the articular cartilage; and (5) root tear concomitant with an ACL tear. Knees were loaded with a 1000-N axial compressive force at 4 flexion angles (0°, 30°, 60°, 90°), and contact area, mean contact pressure, and peak contact pressure were calculated. Contact area was significantly lower after nonanatomic repair than for the intact knee at all flexion angles (mean = 44% reduction) and significantly higher for anatomic versus nonanatomic repair at all flexion angles (mean = 27% increase). At 0° and 90°, and when averaged across flexion angles, the nonanatomic repair significantly increased mean contact pressures in comparison to the intact knee or anatomic repair. When averaged across flexion angles, the peak contact pressures after nonanatomic repair were significantly higher than the intact knee but not the anatomic repair. In contrast, when averaged across all flexion angles, the anatomic repair resulted in a 17% reduction in contact area and corresponding increases in mean and peak contact pressures of 13% and 26%, respectively, compared with the intact knee. For most testing conditions, the nonanatomic repair did not restore the contact area or mean contact pressures to that of the intact knee or anatomic repair. However, the anatomic repair produced near-intact contact area and resulted in relatively minimal increases in mean and peak contact pressures compared with the intact knee. Results emphasize the importance of ensuring an anatomic posterior medial meniscal root repair by releasing the extruded menisci from adhesions and the posteromedial capsule. Similar caution toward preventing displacement of the meniscal root repair construct should be emphasized. © 2015 The Author(s).

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface.

PubMed

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-03-02

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length ( L ), interval ( S ), and height ( H ) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure.

Wettability and Contact Time on a Biomimetic Superhydrophobic Surface

PubMed Central

Liang, Yunhong; Peng, Jian; Li, Xiujuan; Huang, Jubin; Qiu, Rongxian; Zhang, Zhihui; Ren, Luquan

2017-01-01

Inspired by the array microstructure of natural superhydrophobic surfaces (lotus leaf and cicada wing), an array microstructure was successfully constructed by high speed wire electrical discharge machining (HS-WEDM) on the surfaces of a 7075 aluminum alloy without any chemical treatment. The artificial surfaces had a high apparent contact angle of 153° ± 1° with a contact angle hysteresis less than 5° and showed a good superhydrophobic property. Wettability, contact time, and the corresponding superhydrophobic mechanism of artificial superhydrophobic surface were investigated. The results indicated that the micro-scale array microstructure was an important factor for the superhydrophobic surface, while different array microstructures exhibited different effects on the wettability and contact time of the artificial superhydrophobic surface. The length (L), interval (S), and height (H) of the array microstructure are the main influential factors on the wettability and contact time. The order of importance of these factors is H > S > L for increasing the apparent contact angle and reducing the contact time. The method, using HS-WEDM to fabricate superhydrophobic surface, is simple, low-cost, and environmentally friendly and can easily control the wettability and contact time on the artificial surfaces by changing the array microstructure. PMID:28772613

Three-dimensional simulation of rivulet and film flows over an inclined plate: Effects of solvent properties and contact angle

DOE PAGES

Singh, Rajesh K.; Galvin, Janine E.; Sun, Xin

2015-12-10

We numerically investigated the film flow down an inclined plate using the volume of fluid (VOF) method. The flow simulations have been systematically carried out for a wide range of parameters, such as inlet size, inclination angle, contact angle, flow rates and solvent properties (viscosity and surface tension). Based on the simulation results, scaling theory is proposed for both interfacial area and for film thickness in terms of the Kapitza number (Ka).The Kapitza number is advantageous because it depends only on solvent properties. The Kapitza number decreases with increased solvent viscosity and is fixed for a given fluid. Here, tomore » investigate the effects of solvent properties on interfacial area a small inlet cross-section was used. The interfacial area decreases with increased value of Ka. The time to reach pseudo-steady state of rivulet is also observed to increase with decreasing Ka. For a fixed flow rate, the inlet cross-section has marginal effect on the interfacial area; however, the developed width of the rivulet remains unchanged. In addition to inlet size, flow rate and solvent properties, the impact of contact angle on film thickness and interfacial area was also investigated. The contact angle has negligible effect for a fully wetted plate, but it significantly affects the interfacial area of the rivulet. Finally, a scaling theory for interfacial area in terms of the contact angle and Ka is presented.« less

Interaction Between Graphene-Coated SiC Single Crystal and Liquid Copper

NASA Astrophysics Data System (ADS)

Homa, M.; Sobczak, N.; Sobczak, J. J.; Kudyba, A.; Bruzda, G.; Nowak, R.; Pietrzak, K.; Chmielewski, M.; Strupiński, W.

2018-04-01

The wettability of graphene-coated SiC single crystal (CGn/SiCsc) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100 °C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6″ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the CGn/SiCsc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of θ 0 = 121° and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values (θ R = 86° and θ L = 70°, respectively), while in the next 30 min, θ R and θ L achieved the same final value of 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate (θ = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both θ R and θ L decreased in 17 min to the value of 23° and next, they increased to a final value of 65°. Visual observations revealed a presence of 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

Interaction Between Graphene-Coated SiC Single Crystal and Liquid Copper

NASA Astrophysics Data System (ADS)

Homa, M.; Sobczak, N.; Sobczak, J. J.; Kudyba, A.; Bruzda, G.; Nowak, R.; Pietrzak, K.; Chmielewski, M.; Strupiński, W.

2018-05-01

The wettability of graphene-coated SiC single crystal (CGn/SiCsc) by liquid Cu (99.99%) was investigated by a sessile drop method in vacuum conditions at temperature of 1100 °C. The graphene layer was produced via a chemical vapor deposition routine using 4H-SiC single crystal cut out from 6″ wafer. A dispensed drop technique combined with a non-contact heating of a couple of materials was applied. The Cu drop was squeezed from a graphite capillary and deposited on the substrate directly in a vacuum chamber. The first Cu drop did not wet the CGn/SiCsc substrate and showed a lack of adhesion to the substrate: the falling Cu drop only touched the substrate forming a contact angle of θ 0 = 121° and then immediately rolled like a ball along the substrate surface. After settling near the edge of the substrate in about 0.15 s, the Cu drop formed an asymmetric shape with the right and left contact angles of different values ( θ R = 86° and θ L = 70°, respectively), while in the next 30 min, θ R and θ L achieved the same final value of 52°. The second Cu drop was put down on the displacement path of the first drop, and immediately after the deposition, it also did not wet the substrate ( θ = 123°). This drop kept symmetry and the primary position, but its wetting behavior was unusual: both θ R and θ L decreased in 17 min to the value of 23° and next, they increased to a final value of 65°. Visual observations revealed a presence of 2.5-mm-thick interfacial phase layer reactively formed under the second drop. Scanning electron microscopy (SEM) investigations revealed the presence of carbon-enriched precipitates on the top surface of the first Cu drop. These precipitates were identified by the Raman spectroscopy as double-layer graphene. The Raman spectrum taken from the substrate far from the drop revealed the presence of graphene, while that obtained from the first drop displacement path exhibited a decreased intensity of 2D peak. The results of SEM investigations and Raman spectroscopy studies suggest that the presence of graphene layer on the SiC substrate suppresses but does not completely prevent chemical interaction between liquid Cu drop and SiC. Both chemical degradation (etching) and mechanical degradation of the graphene layer during drop rolling due to high adhesion of the Cu drop to the SiC substrate are responsible for mass transfer through the 2nd drop/substrate interface that in turn results in significant changes of structure and chemistry of the drop and the interface.

Investigation of Antibacterial and Fouling Resistance of Silver and Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Composite Membrane

PubMed Central

Macevele, Lutendo E.; Moganedi, Kgabo L. M.; Magadzu, Takalani

2017-01-01

Composite membranes were successfully prepared using a phase-inversion method. The X-ray powder diffraction (XRD) and energy dispersive X-ray (EDX) profiles has confirmed formation of 4.8 wt % Ag/poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), 3 wt % Ag-MWCNTs/PVDF-HFP (EDX surface composition of Ag nanoparticles) and 1.5 wt % MWCNTs/PVDF-HFP composite membranes. The MWCNTs crystallites are mainly encapsulated by a layer of PVDF-HFP, as evidenced by disappearance of graphitic peak. The scanning electron microscopy (SEM) images have depicted the formation of microporous structure, with few MWCNTs on the surface and strongly interacting with PVDF-HFP as demonstrated by thermogravimetric analysis (TGA), XRD and Fourier transform infrared (FTIR) data. The data indicated an increase in porosity, swellability and water content of the PVDF-HFP membrane with the addition of MWCNTs and/or Ag nanoparticles, showing an improved hydrophilicity. The 1.5 wt % MWCNTs/PVDF-HFP composite membrane showed good desalination and fouling resistance rates, which correlates with a low water contact angle. The combined effects of Ag nanoparticles and MWCNTs do not promote fouling resistance of PVDF-HFP membranes, as shown during NaCl microfiltration (this is linked with high water contact angle as compared to that of MWCNTs/PVDF-HFP composite). Both 1.5 wt % MWCNTs/PVDF-HFP and 3 wt % Ag-MWCNTs/PVDF-HFP composite membranes prevented the bacteria passing through the membrane (100% bacterial load reduction). The surface of 3 wt % Ag-MWCNTs/PVDF-HFP showed good bactericidal and non-leaching properties of the dopant materials (MWCNTs and Ag), as evidenced by bacterial growth on the edges of the membranes. PMID:28703740

Particles from bird feather: a novel application of an ionic liquid and waste resource.

PubMed

Sun, Ping; Liu, Zhao-Tie; Liu, Zhong-Wen

2009-10-30

The dissolution and regeneration of the waste chicken feathers in an ionic liquid of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) were demonstrated for preparing chicken feather based particles. The structure and properties of the regenerated chicken feathers were investigated by FT-IR, XRD, SEM, BET and water contact angle. The crystallinity of the regenerated chicken feathers was decreased, and the content of beta-sheet was 31.71%, which was clearly lower than the raw feather (47.19%). The surface property of chicken feather changed from hydrophobicity to hydrophilicity after regenerated from [BMIM]Cl as indicated by the change of the water contact angle from 138 to 76 degrees . The chicken feather particles regenerated from [BMIM]Cl showed an excellent efficiency (63.5-87.7%) for removing Cr(VI) ions in wastewater at the concentrations from 2 to 80 ppm. The Freundlich constant (k(F)) for the adsorption of Cr(VI) ion by the particles of the regenerated chicken feather was four times larger than that of the raw chicken feather, the possible reason is the hydrophilic groups such as amino and carboxyl groups were tend to self-assemble towards surface when the dissolved CF were regenerated by water, amino group will partly hydrate to cationic amino and Cr(VI) ion occurs as an anion in the aqueous phase, so the cationic amino will adsorb the anionic Cr(VI) ion onto the RCF particles through electrostatic attraction. This work demonstrated a new application of the ionic liquid for dissolving chicken feather and a renewable application of waste chicken feather for removing Cr(VI) ion in water.

Inhibitory effect of super-hydrophobicity on silver release and antibacterial properties of super-hydrophobic Ag/TiO2 nanotubes.

PubMed

Zhang, Licheng; Zhang, Lihai; Yang, Yun; Zhang, Wei; Lv, Houchen; Yang, Fei; Lin, Changjian; Tang, Peifu

2016-07-01

The antibacterial properties of super-hydrophobic silver (Ag) on implant surface have not yet to be fully illuminated. In our study, we investigate the protective effects of super-hydrophobic coating of silver/titanium dioxide (Ag/TiO2 ) nanotubes against bacterial pathogens, as well as its pattern of Ag release. Ag/TiO2 nanotubes are prepared by a combination of electrochemical anodization and pulse electrodeposition. The super-hydrophobic coating is prepared by modifying the surface of Ag/TiO2 nanotubes with 1H, 1H, 2H, 2H-perfluorooctyl-triethoxysilane (PTES). Surface features and Ag release are examined by SEM, X-ray photoelectron spectroscopy, contact-angle measurement, and inductively coupled plasma-mass spectrometry (ICP-MS). The antibacterial activity of super-hydrophobic coating Ag/TiO2 nanotubes is investigated both in vitro and in vivo. Consequently, the super-hydrophobic coating on Ag/TiO2 nanotubes shows a regularly arranged structure; and nano-Ag particles (10-30 nm) are evenly distributed on the surface or inside the nanotubes. The contact angles of water on the super-hydrophobic coating Ag/TiO2 nanotubes are all above 150°. In addition, the super-hydrophobic character displays a certain conserved effect that contributes to the sustained release of Ag. The super-hydrophobic Ag/TiO2 nanotubes are also effective in inhibiting bacterial adhesion, killing the adhering bacteria and preventing postoperative infection in rabbits. Therefore, it is expected that the super-hydrophobic Ag/TiO2 nanotubes which can contain the release of Ag, leading to stable release, may show a consistent surface antibacterial capability. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1004-1012, 2016. © 2015 Wiley Periodicals, Inc.

Hydrophobic modification of jute fiber used for composite reinforcement via laccase-mediated grafting

NASA Astrophysics Data System (ADS)

Dong, Aixue; Yu, Yuanyuan; Yuan, Jiugang; Wang, Qiang; Fan, Xuerong

2014-05-01

Jute fiber is a lignocellulosic material which could be utilized for reinforcement of composites. To improve the compatibility of hydrophilic jute fiber with hydrophobic resin, surface hydrophobization of the fiber is often needed. In this study, the feasibility of laccase-mediated grafting dodecyl gallate (DG) on the jute fiber was investigated. First, the grafting products were characterized by FT-IR, XPS, SEM and AFM. And then the grafting percentage (Gp) and the DG content of the modified jute were determined in terms of weighting and saponification, respectively. The parameters of the enzymatic grafting process were optimized to the target application. Lastly, the hydrophobicity of the jute fabrics was estimated by means of contact angle and wetting time. The mechanical properties and the fracture section of the jute fabric/polypropylene (PP) composites were studied. The results revealed covalently coupling of DG to the jute substrates mediated by laccase. The enzymatic process reached the maximum grafting rate of 4.16% when the jute fabric was incubated in the 80/20 (v/v, %) pH 3 0.2 M acetate buffer/ethanol medium with 1.0 U/mL laccase and 5 mM DG at 50 °C for 4 h. The jute fabric modified with laccase and DG showed increased contact angle of 111.49° and wetting time of at least 30 min, indicating that the surface hydrophobicity of the jute fabric was increased after the enzymatic graft modification with hydrophobic DG. The breaking strength of the modified jute fiber/PP composite was also increased and the fracture section became neat and regular due to the laccase-assisted grafting with DG.

In vitro behavior of human mesenchymal stem cells on poly(N-isopropylacrylamide) based biointerfaces obtained by matrix assisted pulsed laser evaporation

NASA Astrophysics Data System (ADS)

Icriverzi, Madalina; Rusen, Laurentiu; Sima, Livia Elena; Moldovan, Antoniu; Brajnicov, Simona; Bonciu, Anca; Mihailescu, Natalia; Dinescu, Maria; Cimpean, Anisoara; Roseanu, Anca; Dinca, Valentina

2018-05-01

The use of smart coatings with tunable characteristics in bioengineering fields is directly correlated with the surface chemical and topographical properties, the method of preparation, and also with the type of cells implied for the specific application. In this work, a versatile surface modification technique based on the use of lasers (Matrix-Assisted Pulsed Laser Evaporation (MAPLE)) was used to yield poly(N-isopropylacrylamide) (pNIPAM) and its derivatives (amine, azide and amide terminated pNIPAM) functional and termoresponsive thin films. Surface properties of pNIPAM and its derivative films such as morphology, roughness and hydrophobic/hydrophilic character, as well as the thermoresponsive capacity were investigated by atomic force microscopy and contact angle measurements. The chemical characteristics of the pNIPAM based thin films were analysed by Fourier Transform Infrared Spectroscopy (FTIR). The chemical functionality was kept for all the samples obtained by MAPLE and the thermoresponse was demonstrated by the change in the contact angle and thickness values when the temperature was shifted from 37 °C to 24 °C for all the materials tested, with a smaller change for maleimide terminated pNIPAM. Biological assays performed in vitro (fluorescence microscopy and Scanning Electron Microscopy (SEM)) confirmed the conditioning of the early mesenchymal stem cell (MSC) growth by specific chemistry of the coatings. The cell imaging analysis revealed no cytotoxic effect of pNIPAM surfaces irrespective of type of functionalization. An increased proliferation rate of the cells grown on pNIPAM-azide surfaces and a lower cell density on pNIPAM-maleimide surfaces compared to the pNIPAM surfaces was observed, which can direct their use to potential surfaces in regenerative medicine approaches.

Gamma radiation effects on random copolymers based on poly(butylene succinate) for packaging applications

NASA Astrophysics Data System (ADS)

Negrin, M.; Macerata, E.; Consolati, G.; Quasso, F.; Genovese, L.; Soccio, M.; Giola, M.; Lotti, N.; Munari, A.; Mariani, M.

2018-01-01

Within the context of new bioplastic materials, poly(butylene succinate) (PBS) and four novel poly(butylene/thiodiethylene succinate) random copolymers (PBS-PTDGS), in sheets as well as in films, were exposed to gamma radiation, in air and in water, and their behavior along with the effect on their biodegradability was investigated. The molecular weight data obtained from gel permeation chromatography indicate that the sensibility to radiation increases with the amount of sulfur-containing co-unit (TDGS). At 200 kGy the average molecular weight of PBS film halves, while for P(BS60TDGS40) the residual molecular weight is about 20%. The calculated intermolecular crosslink Gx and scissioning Gs yields confirmed that degradation is predominant over crosslink for all the aliphatic systems. As shown by thermal analyses, gamma radiation affects the thermal properties, leading to an increased crystallinity of the systems, remarkable for PBS, and lower decomposition temperatures. Variations of crystallinity with the increasing absorbed dose were confirmed also by PALS analyses. Water contact angle measurements revealed post-irradiation wettability alterations that could positively affect polymer biodegradability. In particular, when irradiated in water at 100 kGy PBS film exhibits a water contact angle decrease of about 17%, indicating an enhanced wettability. After degradation in compost, changes in the surface morphology were observed by means of SEM and sample weight losses were determined, at different extent, according to the irradiation environment. Interestingly, after 52 days in compost PBS films, both pristine and irradiated in air at 25 kGy, showed a residual weight of about 60%, while the ones irradiated in water at 25 kGy of about 44%. Experimental data confirmed that gamma irradiation could represent a viable treatment to enhance biodegradation in compost of PBS and PBS-based copolymers.

One-step fabrication of novel superhydrophobic and superoleophilic sponge with outstanding absorbency and flame-retardancy for the selective removal of oily organic solvent from water

NASA Astrophysics Data System (ADS)

Xiang, Yuqian; Pang, Youyou; Jiang, Xiaomei; Huang, Jie; Xi, Fengna; Liu, Jiyang

2018-01-01

Absorbent materials integrated with superhydrophobicity, superoleophilicity and flame-retardancy are highly desired in the adsorption/removal of flammable oils/organic compounds as well as reducing the risk of fire and explosion. Here, one-step fabrication of novel superhydrophobic and superoleophilic sponge with outstanding absorbency and flame-retardancy was presented. Using raw melamine (ME) sponge as the supporting matrix, the formation of polydopamine (PDA) nanoaggregates via in-situ self-polymerization of high-concentrated dopamine and the covalent grafting of hydrophobic n-dodecylthiol (DT) onto PDA were combined in a feasible alkaline water/ethanol medium. As investigated by scanning electron microscopy (SEM) and X-ray energy-dispersive spectroscopy (EDS), the as-prepared ME/PDA/DT sponge possessed hierarchical structure with submicron PDA nanoaggregates containing DT motif (low surface energy) on 3D interconnected porous network. It exhibited superhydrophobic (water contact angle 157.7°) and superoleophilic (oily/organic solvent contact angle 0° properties. Owing to the highly porous structure, superhydrophobic property, chemical and mechanical stability, the ME/PDA/DT sponge exhibited outstanding absorbency properties of oily organic solvents including fast absorption kinetics, high absorption capacity, and easy reusability. Also, the ME/PDA/DT sponge could be used for one-line continuous organic solvent/water separation. More interestingly, the ME/PDA/DT sponge demonstrated improved flame-retardant property as compared to the intrinsic flame-retardant nature of the raw melamine sponge. Consequently, the risk of fire and explosion was expected to reduce when the fabricated sponge was used as an absorbent for flammable oils and organic compounds. The ease of the one-step superhydrophobic/superoleophilic modification and the promising feature of the obtained materials exhibit great potential for application in oils/organic solvents clean-up.

Stereolithography of perfluoropolyethers for the microfabrication of robust omniphobic surfaces

NASA Astrophysics Data System (ADS)

Credi, Caterina; Levi, Marinella; Turri, Stefano; Simeone, Giovanni

2017-05-01

In this work, we provide a simple and straightforward method for the fabrication of stable highly hydrophobic and oleophobic surfaces by applying stereolithography (SL) to perfluoropolyethers (PFPEs). Inspired by the liquid repellency widely shown in nature, our approach enables to easily mimic the interplay between the chemistry and physics by microtexturing low surface tension PFPEs. To this end, UV-curable resins suitable for SL-processing were formulated by blending multifunctional (meth-)acrylates PFPEs oligomers with photoinitiator and visible dyes whose content was tuned to tailor resin SL sensitivities. Photocalorimetric studies were also performed to investigate the curing behavior of the different formulations upon SL light exposure. Being the first example of stereolithography applied to PFPEs, stereolithographic processability of new developed PFPEs photopolymer was compared with a standard photoresist taken as benchmark (DL260®). Optimized formulations were characterized by reduced laser penetration depth (<75 μm) and small critical energies thus enabling for fast printing of micrometric structures. Arrays of cylindrical pillars (85 μm diameter, 400 μm height) characterized by varied pillars spacing (200 ÷ 350 μm) were rapidly printed with high fidelity as attested by SEM examination. Contact angle measurements in static and dynamic conditions were performed to investigate the surface properties of textured samples using water and oil as the probing liquids. PFPEs liquid repellent performances were compared with those from DL260® textured surfaces arrayed by SL. High water contact angles coupled with low hysteresis asserted that high hydrophobic surfaces were successfully obtained and best-performing textured surfaces were also characterized by high oil repellency. Finally, this study demonstrated that omniphobic surfaces can be easily realized via a single-step, cost-effective, and time-saving process.

Wettability of soybean (Glycine max L.) leaves by foliar sprays with respect to developmental changes.

PubMed

Puente, Diana W Moran; Baur, Peter

2011-07-01

Leaf wettability considerably defines the degree of retention of water and agrochemical sprays on crop and non-target plant surfaces. Plant surface structure varies with development therefore the goal was to characterise the wettability of soybean leaf surfaces as a function of growth stage (GS). Adaxial surfaces of leaves developed at GS 16 (BBCH) were 10 times more wettable with water than leaves at the lower canopy (GS 13). By measuring contact angles of a liquid having an intermediate surface tension on different leaf patches, an illustrative wetting profile was elucidated, showing to what degree wetting varies (from > 120° to < 20°) depending on leaf patch and GS. While the critical surface tension of leaf surfaces at different GSs did not correlate with the observed changes, the slope of the Zisman plot accurately represented the increase in wettability of leaves at the upper canopy and lateral shoots (GSs 17 to 19, 21 and 24). The discrimination given by the slopes was even better than that by water contact angles. SEM observations revealed that the low wettability observed at early GSs is mainly due to a dense layer of epicuticular wax crystals. The Zisman plot slope does not represent the changes in leaf roughness (i.e. epicuticular wax deposition), but provides an insight into chemical and compositional surface characteristics at the droplet-leaf interface. The results with different wettability measurement methods demonstrated that wetting is a feature that characterises each developmental stage of soybean leaves. Positional wettability differences among leaves at the same plant and within the same leaf are relevant for performance, selectivity and plant compatibility of agrochemicals. Implications are discussed. Copyright © 2011 Society of Chemical Industry.

Effect of Stratification on Surface Properties of Corneal Epithelial Cells

PubMed Central

Yáñez-Soto, Bernardo; Leonard, Brian C.; Raghunathan, Vijay Krishna; Abbott, Nicholas L.; Murphy, Christopher J.

2015-01-01

Purpose The purpose of this study was to determine the influence of mucin expression in an immortalized human corneal epithelial cell line (hTCEpi) on the surface properties of cells, such as wettability, contact angle, and surface heterogeneity. Methods hTCEpi cells were cultured to confluence in serum-free medium. The medium was then replaced by stratification medium to induce mucin biosynthesis. The mucin expression profile was analyzed using quantitative PCR and Western blotting. Contact angles were measured using a two-immiscible liquid method, and contact angle hysteresis was evaluated by tilting the apparatus and recording advancing and receding contact angles. The spatial distribution of mucins was evaluated with fluorescently labeled lectin. Results hTCEpi cells expressed the three main ocular mucins (MUC1, MUC4, and MUC16) with a maximum between days 1 and 3 of the stratification process. Upon stratification, cells caused a very significant increase in contact angle hysteresis, suggesting the development of spatially discrete and heterogeneously distributed surface features, defined by topography and/or chemical functionality. Although atomic force microscopy measurements showed no formation of appreciable topographic features on the surface of the cells, we observed a significant increase in surface chemical heterogeneity. Conclusions The surface chemical heterogeneity of the corneal epithelium may influence the dynamic behavior of tear film by “pinning” the contact line between the cellular surface and aqueous tear film. Engineering the surface properties of corneal epithelium could potentially lead to novel treatments in dry eye disease. PMID:26747762

Effect of contact angle and contact angle hysteresis on the floatability of spheres at the air-water interface.

PubMed

Feng, Dong-Xia; Nguyen, Anh V

2017-10-01

The floatability of solid particles on the water surface governs many natural phenomena and industrial processes including film flotation and froth flotation separation of coal and valuable minerals. For many years, the contact angle (CA) has been postulated as the key factor in determining the particle floatability. Indeed, the maximum force (tenacity) supporting the flotation of fine spheres was conjectured to occur when the apical angle of the contact circle is equal to the contact angle. In this paper, the model predictions are reviewed and compared with experimental results. It is shown that CA can be affected by many physical and chemical factors such as surface roughness and chemical heterogeneity and can have a range of values known as the CA hysteresis. This multiple-valued CA invalidates the available theories on the floatability of spheres. Even the intuitive replacement of CA by the advancing (maximum) CA in the classical theories can be wrong. A few new examples are also reviewed and analyzed to demonstrate the significance of CA variation in controlling the particle floatability. They include the pinning of the contact line at the sharp edge, known as the Gibbs inequality condition, and the nearby interaction among floating particles, known as lateral inter-particle interaction. It is concluded that our quantitative understanding of the floatability of real particles being irregular and heterogeneous both morphologically and chemically is still far from being satisfactory. Copyright © 2017 Elsevier B.V. All rights reserved.

Stability of Contact Lines in Fluids: 2D Stokes Flow

NASA Astrophysics Data System (ADS)

Guo, Yan; Tice, Ian

2018-02-01

In an effort to study the stability of contact lines in fluids, we consider the dynamics of an incompressible viscous Stokes fluid evolving in a two-dimensional open-top vessel under the influence of gravity. This is a free boundary problem: the interface between the fluid in the vessel and the air above (modeled by a trivial fluid) is free to move and experiences capillary forces. The three-phase interface where the fluid, air, and solid vessel wall meet is known as a contact point, and the angle formed between the free interface and the vessel is called the contact angle. We consider a model of this problem that allows for fully dynamic contact points and angles. We develop a scheme of a priori estimates for the model, which then allow us to show that for initial data sufficiently close to equilibrium, the model admits global solutions that decay to equilibrium exponentially quickly.

Spontaneous Spreading of a Droplet: The Role of Solid Continuity and Advancing Contact Angle.

PubMed

Jiang, Youhua; Sun, Yujin; Drelich, Jaroslaw W; Choi, Chang-Hwan

2018-05-01

Spontaneous spreading of a droplet on a solid surface is poorly understood from a macroscopic level down to a molecular level. Here, we investigate the effect of surface topography and wettability on spontaneous spreading of a water droplet. Spreading force is measured for a suspended droplet that minimizes interference of kinetic energy in the spontaneous spreading during its contact with solid surfaces of discontinuous (pillar) and continuous (pore) patterns with various shapes and dimensions. Results show that a droplet cannot spread spontaneously on pillared surfaces regardless of their shapes or dimensions because of the solid discontinuity. On the contrary, a droplet on pored surfaces can undergo spontaneous spreading whose force increases with a decrease in the advancing contact angle. Theoretical models based on both the system free energy and capillary force along the contact line validate the direct and universal dependency of the spontaneous spreading force on the advancing contact angle.

Study on stair-step liquid triggered capillary valve for microfluidic systems

NASA Astrophysics Data System (ADS)

Zhang, Lei; Jones, Ben; Majeed, Bivragh; Nishiyama, Yukari; Okumura, Yasuaki; Stakenborg, Tim

2018-06-01

In lab-on-a-chip systems, various microfluidic technologies are being developed to handle fluids at very small quantities, e.g. in the scale of nano- or pico-liter. To achieve autonomous fluid handling at a low cost, passive fluidic control, based on the capillary force between the liquid and microchannel surface, is of the utmost interest in the microsystem. Valves are an essential component for flow control in many microfluidic systems, which enables a sequence of fluidic operations to be performed. In this paper, we present a new passive valve structure for a capillary driven microfluidic device. It is a variation of a capillary trigger valve that is amenable to silicon microfabrication; it will be referred to as a stair-step liquid triggered valve. In this paper, the valve functionality and its dependencies on channel geometry, surface contact angle, and surface roughness are studied both experimentally and with numerical modeling. The effect of the contact angle was explored in experiments on the silicon microfabricated valve structure; a maximal working contact angle, above which the valve fails to be triggered, was demonstrated. The fluidic behavior in the stair-step channel structure was further explored computationally using the finite volume method with the volume-of-fluid approach. Surface roughness due to scalloping of the sidewall during the Bosch etch process was hypothesized to reduce the sidewall contact angle. The reduced contact angle has considerable impacts on the capillary pressure as the liquid vapor interface traverses the stair-step structure of the valve. An improved match in the maximal working contact angle between the experiments and model was obtained when considering this surface roughness effect.

Survey of Thermal-Fluids Evaluation and Confirmatory Experimental Validation Requirements of Accident Tolerant Cladding Concepts with Focus on Boiling Heat Transfer Characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Nicholas R.; Wysocki, Aaron J.; Terrani, Kurt A.

The U.S. Department of Energy Office of Nuclear Energy (DOE-NE) Advanced Fuels Campaign (AFC) is working closely with the nuclear industry to develop fuel and cladding candidates with potentially enhanced accident tolerance, also known as accident tolerant fuel (ATF). Thermal-fluids characteristics are a vital element of a holistic engineering evaluation of ATF concepts. One vital characteristic related to boiling heat transfer is the critical heat flux (CHF). CHF plays a vital role in determining safety margins during normal operation and also in the progression of potential transient or accident scenarios. This deliverable is a scoping survey of thermal-fluids evaluation andmore » confirmatory experimental validation requirements of accident tolerant cladding concepts with a focus on boiling heat transfer characteristics. The key takeaway messages of this report are: 1. CHF prediction accuracy is important and the correlations may have significant uncertainty. 2. Surface conditions are important factors for CHF, primarily the wettability that is characterized by contact angle. Smaller contact angle indicates greater wettability, which increases the CHF. Surface roughness also impacts wettability. Results in the literature for pool boiling experiments indicate changes in CHF by up to 60% for several ATF cladding candidates. 3. The measured wettability of FeCrAl (i.e., contact angle and roughness) indicates that CHF should be investigated further through pool boiling and flow boiling experiments. 4. Initial measurements of static advancing contact angle and surface roughness indicate that FeCrAl is expected to have a higher CHF than Zircaloy. The measured contact angle of different FeCrAl alloy samples depends on oxide layer thickness and composition. The static advancing contact angle tends to decrease as the oxide layer thickness increases.« less

Wettability of supercritical carbon dioxide/water/quartz systems: simultaneous measurement of contact angle and interfacial tension at reservoir conditions.

PubMed

Saraji, Soheil; Goual, Lamia; Piri, Mohammad; Plancher, Henry

2013-06-11

Injection of carbon dioxide in deep saline aquifers is considered as a method of carbon sequestration. The efficiency of this process is dependent on the fluid-fluid and rock-fluid interactions inside the porous media. For instance, the final storage capacity and total amount of capillary-trapped CO2 inside an aquifer are affected by the interfacial tension between the fluids and the contact angle between the fluids and the rock mineral surface. A thorough study of these parameters and their variations with temperature and pressure will provide a better understanding of the carbon sequestration process and thus improve predictions of the sequestration efficiency. In this study, the controversial concept of wettability alteration of quartz surfaces in the presence of supercritical carbon dioxide (sc-CO2) was investigated. A novel apparatus for measuring interfacial tension and contact angle at high temperatures and pressures based on Axisymmetric Drop Shape Analysis with no-Apex (ADSA-NA) method was developed and validated with a simple system. Densities, interfacial tensions, and dynamic contact angles of CO2/water/quartz systems were determined for a wide range of pressures and temperatures relevant to geological sequestration of CO2 in the subcritical and supercritical states. Image analysis was performed with ADSA-NA method that allows the determination of both interfacial tensions and contact angles with high accuracy. The results show that supercritical CO2 alters the wettability of quartz surface toward less water-wet conditions compared to subcritical CO2. Also we observed an increase in the water advancing contact angles with increasing temperature indicating less water-wet quartz surfaces at higher temperatures.

Geometrical effect, optimal design and controlled fabrication of bio-inspired micro/nanotextures for superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Ma, F. M.; Li, W.; Liu, A. H.; Yu, Z. L.; Ruan, M.; Feng, W.; Chen, H. X.; Chen, Y.

2017-09-01

Superhydrophobic surfaces with high water contact angles and low contact angle hysteresis or sliding angles have received tremendous attention for both academic research and industrial applications in recent years. In general, such surfaces possess rough microtextures, particularly, show micro/nano hierarchical structures like lotus leaves. Now it has been recognized that to achieve the artificial superhydrophobic surfaces, the simple and effective strategy is to mimic such hierarchical structures. However, fabrications of such structures for these artificial surfaces involve generally expensive and complex processes. On the other hand, the relationships between structural parameters of various surface topography and wetting properties have not been fully understood yet. In order to provide guidance for the simple fabrication and particularly, to promote practical applications of superhydrophobic surfaces, the geometrical designs of optimal microtextures or patterns have been proposed. In this work, the recent developments on geometrical effect, optimal design and controlled fabrication of various superhydrophobic structures, such as unitary, anisotropic, dual-scale hierarchical, and some other surface geometries, are reviewed. The effects of surface topography and structural parameters on wetting states (composite and noncomposite) and wetting properties (contact angle, contact angle hysteresis and sliding angle) as well as adhesive forces are discussed in detail. Finally, the research prospects in this field are briefly addressed.