Thermal stable superhydrophobic polyphenylsilsesquioxane/nanosilica composite coatings

NASA Astrophysics Data System (ADS)

Yang, Haowei; Cheng, Yuanrong; Xiao, Fei

2011-12-01

The superhydrophobic polyphenylsilsesquioxane (PPSQ)/nanosilica composite coatings were prepared by spray coating method with nano fumed silica (NFS) particles embedded in PPSQ matrix. The water contact angle (WCA) increased from 92.9° to 152.5° and the sliding angle (SA) decreased from more than 60° to 3.9° as the NFS content increased. The superhydrophobicity retained up to 500 °C, sustained by the hierarchical micro-nano structures and excellent thermal stability of PPSQ. A superhydrophobic PPSQ coating with WCA of 152.6° and SA of 7.8° was obtained by solvent-nonsolvent method for comparison as well. However, it gradually lost superhydrophobicity at 200 °C because of the elimination of nanostructures by the thermal softening of PPSQ.

Optically transparent, mechanically durable, nanostructured superhydrophobic surfaces enabled by spinodally phase-separated glass thin films

NASA Astrophysics Data System (ADS)

Aytug, Tolga; Simpson, John T.; Lupini, Andrew R.; Trejo, Rosa M.; Jellison, Gerald E.; Ivanov, Ilia N.; Pennycook, Stephen J.; Hillesheim, Daniel A.; Winter, Kyle O.; Christen, David K.; Hunter, Scott R.; Haynes, J. Allen

2013-08-01

We describe the formation and properties of atomically bonded, optical quality, nanostructured thin glass film coatings on glass plates, utilizing phase separation by spinodal decomposition in a sodium borosilicate glass system. Following deposition via magnetron sputtering, thermal processing and differential etching, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties and superior abrasion resistance. After appropriate chemical surface modification, the surfaces display a stable, non-wetting Cassie-Baxter state and exhibit exceptional superhydrophobic performance, with water droplet contact angles as large as 172°. As an added benefit, in both superhydrophobic and superhydrophilic states these nanostructured surfaces can block ultraviolet radiation and can be engineered to be anti-reflective with broadband and omnidirectional transparency. Thus, the present approach could be tailored toward distinct coatings for numerous markets, such as residential windows, windshields, specialty optics, goggles, electronic and photovoltaic cover glasses, and optical components used throughout the US military.

Optically transparent, mechanically durable, nanostructured superhydrophobic surfaces enabled by spinodally phase-separated glass thin films.

PubMed

Aytug, Tolga; Simpson, John T; Lupini, Andrew R; Trejo, Rosa M; Jellison, Gerald E; Ivanov, Ilia N; Pennycook, Stephen J; Hillesheim, Daniel A; Winter, Kyle O; Christen, David K; Hunter, Scott R; Haynes, J Allen

2013-08-09

We describe the formation and properties of atomically bonded, optical quality, nanostructured thin glass film coatings on glass plates, utilizing phase separation by spinodal decomposition in a sodium borosilicate glass system. Following deposition via magnetron sputtering, thermal processing and differential etching, these coatings are structurally superhydrophilic (i.e., display anti-fogging functionality) and demonstrate robust mechanical properties and superior abrasion resistance. After appropriate chemical surface modification, the surfaces display a stable, non-wetting Cassie-Baxter state and exhibit exceptional superhydrophobic performance, with water droplet contact angles as large as 172°. As an added benefit, in both superhydrophobic and superhydrophilic states these nanostructured surfaces can block ultraviolet radiation and can be engineered to be anti-reflective with broadband and omnidirectional transparency. Thus, the present approach could be tailored toward distinct coatings for numerous markets, such as residential windows, windshields, specialty optics, goggles, electronic and photovoltaic cover glasses, and optical components used throughout the US military.

Superhydrophobic Ceramic Coatings by Solution Precursor Plasma Spray

PubMed Central

Cai, Yuxuan; Coyle, Thomas W.; Azimi, Gisele; Mostaghimi, Javad

2016-01-01

This work presents a novel coating technique to manufacture ceramic superhydrophobic coatings rapidly and economically. A rare earth oxide (REO) was selected as the coating material due to its hydrophobic nature, chemical inertness, high temperature stability, and good mechanical properties, and deposited on stainless steel substrates by solution precursor plasma spray (SPPS). The effects of various spraying conditions including standoff distance, torch power, number of torch passes, types of solvent and plasma velocity were investigated. The as-sprayed coating demonstrated a hierarchically structured surface topography, which closely resembles superhydrophobic surfaces found in nature. The water contact angle on the SPPS superhydrophobic coating was up to 65% higher than on smooth REO surfaces. PMID:27091306

Electrically conductive PEDOT coating with self-healing superhydrophobicity.

PubMed

Zhu, Dandan; Lu, Xuemin; Lu, Qinghua

2014-04-29

A self-healing electrically conductive superhydrophobic poly(3,4-ethylenedioxythiophene) (PEDOT) coating has been prepared by chemical vapor deposition of a fluoroalkylsilane (POTS) onto a PEDOT film, which was obtained by electrochemical deposition. The coating not only maintained high conductivity with a low resistivity of 3.2 × 10(-4) Ω·m, but also displayed a water contact angle larger than 156° and a sliding angle smaller than 10°. After being etched with O2 plasma, the coating showed an excellent self-healing ability, spontaneously regaining its superhydrophobicity when left under ambient conditions for 20 h. This superhydrophobicity recovery process was found to be humidity-dependent, and could be accelerated and completed within 2 h under a high humidity of 84%. The coating also exhibited good superhydrophobicity recovering ability after being corroded by strong acid solution at pH 1 or strong base solution at pH 14 for 3 h.

Anti-icing properties of superhydrophobic ZnO/PDMS composite coating

NASA Astrophysics Data System (ADS)

Yang, Chao; Wang, Fajun; Li, Wen; Ou, Junfei; Li, Changquan; Amirfazli, Alidad

2016-01-01

We present the excellent anti-icing performance for a superhydrophobic coating surface based on ZnO/polydimethylsiloxane (ZnO/PDMS) composite. The superhydrophobic ZnO/PDMS coating surface was prepared by a facile solution mixing, drop coating, room-temperature curing and surface abrading procedure. The superhydrophobic ZnO/PDMS composite coating possesses a water contact angle of 159.5° and a water sliding angle of 8.3° at room temperature (5 °C). The anti-icing properties of the superhydrophobic coating were investigated by continuously dropping cold-water droplets (about 0 °C) onto the pre-cooled surface using a home-made apparatus. The sample was placed at different tilting angle (0° and 10°) and pre-cooled to various temperatures (-5, -10 and -15 °C) prior to measure. The pure Al surface was also studied for comparison. It was found that icing accretion on the surface could be reduced apparently because the water droplets merged together and slid away from the superhydrophobic surface at all of the measuring temperatures when the surface is horizontally placed. In addition, water droplet slid away completely from the superhydrophobic surface at -5 and -10 °C when the surface is tilted at 10°, which demonstrates its excellent anti-icing properties at these temperatures. When the temperature decreased to -15 °C, though ice accretion on the tilted superhydrophobic coating surface could not be avoided absolutely, the amount of ice formed on the surface is very small, which indicated that the coating surface with superhydrophobicity could significantly reduce ice accumulation on the surface at very low temperature (-15 °C). Importantly, the sample is also stable against repeated icing/deicing cycles. More meaningfully, once the superhydrophobic surface is damaged, it can be repaired easily and rapidly.

Super-hydrophobic surfaces of SiO₂-coated SiC nanowires: fabrication, mechanism and ultraviolet-durable super-hydrophobicity.

PubMed

Zhao, Jian; Li, Zhenjiang; Zhang, Meng; Meng, Alan

2015-04-15

The interest in highly water-repellent surfaces of SiO2-coated SiC nanowires has grown in recent years due to the desire for self-cleaning and anticorrosive surfaces. It is imperative that a simple chemical treatment with fluoroalkylsilane (FAS, CF3(CF2)7CH2CH2Si(OC2H5)3) in ethanol solution at room temperature resulted in super-hydrophobic surfaces of SiO2-coated SiC nanowires. The static water contact angle of SiO2-coated SiC nanowires surfaces was changed from 0° to 153° and the morphology, microstructure and crystal phase of the products were almost no transformation before and after super-hydrophobic treatment. Moreover, a mechanism was expounded reasonably, which could elucidate the reasons for their super-hydrophobic behavior. It is important that the super-hydrophobic surfaces of SiO2-coated SiC nanowires possessed ultraviolet-durable (UV-durable) super-hydrophobicity. Copyright © 2014 Elsevier Inc. All rights reserved.

Robust and thermal-healing superhydrophobic surfaces by spin-coating of polydimethylsiloxane.

PubMed

Long, Mengying; Peng, Shan; Deng, Wanshun; Yang, Xiaojun; Miao, Kai; Wen, Ni; Miao, Xinrui; Deng, Wenli

2017-12-15

Superhydrophobic surfaces easily lose their excellent water-repellency after damages, which limit their broad applications in practice. Thus, the fabrication of superhydrophobic surfaces with excellent durability and thermal healing should be taken into consideration. In this work, robust superhydrophobic surfaces with thermal healing were successfully fabricated by spin-coating method. To achieve superhydrophobicity, cost-less and fluoride-free polydimethylsiloxane (PDMS) was spin-coated on rough aluminum substrates. After being spin-coated for one cycle, the superhydrophobic PDMS coated hierarchical aluminum (PDMS-H-Al) surfaces showed excellent tolerance to various chemical and mechanical damages in lab, and outdoor damages for 90days. When the PDMS-H-Al surfaces underwent severe damages such as oil contamination (peanut oil with high boiling point) or sandpaper abrasion (500g of force for 60cm), their superhydrophobicity would lose. Interestingly, through a heating process, cyclic oligomers generating from the partially decomposed PDMS acted as low-surface-energy substance on the damaged rough surfaces, leading to the recovery of superhydrophobicity. The relationship between the spin-coating cycles and surface wettability was also investigated. This paper provides a facile, fluoride-free and efficient method to fabricate superhydrophobic surfaces with thermal healing. Copyright © 2017. Published by Elsevier Inc.

How does substrate roughness affect the service life of a superhydrophobic coating?

NASA Astrophysics Data System (ADS)

Zhang, Xin; Mo, Jiliang; Si, Yifan; Guo, Zhiguang

2018-05-01

Although the development of superhydrophobic coatings is rapidly maturing, issues related to their low mechanical durability persist. In this context, the effect of substrate roughness on the service life of superhydrophobic coatings was studied. In this study, superhydrophobic coatings were fabricated on sandpapers of different roughness and reciprocating wear tests were conducted. The wear-resistance number of the superhydrophobic coating, defined as the maximum number of friction cycles after which the superhydrophobic surface started to lose its superhydrophobicity, increased from 50 to 24,000 with an increase in the substrate roughness from 2000 CW to 240 CW (CW is defined as the number of particles arranged in an inch), while it decreased from 24,000 to 17,000 with a further increase in the substrate roughness from 240 CW to 60 CW. Observations of the surface structure and wear analyses indicated that the superhydrophobic material infiltrated the spaces between the sand grains, and the rough peaks could consequently protect the superhydrophobic material during the wear tests. However, this protection weakens when the substrate roughness increases or decreases beyond certain values. Furthermore, these phenomena and results were also verified by applying the superhydrophobic coatings to different types of common substrates.

Highly Stretchable and Conductive Superhydrophobic Coating for Flexible Electronics.

PubMed

Su, Xiaojing; Li, Hongqiang; Lai, Xuejun; Chen, Zhonghua; Zeng, Xingrong

2018-03-28

Superhydrophobic materials integrating stretchability with conductivity have huge potential in the emerging application horizons such as wearable electronic sensors, flexible power storage apparatus, and corrosion-resistant circuits. Herein, a facile spraying method is reported to fabricate a durable superhydrophobic coating with excellent stretchable and electrical performance by combing 1-octadecanethiol-modified silver nanoparticles (M-AgNPs) with polystyrene- b-poly(ethylene- co-butylene)- b-polystyrene (SEBS) on a prestretched natural rubber (NR) substrate. The embedding of M-AgNPs in elastic SEBS matrix and relaxation of prestretched NR substrate construct hierarchical rough architecture and endow the coating with dense charge-transport pathways. The fabricated coating exhibits superhydrophobicity with water contact angle larger than 160° and a high conductivity with resistance of about 10 Ω. The coating not only maintains superhydrophobicity at low/high stretch ratio for the newly generated small/large protuberances but also responds to stretching and bending with good sensitivity, broad sensing range, and stable response cycles. Moreover, the coating exhibits excellent durability to heat and strong acid/alkali and mechanical forces including droplet impact, kneading, torsion, and repetitive stretching-relaxation. The findings conceivably stand out as a new tool to fabricate multifunctional superhydrophobic materials with excellent stretchability and conductivity for flexible electronics under wet or corrosive environments.

Superhydrophobic coatings on wood substrate for self-cleaning and EMI shielding

NASA Astrophysics Data System (ADS)

Xing, Yingjie; Xue, Yaping; Song, Jinlong; Sun, Yankui; Huang, Liu; Liu, Xin; Sun, Jing

2018-04-01

A layer of superhydrophobic coating having good electromagnetic shielding and self-cleaning performance was fabricated on a wood surface through an electroless copper plated process. The superhydrophobic property of the wood surface was measured by contact angle (CA) and roll-off angle (RA) measurements. The microstructure and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The analysis revealed that the microscale particles were uniformly distributed on the wood surface and the main component of the coating is metallic copper. The as-prepared Cu coatings on wood substrate exhibit a good superhydrophobicity with water contact angle about 160° and rolling angle less than 5°.

A study of degradation resistance and cytocompatibility of super-hydrophobic coating on magnesium.

PubMed

Zhang, Yufen; Feyerabend, Frank; Tang, Shawei; Hu, Jin; Lu, Xiaopeng; Blawert, Carsten; Lin, Tiegui

2017-09-01

Calcium stearate based super-hydrophobic coating was deposited on plasma electrolytic oxidation (PEO) pre-treated magnesium substrate. The pre-treated magnesium and super-hydrophobic coating covered sample were characterized by scanning electron microscopy, X-ray diffraction and electrochemical corrosion measurements. The cytocompatibility and degradation resistance of magnesium, pre-treated magnesium and super-hydrophobic coating were analysed in terms of cell adhesion and osteoblast differentiation. The results indicate that the calcium stearate top coating shows super-hydrophobicity and that the surface is composed of micro/nanostructure. The super-hydrophobic coating covered sample shows higher barrier properties compared with the PEO pre-treated magnesium and bare magnesium. Human osteoblast proliferation, but not differentiation is enhanced by the PEO coating. Contrary, the super-hydrophobic coating reduces proliferation, but enhances differentiation of osteoblast, observable by the formation of hydroxyapatite. The combination of corrosion protection and cell reaction indicates that this system could be interesting for biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Superhydrophobic surfaces generated by one-pot spray-coating of chitosan-based nanoparticles.

PubMed

Wang, Shuangfei; Sha, Jiulong; Wang, Wei; Qin, Chengrong; Li, Wei; Qin, Caiqin

2018-09-01

Superhydrophobic surfaces have attracted great attention due to their attractive properties. Biopolymer-based low-cost and environmentally-friendly superhydrophobic coatings with easy-to-perform fabrication methods are always desirable. Herein, we report superhydrophobic surfaces using a one-step spray-coating of chitosan-based nanoparticles. The particles were easily prepared by a nanoprecipitation strategy using synthesized organosoluble chitosan stearoyl ester (CSSE). The resulting particles had an average size of 165 ∼ 235 nm depending on the applied concentration. Subsequently, spray-coating of such particles onto silicon wafer generated a surface with a water contact angle of 155 ± 1°. SEM and AFM images exhibited a nano/microscaled roughness appeared on the coated surface. The superhydrophobic surfaces showed a stable superhydrophobic performance even after storage for 15 days, pH stability between pH 1 to pH 11 and thermal stability until a temperature no more than 50 °C. These properties would broaden the application fields of superhydrophobic surfaces as well as the chitosan itself. Copyright © 2018 Elsevier Ltd. All rights reserved.

Spray-coating process in preparing PTFE-PPS composite super-hydrophobic coating

NASA Astrophysics Data System (ADS)

Weng, Rui; Zhang, Haifeng; Liu, Xiaowei

2014-03-01

In order to improve the performance of a liquid-floated rotor micro-gyroscope, the resistance of the moving interface between the rotor and the floating liquid must be reduced. Hydrophobic treatment can reduce the frictional resistance between such interfaces, therefore we proposed a method to prepare a poly-tetrafluoroethylene (PTFE)-poly-phenylene sulphide (PPS) composite super-hydrophobic coating, based on a spraying process. This method can quickly prepare a continuous, uniform PTFE-PPS composite super-hydrophobic surface on a 2J85 material. This method can be divided into three steps, namely: pre-treatment; chemical etching; and spraying. The total time for this is around three hours. When the PTFE concentration is 4%, the average contact angle of the hydrophobic coating surface is 158°. If silicon dioxide nanoparticles are added, this can further improve the adhesion and mechanical strength of the super-hydrophobic composite coating. The maximum average contact angle can reach as high as 164° when the mass fraction of PTFE, PPS and silicon dioxide is 1:1:1.

Fabrication of the superhydrophobic surface on aluminum alloy by anodizing and polymeric coating

NASA Astrophysics Data System (ADS)

Liu, Wenyong; Luo, Yuting; Sun, Linyu; Wu, Ruomei; Jiang, Haiyun; Liu, Yuejun

2013-01-01

We reported the preparation of the superhydrophobic surface on aluminum alloy via anodizing and polymeric coating. Both the different anodizing processes and different polymeric coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. The results showed that a good superhydrophobic surface was facilely fabricated by polypropylene (PP) coating after anodizing. The optimum conditions for anodizing were determined by orthogonal experiments. When the concentration of oxalic acid was 10 g/L, the concentration of NaCl was 1.25 g/L, anodization time was 40 min, and anodization current was 0.4 A, the best superhydrophobic surface on aluminum alloy with the contact angle (CA) of 162° and the sliding angle of 2° was obtained. On the other hand, the different polymeric coatings, such as polystyrene (PS), polypropylene (PP) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after anodizing. The results showed that the superhydrophobicity was most excellent by coating PP, while the duration of the hydrophobic surface was poor. By modifying the surface with the silane coupling agent before PP coating, the duration of the superhydrophobic surface was improved. The morphologies of the superhydrophobic surface were further confirmed by optical microscope (OM) and scanning electron microscope (SEM). Combined with the material of PP with the low surface free energy, the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.

Buoyancy increase and drag-reduction through a simple superhydrophobic coating.

PubMed

Hwang, Gi Byoung; Patir, Adnan; Page, Kristopher; Lu, Yao; Allan, Elaine; Parkin, Ivan P

2017-06-08

A superhydrophobic paint was fabricated using 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES), TiO 2 nanoparticles and ethanol. The paint has potential for aquatic application of a superhydrophobic coating as it induces increased buoyancy and drag reduction. Buoyance testing showed that the reduction of surface energy by superhydrophobic coating made it feasible that glass, a high density material, was supported by the surface tension of water. In a miniature boat sailing test, it was shown that the low energy surface treatment decreased the adhesion of water molecules to the surface of the boat resulting in a reduction of the drag force. Additionally, a robust superhydrophobic surface was fabricated through layer-by-layer coating using adhesive double side tape and the paint, and after a 100 cm abrasion test with sand paper, the surface still retained its water repellency, enhanced buoyancy and drag reduction.

Optically transparent super-hydrophobic thin film fabricated by reusable polyurethane-acrylate (PUA) mold

NASA Astrophysics Data System (ADS)

Park, J.-S.; Park, J.-H.; Lee, D.-W.

2018-02-01

In this paper, we describe a simple manufacturing method for producing an optically transparent super-hydrophobic polymer thin film using a reusable photo-curable polymer mold. Soluble photoresist (PR) molds were prepared with under-exposed and under-baked processes, which created unique hierarchical micro/nano structures. The reverse phase of the PR mold was replicated on the surface of polydimethylsiloxane (PDMS) substrates. The unique patterns on the replicated PDMS molds were successfully transferred back to the UV curable polyurethane-acrylate (PUA) using a laboratory-made UV exposure system. Continuous production of the super-hydrophobic PDMS thin film was demonstrated using the reusable PUA mold. In addition, hydrophobic nano-silica powder was sprayed onto the micro/nano structured PDMS surfaces to further improve hydrophobicity. The fabricated PDMS thin films with hierarchical surface texturing showed a water contact angle  ⩾150°. Excellent optical transmittance within the range of visible light of wavelengths between 400-800 nm was experimentally confirmed using a spectrophotometer. High efficiency of the super-hydrophobic PDMS film in optical transparency was also confirmed using solar panels. The fabricated PUA molds are very suitable for use in roll-to-roll or roll-to-plate systems which allow continuous production of super-hydrophobic thin films with an excellent optical transparency.

Superhydrophobic Post Treatment and Coating Extenders for Improved Asset Sustainability

NASA Technical Reports Server (NTRS)

Trigwell, Steven; Montgomery, Eliza L.; Calle, Luz M.

2015-01-01

Launch structures, hardware, and ground support equipment, at NASA's John F. Kennedy Space Center in Florida, are exposed to a highly corrosive natural coastal marine environment. In addition, during launches, rocket exhaust deposition is also highly corrosive. Superhydrophobic coatings are being considered for additional corrosion protection on existing structures to enhance corrosion resistance and add an additional layer of protection against harsh environmental elements. These coatings have come into their own recently, and are now being investigated as corrosion protective coatings due to their water repelling capability. These coatings can be used on existing coatings, newly coated materials, or used on bare substrates. The coatings are not suitable for permanent corrosion protection, but can be used where additional corrosion control is desired or only when temporary corrosion control is needed, such as in hardware sitting on a launch pad for 30-45 days prior to a launch. In this study, superhydrophobic coatings were applied on various coated and uncoated substrates and exposed to the spaceport environment for various times up to 60 days. This paper highlights the current results of the superhydrophobic coatings performance evaluated by X-ray photoelectron spectroscopy, and contact angle measurements.

Solvothermal synthesis of nanoporous polymer chalk for painting superhydrophobic surfaces.

PubMed

Zhang, Yong-Lai; Wang, Jian-Nan; He, Yan; He, Yinyan; Xu, Bin-Bin; Wei, Shu; Xiao, Feng-Shou

2011-10-18

Reported here is a facile synthesis of nanoporous polymer chalk for painting superhydrophobic surfaces. Taking this nanoporous polymer as a media, superhydrophobicity is rapidly imparted onto three typical kinds of substrates, including paper, transparent polydimethylsiloxane (PDMS), and finger skin. Quantitative characterization showed that the adhesion between the water droplet and polymer-coated substrates decreased significantly compared to that on the original surface, further indicating the effective wetting mode transformation. The nanoporous polymer coating would open a new door for facile, rapid, safe, and larger scale fabrication of superhydrophobic surfaces on general substrates. © 2011 American Chemical Society

ODS - modified TiO2 nanoparticles for the preparation of self-cleaning superhydrophobic coating

NASA Astrophysics Data System (ADS)

Kokare, Ashvini M.; Sutar, Rajaram S.; Deshmukh, S. G.; Xing, Ruimin; Liu, Shanhu; Latthe, Sanjay S.

2018-05-01

Rolling water drops takes off dust particles from lotus leaf showing self-cleaning performance. Self-cleaning effect has great importance in industry as well as in daily life. The present paper describes the preparation of self-cleaning superhydrophobic coating through simple and low cost dip coating technique. The prepared superhydrophobic surface enact as lotus leaf. Firstly TiO2 nanoparticles were dispersed in ethanol and different concentration of octadecyltrichlorosilane (ODS) was added in TiO2 dispersion. The effect of number of deposition layer on the wettability of the coating was studied. The coating prepared from five deposition layers showed contact angle higher than 150° and sliding angle less than 10°. The superhydrophobicity increases with increasing concentration of ODS. The hierarchical rough morphology which is preferable for superhydrophobicity was obtained. The prepared coatings were stable against water jet impact and showed repellent towards colored and muddy water. Such superhydrophobic coating can find enormous scope in self-cleaning application.

Zirconia based superhydrophobic coatings on cotton fabrics exhibiting excellent durability for versatile use

PubMed Central

Das, Indranee; De, Goutam

2015-01-01

A fluorinated silyl functionalized zirconia was synthesized by the sol-gel method to fabricate an extremely durable superhydrophobic coating on cotton fabrics by simple immersion technique. The fabric surfaces firmly attached with the coating material through covalent bonding, possessed superhydrophobicity with high water contact angle ≈163 ± 1°, low hysteresis ≈3.5° and superoleophilicity. The coated fabrics were effective to separate oil/water mixture with a considerably high separation efficiency of 98.8 wt% through ordinary filtering. Presence of highly stable (chemically and mechanically) superhydrophobic zirconia bonded with cellulose makes such excellent water repelling ability of the fabrics durable under harsh environment conditions like high temperature, strong acidic or alkaline solutions, different organic solvents and mechanical forces including extensive washings. Moreover, these coated fabrics retained self-cleanable superhydrophobic property as well as high water separation efficiency even after several cycles, launderings and abrasions. Therefore, such robust superhydrophobic ZrO2 coated fabrics have strong potential for various industrial productions and uses. PMID:26678754

Highly Stretchable Superhydrophobic Composite Coating Based on Self-Adaptive Deformation of Hierarchical Structures.

PubMed

Hu, Xin; Tang, Changyu; He, Zhoukun; Shao, Hong; Xu, Keqin; Mei, Jun; Lau, Woon-Ming

2017-05-01

With the rapid development of stretchable electronics, functional textiles, and flexible sensors, water-proof protection materials are required to be built on various highly flexible substrates. However, maintaining the antiwetting of superhydrophobic surface under stretching is still a big challenge since the hierarchical structures at hybridized micro-nanoscales are easily damaged following large deformation of the substrates. This study reports a highly stretchable and mechanically stable superhydrophobic surface prepared by a facile spray coating of carbon black/polybutadiene elastomeric composite on a rubber substrate followed by thermal curing. The resulting composite coating can maintain its superhydrophobic property (water contact angle ≈170° and sliding angle <4°) at an extremely large stretching strain of up to 1000% and can withstand 1000 stretching-releasing cycles without losing its superhydrophobic property. Furthermore, the experimental observation and modeling analysis reveal that the stable superhydrophobic properties of the composite coating are attributed to the unique self-adaptive deformation ability of 3D hierarchical roughness of the composite coating, which delays the Cassie-Wenzel transition of surface wetting. In addition, it is first observed that the damaged coating can automatically recover its superhydrophobicity via a simple stretching treatment without incorporating additional hydrophobic materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface adhesive forces: a metric describing the drag-reducing effects of superhydrophobic coatings.

PubMed

Cheng, Mengjiao; Song, Mengmeng; Dong, Hongyu; Shi, Feng

2015-04-08

Nanomaterials with superhydrophobic properties are promising as drag-reducing coatings. However, debates regarding whether superhydrophobic surfaces are favorable for drag reduction require further clarification. A quantified water adhesive force measurement is proposed as a metric and its effectiveness demonstrated using three typical superhydrophobic coatings on model ships with in situ sailing tests. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnet-induced temporary superhydrophobic coatings from one-pot synthesized hydrophobic magnetic nanoparticles.

PubMed

Fang, Jian; Wang, Hongxia; Xue, Yuhua; Wang, Xungai; Lin, Tong

2010-05-01

In this paper, we report on the production of superhydrophobic coatings on various substrates (e.g., glass slide, silicon wafer, aluminum foil, plastic film, nanofiber mat, textile fabrics) using hydrophobic magnetic nanoparticles and a magnet-assembly technique. Fe(3)O(4) magnetic nanoparticles functionalized with a thin layer of fluoroalkyl silica on the surface were synthesized by one-step coprecipitation of Fe(2+)/Fe(3+) under an alkaline condition in the presence of a fluorinated alkyl silane. Under a magnetic field, the magnetic nanoparticles can be easily deposited on any solid substrate to form a thin superhydrophobic coating with water contact angle as high as 172 degrees , and the surface superhydrophobicity showed very little dependence on the substrate type. The particulate coating showed reasonable durability because of strong aggregation effect of nanoparticles, but the coating layer can be removed (e.g., by ultrasonication) to restore the original surface feature of the substrates. By comparison, the thin particle layer deposited under no magnetic field showed much lower hydrophobicity. The main reason for magnet-induced superhydrophobic surfaces is the formation of nano- and microstructured surface features. Such a magnet-induced temporary superhydrophobic coating may have wide applications in electronic, biomedical, and defense-related areas.

Stable superhydrophilic coating on superhydrophobic porous media by functionalized nanoparticles

NASA Astrophysics Data System (ADS)

Khazaei, Masoud; Taghi Sadeghi, Mohammad; Sadat Hosseini, Marzieh

2018-01-01

In this study, the hydrophilicity property of TiO2 nano-coating was improved by zinc acetate-assisted sol-gel method. The stable superhydrophilic coating was fabricated on a superhydrophobic mineral rock surface. The wettability of surface before and after coating was characterized by contact angle measurements. The n-heptane and water droplet contact angle was 0° and 168° respectively, so the untreated rock was superhydrophobic. After nano-treatment, the n-heptane and water contact angle changed to 172° and 0° respectively, so the superhydrophilic coating was formed on the superhydrophobic surface. The thermal, mechanical and salinity stability of the fabricated coatings was investigated. The coatings had high thermal and salinity stability; they also had moderate mechanical stability that was evaluated by abrasion test. The morphology and composition of synthesized nanoparticles were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and x-ray diffraction (XRD) analyses. Characterization of the coated surfaces was conducted by SEM and XRD analyses. Applications of these nano-coatings include surfaces where cleanliness is paramount such as in hospitals as well as the protection of public monuments and building facades from weathering. Novel industrial application includes wettability alteration of oil wet carbonate rock for enhanced oil recovery.

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

NASA Astrophysics Data System (ADS)

Jafari, R.; Menini, R.; Farzaneh, M.

2010-12-01

A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon ®). Scanning electron microscopy images showed a " bird's nest"-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ˜165° with a very low contact angle hysteresis of ˜3°. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF 3 and CF 2 groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate.

Fabrication of Superhydrophobic Calcium Phosphate Coating on Mg-Zn-Ca alloy and Its Corrosion Resistance

NASA Astrophysics Data System (ADS)

Zhang, Lashuang; Jiang, Yue; Zai, Wei; Li, Guangyu; Liu, Shaocheng; Lian, Jianshe; Jiang, Zhonghao

2017-12-01

A novel superhydrophobic calcium phosphate coating was prepared on a magnesium alloy substrate by a highly effective chemical conversion process and subsequent chemical modification. Different methods were employed to characterize the surface morphology and chemical composition as well as measure the wettability of the coating. It was demonstrated that the as-prepared superhydrophobic calcium phosphate coating has a typical three-level hierarchical structure consisted of micro-protrusions, submicro-lumps and nano-grains, conferring excellent superhydrophobicity with a water contact angle of 159°. The electrochemical measurements and appropriate equivalent circuit revealed that the corrosion-resistant performance of the superhydrophobic calcium phosphate coating was significantly improved as compared with that of the substrate, the corrosion potential of the superhydrophobic coating increases from -1.56 to -1.36 V, and its corrosion current density decreases from 1.29 × 10-4 to 1.3 × 10-6 A/cm2. The anti-corrosion mechanism of the superhydrophobic coating was also discussed. It can be indicated that the corrosion inhibitive properties of the coating are in accordance with its hydrophobicity, which is owing to the presence of a protective layer of air trapped in the grooves of the coating surface to isolate the underlying materials from the external environment.

Self-cleaning superhydrophobic epoxy coating based on fibrous silica-coated iron oxide magnetic nanoparticles.

PubMed

Alamri, Haleema; Al-Shahrani, Abdullah; Bovero, Enrico; Khaldi, Turki; Alabedi, Gasan; Obaid, Waleed; Al-Taie, Ihsan; Fihri, Aziz

2018-03-01

Inspired by the self-cleaning lotus leaf, a facile method of fabricating superhydrophobic silica coated magnetite nanoparticles using a cost-effective process is presented in this work. The structural characterizations and magnetic properties of the obtained core-shell magnetic nanoparticles were characterized by means of X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). TEM analysis revealed that the particles present flower-like dendrimeric fibers morphology. The particles were uniformly dispersed on the surface of an epoxy resin coating with the purpose to increase the roughness and reduce the surface energy of the surface. The resulting superhydrophobic surface provides robust water-repellent surface under harsh conditions, thanks to its self-cleaning characteristic. The superhydrophobicity of this surface was confirmed based on the measurements of a water contact angle around 175°, which surpasses the theoretical limit of the superhydrophobicity. The simplicity and the cost-effectiveness of the process developed in this study appears to be a promising route for the preparation of other magnetic superhydrophobic organic-inorganic hybrid materials that would be beneficial in a wide variety of applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Potentiodynamic study of Al-Mg alloy with superhydrophobic coating in photobiologically active/not active natural seawater.

PubMed

Benedetti, Alessandro; Cirisano, Francesca; Delucchi, Marina; Faimali, Marco; Ferrari, Michele

2016-01-01

Superhydrophobic coating technology is regarded as an attractive possibility for the protection of materials in a sea environment. DC techniques are a useful tool to characterize metals' behavior in seawater in the presence/absence of coatings and/or corrosion inhibitors. In this work, investigations concerning Al-5%Mg alloy with and without a sprayed superhydrophobic coating were carried out with potentiodynamic scans in photobiologically active and not active seawater (3 weeks of immersion). In not photobiologically active seawater, the presence of the superhydrophobic coating did not prevent pitting corrosion. With time, the coating underwent local exfoliations, but intact areas still preserved superhydrophobicity. In photobiologically active seawater, on samples without the superhydrophobic coating (controls) pitting was inhibited, probably due to the adsorption of organic compounds produced by the photobiological activity. After 3 weeks of immersion, the surface of the coating became hydrophilic due to diatom coverage. As suggested by intermediate observations, the surface below the diatom layer is suspected of having lost its superhydrophobicity due to early stages of biofouling processes (organic molecule adsorption and diatom attachment/gliding). Polarization curves also revealed that the metal below the coating underwent corrosion inhibiting phenomena as observed in controls, likely due to the permeation of organic molecules through the coating. Hence, the initial biofouling stages (days) occurring in photobiologically active seawater can both accelerate the loss of superhydrophobicity of coatings and promote corrosion inhibition on the underlying metal. Finally, time durability of superhydrophobic surfaces in real seawater still remains the main challenge for applications, where the early stages of immersion are demonstrated to be of crucial importance. Copyright © 2015 Elsevier B.V. All rights reserved.

The effect of composition and thermodynamics on the surface morphology of durable superhydrophobic polymer coatings.

PubMed

Nahum, Tehila; Dodiuk, Hanna; Kenig, Samuel; Panwar, Artee; Barry, Carol; Mead, Joey

2017-01-01

Durable superhydrophobic coatings were synthesized using a system of silica nanoparticles (NPs) to provide nanoscale roughness, fluorosilane to give hydrophobic chemistry, and three different polymer binders: urethane acrylate, ethyl 2-cyanoacrylate, and epoxy. Coatings composed of different binders incorporating NPs in various concentrations exhibited different superhydrophobic attributes when applied on polycarbonate (PC) and glass substrates and as a function of coating composition. It was found that the substrate surface characteristics and wettability affected the superhydrophobic characteristics of the coatings. Interfacial tension and spreading coefficient parameters (thermodynamics) of the coating components were used to predict the localization of the NPs for the different binders' concentrations. The thermodynamic analysis of the NPs localization was in good agreement with the experimental observations. On the basis of the thermodynamic analysis and the experimental scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy results, it was concluded that localization of the NPs on the surface was critical to provide the necessary roughness and resulting superhydrophobicity. The durability evaluated by tape testing of the epoxy formulations was the best on both glass and PC. Several coating compositions retained their superhydrophobicity after the tape test. In summary, it was concluded that thermodynamic analysis is a powerful tool to predict the roughness of the coating due to the location of NPs on the surface, and hence can be used in the design of superhydrophobic coatings.

Spray-coating of superhydrophobic aluminum alloys with enhanced mechanical robustness.

PubMed

Zhang, Youfa; Ge, Dengteng; Yang, Shu

2014-06-01

A superhydrophobic aluminum alloy was prepared by one-step spray coating of an alcohol solution consisting of hydrophobic silica nanoparticles (15-40 nm) and methyl silicate precursor on etched aluminum alloy with pitted morphology. The as-sprayed metal surface showed a water contact angle of 155° and a roll-off angle of 4°. The coating was subjected to repeated mechanical tests, including high-pressure water jetting, sand particles impacting, and sandpaper shear abrasion. It remained superhydrophobic with a roll-off angle <10° up to three cycles of water jetting (25 kPa for 10 min) and sand particle impinging. After five cycles, the roll-off angle increased, but no more than 19° while the water contact angle remained greater than 150°. The superhydrophobic state was also maintained after three cycles of sandpaper abrasion. It was found that the micro-protrusion structures on the etched aluminum alloy played an important role to enhance the coating mechanical robustness, where the nanoparticles could grab on the rough surface, specifically in the groove structures, in comparison with the smooth glass substrates spray coated with the same materials. Further, we showed that the superhydrophobicity could be restored by spray a new cycle of the nanocomposite solution on the damaged surface. Copyright © 2014 Elsevier Inc. All rights reserved.

Fabrication of a superhydrophobic and high-glossy copper coating on aluminum substrates

NASA Astrophysics Data System (ADS)

Yang, Hao; He, Yuantao; Wu, Zhongqiang; Miao, Jing; Yang, Fang; Lu, Zhong

2018-03-01

Superhydrophobic metal coatings have been extensively studied in recent years because of their significant potential applications. Unfortunately, most of them lost the original metallic luster due to the micro/nano binary structures. In this paper, a facile method was developed to prepare a superhydrophobic and high-glossy copper coating on aluminum substrates. The bionic lotus leaf surfaces were constructed by electroless plating method and further modified with octadecanethiol. The wettability and gloss could be tuned by the concentration of the precursor. With the increase of CuSO4 concentration, the surface roughness of the coating raised, thus resulting in increase of contact angle and decrease of glossiness. When the CuSO4 concentration was 30 mmol/L, the coating exhibited a sub-micro/nano binary structure, in which 20-30 nm protuberances were grown on 300-500 nm mastoids. Such special morphology endowed the coating with superhydrophobic and high-glossy properties, and the coating also showed ultra-low water adhesion and stable dynamic water repellence.

A Co-Precursor Approach Coupled with a Supercritical Modification Method for Constructing Highly Transparent and Superhydrophobic Polymethylsilsesquioxane Aerogels.

PubMed

Lei, Chaoshuai; Li, Junning; Sun, Chencheng; Yang, Hailong; Xia, Tao; Hu, Zijun; Zhang, Yue

2018-03-30

Polymethylsilsesquioxane (PMSQ) aerogels obtained from methyltrimethoxysilane (MTMS) are well-known high-performance porous materials. Highly transparent and hydrophobic PMSQ aerogel would play an important role in transparent vacuum insulation panels. Herein, the co-precursor approach and supercritical modification method were developed to prepare the PMSQ aerogels with high transparency and superhydrophobicity. Firstly, benefiting from the introduction of tetramethoxysilane (TMOS) in the precursor, the pore structure became more uniform and the particle size was decreased. As the TMOS content increased, the light transmittance increased gradually from 54.0% to 81.2%, whereas the contact angle of water droplet decreased from 141° to 99.9°, ascribed to the increase of hydroxyl groups on the skeleton surface. Hence, the supercritical modification method utilizing hexamethyldisilazane was also introduced to enhance the hydrophobic methyl groups on the aerogel's surface. As a result, the obtained aerogels revealed superhydrophobicity with a contact angle of 155°. Meanwhile, the developed surface modification method did not lead to any significant changes in the pore structure resulting in the superhydrophobic aerogel with a high transparency of 77.2%. The proposed co-precursor approach and supercritical modification method provide a new horizon in the fabrication of highly transparent and superhydrophobic PMSQ aerogels.

All-organic superhydrophobic coatings with mechanochemical robustness and liquid impalement resistance

NASA Astrophysics Data System (ADS)

Peng, Chaoyi; Chen, Zhuyang; Tiwari, Manish K.

2018-03-01

Superhydrophobicity is a remarkable evolutionary adaption manifested by several natural surfaces. Artificial superhydrophobic coatings with good mechanical robustness, substrate adhesion and chemical robustness have been achieved separately. However, a simultaneous demonstration of these features along with resistance to liquid impalement via high-speed drop/jet impact is challenging. Here, we describe all-organic, flexible superhydrophobic nanocomposite coatings that demonstrate strong mechanical robustness under cyclic tape peels and Taber abrasion, sustain exposure to highly corrosive media, namely aqua regia and sodium hydroxide solutions, and can be applied to surfaces through scalable techniques such as spraying and brushing. In addition, the mechanical flexibility of our coatings enables impalement resistance to high-speed drops and turbulent jets at least up to 35 m s-1 and a Weber number of 43,000. With multifaceted robustness and scalability, these coatings should find potential usage in harsh chemical engineering as well as infrastructure, transport vehicles and communication equipment.

The effect of composition and thermodynamics on the surface morphology of durable superhydrophobic polymer coatings

PubMed Central

Nahum, Tehila; Dodiuk, Hanna; Kenig, Samuel; Panwar, Artee; Barry, Carol; Mead, Joey

2017-01-01

Durable superhydrophobic coatings were synthesized using a system of silica nanoparticles (NPs) to provide nanoscale roughness, fluorosilane to give hydrophobic chemistry, and three different polymer binders: urethane acrylate, ethyl 2-cyanoacrylate, and epoxy. Coatings composed of different binders incorporating NPs in various concentrations exhibited different superhydrophobic attributes when applied on polycarbonate (PC) and glass substrates and as a function of coating composition. It was found that the substrate surface characteristics and wettability affected the superhydrophobic characteristics of the coatings. Interfacial tension and spreading coefficient parameters (thermodynamics) of the coating components were used to predict the localization of the NPs for the different binders’ concentrations. The thermodynamic analysis of the NPs localization was in good agreement with the experimental observations. On the basis of the thermodynamic analysis and the experimental scanning electron microscopy, X-ray photoelectron spectroscopy, profilometry, and atomic force microscopy results, it was concluded that localization of the NPs on the surface was critical to provide the necessary roughness and resulting superhydrophobicity. The durability evaluated by tape testing of the epoxy formulations was the best on both glass and PC. Several coating compositions retained their superhydrophobicity after the tape test. In summary, it was concluded that thermodynamic analysis is a powerful tool to predict the roughness of the coating due to the location of NPs on the surface, and hence can be used in the design of superhydrophobic coatings. PMID:28243071

Water-based acrylate copolymer/silica hybrids for facile preparation of robust and durable superhydrophobic coatings

NASA Astrophysics Data System (ADS)

Li, Meng; Li, Yu; Xue, Fang; Jing, Xinli

2018-07-01

Resin based superhydrophobic coatings are effective to construct robust superhydrophobic surfaces on large scale without limitation of substrates. However, for most of the common resin based superhydrophobic coatings, it is inevitable to deteriorate environmental or health problems due to release of a large amount volatile solvents. In this work, a kind of water-based organic/inorganic hybrid consisted of acrylate copolymers and superhydrophobic silica nanoparticles were synthesized. The highly water-repellent silica nanoparticles were successfully involved into the aqueous dispersion of acrylate copolymers without additional surfactants. The as-synthesized hybrids simultaneously retain the excellent film-forming property of acrylate resins and amplify the contributions of low surface energy nanoparticles to the superhydrophobicity. Robust superhydrophobic coatings (CA > 160°, CA < 7°) with high adhesion strength, good scratch-resistance and excellent abrasion-resistance were constructed using the synthesized hybrids with significantly reduced content of low surface energy particles and organic solvent. The hybrid coating can stand abrasion up to 300 cycles with a fine sand paper and up to 1200 cycles under rough sand paper abrasion. Benefited from its good water-repellence property, the hybrid coating with a water-based formula not only showed improved water-resistance in comparison with commercial products; but also displayed attractive performances in self-cleaning and oil/water separation processes.

Robust Superhydrophobic Graphene-Based Composite Coatings with Self-Cleaning and Corrosion Barrier Properties.

PubMed

Nine, Md J; Cole, Martin A; Johnson, Lucas; Tran, Diana N H; Losic, Dusan

2015-12-30

Superhydrophobic surfaces for self-cleaning applications often suffer from mechanical instability and do not function well after abrasion/scratching. To address this problem, we present a method to prepare graphene-based superhydrophobic composite coatings with robust mechanical strength, self-cleaning, and barrier properties. A suspension has been formulated that contains a mixture of reduced graphene oxide (rGO) and diatomaceous earth (DE) modified with polydimethylsiloxane (PDMS) that can be applied on any surface using common coating methods such as spraying, brush painting, and dip coating. Inclusion of TiO2 nanoparticles to the formulation shows further increase in water contact angle (WCA) from 159 ± 2° to 170 ± 2° due to the structural improvement with hierarchical surface roughness. Mechanical stability and durability of the coatings has been achieved by using a commercial adhesive to bond the superhydrophobic "paint" to various substrates. Excellent retention of superhydrophobicity was observed even after sandpaper abrasion and crosscut scratching. A potentiodynamic polarization study revealed excellent corrosion resistance (96.78%) properties, and an acid was used to provide further insight into coating barrier properties. The ease of application and remarkable properties of this graphene-based composite coating show considerable potential for broad application as a self-cleaning and protective layer.

Dual-scale rough multifunctional superhydrophobic ITO coatings prepared by air annealing of sputtered indium-tin alloy thin films

NASA Astrophysics Data System (ADS)

Gupta, Nitant; Sasikala, S.; Mahadik, D. B.; Rao, A. V.; Barshilia, Harish C.

2012-10-01

A novel method to fabricate multifunctional indium tin oxide (ITO) coatings is discussed. Superhydrophobic ITO coatings are fabricated by radio frequency balanced magnetron sputter deposition of indium-tin alloy on glass substrates followed by complete oxidation of the samples in air. The chemical nature and structure of the coatings are verified by X-ray diffraction, X-ray photoelectron spectroscopy and micro-Raman spectroscopy. Field emission scanning electron microscopic studies of the coatings display rod-like and blob-like microstructures, together with fractal-like nanostructures infused on top. Microscale roughness of the ITO coatings is measured by three-dimensional profilometry and is found to be in the range of 0.1-3 μm. Thus the presence of micro- and nano- sized structures result in dual-scale roughness. The variation in the contact angle with the deposition time is studied using a contact angle goniometer. High water contact angles (>160°) and low contact angle hysteresis (5°) are obtained at an optimum microscale roughness. The ITO coatings also exhibit other functional properties, such as low sheet resistance and semi-transparent behaviour in the visible region. The loss in the transparency of the ITO coatings is attributed to the presence of higher scale of roughness. The photoluminescence measurements show large photoemission in the visible region. It is expected that further improvements in the multifunctional properties of transparent conducting oxides will open new frontiers in designing novel materials with exotic properties.

A Robust Epoxy Resins @ Stearic Acid-Mg(OH)2 Micronanosheet Superhydrophobic Omnipotent Protective Coating for Real-Life Applications.

PubMed

Si, Yifan; Guo, Zhiguang; Liu, Weimin

2016-06-29

Superhydrophobic coating has extremely high application value and practicability. However, some difficult problems such as weak mechanical strength, the need for expensive toxic reagents, and a complex preparation process are all hard to avoid, and these problems have impeded the superhydrophobic coating's real-life application for a long time. Here, we demonstrate one kind of omnipotent epoxy resins @ stearic acid-Mg(OH)2 superhydrophobic coating via a simple antideposition route and one-step superhydrophobization process. The whole preparation process is facile, and expensive toxic reagents needed. This omnipotent coating can be applied on any solid substrate with great waterproof ability, excellent mechanical stability, and chemical durability, which can be stored in a realistic environment for more than 1 month. More significantly, this superhydrophobic coating also has four protective abilities, antifouling, anticorrosion, anti-icing, and flame-retardancy, to cope with a variety of possible extreme natural environments. Therefore, this omnipotent epoxy resins @ stearic acid-Mg(OH)2 superhydrophobic coating not only satisfies real-life need but also has great application potential in many respects.

Bioinspired nanoparticle spray-coating for superhydrophobic flexible materials with oil/water separation capabilities.

PubMed

Geraldi, Nicasio R; Dodd, Linzi E; Xu, Ben B; Wood, David; Wells, Gary G; McHale, Glen; Newton, Michael I

2018-02-02

Much of the inspiration for the creation of superhydrophobic surfaces has come from nature, from plants such as the sacred lotus (Nelumbo nucifera), where the micro-scale papillae epidermal cells on the surfaces of the leaves are covered with nano-scale epicuticular wax crystalloids. The combination of the surface roughness and the hydrophobic wax coating produces a superhydrophobic wetting state on the leaves, allowing them to self-clean and easily shed water. Here, a simple scaled-up carbon nanoparticle spray coating is presented that mimics the surface of sacred lotus leaves and can be applied to a wide variety of materials, complex structures, and flexible substrates, rendering them superhydrophobic, with contact angles above 160°. The sprayable mixture is produced by combining toluene, polydimethylsiloxane, and inherently hydrophobic rapeseed soot. The ability to spray the superhydrophobic coating allows for the hydrophobisation of complex structures such as metallic meshes, which allows for the production of flexible porous superhydrophobic materials that, when formed into U-shaped channels, can be used to direct flows. The porous meshes, whilst being superhydrophobic, are also oleophilic. Being both superhydrophobic and oleophilic allows oil to pass through the mesh, whilst water remains on the surface. The meshes were tested for their ability to separate mixtures of oil and water in flow conditions. When silicone oil/water mixtures were passed over the meshes, all meshes tested were capable of separating more than 93% of the oil from the mixture.

Facile Preparation of a Robust and Durable Superhydrophobic Coating Using Biodegradable Lignin-Coated Cellulose Nanocrystal Particles

PubMed Central

Huang, Jingda; Lyu, Shaoyi

2017-01-01

It is a challenge for a superhydrophobic coating to overcome the poor robustness and the rough surface structure that is usually built using inorganic particles that are difficult to degrade. In this study, a robust superhydrophobic coating is facilely prepared by using commercial biodegradable lignin-coated cellulose nanocrystal (L-CNC) particles after hydrophobic modification to build rough surface structures, and by choosing two different adhesives (double-sided tape and quick-setting epoxy) to support adhesion between the L-CNC particles and the substrates. In addition to excellent self-cleaning and water repellence properties, the resulting coatings show outstanding mechanical strength and durability against sandpaper abrasion, finger-wipe, knife-scratch, water jet, UV radiation, high temperature, and acidic and alkali solutions, possessing a wide application prospect. PMID:28906449

A superhydrophobic EP/PDMS nanocomposite coating with high gamma radiation stability

NASA Astrophysics Data System (ADS)

Zhang, Yan; Ren, Fule; Liu, Yujian

2018-04-01

The superhydrophobic coatings with high gamma radiation stability were prepared by using epoxy/polydimethylsiloxane (EP/PDMS) resins as the matrix and silica nanoparticles as the fillers. The nanocomposite coatings exhibit superhydrophobicity with a high water contact angle (WCA) of 154° and a low sliding angle of 7°. With the amount of SiO2 increasing from 0 to 30%, the surface shows the hierarchically structure gradually and its roughness raised from 4 nm to 278 nm. And little change in the WCA of the coatings (from 155° to 149°) was observed when the pH of the droplets varied from 2 to 14. In addition, the coatings also show good adhesion grade (5B), high hardness (6H) and outstanding stability for high dose gamma radiation.

Synthesis of ceria based superhydrophobic coating on Ni20Cr substrate via cathodic electrodeposition.

PubMed

Pedraza, F; Mahadik, S A; Bouchaud, B

2015-12-21

In this work, superhydrophobic cerium oxide coating surface (111) with dual scale texture on Ni20Cr substrate is obtained by combination of electropolishing the substrate and subsequent cathodic electrodeposition and long-term UVH surface relaxation. To form hierarchical structures of CeO2 is controllable by varying the substrate roughness, and electropolishing period. The results indicated that at the optimal condition, the surface of the cerium oxide coating showed a superhydrophobicity with a great water contact angle (151.0 ± 1.4°) with Gecko state. An interface model for electropolishing of substrate surface in cerium nitrate medium is proposed. We expect that this facile process can be readily and widely adopted for the design of superhydrophobic coating on engineering materials.

One-step microwave plasma enhanced chemical vapor deposition (MW-PECVD) for transparent superhydrophobic surface

NASA Astrophysics Data System (ADS)

Thongrom, Sukrit; Tirawanichakul, Yutthana; Munsit, Nantakan; Deangngam, Chalongrat

2018-02-01

We demonstrate a rapid and environmental friendly fabrication technique to produce optically clear superhydrophobic surfaces using poly (dimethylsiloxane) (PDMS) as a sole coating material. The inert PDMS chain is transformed into a 3-D irregular solid network through microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. Thanks to high electron density in the microwave-activated plasma, coating can be done in just a single step with rapid deposition rate, typically much shorter than 10 s. Deposited layers show excellent superhydrophobic properties with water contact angles of ∼170° and roll-off angles as small as ∼3°. The plasma-deposited films can be ultrathin with thicknesses under 400 nm, greatly diminishing the optical loss. Moreover, with appropriate coating conditions, the coating layer can even enhance the transmission over the entire visible spectrum due to a partial anti-reflection effect.

Superhydrophobic diatomaceous earth

DOEpatents

Simpson, John T [Clinton, TN; D& #x27; Urso, Brian R [Clinton, TN

2012-07-10

A superhydrophobic powder is prepared by coating diatomaceous earth (DE) with a hydrophobic coating on the particle surface such that the coating conforms to the topography of the DE particles. The hydrophobic coating can be a self assembly monolayer of a perfluorinated silane coupling agent. The DE is preferably natural-grade DE where organic impurities have been removed. The superhydrophobic powder can be applied as a suspension in a binder solution to a substrate to produce a superhydrophobic surface on the substrate.

Samsung Licenses ORNL Transparent Superhydrophobic Glass Coating Technology for Electronic Devices

ScienceCinema

Aytug, Tolga

2018-06-12

Samsung Electronics has exclusively licensed optically clear superhydrophobic film technology from the Department of Energy’s Oak Ridge National Laboratory to improve the performance of glass displays on smartphones, tablets and other electronic devices.

Laser Tailoring the Surface Chemistry and Morphology for Wear, Scale and Corrosion Resistant Superhydrophobic Coatings.

PubMed

Boinovich, Ludmila B; Emelyanenko, Kirill A; Domantovsky, Alexander G; Emelyanenko, Alexandre M

2018-06-04

A strategy, combining laser chemical modification with laser texturing, followed by chemisorption of the fluorinated hydrophobic agent was used to fabricate the series of superhydrophobic coatings on an aluminum alloy with varied chemical compositions and parameters of texture. It was shown that high content of aluminum oxynitride and aluminum oxide formed in the surface layer upon laser treatment allows solving the problem of enhancement of superhydrophobic coating resistance to abrasive loads. Besides, the multimodal structure of highly porous surface layer leads to self-healing ability of fabricated coatings. Long-term behavior of designed coatings in "hard" hot water with an essential content of calcium carbonate demonstrated high antiscaling resistance with self-cleaning potential against solid deposits onto the superhydrophobic surfaces. Study of corrosion protection properties and the behavior of coatings at long-term contact with 0.5 M NaCl solution indicated extremely high chemical stability and remarkable anticorrosion properties.

Surface studies on superhydrophobic and oleophobic polydimethylsiloxane-silica nanocomposite coating system

NASA Astrophysics Data System (ADS)

Basu, Bharathibai J.; Dinesh Kumar, V.; Anandan, C.

2012-11-01

Superhydrophobic and oleophobic polydimethylsiloxane (PDMS)-silica nanocomposite double layer coating was fabricated by applying a thin layer of low surface energy fluoroalkyl silane (FAS) as topcoat. The coatings exhibited WCA of 158-160° and stable oleophobic property with oil CA of 79°. The surface morphology was characterized by field emission scanning electron microscopy (FESEM) and surface chemical composition was determined by energy dispersive X-ray spectrometery (EDX) and X-ray photoelectron spectroscopy (XPS). FESEM images of the coatings showed micro-nano binary structure. The improved oleophobicity was attributed to the combined effect of low surface energy of FAS and roughness created by the random distribution of silica aggregates. This is a facile, cost-effective method to obtain superhydrophobic and oleophobic surfaces on larger area of various substrates.

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.

Fabrication of the micro/nano-structure superhydrophobic surface on aluminum alloy by sulfuric acid anodizing and polypropylene coating.

PubMed

Wu, Ruomei; Liang, Shuquan; Liu, Jun; Pan, Anqiang; Yu, Y; Tang, Yan

2013-03-01

The preparation of the superhydrophobic surface on aluminum alloy by anodizing and polypropylene (PP) coating was reported. Both the different anodizing process and different PP coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. By PP coating after anodizing, a good superhydrophobic surface was facilely fabricated. The optimum conditions for anodizing were determined by orthogonal experiments. After the aluminium-alloy was grinded with 600# sandpaper, pretreated by 73 g/L hydrochloric acid solution at 1 min, when the concentration of sulfuric acid was 180 g/L, the concentration of oxalic acid was 5 g/L, the concentration of potassium dichromate was 10 g/L, the concentration of chloride sodium was 50 g/L and 63 g/L of glycerol, anodization time was 20 min, and anodization current was 1.2 A/dm2, anodization temperature was 30-35 degrees C, the best micro-nanostructure aluminum alloy films was obtained. On the other hand, the PP with different concentrations was used to the PP with different concentrations was used to coat the aluminum alloy surface after anodizing. The results showed that the best superhydrophobicity was achieved by coating PP, and the duration of the superhydrophobic surface was improved by modifying the coat the aluminum alloy surface after anodizing. The results showed that the best superhydrophobicity was surface with high concentration PP. The morphologies of micro/nano-structure superhydrophobic surface were further confirmed by scanning electron microscope (SEM). The material of PP with the low surface free energy combined with the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.

Preparation of silane-functionalized silica films via two-step dip coating sol-gel and evaluation of their superhydrophobic properties

NASA Astrophysics Data System (ADS)

Ramezani, Maedeh; Vaezi, Mohammad Reza; Kazemzadeh, Asghar

2014-10-01

In this paper, we study the two-step dip coating via a sol-gel process to prepare superhydrophobic silica films on the glass substrate. The water repellency of the silica films was controlled by surface silylation method using isooctyltrimethoxysilane (iso-OTMS) as a surface modifying agent. Silica alcosol was synthesized by keeping the molar ratio of ethyltriethoxysilane (ETES) precursor, ethanol (EtOH) solvent, water (H2O) was kept constant at 1:36:6.6 respectively, with 6 M NH4OH throughout the experiment and the percentages of hydrophobic agent in hexane bath was varied from 0 to 15 vol.%. The static water contact angle values of the silica films increased from 108° to 160° with an increase in the vol.% of iso-OTMS. At 15 vol%. of iso-OTMS, the silica film shows static water contact angle as high as 160°. The superhydrophobic silica films are thermally stable up to 440 °C and above this temperature, the silica films lose superhydrophobicity. By controlling the primer particle size of SiO2 about 26 nm, leading to decrease the final size of silica nanoparticles after modification of nanoparticles by isooctyltrimethoxysilane about 42 nm. The films are transparent and have uniform size on the surface. The silica films have been characterized by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FT-IR), transparency, contact angle measurement (CA), Zeta-potential, Thermal stability by TG-DTA analysis.

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.

Flower-like Rh/Cu superhydrophobic coating via electrodeposition and its self-cleaning property

NASA Astrophysics Data System (ADS)

Zhao, N.; Lu, S. X.; Xu, W. G.; Cheng, X. L.

2017-01-01

Rh/Cu superhydrophobic coatings with textured flower-like dual micro-nano structures were fabricated on copper substrates via electrodesposition of Rh followed by annealing treatment. The scanning electron microscopy and X-ray diffraction pattern were conducted to analyse the morphology and chemical composition of the coating surfaces, respectively. The water drops exhibited a water contact angle of 168±1° and a sliding angle of 0±1° on the coating surfaces which were obtained by etching in concentrated hydrochloric acid and nitric acid, electrodeposited at -1.0 V for 30 min and annealing in an oven at 180°C for 60 min. The prepared superhydrophobic coatings showed excellent water repellence and self-cleaning property due to its extremely high water contact angle.

Self-assembled biomimetic superhydrophobic CaCO3 coating inspired from fouling mineralization in geothermal water.

PubMed

Wang, Gong G; Zhu, Li Q; Liu, Hui C; Li, Wei P

2011-10-18

Inspired from fouling self-mineralization in geothermal water, a novel biomimetic cactuslike CaCO(3) coating with superhydrophobic features is reported in this letter. The structure, morphologies, and phases of the CaCO(3) coating were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and infrared spectrophotometry. After prenucleation treatment, a continuous cactuslike CaCO(3) coating with hierarchical nano- and microstructures was self-assembled on stainless steel surfaces after immersion in simulated geothermal water at 50 °C for 48 h. After being modified with a low-surface-energy monolayer of sodium stearate, the as-prepared coating exhibited superhydrophobic properties with a water contact angle of 158.9° and a sliding angle of 2°. Therefore, this work might open up a new application field of geothermal resources and provide insight into designing multidimensional structures with functional applications, including superhydrophobic surfaces. © 2011 American Chemical Society

Nanostructured superhydrophobic polysiloxane coating for high barrier and anticorrosion applications in marine environment.

PubMed

Arukalam, Innocent O; Oguzie, Emeka E; Li, Ying

2018-02-15

The use of epoxy and polyurethane coatings as marine topcoats, have been influenced by their inherent high surface energy property which increases their affinity to water and microorganisms. Thus, their susceptibility to degradation is enhanced. Because of this defect, recently, nanostructured hydrophobic and superhydrophobic polysiloxane coatings are being preferred as topcoats. But the appropriate nanoparticle size and matrix:filler ratio which provide guide for the design of desired topcoats are scarcely available. In view of this, a series of hydrophobic and superhydrophobic coatings were prepared by sol-gel process based on perfluorodecyltrichlorosilane (FDTS), different nanoZnO particles and poly(dimethylsiloxane) (PDMS):nanoZnO ratios. The liquid repellency, surface morphology and roughness of the coatings were conducted by use of contact angle goniometer, field emission scanning electron microscopy and atomic force microscopy, respectively. Additionally, the electrochemical and salt spray corrosion tests were conducted. According to the results, modifications of the coatings showed that anticorrosion performance was considerably influenced by the surface properties which were dependent on nanoZnO size and PDMS:nanoZnO ratio. Remarkably, the optimum effect was observed on the superhydrophobic coating based on 30 nm ZnO and 1:1 ratio. This displayed highest anticorrosion performance, and is therefore recommended as a guide for the design of marine topcoats. Copyright © 2017 Elsevier Inc. All rights reserved.

Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine

PubMed Central

Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

2016-01-01

A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications. PMID:27264995

One-step preparation of superhydrophobic acrylonitrile-butadiene-styrene copolymer coating for ultrafast separation of water-in-oil emulsions.

PubMed

Deng, Wanshun; Long, Mengying; Zhou, Qiannan; Wen, Ni; Deng, Wenli

2018-02-01

Superhydrophobic membranes with opposite wettability toward water and oil are able to separate water-in-oil emulsions. By constructing porous and hierarchal-structured superhydrophobic coating on filter paper, we hope a quick separation process could be achieved due to the acceleration of both demulsification and penetration process. Here, superhydrophobic coatings were prepared by simply spraying environmental and cost-effective acrylonitrile-butadiene-styrene copolymer (ABS) colloid in dichloromethane onto filter paper. The morphologies and wettability of the obtained coatings were carefully studied. Moreover, the separation performances in dealing with various surfactant-stabilized water-in-oil emulsions (SSWOE) were also investigated to verify our hypothesis. The morphologies of the ABS coatings varied with its weight concentration in dichloromethane and they changed from porous and plain surface into porous and hierarchal-structured surface. Besides, the hydrophobicity of the above coatings varied form hydrophobic to superhydrophobic. Moreover, the resulted superhydrophobic membranes show great separation capability in separating various span 80-stabilized water-in-oil emulsions with oil filtrate purities larger than 99.90% and huge penetration fluxes whose maximum is over 13,000L/(m 2 h). Thus, we envision that such membrane can be a practical candidate in dealing with water-in-oil emulsions to obtain pure oils. Copyright © 2017 Elsevier Inc. All rights reserved.

Antifouling Transparent ZnO Thin Films Fabricated by Atmospheric Pressure Cold Plasma Deposition

NASA Astrophysics Data System (ADS)

Suzaki, Yoshifumi; Du, Jinlong; Yuji, Toshifumi; Miyagawa, Hayato; Ogawa, Kazufumi

2015-09-01

One problem with outdoor-mounted solar panels is that power generation efficiency is reduced by face plate dirt; a problem with electronic touch panels is the deterioration of screen visibility caused by finger grease stains. To solve these problems, we should fabricate antifouling surfaces which have superhydrophobic and oil-repellent properties without spoiling the transparency of the transparent substrate. In this study, an antifouling surface with both superhydrophobicity and oil-repellency was fabricated on a glass substrate by forming a fractal microstructure. The fractal microstructure was constituted of transparent silica particles 100 nm in diameter and transparent zinc-oxide columns grown on silica particles through atmospheric pressure cold plasma deposition; the sample surface was coated with a chemically adsorbed monomolecular layer. Samples were obtained which had a superhydrophobic property (with a water droplet contact angle of more than 150°) and a high average transmittance of about 90% (with wavelengths ranging from 400 nm to 780 nm).

Multifunctional polymer nano-composite based superhydrophobic surface

NASA Astrophysics Data System (ADS)

Maitra, Tanmoy; Asthana, Ashish; Buchel, Robert; Tiwari, Manish K.; Poulikakos, Dimos

2014-11-01

Superhydrophobic surfaces become desirable in plethora of applications in engineering fields, automobile industry, construction industries to name a few. Typical fabrication of superhydrophobic surface consists of two steps: first is to create rough morphology on the substrate of interest, followed by coating of low energy molecules. However, typical exception of the above fabrication technique would be direct coating of functional polymer nanocomposites on substrate where superhydrophobicity is needed. Also in this case, the use of different nanoparticles in the polymer matrix can be exploited to impart multi-functional properties to the superhydrophobic coatings. Herein, different carbon nanoparticles like graphene nanoplatelets (GNP), carbon nanotubes (CNT) and carbon black (CB) are used in fluropolymer matrix to prepare superhydrophobic coatings. The multi-functional properties of coatings are enhanced by combining two different carbon fillers in the matrix. The aforementioned superhydrophobic coatings have shown high electrical conductivity and excellent droplet meniscus impalement resistance. Simultaneous superhydrophobic and oleophillic character of the above coating is used to separate mineral oil and water through filtration of their mixture. Swiss National Science Foundation (SNF) Grant 200021_135479.

Gas-driven ultrafast reversible switching of super-hydrophobic adhesion on palladium-coated silicon nanowires.

PubMed

Seo, Jungmok; Lee, Soonil; Han, Heetak; Jung, Hwae Bong; Hong, Juree; Song, Giyoung; Cho, Suk Man; Park, Cheolmin; Lee, Wooyoung; Lee, Taeyoon

2013-08-14

A gas-driven ultrafast adhesion switching of water droplets on palladium-coated Si nanowire arrays is demonstrated. By regulating the gas-ambient between the atmosphere and H2 , the super-hydrophobic adhesion is repeatedly switched between water-repellent and water-adhesive. The capability of modulating the super-hydrophobic adhesion on a super-hydrophobic surface with a non-contact mode could be applicable to novel functional lab-on-a-chip platforms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Durable superhydrophobic carbon soot coatings for sensor applications

NASA Astrophysics Data System (ADS)

Esmeryan, K. D.; Radeva, E. I.; Avramov, I. D.

2016-01-01

A novel approach for the fabrication of durable superhydrophobic (SH) carbon soot coatings used in quartz crystal microbalance (QCM) based gas or liquid sensors is reported. The method uses modification of the carbon soot through polymerization of hexamethyldisiloxane (HMDSO) by means of glow discharge RF plasma. The surface characterization shows a fractal-like network of carbon nanoparticles with diameter of ~50 nm. These particles form islands and cavities in the nanometer range, between which the plasma polymerized hexamethyldisiloxane (PPHMDSO) embeds and binds to the carbon chains and QCM surface. Such modified surface structure retains the hydrophobic nature of the soot and enhances its robustness upon water droplet interactions. Moreover, it significantly reduces the insertion loss and dynamic resistance of the QCM compared to the commonly used carbon soot/epoxy resin approach. Furthermore, the PPHMDSO/carbon soot coating demonstrates durability and no aging after more than 40 probing cycles in water based liquid environments. In addition, the surface layer keeps its superhydrophobicity even upon thermal annealing up to 540 °C. These experiments reveal an opportunity for the development of soot based SH QCMs with improved electrical characteristics, as required for high-resolution gas or liquid measurements.

Low-Cost and Scaled-Up Production of Fluorine-Free, Substrate-Independent, Large-Area Superhydrophobic Coatings Based on Hydroxyapatite Nanowire Bundles.

PubMed

Chen, Fei-Fei; Yang, Zi-Yue; Zhu, Ying-Jie; Xiong, Zhi-Chao; Dong, Li-Ying; Lu, Bing-Qiang; Wu, Jin; Yang, Ri-Long

2018-01-09

To date, the scaled-up production and large-area applications of superhydrophobic coatings are limited because of complicated procedures, environmentally harmful fluorinated compounds, restrictive substrates, expensive equipment, and raw materials usually involved in the fabrication process. Herein, the facile, low-cost, and green production of superhydrophobic coatings based on hydroxyapatite nanowire bundles (HNBs) is reported. Hydrophobic HNBs are synthesised by using a one-step solvothermal method with oleic acid as the structure-directing and hydrophobic agent. During the reaction process, highly hydrophobic C-H groups of oleic acid molecules can be attached in situ to the surface of HNBs through the chelate interaction between Ca 2+ ions and carboxylic groups. This facile synthetic method allows the scaled-up production of HNBs up to about 8 L, which is the largest production scale of superhydrophobic paint based on HNBs ever reported. In addition, the design of the 100 L reaction system is also shown. The HNBs can be coated on any substrate with an arbitrary shape by the spray-coating technique. The self-cleaning ability in air and oil, high-temperature stability, and excellent mechanical durability of the as-prepared superhydrophobic coatings are demonstrated. More importantly, the HNBs are coated on large-sized practical objects to form large-area superhydrophobic coatings. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Brochosomal coats turn leafhopper (Insecta, Hemiptera, Cicadellidae) integument to superhydrophobic state

PubMed Central

Rakitov, Roman; Gorb, Stanislav N.

2013-01-01

Leafhoppers (Insecta, Hemiptera, Cicadellidae) actively coat their integuments with brochosomes, hollow proteinaceous spheres of usually 200–700 nm in diameter, with honeycombed walls. The coats have been previously suggested to act as a water-repellent and anti-adhesive protective barrier against the insect's own exudates. We estimated their wettability through contact angle (CA) measurements of water, diiodomethane, ethylene glycol and ethanol on detached wings of the leafhoppers Alnetoidia alneti, Athysanus argentarius and Cicadella viridis. Intact brochosome-coated integuments were repellent to all test liquids, except ethanol, and exhibited superhydrophobicity, with the average water CAs of 165–172°, and the apparent surface free energy (SFE) estimates not exceeding 0.74 mN m−1. By contrast, the integuments from which brochosomes were removed with a peeling technique using fluid polyvinylsiloxane displayed water CAs of only 103–129° and SFEs above 20 mN m−1. Observations of water-sprayed wings in a cryo-scanning electron microscope confirmed that brochosomal coats prevented water from contacting the integument. Their superhydrophobic properties appear to result from fractal roughness, which dramatically reduces the area of contact with high-surface-tension liquids, including, presumably, leafhopper exudates. PMID:23235705

Roll-to-Roll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials.

PubMed

Dong, Shuliang; Wang, Zhenlong; Wang, Yukui; Bai, Xuelin; Fu, Yong Qing; Guo, Bin; Tan, Chaoliang; Zhang, Jia; Hu, PingAn

2018-01-17

Creating a robust superhydrophobic surface on the conventional engineering materials at mass production is of great importance for a self-cleaning, anti-icing, nonwetting surface and low flow resistance in industrial applications. Herein, we report a roll-to-roll strategy to create durable and robust superhydrophobic surfaces with designed micro-/nanoscale hierarchical structures on many conventional engineering materials by combining electrical discharge machining and coating of carbon nanoparticles, followed by oil penetration and drying. The treated surface shows good superhydrophobic properties with a static water contact angle of 170 ± 2° and slide angle of 3 ± 1°. The treated surface also exhibits good resilience and maintains the performance after being tested in various harsh conditions, including water flushing for several days, sand abrasion, scratching with sandpapers, and corrosive solution. Significantly, the superhydrophobic surfaces also show a high efficiency of self-cleaning properties even after oil contamination during applications.

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

(Super)hydrophobic coating of orthodontic dental devices and reduction of early oral biofilm retention.

PubMed

Oliveira, Adauê S; Kaizer, Marina R; Azevedo, Marina S; Ogliari, Fabrício A; Cenci, Maximiliano S; Moraes, Rafael R

2015-11-03

This study was designed to apply (super)hydrophobic crosslinked coatings by means of a sol-gel process on the surface of orthodontic devices and investigate the potential effect of these coatings in reducing the early retention of oral biofilm. Two organosilane-based hydrophobic solutions (HSs) were prepared containing hexadecyltrimethoxysilane diluted in ethanol (HS1) or 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane diluted in dimethyl sulfoxide (HS2). Stainless steel plates and ceramic discs were coated with HS1 or HS2 and heated at 150 °C for 2 h for condensation of a crosslinked SiO x network. Organosilane coatings were applied after previous, or no, surface sandblasting. Commercial stainless steel and ceramic brackets were used to evaluate oral biofilm retention after 12 h or 24 h of biofilm growth, using a microcosm model with human saliva as the inoculum. Surface roughness analysis (Ra, μm) indicated that sandblasting associated with organosilane coatings increased roughness for stainless steel brackets only. Analysis of the water contact angle showed that the stainless steel surface treated with HS1 was hydrophobic (~123°), while the ceramic surface treated with HS2 was superhydrophobic (~155°). Biofilm retention after 24 h was significantly lower in groups treated with hydrophobic coatings. An exponential reduction in biofilm accumulation was associated with increased water contact angle for both stainless steel and ceramic at 24 h. Application of (super)hydrophobic coatings on the surface of stainless steel and ceramic orthodontic devices might reduce the retention of oral biofilm.

Article coated with flash bonded superhydrophobic particles

DOEpatents

Simpson, John T [Clinton, TN; Blue, Craig A [Knoxville, TN; Kiggans, Jr., James O [Oak Ridge, TN

2010-07-13

A method of making article having a superhydrophobic surface includes: providing a solid body defining at least one surface; applying to the surface a plurality of diatomaceous earth particles and/or particles characterized by particle sizes ranging from at least 100 nm to about 10 .mu.m, the particles being further characterized by a plurality of nanopores, wherein at least some of the nanopores provide flow through porosity, the particles being further characterized by a plurality of spaced apart nanostructured features that include a contiguous, protrusive material; flash bonding the particles to the surface so that the particles are adherently bonded to the surface; and applying a hydrophobic coating layer to the surface and the particles so that the hydrophobic coating layer conforms to the nanostructured features.

Nano-micro structured superhydrophobic zinc coating on steel for prevention of corrosion and ice adhesion.

PubMed

Brassard, J D; Sarkar, D K; Perron, J; Audibert-Hayet, A; Melot, D

2015-06-01

Thin films of zinc have been deposited on steel substrates by electrodeposition process and further functionalized with ultra-thin films of commercial silicone rubber, in order to obtain superhydrophobic properties. Morphological feature, by scanning electron microscope (SEM), shows that the electrodeposited zinc films are composed of micro-nano rough patterns. Furthermore, chemical compositions of these films have been analyzed by X-ray diffraction (XRD) and infra-red (IRRAS). An optimum electrodeposition condition, based on electrical potential and deposition time, has been obtained which provides superhydrophobic properties with a water contact angle of 155±1°. The corrosion resistance properties, in artificial seawater, of the superhydrophobic zinc coated steel are found to be superior to bare steel. Similarly, the measured ice adhesion strength on superhydrophobic surfaces, using the centrifugal adhesion test (CAT), is found to be 6.3 times lower as compared to bare steel. This coating has promising applications in offshore environment, to mitigate corrosion and reduce ice adhesion. Copyright © 2014 Elsevier Inc. All rights reserved.

Super-hydrophobic graphene coated polyurethane (GN@PU) sponge with great oil-water separation performance

NASA Astrophysics Data System (ADS)

Zhang, Xiaotan; Liu, Dongyan; Ma, Yuling; Nie, Jing; Sui, Guoxin

2017-11-01

The graphene/polyurethane (GN@PU) sponge was prepared via simple dip-coating PU sponges in graphene aqueous suspension containing cellulose nanowhiskers (CNWs), where CNWs played a vital role to facilitate the uniform graphene sheets coated on the skeletons of polyurethane sponge (PU). The super-hydrophobic GN@PU sponge was obtained by optimizing the ratio of GN and CNWs to choose the final coating suspensions of GN/CNWs mixture or pure graphene. The GN@PU sponge showed densely packed graphene sheets, contributing super-hydrophobicity to the sponge with water contact angle of 152° and a large lubricating oil absorption value of 31 g g-1. The elasticity, mechanical durability, thermal and chemical stability were all found to be improved after coating with the thin GN layers. Moreover, the GN@PU sponges possess outstanding recyclability and stability since no decline in absorption efficiency was observed after more than 100 cycles.

Sprayable superhydrophobic nano-chains coating with continuous self-jumping of dew and melting frost

PubMed Central

Wang, Shanlin; Zhang, Wenwen; Yu, Xinquan; Liang, Caihua; Zhang, Youfa

2017-01-01

Spontaneous movement of condensed matter provides a new insight to efficiently improve condensation heat transfer on superhydrophobic surface. However, very few reports have shown the jumping behaviors on the sprayable superhydrophobic coatings. Here, we developed a sprayable silica nano-porous coating assembled by fluorinated nano-chains to survey the condensates’ dynamics. The dewdrops were continuously removed by self- and/or trigger-propelling motion due to abundant nano-pores from random multilayer stacking of nano-chains. In comparison, the dewdrops just could be slipped under the gravity effect on lack of nano-pores coatings stacked by silica nano-spheres and nano-aggregates. More interestingly, the spontaneous jumping effect also occurred on micro-scale frost crystals under the defrosting process on nano-chains coating surfaces. Different from self-jumping of dewdrops motion, the propelling force of frost crystals were provided by a sudden increase of the pressure under the frost crystal. PMID:28074938

One-way water permeable valve via water-based superhydrophobic coatings

NASA Astrophysics Data System (ADS)

Mates, Joseph E.; Megaridis, Constantine M.

2013-11-01

Spray-cast superhydrophobic coatings have shown promise in commercial applications for fluid management due to their intrinsic low-cost, large-area capabilities and substrate independence (Schutzius et al. 2011). A technique of applying a light (< 2 gsm) water-based superhydrophobic coating on inherently hydrophilic cellulosic substrates to generate a preferred directionality for water absorption and transmission is presented. The mechanism described allows water to pass through a thin treated porous substrate in one direction under negligible pressure, but does not allow water to return from the opposite direction unless much greater pressure is applied. This pressure disparity ``window'' effectively creates a one-way fluid valve, with envisioned applications ranging from personal hygiene products, to oil-water separation and filtration. Combining SEM imaging with theoretical robustness factors (Tuteja et al. 2008), the penetration pressures are found to be tunable for application-specific designs by choosing a substrate based on limiting factors of fiber diameter and spacing. The process can also be modified with the addition of functionalized (e.g. antibacterial, conductive) nanoparticle fillers suited for the desired application.

The super-hydrophobic IR-reflectivity TiO2 coated hollow glass microspheres synthesized by soft-chemistry method

NASA Astrophysics Data System (ADS)

Hu, Yan; Wang, Yuanhao; An, Zhenguo; Zhang, Jingjie; Yang, Hongxing

2016-11-01

The super-hydrophobic and IR-reflectivity hollow glass microspheres (HGM) was synthesized by being coated with anatase TiO2 and a super-hydrophobic material. The super-hydrophobic self-cleaning property prolong the life time of the IR reflectivity. TBT and PFOTES were firstly applied and hydrolyzed on HGM and then underwent hydrothermal reaction to synthesis anatase TiO2 film. For comparison, the PFOTES/TiO2 mutual-coated HGM (MCHGM), PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The MCHGM had bigger contact angle (153°) but smaller sliding angle (16°) than F-SCHGM (contact angle: 141.2°; sliding angle: 67°). Ti-SCHGM and MCHGM both showed similar IR reflectivity with ca. 5.8% increase compared with original HGM and F-SCHGM. For the thermal conductivity, coefficients of F-SCHGM (0.0479 W/(m K)) was basically equal to that of the original HGM (0.0475 W/(m K)). Negligible difference was found between the thermal conductivity coefficients of MCHGM-coated HGM (0.0543 W/(m K)) and Ti-SCHGM (0.0546 W/(m K)).

A sturdy self-cleaning and anti-corrosion superhydrophobic coating assembled by amino silicon oil modifying potassium titanate whisker-silica particles

NASA Astrophysics Data System (ADS)

Lv, Chongjiang; Wang, Huaiyuan; Liu, Zhanjian; Zhang, Wenbo; Wang, Chijia; Tao, Ruifeng; Li, Meiling; Zhu, Yanji

2018-03-01

A sturdy self-cleaning and anticorrosion superhydrophobic coating based on poly(phenylene sulfide) (PPS) matrix has been successfully fabricated by combination of sol-gel and spraying technology without using any fluorine materials. The prepared coating possessed excellent superhydrophobicity with the water contact angle (WCA) (161 ± 1.2)° and slide angle (SA) (2 ± 1.5)°, which was ascribed to the synergistic effect of low-surface energy material amino silicon oil (ASO) and the binary potassium titanate whisker-silica (PTW-SiO2) composite particles formed by in-situ growth of SiO2 on modified PTW via sol-gel. Moreover, The PPS/ASO/PTW-SiO2 superhydrophobic coating exhibited decent self-cleaning property with clean surface even after 100 times immersion in muddy solution. The abrasion test demonstrated that the mechanical stability of prepared coating was about 2 times of the pure PPS coating. Simultaneously, the potentiodynamic polarization and electrochemical impedance spectroscopy testified the excellent corrosion resistance of prepared coating with the performance of lower corrosion current (1.289 × 10-10 A/cm2) and high protection efficiency (99.999%) even after immersion in 3.5 wt.% NaCl solution for 28 days. It is believed that this sturdy self-cleaning and anti-corrosion superhydrophobic coating might have a promising application prospect in industry.

Improvement of mechanical robustness of the superhydrophobic wood surface by coating PVA/SiO2 composite polymer

NASA Astrophysics Data System (ADS)

Liu, Feng; Wang, Shuliang; Zhang, Ming; Ma, Miaolian; Wang, Chengyu; Li, Jian

2013-09-01

Improvement of the robustness of superhydrophobic surfaces is crucial for the purpose of achieving commercial applications of these surfaces in such various areas as self-cleaning, water repellency and corrosion resistance. We have investigated a fabrication of polyvinyl alcohol (PVA)/silica (SiO2) composite polymer coating on wooden substrates with super repellency toward water, low sliding angles, low contact angle hysteresis, and relatively better mechanical robustness. The composite polymer slurry, consisting of well-mixing SiO2 particles and PVA, is prepared simply and subsequently coated over wooden substrates with good adhesion. In this study, the mechanical robustness of superhydrophobic wood surfaces was evaluated. The effect of petaloid structures of the composite polymer on robustness was investigated using an abrasion test and the results were compared with those of superhydrophobic wood surfaces fabricated by other processes. The produced wood surfaces exhibited promising superhydrophobic properties with a contact angle of 159̊ and a sliding angle of 4̊, and the relatively better mechanical robustness.

Particle morphology dependent superhydrophobicity in treated diatomaceous earth/polystyrene coatings

NASA Astrophysics Data System (ADS)

Sedai, Bhishma R.; Alavi, S. Habib; Harimkar, Sandip P.; McCollum, Mark; Donoghue, Joseph F.; Blum, Frank D.

2017-09-01

Superhydrophobic surfaces have been prepared from three different types of diatomaceous earth (DE) particles treated with 3-(heptafluoroisopropoxy)propyltrimethoxysilane (HFIP-TMS) and low molecular mass polystyrene. The untreated particles, consisting of CelTix DE (disk shape), DiaFil DE (rod shape) and EcoFlat DE (irregular), were studied using particle size analysis, bulk density, pore volume and surface area analysis (via Brunauer-Emmett-Teller, BET, methods). The treated particles were characterized with thermogravimetric analysis (TGA), contact angles, scanning electron microscopy, profilometry, and FTIR spectroscopy. The minimum amount of silane coupling agent on the DE surfaces required to obtain superhydrophobicity of the particles was determined and found to be dependent on the particle morphology. In the coatings made from different particles with 2.4 wt% HFIP-TMS, the minimum amounts of treated particles (loadings) for superhydrophobicity was determined with the less dense CelTix DE requiring about 30 wt%, DiaFil DE requiring about 40 wt%, and EcoFlat DE each requiring about 60 wt% loading of treated particles.

Superhydrophobic coated apparatus for liquid purification by evaporative condensation

DOEpatents

Simpson, John T; McNeany, Steve R; Dinsmore, Thomas V; Hunter, Scott R; Ivanov, Ilia N

2014-03-11

Disclosed are examples of apparatuses for evaporative purification of a contaminated liquid. In each example, there is a first vessel for storing the contaminated fluid. The first vessel includes a surface coated with a layer of superhydrophobic material and the surface is at least partially in contact with the contaminated liquid. The contaminants do not adhere to the surface as the purified liquid evaporates, thus simplifying maintenance of the apparatus.

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.

Block Copolymer as a Surface Modifier to Monodisperse Patchy Silica Nanoparticles for Superhydrophobic Surfaces.

PubMed

Lou, Shuo; Wang, Junzheng; Yin, Xiaohong; Qu, Wenxiu; Song, Yuexiao; Xin, Feng; Qaraah, Fahim Abdo Ali

2018-06-18

Monodisperse patchy silica nanoparticles (PSNPs) less than 100 nm are prepared based on the seed-regrowth method using a poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO-type block copolymer as a surface modifier. Well-defined patches are controllably synthesized through area-selective deposition of silica onto the surface of seeds. After colloidal PSNPs are further modified with trimethylchlorosilane, the advancing and receding contact angles of water for PSNPs are 168 ± 2° and 167 ± 2°, respectively. The superhydrophobic and transparent coatings on the various types of substrates are obtained by a simple drop-casting procedure. Additionally, almost the same superhydrophobicity can be achieved by using colloidal PSNPs via redispersing the powder of superhydrophobic PSNPs in ethanol.

Super-hydrophobic coatings with nano-size roughness prepared with simple PECVD method

NASA Astrophysics Data System (ADS)

Choi, Yoon S.; Lee, Joon S.; Jin, Su B.; Han, Jeon G.

2013-08-01

A simple and conventional method to synthesize nearly flat super-hydrophobic coatings was studied. Conventional plasma enhanced chemical vapour deposition (PECVD) was adopted to synthesize hydrophobic coatings on plastic and glass substrates at room temperature. Hexamethyldisilane was used as a precursor, and hydrogen gas was added to modulate the surface roughness and passivate defects, such as dangling bond and electrically uncovered polar sites rendering non-hydrophobicity. The static water contact angle (WCA) was controlled in the range 120°-160° by adjusting process parameters, especially the hydrogen flow rate and power. AFM showed that the film with a WCA of 145° has as small as 2.5 nm roughness in rms value. In the resistance test of salt water and cosmetics, this film showed excellent results owing to super-hydrophobicity and defect passivation which keeps the surface isolated from external agents. In order to exploit these results, Rare gas analysis was used to examine the process plasma and Fourier transform infrared (FTIR) was used to analyse the chemical structures of the super-hydrophobic films. In the FTIR results, the remarkable increase in the modes of Si-Hx and Si-C bonds as well as Si-CH2-Si in the film was observed indicating the defect passivation and closely packed dense film structure.

Superhydrophobic ceramic coating: Fabrication by solution precursor plasma spray and investigation of wetting behavior.

PubMed

Xu, Pengyun; Coyle, Thomas W; Pershin, Larry; Mostaghimi, Javad

2018-08-01

Superhydrophobic surfaces are often created by fabricating suitable surface structures from low-surface-energy organic materials using processes that are not suitable for large-scale fabrication. Rare earth oxides (REO) exhibit hydrophobic behavior that is unusual among oxides. Solution precursor plasma spray (SPPS) deposition is a rapid, one-step process that can produce ceramic coatings with fine scale columnar structures. Manipulation of the structure of REO coatings through variation in deposition conditions may allow the wetting behavior to be controlled. Yb 2 O 3 coatings were fabricated via SPPS. Coating structure was investigated by scanning electron microscopy, digital optical microscopy, and x-ray diffraction. The static water contact angle and roll-off angle were measured, and the dynamic impact of water droplets on the coating surface recorded. Superhydrophobic behavior was observed; the best coating exhibited a water contact angle of ∼163°, a roll-off angle of ∼6°, and complete droplet rebound behavior. All coatings were crystalline Yb 2 O 3 , with a nano-scale roughness superimposed on a micron-scale columnar structure. The wetting behaviors of coatings deposited at different standoff distances were correlated with the coating microstructures and surface topographies. The self-cleaning, water flushing and water jetting tests were conducted and further demonstrated the excellent and durable hydrophobicity of the coatings. Copyright © 2018 Elsevier Inc. All rights reserved.

Dark, Infrared Reflective, and Superhydrophobic Coatings by Waterborne Resins.

PubMed

Zhang, Jing; Lin, Weiqiang; Zhu, Chenxi; Lv, Jian; Zhang, Weicheng; Feng, Jie

2018-05-15

Recently, infrared reflective pigments possessing deep colors have attracted much attention. However, in polluted air, the coatings consisting of such pigments are easily contaminated which abates infrared reflectivity. In this work, black and infrared reflective pigments, fluorine silicon sol and a small number of SiO 2 nanoparticles were introduced into waterborne epoxy resin emulsion and then coated on an aluminum plate. After drying, black coatings with infrared reflective and superhydrophobic (SH) properties were obtained. The average near-infrared (NIR) reflectivity of the coating over wavelength range of 780-2600 nm can reach 68%, which is much larger than that of carbon black coatings and even approaches that of white nano SiO 2 coatings. Under the irradiation of a 275-W infrared lamp (with height 40 cm), the surface temperature of the coating is 63 °C, which is much lower than that of the carbon black coating (90 °C) and only 7 °C higher than that of the white nano SiO 2 coating. Furthermore, the NIR reflective coating exhibited a typical SH property due to its low surface energy and high surface roughness, which may allow for self-cleaning performance in a practical environment, maintaining the coating's NIR reflective property.

Preparation of superhydrophobic coatings on zinc as effective corrosion barriers.

PubMed

Liu, Hongqin; Szunerits, Sabine; Xu, Wenguo; Boukherroub, Rabah

2009-06-01

Stable superhydrophobic films with a contact angle of 151 +/- 2 degrees were prepared on zinc substrates by a simple immersion technique into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltrichlorosilane [CF3(CF2)5(CH2)2SiCl3, PFTS] for 5 days at room temperature followed by a short annealing at 130 degrees C in air for 1 h. The superhydrophobic film provides an effective corrosion-resistant coating for the zinc interface when immersed in an aqueous solution of sodium chloride (3% NaCl) for up to 29 days. The corrosion process was investigated by following the change of the water contact angle over time and by electrochemical means. The results are compared to those of unprotected zinc interfaces.

Superhydrophobic aerogel that does not require per-fluoro compounds or contain any fluorine

DOEpatents

Kissel, David J.; Brinker, Charles Jeffrey

2015-05-26

Provided are superhydrophobic coatings, devices and articles including superhydrophobic coatings, and methods for preparing the superhydrophobic coatings. The exemplary superhydrophobic device can include a substrate component and one or more superhydrophobic coatings disposed over the substrate component, wherein at least one of the one or more superhydrophobic coatings has a water contact angle of at least about 150.degree. and a contact angle hysteresis of less than about 1.degree.. The one or more superhydrophobic coatings can include an ultra high water content acid catalyzed polysilicate gel, the polysilicate gel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

Improved performance of Mg-Y alloy thin film switchable mirrors after coating with a superhydrophobic surface

NASA Astrophysics Data System (ADS)

La, Mao; Zhou, Huaijuan; Li, Ning; Xin, Yunchuan; Sha, Ren; Bao, Shanhu; Jin, Ping

2017-05-01

The magnesium based switchable mirrors can reversibly change their optical properties between the transparent and the reflective state as a result of hydrogenation and dehydrogenation. These films can potentially be applied as new energy-saving windows, by controlling the transmittance of solar radiation through the regulation of their reflective state. In this study, magnesium-yttrium (Mg-Y) alloy thin films were prepared using a DC magnetron sputtering method. However, the luminous transmittance in the transparent state and the switching durability of switchable mirrors are too poor to satisfy practical demands. In order to improve the films switching durability, luminous transmittance and the surface functionalization, polytetrafluoroethylene (PTFE) was coated with thermal vacuum deposition for use as the top layer of Mg-Y/Pd switchable mirrors. The PTFE layer had a porous network structure and exhibited a superhydrophobic surface with a water contact angle of approximately 152°. By characterization, PTFE thin films shows the excellent protection role against the oxidization of Mg, the switching durability of the films were improved 3 times, and also shows the antireflection role the luminous transmission of films was enhanced by 7% through the top covered with PTFE.

Transparent conductive coatings

NASA Technical Reports Server (NTRS)

Ashok, S.

1983-01-01

Thin film transparent conductors are discussed. Materials with electrical conductivity and optical transparency are highly desirable in many optoelectronic applications including photovoltaics. Certain binary oxide semiconductors such as tin oxide (SnO2) and indium oxide (In2O3) offer much better performance tradeoff in optoelectronics as well as better mechanical and chemical stability than thin semitransparent films. These thin-film transparent conductors (TC) are essentially wide-bandgap degenerate semiconductors - invariably n-type - and hence are transparent to sub-bandgap (visible) radiation while affording high electrical conductivity due to the large free electron concentration. The principal performance characteristics of TC's are, of course, electrical conductivity and optical transmission. The TC's have a refractive index of around 2.0 and hence act as very efficient antireflection coatings. For using TC's in surface barrier solar cells, the photovoltaic barrier is of utmost importance and so the work function or electron affinity of the TC is also a very important material parameter. Fabrication processes are discussed.

Synthesis of polymeric fluorinated sol-gel precursor for fabrication of superhydrophobic coating

NASA Astrophysics Data System (ADS)

Li, Qianqian; Yan, Yuheng; Yu, Miao; Song, Botao; Shi, Suqing; Gong, Yongkuan

2016-03-01

A fluorinated polymeric sol-gel precursor (PFT) is synthesized by copolymerization of 2,3,4,5,5,5-hexafluoro-2,4-bis(trifluorinated methyl)pentyl methacrylate (FMA) and 3-methacryloxypropyltrimethoxysilane (TSMA) to replace the expensive long chain fluorinated alkylsilanes. The fluorinated silica sol is prepared by introducing PFT as co-precursor of tetraethyl orthosilicate (TEOS) in the sol-gel process with ammonium hydroxide as catalyst, which is then used to fabricate superhydrophobic coating on glass substrate through a simple dip-coating method. The effects of PFT concentrations on the chemical structure of the formed fluorinated silica, the surface chemical composition, surface morphology, wetting and self-cleaning properties of the resultant fluorinated silica coatings were studied by using X-ray powder diffraction (XRD), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrophotometer (XPS), scanning electron microscopy (SEM) and water contact angle measurements (WCA). The results show that the fluorinated silica sols are successfully obtained. The size and size distribution of the fluorinated silica particles are found greatly dependent on the concentration of PFT, which play a crucial role in the surface morphology of the corresponding fluorinated silica coatings. The suitable PFT concentration added in the sol-gel stage, i.e. for F-sol-1 and F-sol-2, is helpful to achieve both the low surface energy and multi-scaled microstructures, leading to the formation of the superhydrophobic coatings with bio-mimicking self-cleaning property similar to lotus leaves.

Constructing a superhydrophobic surface on polydimethylsiloxane via spin coating and vapor-liquid sol-gel process.

PubMed

Peng, Yu-Ting; Lo, Kuo-Feng; Juang, Yi-Je

2010-04-06

In this study, a superhydrophobic surface on polydimethylsiloxane (PDMS) substrate was constructed via the proposed vapor-liquid sol-gel process in conjunction with spin coating of dodecyltrichlorosilane (DTS). Unlike the conventional sol-gel process where the reaction takes place in the liquid phase, layers of silica (SiO(2)) particles were formed through the reaction between the reactant spin-coated on the PDMS surface and vapor of the acid solution. This led to the SiO(2) particles inlaid on the PDMS surface. Followed by subsequent spin coating of DTS solution, the wrinkle-like structure was formed, and the static contact angle of the water droplet on the surface could reach 162 degrees with 2 degrees sliding angle and less than 5 degrees contact angle hysteresis. The effect of layers of SiO(2) particles, concentrations of DTS solution and surface topography on superhydrophobicity of the surface is discussed.

Influence of the type of solvent on the development of superhydrophobicity from silane-based solution containing nanoparticles

NASA Astrophysics Data System (ADS)

Pantoja, M.; Abenojar, J.; Martinez, M. A.

2017-03-01

Superhydrophobic surfaces are very appealing for numerous industrial applications due to their self-cleaning capacity. Although there are different methods to manufacture superhydrophobic surfaces, some of them do not keep the aesthetic appearance of the neat surface. Sol-gel processes are a valid alternative when transparent coatings are desired. The main goal of this research is to study the viability of this method by making superhydrophobic coatings from silane-based solution containing SiO2 nanoparticles. The effect of using different solvents is investigated, as well as the role played by the different components of the solution (silane, nanoparticles and solvent). Solutions of methyltrimethoxisilane (MTS) and tetraethoxysilane (TEOS) and 1% of SiO2 (%wt) were prepared with different solvents (ethanol, ethanol/water and white spirit). The hydrophobicity of the developed coatings is studied using contact angle measurements, while the aesthetic appearance is evaluated with gloss and color measurements. Also, infrared spectroscopy, dynamic light scattering (DSL), and surface tension measurements are used to study the silane solutions. The results show that the capacity of solvents to promote the dispersion of the nanoparticles is crucial to ensuring superhydrophobicity, since these agglomerates provide the micro- and nano- surface roughness required to get a hierarchical structure. However, the combined use of silanes and nanoparticles is key to make a superhydrophobic surface because physical (the surface roughness provided by nanoparticles) and chemical characteristics (hydrophobicity provided by silanes) are coupled.

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.

Bioinspired Superhydrophobic Highly Transmissive Films for Optical Applications.

PubMed

Vüllers, Felix; Gomard, Guillaume; Preinfalk, Jan B; Klampaftis, Efthymios; Worgull, Matthias; Richards, Bryce; Hölscher, Hendrik; Kavalenka, Maryna N

2016-11-01

Inspired by the transparent hair layer on water plants Salvinia and Pistia, superhydrophobic flexible thin films, applicable as transparent coatings for optoelectronic devices, are introduced. Thin polymeric nanofur films are fabricated using a highly scalable hot pulling technique, in which heated sandblasted steel plates are used to create a dense layer of nano- and microhairs surrounding microcavities on a polymer surface. The superhydrophobic nanofur surface exhibits water contact angles of 166 ± 6°, sliding angles below 6°, and is self-cleaning against various contaminants. Additionally, subjecting thin nanofur to argon plasma reverses its surface wettability to hydrophilic and underwater superoleophobic. Thin nanofur films are transparent and demonstrate reflection values of less than 4% for wavelengths ranging from 300 to 800 nm when attached to a polymer substrate. Moreover, used as translucent self-standing film, the nanofur exhibits transmission values above 85% and high forward scattering. The potential of thin nanofur films for extracting substrate modes from organic light emitting diodes is tested and a relative increase of the luminous efficacy of above 10% is observed. Finally, thin nanofur is optically coupled to a multicrystalline silicon solar cell, resulting in a relative gain of 5.8% in photogenerated current compared to a bare photovoltaic device. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of superhydrophobic alumina membrane: Effects of sol-gel coating, steam impingement and water treatment

NASA Astrophysics Data System (ADS)

Ahmad, N. A.; Leo, C. P.; Ahmad, A. L.

2013-11-01

Ceramic membranes possess natural hydrophilicity thus tending to absorb water droplets. The absorption of water molecules on membrane surface reduces their application in filtration, membrane distillation, osmotic evaporation and membrane gas absorption. Fluoroalkylsilane (FAS) grafting allows the conversion of hydrophilic ceramic membranes into superhydrophobic thin layer, but it usually introduces a great increment of mass transfer resistance. In this study, superhydrophobic alumina membranes were synthesized by dip coating alumina support into sol-gel and grafted with the fluoroalkylsilane (FAS) named (heptadecafluoro-1,1,2,2-tetra hydrodecyl) triethoxysilane. Steam impingement and water treatment acted as additional steps to generate surface roughness on sol-gel and most importantly to reduce mass transfer resistance. Superhydrophobic alumina membrane with high water contact angle (158.4°) and low resistance (139.5 ± 24.9 G m-1) was successfully formed when the alumina membrane was dip coated into sol-gel for 7 s, treated with steam impingement for 1 min and immersed in hot water at 100 °C. However, the mass transfer resistance was greatly induced to 535.6 ± 23.5 G m-1 when the dip coating time was increased to 60 s. Long dip coating time contributes more on the blockage of porous structure rather than creates a thin film on the top of membrane surface. Reducing the pore size and porosity significantly due to increase of coating molecules deposited on the membrane. Steam impingement for 1 min promoted the formation of cones and valleys on the sol-gel, but the macro-roughness was destroyed when the steam impingement duration was extended to more than 3 min. The immersions of membranes into hot water at temperatures higher than 60 °C encouraged the formation of boehmite which enhances the formation of additional roughness and enlarges pore size greatly. Thus, this work showed that the formation of superhydrophobic alumina membrane with low resistance is

Fabrication of superhydrophobic surfaces based on ZnO-PDMS nanocomposite coatings and study of its wetting behaviour

NASA Astrophysics Data System (ADS)

Chakradhar, R. P. S.; Kumar, V. Dinesh; Rao, J. L.; Basu, Bharathibai J.

2011-08-01

Superhydrophobic surfaces based on ZnO-PDMS nanocomposite coatings are demonstrated by a simple, facile, time-saving, wet chemical route. ZnO nanopowders with average particle size of 14 nm were synthesized by a low temperature solution combustion method. Powder X-ray diffraction results confirm that the nanopowders exhibit hexagonal wurtzite structure and belong to space group P63 mc. Field emission scanning electron micrographs reveal that the nanoparticles are connected to each other to make large network systems consisting of hierarchical structure. The as formed ZnO coating exhibits wetting behaviour with Water Contact Angle (WCA) of ˜108°, however on modification with polydimethylsiloxane (PDMS), it transforms to superhydrophobic surface with measured contact and sliding angles for water at 155° and less than 5° respectively. The surface properties such as surface free energy ( γp), interfacial free energy ( γpw), and the adhesive work ( Wpw) were evaluated. Electron paramagnetic resonance (EPR) studies on superhydrophobic coatings revealed that the surface defects play a major role on the wetting behaviour. Advantages of the present method include the cheap and fluorine-free raw materials, environmentally benign solvents, and feasibility for applying on large area of different substrates.

Underwater drag-reducing effect of superhydrophobic submarine model.

PubMed

Zhang, Songsong; Ouyang, Xiao; Li, Jie; Gao, Shan; Han, Shihui; Liu, Lianhe; Wei, Hao

2015-01-01

To address the debates on whether superhydrophobic coatings can reduce fluid drag for underwater motions, we have achieved an underwater drag-reducing effect of large superhydrophobic submarine models with a feature size of 3.5 cm × 3.7 cm × 33.0 cm through sailing experiments of submarine models, modified with and without superhydrophobic surface under similar power supply and experimental conditions. The drag reduction rate reached as high as 15%. The fabrication of superhydrophobic coatings on a large area of submarine model surfaces was realized by immobilizing hydrophobic copper particles onto a precross-linked polydimethylsiloxane (PDMS) surface. The pre-cross-linking time was optimized at 20 min to obtain good superhydrophobicity for the underwater drag reduction effect by investigating the effect of pre-cross-linking on surface wettability and water adhesive property. We do believe that superhydrophobic coatings may provide a promising application in the field of drag-reducing of vehicle motions on or under the water surface.

Super-hydrophobic multilayer coatings with layer number tuned swapping in surface wettability and redox catalytic anti-corrosion application.

PubMed

Syed, Junaid Ali; Tang, Shaochun; Meng, Xiangkang

2017-06-30

The wetting characteristic of a metal surface can be controlled by employing different coating materials and external stimuli, however, layer number (n) modulated surface swapping between hydrophobicity and hydrophilicity in a multilayer structure to achieve prolonged anti-corrosion ability was not taken into consideration. In this study, we proposed a layer-by-layer (LbL) spin assembled polyaniline-silica composite/tetramethylsilane functionalized silica nanoparticles (PSC/TMS-SiO 2 ) coating with the combined effect of super-hydrophobicity and enhanced anti-corrosion ability. Interestingly, the hierarchical integration of two coating materials with inherently different surface roughness and energy in a multilayer structure allows the wetting feature to swap from hydrophobic to hydrophilic state by modulating n with decreasing hydrophilicity. The samples with odd n (TMS-SiO 2 surface) are hydrophobic while the samples with even n (PSC surface) exhibits the hydrophilic character. The TMS-SiO 2 content was optimized to achieve super-hydrophobic coating with significantly high water contact angle (CA) 153° ± 2° and small sliding angle (SA) 6° ± 2°. Beside its self-cleaning behavior, the electro-active PSC/TMS-SiO 2 coating also exhibits remarkably enhanced corrosion resistance against aggressive media. The corrosion resistance of the coating was remained stable even after 240 h of exposure, this enhancement is attributed to super-hydrophobicity and anodic shift in corrosion potential.

Robust, heat-resistant and multifunctional superhydrophobic coating of carbon microflowers with molybdenum trioxide nanoparticles.

PubMed

Wu, Yang; Zhao, Meiyun; Guo, Zhiguang

2017-11-15

Superhydrophobic materials have triggered large interest due to their widespread applications, such as self-cleaning, corrosion resistance, anti-icing, and oil/water separation. However, suffering from weak mechanical strength, plenty of superhydrophobic materials are limited in practical application. Herein, we prepared hierarchical carbon microflowers (CMF) dispersed with molybdenum trioxide (MoO 3 ) nanoparticles (MoO 3 /CMF) via a two-step preparation method. Taking advantage of high-adhesion epoxy resin and the modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PDES), the modified MoO 3 /CMF (PDES-MoO 3 /CMF) coating on various substrates shows great waterproof ability, excellent chemical stability, good mechanical durability, and self-cleaning property. More significantly, the prepared PDES-MoO 3 /CMF powder with high thermal stability (250°C) can be used for oil/water separation due to its special flower-like structure and superhydrophobicity/superoleophilicity. All of these advantages endow the superhydrophobic powders with huge potential in the practical applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Structuring of Functional Spider Silk Wires, Coatings, and Sheets by Self-Assembly on Superhydrophobic Pillar Surfaces.

PubMed

Gustafsson, Linnea; Jansson, Ronnie; Hedhammar, My; van der Wijngaart, Wouter

2018-01-01

Spider silk has recently become a material of high interest for a large number of biomedical applications. Previous work on structuring of silk has resulted in particles (0D), fibers (1D), films (2D), and foams, gels, capsules, or microspheres (3D). However, the manufacturing process of these structures is complex and involves posttreatment of chemicals unsuitable for biological applications. In this work, the self-assembly of recombinant spider silk on micropatterned superhydrophobic surfaces is studied. For the first time, structuring of recombinant spider silk is achieved using superhydrophobic surfaces under conditions that retain the bioactivity of the functionalized silk. By tuning the superhydrophobic surface geometry and the silk solution handling parameters, this approach allows controlled generation of silk coatings, nanowires, and sheets. The underlying mechanisms and governing parameters are discussed. It is believed that the results of this work pave the way for fabrication of silk formations for applications including vehicles for drug delivery, optical sensing, antimicrobial coatings, and cell culture scaffolds. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of durable fluorine-free superhydrophobic polyethersulfone (PES) composite coating enhanced by assembled MMT-SiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Zhang, Xiguang; Wang, Huaiyuan; Liu, Zhanjian; Zhu, Yixing; Wu, Shiqi; Wang, Chijia; Zhu, Yanji

2017-02-01

A durable fluorine-free polyethersulfone (PES) superhydrophobic composite coating with excellent wear-resistant and anti-corrosion properties has been successfully fabricated by combining sol-gel and spray technology. The robust micro/nano-structures of the prepared surface were established by introducing binary montmorillonite-silica (MMT-SiO2) assembled composite particles, which were formed by in-situ growth of SiO2 on MMT surfaces via sol-gel. Combined with the low surface energy of amino silicon oil (APDMS), the fluorine-free superhydrophoic PES coating was obtained with high water contact angle 156.1 ± 1.1° and low sliding angle 4.8 ± 0.7°. The anti-wear of the final PES/APDMS/MMT-SiO2 superhydrophobic coating can reach up to 60,100 cycles, which is outdistancing the pure PES coating (6800 cycles) and the PES/MMT/SiO2 coating prepared by simple physical mixture (18,200 cycles). The enhanced wear resistance property can be mainly attributed to the lubrication performance of APDMS and stable interface bonding force between the MMT surface and SiO2. Simultaneously, potentiodynamic polarization curves and electrochemical impedance spectroscopy exhibited the outstanding anti-corrosion property of PES/APDMS/MMT-SiO2 composite coating, with low corrosion current (1.6 × 10-10 A/cm2) and high protection efficiency (99.999%) even after 30 d immersion process. These test results show that this durable superhydrophobic PES composite coating can be hopefully to provide the possibility of industrial application.

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.

Characteristics and self-cleaning effect of the transparent super-hydrophobic film having nanofibers array structures

NASA Astrophysics Data System (ADS)

Lee, Kyungjun; Lyu, Sungnam; Lee, Sangmin; Kim, Youn Sang; Hwang, Woonbong

2010-09-01

Transparent super-hydrophobic films were fabricated using the PDMS method and silane process, based on anodization in phosphoric acid. Contact angle tests were performed to determine the contact angle of each film according to the anodizing time. Transmittance tests also were performed to obtain the transparency of each TPT (trimethylolpropane propoxylate triacrylate) replica film according to the anodizing time. The contact angle was determined by studying the drop shape, and the transmittance was measured using a UV-spectrometer. The contact angle increases with increasing anodizing time, because increasing pillar length can trap more air between the TPT replica film and a drop of water. The transmittance falls with increasing anodizing time because the increasing pillar length causes a scattering effect. This study shows that the pillar length and transparency are inversely proportional. The TPT replica film having nanofibers array structures was better than other films in aspect of self-cleaning by doing quantitative experimentation.

Super-Hydrophobic Green Corrosion Inhibitor On Carbon Steel

NASA Astrophysics Data System (ADS)

Hassan, H.; Ismail, A.; Ahmad, S.; Soon, C. F.

2017-06-01

There are many examples of organic coatings used for corrosion protection. In particular, hydrophobic and super-hydrophobic coatings are shown to give good protection because of their enhanced ability to slow down transport of water and ions through the coating. The purpose of this research is to develop water repellent coating to avoid direct contact between metal and environment corrosive and mitigate corrosion attack at pipeline system. This water repellent characteristic on super-hydrophobic coating was coated by electrodeposition method. Wettability of carbon steel with super-hydrophobic coating (cerium chloride and myristic acid) and oxidized surface was investigated through contact angle and inhibitor performance test. The inhibitor performance was studied in 25% tannin acid corrosion test at 30°C and 3.5% sodium chloride (NaCl). The water contact angle test was determined by placing a 4-μL water droplet of distilled water. It shows that the wettability of contact angle super-hydrophobic with an angle of 151.60° at zero minute can be classified as super-hydrophobic characteristic. By added tannin acid as inhibitor the corrosion protection on carbon steel becomes more consistent. This reveals that the ability of the coating to withstand with the corrosion attack in the seawater at different period of immersions. The results elucidate that the weight loss increased as the time of exposure increased. However, the corrosion rates for uncoated carbon steel is high compared to coated carbon steel. As a conclusion, from both samples it can be seen that the coated carbon steel has less corrosion rated compared to uncoated carbon steel and addition of inhibitor to the seawater provides more protection to resist corrosion attack on carbon steel.

Facile preparation of super durable superhydrophobic materials.

PubMed

Wu, Lei; Zhang, Junping; Li, Bucheng; Fan, Ling; Li, Lingxiao; Wang, Aiqin

2014-10-15

The low stability, complicated and expensive fabrication procedures seriously hinder practical applications of superhydrophobic materials. Here we report an extremely simple method for preparing super durable superhydrophobic materials, e.g., textiles and sponges, by dip coating in fluoropolymers (FPs). The morphology, surface chemical composition, mechanical, chemical and environmental stabilities of the superhydrophobic textiles were investigated. The results show how simple the preparation of super durable superhydrophobic textiles can be! The superhydrophobic textiles outperform their natural counterparts and most of the state-of-the-art synthetic superhydrophobic materials in stability. The intensive mechanical abrasion, long time immersion in various liquids and repeated washing have no obvious influence on the superhydrophobicity. Water drops are spherical in shape on the samples and could easily roll off after these harsh stability tests. In addition, this simple dip coating approach is applicable to various synthetic and natural textiles and can be easily scaled up. Furthermore, the results prove that a two-tier roughness is helpful but not essential with regard to the creation of super durable superhydrophobic textiles. The combination of microscale roughness of textiles and materials with very low surface tension is enough to form super durable superhydrophobic textiles. According to the same procedure, superhydrophobic polyurethane sponges can be prepared, which show high oil absorbency, oil/water separation efficiency and stability. Copyright © 2014 Elsevier Inc. All rights reserved.

Superhydrophobic coating (2008 R&D 100 winner)

ScienceCinema

Jeff Brinker

2017-12-09

A transparent coating that is not just impermeable to water, but actually makes it bounce off a surface to help prevent corrosion, protect electronic and antiquities, or provide a new, more efficient surface to collect pure water. 2008 R&D 100 winner (SAND2008-2215W)

Reduced platelet adhesion and improved corrosion resistance of superhydrophobic TiO₂-nanotube-coated 316L stainless steel.

PubMed

Huang, Qiaoling; Yang, Yun; Hu, Ronggang; Lin, Changjian; Sun, Lan; Vogler, Erwin A

2015-01-01

Superhydrophilic and superhydrophobic TiO2 nanotube (TNT) arrays were fabricated on 316L stainless steel (SS) to improve corrosion resistance and hemocompatibility of SS. Vertically-aligned superhydrophilic amorphous TNTs were fabricated on SS by electrochemical anodization of Ti films deposited on SS. Calcination was carried out to induce anatase phase (superhydrophilic), and fluorosilanization was used to convert superhydrophilicity to superhydrophobicity. The morphology, structure and surface wettability of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and contact angle goniometry. The effects of surface wettability on corrosion resistance and platelet adhesion were investigated. The results showed that crystalline phase (anatase vs. amorphous) and wettability strongly affected corrosion resistance and platelet adhesion. The superhydrophilic amorphous TNTs failed to protect SS from corrosion whereas superhydrophobic amorphous TNTs slightly improved corrosion resistance of SS. Both superhydrophilic and superhydrophobic anatase TNTs significantly improved corrosion resistance of SS. The superhydrophilic amorphous TNTs minimized platelet adhesion and activation whereas superhydrophilic anatase TNTs activated the formation of fibrin network. On the contrary, both superhydrophobic TNTs (superhydrophobic amorphous TNTs and superhydrophobic anatase TNTs) reduced platelet adhesion significantly and improved corrosion resistance regardless of crystalline phase. Superhydrophobic anatase TNTs coating on SS surface offers the opportunity for the application of SS as a promising permanent biomaterial in blood contacting biomedical devices, where both reducing platelets adhesion/activation and improving corrosion resistance can be effectively combined. Copyright © 2014 Elsevier B.V. All rights reserved.

Fabrication of Water Jet Resistant and Thermally Stable Superhydrophobic Surfaces by Spray Coating of Candle Soot Dispersion.

PubMed

Qahtan, Talal F; Gondal, Mohammed A; Alade, Ibrahim O; Dastageer, Mohammed A

2017-08-08

A facile synthesis method for highly stable carbon nanoparticle (CNP) dispersion in acetone by incomplete combustion of paraffin candle flame is presented. The synthesized CNP dispersion is the mixture of graphitic and amorphous carbon nanoparticles of the size range of 20-50 nm and manifested the mesoporosity with an average pore size of 7 nm and a BET surface area of 366 m 2 g -1 . As an application of this material, the carbon nanoparticle dispersion was spray coated (spray-based coating) on a glass surface to fabricate superhydrophobic (water contact angle > 150° and sliding angle < 10 °) surfaces. The spray coated surfaces were found to exhibit much improved water jet resistance and thermal stability up to 400 °C compared to the surfaces fabricated from direct candle flame soot deposition (candle-based coating). This study proved that water jet resistant and thermally stable superhydrophobic surfaces can be easily fabricated by simple spray coating of CNP dispersion gathered from incomplete combustion of paraffin candle flame and this technique can be used for different applications with the potential for the large scale fabrication.

Fluoroalkyl silane modified silicone rubber/nanoparticle composite: a super durable, robust superhydrophobic fabric coating.

PubMed

Zhou, Hua; Wang, Hongxia; Niu, Haitao; Gestos, Adrian; Wang, Xungai; Lin, Tong

2012-05-08

A superhydrophobic fabric coating made of a crosslinked polydimethylsiloxane elastomer, containing well-dispersed hydrophobic silica nanoparticles and fluorinated alkyl silane, shows remarkable durability against repeated machine washes, severe abrasion, strong acid or base, boiling water or beverages and excellent stain resistance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of Superhydrophobic Properties on Deicing

NASA Astrophysics Data System (ADS)

Nazhipkyzy, M.; Mansurov, Z. A.; Amirfazli, A.; Esbosin, A.; Temirgaliyeva, T. S.; Lesbayev, B. T.; Aliyev, E. T.; Prikhodko, N. G.

2016-11-01

Nowadays the creation of anti-icing, or deicing, surfaces is one of the most important problems, as such surfaces are widely used in aeronautics, wind turbines, and telecommunication antennas. In this paper, we focus mainly on reducing the ice adhesion forces and easy ice removal, once ice has formed. Removal of a liquid from a surface can be provided by modification of the surface wettability by means of applying superhydrophobic coatings. Such coatings are water-resistant, i.e., are characterized by low water adhesion forces. To study the impact of superhydrophobic coatings, tests were performed on the surface of a wing in a wind tunnel. By spraying Teflon and polyphenylene sulfide (PPS) on the wing, we obtained a superhydrophobic film. This film has a structure that provides superhydrophobic properties, so that the wetting angle is above 140°. A comparison of the resulting surface with a clean Teflon one shows that adhesion of the Teflon + PPS mixture to an aluminum surface is five times higher. We also investigate the degree of ice formation on the surfaces of simple and superhydrophobic aircraft wings at a temperature of -18°C. It was shown that ice was formed on a simple wing within 40 s and on a superhydrophobic wing within 25 s. When the simple wing with a mass of 23 g was inserted into the wind tunnel, its mass reached 50 g, and for a superhydrophobic wing with a mass of 26 g the latter reached 42 g. The sample of the airfoil wing we prepared has a low adhesion, which helps in easy ice removal.

Bulk water freezing dynamics on superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Chavan, S.; Carpenter, J.; Nallapaneni, M.; Chen, J. Y.; Miljkovic, N.

2017-01-01

In this study, we elucidate the mechanisms governing the heat-transfer mediated, non-thermodynamic limited, freezing delay on non-wetting surfaces for a variety of characteristic length scales, Lc (volume/surface area, 3 mm < Lc < 6 mm) using carefully designed freezing experiments in a temperature-controlled, zero-humidity environment on thin water slabs. To probe the effect of surface wettability, we investigated the total time for room temperature water to completely freeze into ice on superhydrophilic ( θaapp→ 0°), hydrophilic (0° < θa < 90°), hydrophobic (90° < θa < 125°), and superhydrophobic ( θaapp→ 180°) surfaces. Our results show that at macroscopic length scales, heat conduction through the bulk water/ice layer dominates the freezing process when compared to heat conduction through the functional coatings or nanoscale gaps at the superhydrophobic substrate-water/ice interface. In order to verify our findings, and to determine when the surface structure thermal resistance approaches the water/ice resistance, we fabricated and tested the additional substrates coated with commercial superhydrophobic spray coatings, showing a monotonic increase in freezing time with coating thickness. The added thermal resistance of thicker coatings was much larger than that of the nanoscale superhydrophobic features, which reduced the droplet heat transfer and increased the total freezing time. Transient finite element method heat transfer simulations of the water slab freezing process were performed to calculate the overall heat transfer coefficient at the substrate-water/ice interface during freezing, and shown to be in the range of 1-2.5 kW/m2K for these experiments. The results shown here suggest that in order to exploit the heat-transfer mediated freezing delay, thicker superhydrophobic coatings must be deposited on the surface, where the coating resistance is comparable to the bulk water/ice conduction resistance.

Facile fabrication of superhydrophobic films with fractal structures using epoxy resin microspheres

NASA Astrophysics Data System (ADS)

Quan, Yun-Yun; Zhang, Li-Zhi

2014-02-01

A simple method has been developed to fabricate superhydrophobic surfaces with fractal structures with epoxy resin microspheres (ERMs). The ERMs is produced by phase separation in an epoxy-amine curing system with a silica sol (SS) dispersant. The transparent epoxy solution becomes cloudy and turns into epoxy suspension (ES) in this process. The fractal structure (two tier structure) generated by synthetic epoxy resin microspheres (ERMs) and deposited nanoincrutations on the surfaces of these ERMs, which have been observed by scanning electron microscope (SEM). The curing time of ES is an important condition to obtain films with good comprehensive performances. Superhydrophobic films can be prepared by adding extra SS into ES with a curing time longer than 5 h. The optimal curing time is 10 h to fabricate a film with good mechanical stability and high superhydrophobicity. In addition, a surface with anti-wetting property of impacting microdroplets can be fabricated by prolonging the curing time of ES to 24 h. The gradually decreased hydrophilic groups resulted from a longer curing time enable the surface to have smaller surface adhesions to water droplets, which is the main reason to keep its superhydrophobicity under impacting conditions. The coated surface is highly hydrophobic and the impacting water droplets are bounced off from the surface.

A Thermochromic Superhydrophobic Surface

PubMed Central

Cataldi, Pietro; Bayer, Ilker S.; Cingolani, Roberto; Marras, Sergio; Chellali, Ryad; Athanassiou, Athanassia

2016-01-01

Highly enhanced solid-state thermochromism is observed in regioregular poly(3-hexylthiophene), P3HT, when deposited on a superhydrophobic polymer-SiO2 nanocomposite coating. The conformal P3HT coating on the nanocomposite surface does not alter or reduce superhydrophicity while maintaining its reversible enhanced thermochromism. The polymeric matrix of the superhydrophobic surface is comprised of a blend of poly(vinylidene fluoride-co-hexafluoropropylene) copolymer and an acrylic adhesive. Based on detailed X-ray diffraction measurements, this long-lasting, repeatable and hysteresis-free thermochromic effect is attributed to the enhancement of the Bragg peak associated with the d-spacing of interchain directional packing (100) which remains unaltered during several heating-cooling cycles. We propose that the superhydrophobic surface confines π–π interchain stacking in P3HT with uniform d-spacing into its nanostructured texture resulting in better packing and reduction in face-on orientation. The rapid response of the system to sudden temperature changes is also demonstrated by water droplet impact and bounce back on heated surfaces. This effect can be exploited for embedded thin film temperature sensors for metal coatings. PMID:27301422

Transparent nanocrystalline diamond coatings and devices

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

Sumant, Anirudha V.; Khan, Adam

2017-08-22

A method for coating a substrate comprises producing a plasma ball using a microwave plasma source in the presence of a mixture of gases. The plasma ball has a diameter. The plasma ball is disposed at a first distance from the substrate and the substrate is maintained at a first temperature. The plasma ball is maintained at the first distance from the substrate, and a diamond coating is deposited on the substrate. The diamond coating has a thickness. Furthermore, the diamond coating has an optical transparency of greater than about 80%. The diamond coating can include nanocrystalline diamond. The microwavemore » plasma source can have a frequency of about 915 MHz.« less

Supramolecular polymers as surface coatings: rapid fabrication of healable superhydrophobic and slippery surfaces.

PubMed

Wei, Qiang; Schlaich, Christoph; Prévost, Sylvain; Schulz, Andrea; Böttcher, Christoph; Gradzielski, Michael; Qi, Zhenhui; Haag, Rainer; Schalley, Christoph A

2014-11-19

Supramolecular polymerization for non-wetting surface coatings is described. The self-assembly of low-molecular-weight gelators (LMWGs) with perfluorinated side chains can be utilized to rapidly construct superhydrophobic, as well as liquid-infused slippery surfaces within minutes. The lubricated slippery surface exhibits impressive repellency to biological li-quids, such as human serum and blood, and very fast self-healing. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reinforced Superhydrophobic Coating on Silicone Rubber for Longstanding Anti-Icing Performance in Severe Conditions.

PubMed

Emelyanenko, Alexandre M; Boinovich, Ludmila B; Bezdomnikov, Alexey A; Chulkova, Elizaveta V; Emelyanenko, Kirill A

2017-07-19

We present a simple method for fabricating the superhydrophobic coatings on composite silicone rubber used for electrical outdoor applications. The coating is characterized by contact angles as high as 170° and is mechanically durable in contact with the aqueous phase. We discuss the impact of mechanical durability of the surface texture on the anti-icing performance of the coating on the basis of the experimental data on freezing delay of sessile aqueous droplets. A set of complementary data obtained in laboratory and outdoor experiments on freezing delay time, variation of wettability and practical work of adhesion for supercooled aqueous sessile droplets, impacting behavior of droplets at low negative temperatures, as well as the results of snow and ice accumulation in outdoor experiments indicate the very prospective icephobic properties of the developed coating.

The effect of superhydrophobic wetting state on corrosion protection--the AKD example.

PubMed

Ejenstam, Lina; Ovaskainen, Louise; Rodriguez-Meizoso, Irene; Wågberg, Lars; Pan, Jinshan; Swerin, Agne; Claesson, Per M

2013-12-15

Corrosion is of considerable concern whenever metal is used as construction material. In this study we address whether superhydrophobic coatings could be used as part of an environmentally friendly corrosion-protective system, and specific focus is put on how the wetting regime of a superhydrophobic coating affects corrosion inhibition. Superhydrophobic alkyl ketene dimer (AKD) wax coatings were produced, using different methods resulting in hierarchical structures, where the coatings exhibit the same surface chemistry but different wetting regimes. Contact angle measurements, ESEM, confocal Raman microscopy, open circuit potential and electrochemical impedance spectroscopy were used to evaluate the surfaces. Remarkably high impedance values of 10(10)Ω cm(2) (at 10(-2) Hz) were reached for the sample showing superhydrophobic lotus-like wetting. Simultaneous open circuit potential measurements suggest that the circuit is broken, most likely due to the formation of a thin air layer at the coating-water interface that inhibits ion transport from the electrolyte to the metal substrate. The remaining samples, showing superhydrophobic wetting in the rose state and hydrophobic Wenzel-like wetting, showed less promising corrosion-protective properties. Due to the absence of air films on these surfaces the coatings were penetrated by the electrolyte, which allowed the corrosion reaction to proceed. Copyright © 2013 Elsevier Inc. All rights reserved.

Fabrication of a superhydrophobic surface with fungus-cleaning properties on brazed aluminum for industrial application in heat exchangers

NASA Astrophysics Data System (ADS)

Lee, Jeong-Won; Hwang, Woonbong

2018-06-01

Extensive research has been carried out concerning the application of superhydrophobic coating in heat exchangers, but little is known about the application of this technique to brazed aluminum heat exchangers (BAHEs). In this work, we describe a new superhydrophobic coating method, which is suitable for BAHE use on an industrial scale. We first render the BAHE superhydrophobic by fabricating micro/nanostructures using solution dipping followed by fluorination. After the complete removal of the silicon residue, we verify using surface analysis that the BAHE surface is perfectly superhydrophobic. We also studied the fungus-cleaning properties of the superhydrophobic surface by growing fungus for 4 weeks in a moist environment on BAHE fins with and without superhydrophobic coating. We observed that, whereas the fungus grown on the untreated fins is extremely difficult to remove, the fungus on the fins with the superhydrophobic coating can be removed easily with only a modest amount of water. We also found that the coated BAHE fins exhibit excellent resistance to moisture. The superhydrophobic coating method that we propose is therefore expected to have a major impact in the heating, ventilating and air conditioning industry market.

Substrate-Versatile Approach to Robust Antireflective and Superhydrophobic Coatings with Excellent Self-Cleaning Property in Varied Environments.

PubMed

Ren, Tingting; He, Junhui

2017-10-04

Robust antireflective and superhydrophobic coatings are highly desired in wide applications, such as optical devices, solar cell panels, architectural and automotive glasses, lab-on chip systems, and windows for electronic devices. Meanwhile, simple, low-cost, and substrate-versatile fabrication is also essential toward real applications of such coatings. Herein, we developed a substrate-versatile strategy to fabricate robust antireflective and superhydrophobic coatings with excellent self-cleaning property in varied environments, including air and oil and after oil contamination. A mixed ethanol suspension, which consists of 1H,1H,2H,2H-perfluorooctyltriethoxysilane modified dual-sized silica nanoparticles and acid-catalyzed silica precursor, was first synthesized. The acid-catalyzed silica precursor could help to form a highly cross-linked silica network by connecting the silica nanoparticles, thus significantly enhancing the robustness of coatings. The as-prepared coatings were able to withstand a water drop impact test, sand abrasion test, tape adhesion test, and knife and pencil scratching tests. More importantly, it was also found that the wettability and self-cleaning property of coatings after oil contamination were surprisingly different from those in air and oil. These observations are explainable by the alteration of interface; i.e., the alteration of interface has significant effects on the functional properties of coatings. Additionally, the mixed suspension could be sprayed onto various hard and soft substrates including glass, polyethylene terephthalate (PET), polycarbonate (PC), and poly(methyl methacrylate) (PMMA), opening up a feasible route toward varied practical applications in solar cell panels, optical devices, architectural and automotive glasses, droplet manipulators, and fluid control.

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.

Facile Synthesis of Smart Nanocontainers as Key Components for Construction of Self-Healing Coating with Superhydrophobic Surfaces.

PubMed

Liang, Yi; Wang, MingDong; Wang, Cheng; Feng, Jing; Li, JianSheng; Wang, LianJun; Fu, JiaJun

2016-12-01

SiO2-imidazoline nanocomposites (SiO2-IMI) owning high loading capacity of corrosion inhibitor, 1-hexadecyl-3-methylimidazolium bromide (HMID), and a special acid/alkali dual-stimuli-accelerated release property have been synthesized via a one-step modified Stöber method. SiO2-IMI were uniformly distributed into the hydrophobic SiO2 sol to construct "host"-"guest" feedback active coating with a superhydrophobic surface (SiO2-IMI@SHSC) on aluminium alloy, AA2024, by dip-coating technique. SiO2-IMI as "guest" components have good compatibility with "host" sol-gel coating, and more importantly, once localized corrosion occurs on the surface of AA2024, SiO2-IMI can simultaneously respond to the increase in environmental pH around corrosive micro-cathodic regions and decrease in pH near micro-anodic regions, promptly releasing HMID to form a compact molecular film on the damaged surface, inhibiting corrosion spread and executing a self-healing function. The scanning vibrating electrode technique (SVET) was applied to illustrate the suppression process of cathodic/anodic corrosion activities. Furthermore, benefiting from the superhydrophobic surface, SiO2-IMI@SHSC remained its protective ability after immersion in 0.5 M NaCl solution for 35 days, which is far superior to the conventional sol-gel coating with the same coating thickness. The facile fabrication method of SiO2-IMI simplifies the construction procedure of SiO2-IMI@SHSC, which have great potential to replace non-environmental chromate conversion coatings for practical use.

Durable superhydrophobic paper enabled by surface sizing of starch-based composite films

NASA Astrophysics Data System (ADS)

Chen, Gang; Zhu, Penghui; Kuang, Yudi; Liu, Yu; Lin, Donghan; Peng, Congxing; Wen, Zhicheng; Fang, Zhiqiang

2017-07-01

Superhydrophobic paper with remarkable durability is of considerable interest for its practical applications. In this study, a scalable, inexpensive, and universal surface sizing technique was implemented to prepare superhydrophobic paper with enhanced durability. A thin layer of starch-based composite, acting as a bio-binder, was first coated onto the paper surface by a sophisticated manufacturing technique called surface sizing, immediately followed by a spray coating of hexamethyl disilazane treated silica nanoparticles (HMDS-SiNPs) dispersed in ethanol on the surface of the wet starch-coated sheet, and the dual layers dried at the same time. Consequently, durable superhydrophobic paper with bi-layer structure was obtained after air drying. The as-prepared superhydrophobic paper not only exhibited a self-cleaning behavior, but also presented an enhanced durability against scratching, bending/deformation, as well as moisture. The universal surface sizing of starch-based composites may pave the way for the up-scaled and cost-effective production of durable superhydrophobic paper.

Fabrication of biomimetic superhydrophobic surface using hierarchical polyaniline spheres.

PubMed

Dong, Xiaofei; Wang, Jixiao; Zhao, Yanchai; Wang, Zhi; Wang, Shichang

2011-06-01

Wettability and water-adhesion behavior are the most important properties of solid surfaces from both fundamental and practical aspects. Here, the biomimetic superhydrophobic surface was fabricated via a simple coating process using polyaniline (PANI) microspheres which is covered with PANI nanowires as functional component, and poly-vinyl butyral (PVB, poly-vinyl alcohol crosslinked with n-butylaldehyde) as PANI microsphere adhering improvement agent to the substrate. The obtained surface displays superhydrophobic behavior without any modification with low-surface-energy materials such as thiol- or fluoroalkylsilane. The effects of coating process and the content of PANI microspheres on superhydropbobic behavior were discussed. Combine contact angle, water-adhesion measurements, scanning electronic microscopy (SEM) observations with selected areas energy dispersion spectrometer (EDS), the hydrophobic mechanism was proposed. The superhydrophobicity is attributed to a hierarchical morphology of PANI microspheres and the nature of the material itself. In addition, induced by van der Waals forces, the created superhydrophobic surface here shows the strong water-adhesion behavior. The surface has the combination performance of Lotus leaf and gecko's pad. The special wettability would be of great significance to the liquid microtransport in microfluid devices. The experimental results show that the ordinary coating process is a facile approach for fabrication of superhydrophobic surfaces.

Fabrication of superhydrophobic copper surface on various substrates for roll-off, self-cleaning, and water/oil separation.

PubMed

Sasmal, Anup Kumar; Mondal, Chanchal; Sinha, Arun Kumar; Gauri, Samiran Sona; Pal, Jaya; Aditya, Teresa; Ganguly, Mainak; Dey, Satyahari; Pal, Tarasankar

2014-12-24

Superhydrophobic surfaces prevent percolation of water droplets and thus render roll-off, self-cleaning, corrosion protection, etc., which find day-to-day and industrial applications. In this work, we developed a facile, cost-effective, and free-standing method for direct fabrication of copper nanoparticles to engender superhydrophobicity for various flat and irregular surfaces such as glass, transparency sheet (plastic), cotton wool, textile, and silicon substrates. The fabrication of as-prepared superhydrophobic surfaces was accomplished using a simple chemical reduction of copper acetate by hydrazine hydrate at room temperature. The surface morphological studies demonstrate that the as-prepared surfaces are rough and display superhydrophobic character on wetting due to generation of air pockets (The Cassie-Baxter state). Because of the low adhesion of water droplets on the as-prepared surfaces, the surfaces exhibited not only high water contact angle (164 ± 2°, 5 μL droplets) but also superb roll-off and self-cleaning properties. Superhydrophobic copper nanoparticle coated glass surface uniquely withstands water (10 min), mild alkali (5 min in saturated aqueous NaHCO3 of pH ≈ 9), acids (10 s in dilute HNO3, H2SO4 of pH ≈ 5) and thiol (10 s in neat 1-octanethiol) at room temperature (25-35 °C). Again as-prepared surface (cotton wool) was also found to be very effective for water-kerosene separation due to its superhydrophobic and oleophilic character. Additionally, the superhydrophobic copper nanoparticle (deposited on glass surface) was found to exhibit antibacterial activity against both Gram-negative and Gram-positive bacteria.

Bioinspired, roughness-induced, water and oil super-philic and super-phobic coatings prepared by adaptable layer-by-layer technique

PubMed Central

Brown, Philip S.; Bhushan, Bharat

2015-01-01

Coatings with specific surface wetting properties are of interest for anti-fouling, anti-fogging, anti-icing, self-cleaning, anti-smudge, and oil-water separation applications. Many previous bioinspired surfaces are of limited use due to a lack of mechanical durability. Here, a layer-by-layer technique is utilized to create coatings with four combinations of water and oil repellency and affinity. An adapted layer-by-layer approach is tailored to yield specific surface properties, resulting in a durable, functional coating. This technique provides necessary flexibility to improve substrate adhesion combined with desirable surface chemistry. Polyelectrolyte binder, SiO2 nanoparticles, and silane or fluorosurfactant layers are deposited, combining surface roughness and necessary chemistry to result in four different coatings: superhydrophilic/superoleophilic, superhydrophobic/superoleophilic, superhydrophobic/superoleophobic, and superhydrophilic/superoleophobic. The superoleophobic coatings display hexadecane contact angles >150° with tilt angles <5°, whilst the superhydrophobic coatings display water contact angles >160° with tilt angles <2°. One coating combines both oleophobic and hydrophobic properties, whilst others mix and match oil and water repellency and affinity. Coating durability was examined through the use of micro/macrowear experiments. These coatings display transparency acceptable for some applications. Fabrication via this novel combination of techniques results in durable, functional coatings displaying improved performance compared to existing work where either durability or functionality is compromised. PMID:26353971

Superhydrophobic properties induced by sol-gel routes on copper surfaces

NASA Astrophysics Data System (ADS)

Raimondo, M.; Veronesi, F.; Boveri, G.; Guarini, G.; Motta, A.; Zanoni, R.

2017-11-01

Superhydrophobic surfaces are attracting increasing attention in different fields such as energy, transportation, building industry and electronics, as they exhibit many interesting properties such as high water repellence, anti-fogging, anti-corrosion, anti-fouling and self-cleaning abilities. Here, superhydrophobic nanostructured hybrid materials obtained by depositing alumina nanoparticles on copper surfaces via dip coating in Al2O3 sol are presented. Two different preparation routes were explored, based on either an alcoholic or an aqueous Al2O3 sol, and the resulting wetting properties were compared. Wettability measurements showed that when the alcoholic sol is used superhydrophobicity is attained, with values of water contact angle very close to the upper limit of 180°, while highly hydrophobic coatings are obtained with the aqueous sol. These findings were further supported by electron microscopy and X-ray photoelectron spectroscopy, which revealed that the surface layer deposited on Cu is more homogenous and richer in alumina nanoparticles when the alcoholic sol was used. Durability of the superhydrophobic coating was assessed by performing ageing tests in chemically aggressive environments. A remarkable resistance is displayed by the superhydrophobic coating in acid environment, while alkaline conditions severely affect its properties. Such behaviors were investigated by XPS and FE-SEM measurements, which disclosed the nature of the surface reactions under the different conditions tested. The present results underline that a thorough investigation of surface morphology, chemical composition and wetting properties reveals their strongly connection and helps optimizing the combination of substrate nanostructuring and suitable chemical coating for an improved durability in different aggressive environments.

Facile Fabrication and Characterization of a PDMS-Derived Candle Soot Coated Stable Biocompatible Superhydrophobic and Superhemophobic Surface.

PubMed

Iqbal, R; Majhy, B; Sen, A K

2017-09-13

We report a simple, inexpensive, rapid, and one-step method for the fabrication of a stable and biocompatible superhydrophobic and superhemophobic surface. The proposed surface comprises candle soot particles embedded in a mixture of PDMS+n-hexane serving as the base material. The mechanism responsible for the superhydrophobic behavior of the surface is explained, and the surface is characterized based on its morphology and elemental composition, wetting properties, mechanical and chemical stability, and biocompatibility. The effect of %n-hexane in PDMS, the thickness of the PDMS+n-hexane layer (in terms of spin coating speed) and sooting time on the wetting property of the surface is studied. The proposed surface exhibits nanoscale surface asperities (average roughness of 187 nm), chemical compositions of soot particles, very high water and blood repellency along with excellent mechanical and chemical stability and excellent biocompatibility against blood sample and biological cells. The water contact angle and roll-off angle is measured as 160° ± 1° and 2°, respectively, and the blood contact angle is found to be 154° ± 1°, which indicates that the surface is superhydrophobic and superhemophobic. The proposed superhydrophobic and superhemophobic surface offers significantly improved (>40%) cell viability as compared to glass and PDMS surfaces.

Electrical properties of transparent conductive ATO coatings obtained by spray pyrolysis

NASA Astrophysics Data System (ADS)

Zinchenko, T. O.; Kondrashin, V. I.; Pecherskaya, E. A.; Kozlyakov, A. S.; Nikolaev, K. O.; Shepeleva, J. V.

2017-08-01

Transparent conductive coatings based on thin films of metal oxides have been widely spread in various optoelectronic devices and appliances. It is necessary to determine the influence of preparation conditions on coatings properties for their use in the solution of certain tasks. Thin films of tin dioxide were obtained by the method of spray pyrolysis on glass substrates. Surface resistance and resistivity, concentration and mobility of charge carriers, the conductivity were measured, and the dependences showing the effect of preparation conditions on electrical properties of optically transparent coatings.

Optically transparent, scratch-resistant, diamond-like carbon coatings

DOEpatents

He, Xiao-Ming; Lee, Deok-Hyung; Nastasi, Michael A.; Walter, Kevin C.; Tuszewski, Michel G.

2003-06-03

A plasma-based method for the deposition of diamond-like carbon (DLC) coatings is described. The process uses a radio-frequency inductively coupled discharge to generate a plasma at relatively low gas pressures. The deposition process is environmentally friendly and scaleable to large areas, and components that have geometrically complicated surfaces can be processed. The method has been used to deposit adherent 100-400 nm thick DLC coatings on metals, glass, and polymers. These coatings are between three and four times harder than steel and are therefore scratch resistant, and transparent to visible light. Boron and silicon doping of the DLC coatings have produced coatings having improved optical properties and lower coating stress levels, but with slightly lower hardness.

Self-Healing Superhydrophobic Materials Showing Quick Damage Recovery and Long-Term Durability.

PubMed

Wang, Liming; Urata, Chihiro; Sato, Tomoya; England, Matt W; Hozumi, Atsushi

2017-09-26

Superhydrophobic coatings/materials are important for a wide variety of applications, but the majority of these man-made coatings/materials still suffer from poor durability because of their lack of self-healing ability. Here, we report novel superhydrophobic materials which can quickly self-heal from various severe types of damage. In this study, we used poly(dimethylsiloxane) (PDMS) infused with two liquids: trichloropropylsilane, which reacts with ambient moisture to self-assemble into grass-like microfibers (named silicone micro/nanograss) on the surfaces and low-viscosity silicone oil (SO), which remains within the PDMS matrices and acts as a self-healing agent. Because of the silicone micro/nanograss structures on the PDMS surfaces and the effective preserve/protection system of a large quantity of SO within the PDMS matrices, our superhydrophobic materials showed quick superhydrophobic recovery under ambient conditions (within 1-2 h) even after exposure to plasma (24 h), boiling water, chemicals, and outside environments. Such an ability is superior to the best self-healing superhydrophobic coatings/materials reported so far.

Biomimetic hairy surfaces as superhydrophobic highly transmissive films for optical applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Vuellers, Felix; Gomard, Guillaume; Preinfalk, Jan B.; Klampaftis, Efthymios; Worgull, Matthias; Richards, Bryce S.; Hölscher, Hendrik; Kavalenka, Maryna N.

2017-02-01

Combining high optical transmission, water-repellency and self-cleaning is of great interest for optoelectronic devices operating in outdoor conditions, such as photovoltaics where shading can significantly reduce the power output. The surface of water plant Pistia stratiotes combines these functionalities through a dense layer of transparent microhairs. It renders the surface superhydrophobic without affecting absorption of sunlight necessary for photosynthesis. Inspired by this surface, we fabricated a superhydrophobic flexible thin nanofur film made from optical grade polycarbonate using a scalable combination of hot embossing and hot pulling techniques. During fabrication, heated sandblasted steel plates locally elongate softened polymer, thus covering its surface in microcavities surrounded by high aspect ratio micro- and nanohairs. The superhydrophobic nanofur exhibits contact angles of (166+/-6°), low sliding angles (<6°) and is self-cleaning against various contaminants. The overall transmission of the self-standing nanofur film stands above 85% over the visible range, with 97% of the transmitted light scattered forward. Reflection drops below 4% when coated on a polymeric substrate, which can enhance light extraction in organic light emitting diodes (OLEDs). We report an increase of more than 10% in luminous efficacy for a nanofur coated OLED compared to a bare device. Finally, the nanofur film can be used for enhancing the incoupling of light to solar cells, while additionally providing self-cleaning properties. Optical coupling of the nanofur to a multi-crystalline silicon solar cell results in a 5.8% gain in photocurrent compared to a bare device under normal incidence.

Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution.

PubMed

Ishizaki, Takahiro; Masuda, Yoshitake; Sakamoto, Michiru

2011-04-19

The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed. © 2011 American Chemical Society

Producing superhydrophobic roof tiles.

PubMed

Carrascosa, Luis A M; Facio, Dario S; Mosquera, Maria J

2016-03-04

Superhydrophobic materials can find promising applications in the field of building. However, their application has been very limited because the synthesis routes involve tedious processes, preventing large-scale application. A second drawback is related to their short-term life under outdoor conditions. A simple and low-cost synthesis route for producing superhydrophobic surfaces on building materials is developed and their effectiveness and their durability on clay roof tiles are evaluated. Specifically, an organic-inorganic hybrid gel containing silica nanoparticles is produced. The nanoparticles create a densely packed coating on the roof tile surface in which air is trapped. This roughness produces a Cassie-Baxter regime, promoting superhydrophobicity. A surfactant, n-octylamine, was also added to the starting sol to catalyze the sol-gel process and to coarsen the pore structure of the gel network, preventing cracking. The application of ultrasound obviates the need to use volatile organic compounds in the synthesis, thereby making a 'green' product. It was also demonstrated that a co-condensation process effective between the organic and inorganic species is crucial to obtain durable and effective coatings. After an aging test, high hydrophobicity was maintained and water absorption was completely prevented for the roof tile samples under study. However, a transition from a Cassie-Baxter to a Wenzel state regime was observed as a consequence of the increase in the distance between the roughness pitches produced by the aging of the coating.

Superhydrophobic cotton fabrics prepared by sol–gel coating of TiO2 and surface hydrophobization

PubMed Central

Xue, Chao-Hua; Jia, Shun-Tian; Chen, Hong-Zheng; Wang, Mang

2008-01-01

By coating fibers with titania sol to generate a dual-size surface roughness, followed by hydrophobization with stearic acid, 1H,1H,2H,2H-perfluorodecyltrichlorosilane or their combination, hydrophilic cotton fabrics were made superhydrophobic. The surface wettability and topology of cotton fabrics were studied by contact angle measurement and scanning electron microscopy. The UV-shielding property of the treated fabrics was also characterized by UV-vis spectrophotometry. PMID:27877998

Multifunctional hollow superhydrophobic SiO2 microspheres with robust and self-cleaning and separation of oil/water emulsions properties.

PubMed

Guo, Fei; Wen, Qiuying; Peng, Yubing; Guo, Zhiguang

2017-05-15

Superhydrophobic materials have drawn great attention due to its' remarkable non-wetting properties and applications in many fields. In this paper, we synthesize a hollow superhydrophobic SiO 2 powder by typical template method and self-assembly functionalization. Robustness of many superhydrophobic surfaces has become the development bottleneck for industrial applications. Aiming at this problem, the adhesive epoxy resin is specially taken to use as the binding layer between superhydrophobic SiO 2 powder and substrates to create robust superhydrophobic coating. The mechanical durability of the obtained superhydrophobic coating is evaluated by a cyclic sandpaper abrasion. Also, the chemical stability of this superhydrophobic coating is assessed by exposuring it to different pH conditions and UV irradiation, respectively. Significantly, because of the special structure and superhydrophobicity/superoleophilicity of the hollow microspheres, these hollow superhydrophobic SiO 2 powders manifest great oil-adsorbing capacity, which thus can be used to separate oil/water mixtures and remove oil from oil-in-water emulsions. Copyright © 2017 Elsevier Inc. All rights reserved.

Diagnostics of transparent polymer coatings of metal items

NASA Astrophysics Data System (ADS)

Varepo, L. G.; Ermakova, I. N.; Nagornova, I. V.; Kondratov, A. P.

2017-08-01

The methods of visual and instrumental express diagnostics of safety critical defects and non-uniform thickness of transparent mono- and multilayer polyolefin surface coating of metal items are analyzed in the paper. The instrumental diagnostics method relates to colorimetric measuring based on effects, which appear in the polarized light for extrusion polymer coatings. A color coordinates dependence (in the color system CIE La*b*) on both HDPE / PVC coating thickness fluctuation values (from average ones) and coating interlayer or adhesion layer delaminating is shown. A variation of color characteristics in the polarized light at a liquid penetration into delaminated polymer layers is found. Measuring parameters and critical uncertainties are defined.

Laser-Generated Rayleigh Waves Propagating in Transparent Viscoelastic Adhesive Coating/Metal Substrate Systems

NASA Astrophysics Data System (ADS)

Guan, Yi-jun; Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi; Ge, Yong

2016-10-01

We have established numerical models for simulating laser-generated Rayleigh waves in coating/substrate systems by a finite element method and investigated the propagation characteristics of Rayleigh waves in systems concerning the viscoelasticity and transparency of adhesive coatings. In this way, we have studied the influence of the mechanical properties of the coating, such as the elastic moduli, viscoelastic moduli, coating thickness, transparency, and coating material, on the propagation characteristics of the Rayleigh waves. The results show that the propagation characteristics of the Rayleigh waves can be divided into low- and high-frequency parts. The high-frequency propagation characteristics of the Rayleigh wave are closely related to the properties of the adhesive coating.

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation.

PubMed

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-02-20

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO 2 @polycarbonate (TiO 2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the "dipping and drying" process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO 2 (Ag)@PC (DA-TiO 2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO 2 (Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning.

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation

NASA Astrophysics Data System (ADS)

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-02-01

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO2@polycarbonate (TiO2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the “dipping and drying” process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO2 (Ag)@PC (DA-TiO2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO2(Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning.

Ellipsometry of single-layer antireflection coatings on transparent substrates

NASA Astrophysics Data System (ADS)

Azzam, R. M. A.

2017-11-01

The complex reflection coefficients of p- and s-polarized light and ellipsometric parameters of a transparent substrate of refractive index n2, which is coated by a transparent thin film whose refractive index n1 =√{n2 } satisfies the anti-reflection condition at normal incidence, are considered as functions of film thickness d and angle of incidence ϕ. A unique coated surface, with n1 =√{n2 } and film thickness d equal to half of the film-thickness period Dϕ at angle ϕ and wavelength λ, reflects light of the same wavelength without change of polarization for all incident polarization states. (The reflection Jones matrix of such coated surface is the 2 × 2 identity matrix pre-multiplied by a scalar, hence tanΨ = 1,Δ = 0.) To monitor the deposition of an antireflection coating, the normalized Stokes parameters of obliquely reflected light (e.g. at ϕ =70∘) are measured until predetermined target values of those parameters are detected. This provides a more accurate means of film thickness control than is possible using a micro-balance technique or an intensity reflectance method.

Recent Progress in Fabrication and Applications of Superhydrophobic Coating on Cellulose-Based Substrates

PubMed Central

Liu, Hui; Gao, Shou-Wei; Cai, Jing-Sheng; He, Cheng-Lin; Mao, Jia-Jun; Zhu, Tian-Xue; Chen, Zhong; Huang, Jian-Ying; Meng, Kai; Zhang, Ke-Qin; Al-Deyab, Salem S.; Lai, Yue-Kun

2016-01-01

Multifuntional fabrics with special wettability have attracted a lot of interest in both fundamental research and industry applications over the last two decades. In this review, recent progress of various kinds of approaches and strategies to construct super-antiwetting coating on cellulose-based substrates (fabrics and paper) has been discussed in detail. We focus on the significant applications related to artificial superhydrophobic fabrics with special wettability and controllable adhesion, e.g., oil-water separation, self-cleaning, asymmetric/anisotropic wetting for microfluidic manipulation, air/liquid directional gating, and micro-template for patterning. In addition to the anti-wetting properties and promising applications, particular attention is paid to coating durability and other incorporated functionalities, e.g., air permeability, UV-shielding, photocatalytic self-cleaning, self-healing and patterned antiwetting properties. Finally, the existing difficulties and future prospects of this traditional and developing field are briefly proposed and discussed. PMID:28773253

Superhydrophobic materials for drug delivery

NASA Astrophysics Data System (ADS)

Yohe, Stefan Thomas

Superhydrophobicity is a property of material surfaces reflecting the ability to maintain air at the solid-liquid interface when in contact with water. These surfaces have characteristically high apparent contact angles, by definition exceeding 150°, as a result of the composite material-air surface formed under an applied water droplet. Superhydrophobic surfaces were first discovered on naturally occurring substrates, and have subsequently been fabricated in the last several decades to harness these favorable surface properties for a number of emerging applications, including their use in biomedical settings. This work describes fabrication and characterization of superhydrophobic 3D materials, as well as their use as drug delivery devices. Superhydrophobic 3D materials are distinct from 2D superhydrophobic surfaces in that air is maintained not just at the surface of the material, but also within the bulk. When the superhydrophobic 3D materials are submerged in water, water infiltrates slowly and continuously as a new water-air-material interface is formed with controlled displacement of air. Electrospinning and electrospraying are used to fabricate superhydrophobic 3D materials utilizing blends of the biocompatible polymers poly(epsilon-caprolactone) and poly(caprolactone-co-glycerol monostearate) (PGC-C18). PGC-C18 is significantly more hydrophobic than PCL (contact angle of 116° versus 83° for flat materials), and further additions of PGC-C18 into electrospun meshes and electrosprayed coatings affords increased stability of the entrapped air layer. For example, PCL meshes alone (500 mum thick) take 10 days to fully wet, and with 10% or 30% PGC-C18 addition wetting rates are dramatically slowed to 60% wetted by 77 days and 4% by 75 days, respectively. Stability of the superhydrophobic materials can be further probed with a variety of physio-chemical techniques, including pressure, surfactant containing solutions, and solvents of varying surface tension

Fabrication of porous hierarchical polymer/ceramic composites by electron irradiation of organic/inorganic polymers: route to a highly durable, large-area superhydrophobic coating.

PubMed

Lee, Eun Je; Kim, Jae Joon; Cho, Sung Oh

2010-03-02

Polymer/ceramic composite films with micro- and nanocombined hierarchical structures are fabricated by electron irradiation of poly(methyl methacrylate) (PMMA) microspheres/silicone grease. Electron irradiation induces volume contraction of PMMA microspheres and simultaneously transforms silicone grease into a ceramic material of silicon oxycarbide with many nanobumps. As a result, highly porous structures that consist of micrometer-sized pores and microparticles decorated with nanobumps are created. The fabricated films with the porous hierarchical structure exhibit good superhydrophobicity with excellent self-cleaning and antiadhesion properties after surface treatment with fluorosilane. In addition, the porous hierarchical structures are covered with silicon oxycarbide, and thus the superhydrophobic coatings have high hardness and strong adhesion to the substrate. The presented technique provides a straightforward route to producing large-area, mechanically robust superhydrophobic films on various substrate materials.

Super-hydrophobic Silver-Doped TiO2 @ Polycarbonate Coatings Created on Various Material Substrates with Visible-Light Photocatalysis for Self-Cleaning Contaminant Degradation

PubMed Central

Li, Zhengjian; Sun, Zongzhao; Duan, Zhiqiang; Li, Rui; Yang, Yanli; Wang, Jingyi; Lv, Xiaoxia; Qi, Wei; Wang, Hua

2017-01-01

In the present work, a facile and efficient fabrication method has been developed for creating super-hydrophobic coatings of silver-doped TiO2@polycarbonate (TiO2 (Ag)@PC) on the substrates of different materials with photocatalytic self-cleaning performances simply by the “dipping and drying” process. The substrates were first patterned with glue and then deposited with the dopamine-capped TiO2 (Ag)@PC (DA-TiO2 (Ag)@PC) nanocomposites, followed by the further etching with dimethylbenzene. The so prepared super-hydrophobic E-DA-TiO2(Ag)@PC coatings could present the lotus leaf-like porous architectures, high adhesion stability, and especially the visible-light photocatalysis for organic contaminant degradation, thus promising the wide outdoor and indoor applications like water proofing, metal erosion protection, and surface self-cleaning. PMID:28218285

Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass.

PubMed

Paniagua-Domínguez, R; Abujetas, D R; Froufe-Pérez, L S; Sáenz, J J; Sánchez-Gil, J A

2013-09-23

Metallic nanowires (NW) coated with a high permittivity dielectric are proposed as means to strongly reduce the light scattering of the conducting NW, rendering them transparent at infrared wavelengths of interest in telecommunications. Based on a simple, universal law derived from electrostatics arguments, we find appropriate parameters to reduce the scattering efficiency of hybrid metal-dielectric NW by up to three orders of magnitude as compared with the scattering efficiency of the homogeneous metallic NW. We show that metal@dielectric structures are much more robust against fabrication imperfections than analogous dielectric@metal ones. The bandwidth of the transparent region entirely covers the near IR telecommunications range. Although this effect is optimum at normal incidence and for a given polarization, rigorous theoretical and numerical calculations reveal that transparency is robust against changes in polarization and angle of incidence, and also holds for relatively dense periodic or random arrangements. A wealth of applications based on metal-NWs may benefit from such invisibility.

Superhydrophobics

ScienceCinema

Schaeffer, Daniel; Winter, Kyle

2018-06-06

A water repellent developed by researchers at the Department of Energy's Oak Ridge National Laboratory outperforms nature at its best and could open a floodgate of commercial possibilities. The super-water repellent (superhydrophobic) material, developed by John Simpson, is easy to fabricate and uses inexpensive base materials. The process could lead to the creation of a new class of water repellant products, including windshields, eyewear, clothing, building materials, road surfaces, ship hulls and self-cleaning coatings. The list of likely applications is virtually endless.

Superhydrophobic Copper Surfaces with Anticorrosion Properties Fabricated by Solventless CVD Methods.

PubMed

Vilaró, Ignasi; Yagüe, Jose L; Borrós, Salvador

2017-01-11

Due to continuous miniaturization and increasing number of electrical components in electronics, copper interconnections have become critical for the design of 3D integrated circuits. However, corrosion attack on the copper metal can affect the electronic performance of the material. Superhydrophobic coatings are a commonly used strategy to prevent this undesired effect. In this work, a solventless two-steps process was developed to fabricate superhydrophobic copper surfaces using chemical vapor deposition (CVD) methods. The superhydrophobic state was achieved through the design of a hierarchical structure, combining micro-/nanoscale domains. In the first step, O 2 - and Ar-plasma etchings were performed on the copper substrate to generate microroughness. Afterward, a conformal copolymer, 1H,1H,2H,2H-perfluorodecyl acrylate-ethylene glycol diacrylate [p(PFDA-co-EGDA)], was deposited on top of the metal via initiated CVD (iCVD) to lower the surface energy of the surface. The copolymer topography exhibited a very characteristic and unique nanoworm-like structure. The combination of the nanofeatures of the polymer with the microroughness of the copper led to achievement of the superhydrophobic state. AFM, SEM, and XPS were used to characterize the evolution in topography and chemical composition during the CVD processes. The modified copper showed water contact angles as high as 163° and hysteresis as low as 1°. The coating withstood exposure to aggressive media for extended periods of time. Tafel analysis was used to compare the corrosion rates between bare and modified copper. Results indicated that iCVD-coated copper corrodes 3 orders of magnitude slower than untreated copper. The surface modification process yielded repeatable and robust superhydrophobic coatings with remarkable anticorrosion properties.

Cicada-Wing-Inspired Self-Cleaning Antireflection Coatings on Polymer Substrates.

PubMed

Chen, Ying-Chu; Huang, Zhe-Sheng; Yang, Hongta

2015-11-18

The cicada has transparent wings with remarkable self-cleaning properties and high transmittance over the whole visible spectral range, which is derived from periodic conical structures covering the wing surface. Here we report a scalable self-assembly technique for fabricating multifunctional optical coatings that mimic cicada-wing structures. Spin-coated two-dimensional non-close-packed colloidal crystals are utilized as etching masks to pattern subwavelength-structured cone arrays directly on polymer substrates. The resulting gratings exhibit broadband antireflection performance and superhydrophobic properties after surface modification. The dependence of the cone shape and size on the antireflective and self-cleaning properties has also been investigated in this study.

Facile Fabrication of a PDMS@Stearic Acid-Kaolin Coating on Lignocellulose Composites with Superhydrophobicity and Flame Retardancy

PubMed Central

Wang, Zhe; Shen, Xiaoping; Qian, Temeng; Wang, Junjie; Sun, Qingfeng; Jin, Chunde

2018-01-01

The disadvantages such as swelling after absorbing water and flammability restrict the widespread applications of lignocellulose composites (LC). Herein, a facile and effective method to fabricate superhydrophobic surfaces with flame retardancy on LC has been investigated by coating polydimethylsiloxane (PDMS) and stearic acid (STA) modified kaolin (KL) particles. The as-prepared coatings on the LC exhibited a good repellency to water (a contact angle = 156°). Owing to the excellent flame retardancy of kaolin particles, the LC coated with PDMS@STA-KL displayed a good flame retardancy during limiting oxygen index and cone calorimeter tests. After the coating treatment, the limiting oxygen index value of the LC increased to 41.0. Cone calorimetry results indicated that the ignition time of the LC coated with PDMS@STA-KL increased by 40 s compared with that of uncoated LC. Moreover, the peak heat release rate (PHRR) and the total heat release (THR) of LC coated with PDMS@STA-KL reduced by 18.7% and 19.2% compared with those of uncoated LC, respectively. This LC coating with improved water repellency and flame retardancy can be considered as a potential alternative to protect the lignocellulose composite. PMID:29751575

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.

Nanoporous Superhydrophobic Coatings that Promote the Extended Release of Water-Labile Quorum Sensing Inhibitors and Enable Long-Term Modulation of Quorum Sensing in Staphylococcus aureus

PubMed Central

2015-01-01

Materials and coatings that inhibit bacterial colonization are of interest in a broad range of biomedical, environmental, and industrial applications. In view of the rapid increase in bacterial resistance to conventional antibiotics, the development of new strategies that target nonessential pathways in bacterial pathogens—and that thereby limit growth and reduce virulence through nonbiocidal means—has attracted considerable attention. Bacterial quorum sensing (QS) represents one such target, and is intimately connected to virulence in many human pathogens. Here, we demonstrate that the properties of nanoporous, polymer-based superhydrophobic coatings can be exploited to host and subsequently sustain the extended release of potent and water-labile peptide-based inhibitors of QS (QSIs) in Staphylococcus aureus. Our results demonstrate that these peptidic QSIs can be released into surrounding media for periods of at least 8 months, and that they strongly inhibit agr-based QS in S. aureus for at least 40 days. These results also suggest that these extremely nonwetting coatings can confer protection against the rapid hydrolysis of these water-labile peptides, thereby extending their useful lifetimes. Finally, we demonstrate that these peptide-loaded superhydrophobic coatings can strongly modulate the QS-controlled formation of biofilm in wild-type S. aureus. These nanoporous superhydrophobic films provide a new, useful, and nonbiocidal approach to the design of coatings that attenuate bacterial virulence. This approach has the potential to be general, and could prove suitable for the encapsulation, protection, and release of other classes of water-sensitive agents. We anticipate that the materials, strategies, and concepts reported here will enable new approaches to the long-term attenuation of QS and associated bacterial phenotypes in a range of basic research and applied contexts. PMID:26501126

Facile preparation of superhydrophobic surfaces based on metal oxide nanoparticles

NASA Astrophysics Data System (ADS)

Bao, Xue-Mei; Cui, Jin-Feng; Sun, Han-Xue; Liang, Wei-Dong; Zhu, Zhao-Qi; An, Jin; Yang, Bao-Ping; La, Pei-Qing; Li, An

2014-06-01

A novel method for fabrication of superhydrophobic surfaces was developed by facile coating various metal oxide nanoparticles, including ZnO, Al2O3 and Fe3O4, on various substrates followed by treatment with polydimethylsiloxane (PDMS) via chemical vapor deposition (CVD) method. Using ZnO nanoparticles as a model, the changes in the surface chemical composition and crystalline structures of the metal oxide nanoparticles by PDMS treatment were investigated by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The results show that the combination of the improved surface roughness generated from of the nanoparticles aggregation with the low surface-energy of silicon-coating originated from the thermal pyrolysis of PDMS would be responsible for the surface superhydrophobicity. By a simple dip-coating method, we show that the metal oxide nanoparticles can be easily coated onto the surfaces of various textural and dimensional substrates, including glass slide, paper, fabric or sponge, for preparation of superhydrophobic surfaces for different purpose. The present strategy may provide an inexpensive and new route to surperhydrophobic surfaces, which would be of technological significance for various practical applications especially for separation of oils or organic contaminates from water.

Fabrication of Biomimetic Fog-Collecting Superhydrophilic-Superhydrophobic Surface Micropatterns Using Femtosecond Lasers.

PubMed

Kostal, Elisabeth; Stroj, Sandra; Kasemann, Stephan; Matylitsky, Victor; Domke, Matthias

2018-03-06

The exciting functionalities of natural superhydrophilic and superhydrophobic surfaces served as inspiration for a variety of biomimetic designs. In particular, the combination of both extreme wetting states to micropatterns opens up interesting applications, as the example of the fog-collecting Namib Desert beetle shows. In this paper, the beetle's elytra were mimicked by a novel three-step fabrication method to increase the fog-collection efficiency of glasses. In the first step, a double-hierarchical surface structure was generated on Pyrex wafers using femtosecond laser structuring, which amplified the intrinsic wetting property of the surface and made it superhydrophilic (water contact angle < 10°). In the second step, a Teflon-like polymer (CF 2 ) n was deposited by a plasma process that turned the laser-structured surface superhydrophobic (water contact angle > 150°). In the last step, the Teflon-like coating was selectively removed by fs-laser ablation to uncover superhydrophilic spots below the superhydrophobic surface, following the example of the Namib Desert beetle's fog-collecting elytra. To investigate the influence on the fog-collection behavior, (super)hydrophilic, (super)hydrophobic, and low and high contrast wetting patterns were fabricated on glass wafers using selected combinations of these three processing steps and were exposed to fog in an artificial nebulizer setup. This experiment revealed that high-contrast wetting patterns collected the highest amount of fog and enhanced the fog-collection efficiency by nearly 60% compared to pristine Pyrex glass. The comparison of the fog-collection behavior of the six samples showed that the superior fog-collection efficiency of surface patterns with extreme wetting contrast is due to the combination of water attraction and water repellency: the superhydrophilic spots act as drop accumulation areas, whereas the surrounding superhydrophobic areas allow a fast water transportation caused by gravity. The

Transparent anti-stain coatings with good thermal and mechanical properties based on polyimide-silica nanohybrids.

PubMed

Choi, Myeon-Cheon; Sung, Giju; Nagappan, Saravanan; Han, Mi-Jeong; Ha, Chang-Sik

2012-07-01

In this work, we synthesized polyimide/silica hybrid materials via sol-gel method using a fluorinated poly(amic acid) silane precursor and a variety of perfluorosilane contents. We studied the influence of a hybrid coating film with the following characteristics; hydrophobicity, oleophobicity, optical transparency, and surface hardness of the coating films. The hybrid coatings with the fluorosilane contents up to 10 wt% are optically transparent and present good thermal stability with a degradation temperature of > 500 degrees C as well as a glass transition of > 300 degrees C. Both water contact angle and oil contact angle increase rapidly with introducing small amount of the fluorosilane in the hybrids and reaches the maximum of 115 degrees and 61 degrees, respectively. The hardness of the hybrid coatings increases up to 5H with an increase of the FTES content in the hybrids. These colorless, transparent, and thermally stable hybrid materials could be suitable for applications as anti-stain coatings.

Zwitterionic Nanofibers of Super-Glue for Transparent and Biocompatible Multi-Purpose Coatings

PubMed Central

Mele, Elisa; Heredia-Guerrero, José A.; Bayer, Ilker S.; Ciofani, Gianni; Genchi, Giada G.; Ceseracciu, Luca; Davis, Alexander; Papadopoulou, Evie L.; Barthel, Markus J.; Marini, Lara; Ruffilli, Roberta; Athanassiou, Athanassia

2015-01-01

Here we show that macrozwitterions of poly(ethyl 2-cyanoacrylate), commonly called Super Glue, can easily assemble into long and well defined fibers by electrospinning. The resulting fibrous networks are thermally treated on glass in order to create transparent coatings whose superficial morphology recalls the organization of the initial electrospun mats. These textured coatings are characterized by low liquid adhesion and anti-staining performance. Furthermore, the low friction coefficient and excellent scratch resistance make them attractive as solid lubricants. The inherent texture of the coatings positively affects their biocompatibility. In fact, they are able to promote the proliferation and differentiation of myoblast stem cells. Optically-transparent and biocompatible coatings that simultaneously possess characteristics of low water contact angle hysteresis, low friction and mechanical robustness can find application in a wide range of technological sectors, from the construction and automotive industries to electronic and biomedical devices. PMID:26357936

Zwitterionic Nanofibers of Super-Glue for Transparent and Biocompatible Multi-Purpose Coatings

NASA Astrophysics Data System (ADS)

Mele, Elisa; Heredia-Guerrero, José A.; Bayer, Ilker S.; Ciofani, Gianni; Genchi, Giada G.; Ceseracciu, Luca; Davis, Alexander; Papadopoulou, Evie L.; Barthel, Markus J.; Marini, Lara; Ruffilli, Roberta; Athanassiou, Athanassia

2015-09-01

Here we show that macrozwitterions of poly(ethyl 2-cyanoacrylate), commonly called Super Glue, can easily assemble into long and well defined fibers by electrospinning. The resulting fibrous networks are thermally treated on glass in order to create transparent coatings whose superficial morphology recalls the organization of the initial electrospun mats. These textured coatings are characterized by low liquid adhesion and anti-staining performance. Furthermore, the low friction coefficient and excellent scratch resistance make them attractive as solid lubricants. The inherent texture of the coatings positively affects their biocompatibility. In fact, they are able to promote the proliferation and differentiation of myoblast stem cells. Optically-transparent and biocompatible coatings that simultaneously possess characteristics of low water contact angle hysteresis, low friction and mechanical robustness can find application in a wide range of technological sectors, from the construction and automotive industries to electronic and biomedical devices.

One-step fabrication of robust superhydrophobic and superoleophilic surfaces with self-cleaning and oil/water separation function.

PubMed

Zhang, Zhi-Hui; Wang, Hu-Jun; Liang, Yun-Hong; Li, Xiu-Juan; Ren, Lu-Quan; Cui, Zhen-Quan; Luo, Cheng

2018-03-01

Superhydrophobic surfaces have great potential for application in self-cleaning and oil/water separation. However, the large-scale practical applications of superhydrophobic coating surfaces are impeded by many factors, such as complicated fabrication processes, the use of fluorinated reagents and noxious organic solvents and poor mechanical stability. Herein, we describe the successful preparation of a fluorine-free multifunctional coating without noxious organic solvents that was brushed, dipped or sprayed onto glass slides and stainless-steel meshes as substrates. The obtained multifunctional superhydrophobic and superoleophilic surfaces (MSHOs) demonstrated self-cleaning abilities even when contaminated with or immersed in oil. The superhydrophobic surfaces were robust and maintained their water repellency after being scratched with a knife or abraded with sandpaper for 50 cycles. In addition, stainless-steel meshes sprayed with the coating quickly separated various oil/water mixtures with a high separation efficiency (>93%). Furthermore, the coated mesh maintained a high separation efficiency above 95% over 20 cycles of separation. This simple and effective strategy will inspire the large-scale fabrication of multifunctional surfaces for practical applications in self-cleaning and oil/water separation.

Bacterial growth on a superhydrophobic surface containing silver nanoparticles

NASA Astrophysics Data System (ADS)

Heinonen, S.; Nikkanen, J.-P.; Laakso, J.; Raulio, M.; Priha, O.; Levänen, E.

2013-12-01

The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.

Fabrication of recyclable and durable superhydrophobic materials with wear/corrosion-resistance properties from kaolin and polyvinylchloride

NASA Astrophysics Data System (ADS)

Qu, Mengnan; Liu, Shanshan; He, Jinmei; Feng, Juan; Yao, Yali; Ma, Xuerui; Hou, Lingang; Liu, Xiangrong

2017-07-01

In this study, mechanically stable and recyclable superhydrophobic materials were prepared from polyvinylchloride (PVC) and kaolin nanoparticles modified by stearic acid using a simple and low-cost drop-coating. The obtained materials displayed liquid-repellent toward water and several other liquids of daily life (such as orange juice, coffee, milk, coca cola and ink). These superhydrophobic materials showed remarkable robustness against sandpaper abrasion, UV-irradiation and ultrasonication test, while retaining its superhydrophobicity even after 60 abrasion cycles loaded of 500 g with sandpaper, 7 days UV-irradiation or 120 min ultrasonication test. The excellent durability against complex conditions was attributed to the hierarchical structure and strong interfacial adhesion of the materials. More significantly, the materials used in the coating could be recycled and reconstructed without losing its superhydrophobicity. The current superhydrophobic materials tolerate rigorous environment, opening a new avenue to a variety of practical applications.

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.

Synergistic Effect of Superhydrophobicity and Oxidized Layers on Corrosion Resistance of Aluminum Alloy Surface Textured by Nanosecond Laser Treatment.

PubMed

Boinovich, Ludmila B; Emelyanenko, Alexandre M; Modestov, Alexander D; Domantovsky, Alexandr G; Emelyanenko, Kirill A

2015-09-02

We report a new efficient method for fabricating a superhydrophobic oxidized surface of aluminum alloys with enhanced resistance to pitting corrosion in sodium chloride solutions. The developed coatings are considered very prospective materials for the automotive industry, shipbuilding, aviation, construction, and medicine. The method is based on nanosecond laser treatment of the surface followed by chemisorption of a hydrophobic agent to achieve the superhydrophobic state of the alloy surface. We have shown that the surface texturing used to fabricate multimodal roughness of the surface may be simultaneously used for modifying the physicochemical properties of the thick surface layer of the substrate itself. Electrochemical and wetting experiments demonstrated that the superhydrophobic state of the metal surface inhibits corrosion processes in chloride solutions for a few days. However, during long-term contact of a superhydrophobic coating with a solution, the wetted area of the coating is subjected to corrosion processes due to the formation of defects. In contrast, the combination of an oxide layer with good barrier properties and the superhydrophobic state of the coating provides remarkable corrosion resistance. The mechanisms for enhancing corrosion protective properties are discussed.

Functional superhydrophobic surfaces made of Janus micropillars

PubMed Central

Mammen, Lena; Bley, Karina; Papadopoulos, Periklis; Schellenberger, Frank; Encinas, Noemí; Butt, Hans-Jürgen; Weiss, Clemens K.

2015-01-01

We demonstrate the fabrication of superhydrophobic surfaces consisting of micropillars with hydrophobic sidewalls and hydrophilic tops, referred to as Janus micropillars. Therefore we first coat a micropillar array with a mono- or bilayer of polymeric particles, and merge the particles together to shield the top faces while hydrophobizing the walls. After removing the polymer film, the top faces of the micropillar arrays can be selectively chemically functionalised with hydrophilic groups. The Janus arrays remain superhydrophobic even after functionalisation as verified by laser scanning confocal microscopy. The robustness of the superhydrophobic behaviour proves that the stability of the entrapped air cushion is determined by the forces acting at the rim of the micropillars. This insight should stimulate a new way of designing super liquid-repellent surfaces with tunable liquid adhesion. In particular, combining superhydrophobicity with the functionalisation of the top faces of the protrusions with hydrophilic groups may have exciting new applications, including high-density microarrays for high-throughput screening of bioactive molecules, cells, or enzymes or efficient water condensation. However, so far chemical attachment of hydrophilic molecules has been accompanied with complete wetting of the surface underneath. The fabrication of superhydrophobic surfaces where the top faces of the protrusions can be selectively chemically post-functionalised with hydrophilic molecules, while retaining their superhydrophobic properties, is both promising and challenging. PMID:25415839

A simple way to an ultra-robust superhydrophobic fabric with mechanical stability, UV durability, and UV shielding property.

PubMed

Ren, Guina; Song, Yuanming; Li, Xiangming; Wang, Bo; Zhou, Yanli; Wang, Yuyan; Ge, Bo; Zhu, Xiaotao

2018-07-15

Development of an ultra-robust superhydrophobic fabric with mechanical stability, UV durability, and UV shielding by a simple method is highly desirable, yet it remains a challenge that current technologies have been unable to fully address. Herein, the original fabric is immersed into the solution containing ZnO nanoparticle and PDMS (polydimethylsiloxane), and the fiber surfaces are uniformly covered by a ZnO-PDMS layer after thermal treatment at 110 °C for 30 min. Droplets of water and corrosive liquids including strong acid, strong alkali, and saturated salt solution display sphere shape on the ZnO-PDMS coated fabric surface. The stable binding of ZnO-PDMS layer onto the fibers allows for the fabric coating with robust superhydrophobicity, and the coated fabric still displays superhydrophobicity after hand twisting, knife scratching, finger touching, and even cycles of sandpaper abrasion. The ZnO-PDMS coated fabric can also keep its superhydrophobic property when exposed to long term UV illumination, demonstrating its UV resistance. Moreover, the uniformly distribution of ZnO nanoparticles on fibers allows the ZnO-PDMS coated fabric to display UV shielding property. Copyright © 2018 Elsevier Inc. All rights reserved.

Superhydrophobic copper tubes with possible flow enhancement and drag reduction.

PubMed

Shirtcliffe, Neil J; McHale, Glen; Newton, Michael I; Zhang, Yong

2009-06-01

The transport of a Newtonian liquid through a smooth pipe or tube is dominated by the frictional drag on the liquid against the walls. The resistance to flow against a solid can, however, be reduced by introducing a layer of gas at or near the boundary between the solid and liquid. This can occur by the vaporization of liquid at a surface at a temperature above the Leidenfrost point, by a cushion of air (e.g. below a hovercraft), or by producing bubbles at the interface. These methods require a continuous energy input, but a more recent discovery is the possibility of using a superhydrophobic surface. Most reported research uses small sections of lithographically patterned surfaces and rarely considers pressure differences or varying flow rates. In this work we present a method for creating a uniform superhydrophobic nanoribbon layer on the inside of round copper tubes of millimetric internal radius. Two types of experiments are described, with the first involving a simultaneous comparison of four tubes with different surface finishes (as received, as received with hydrophobic coating, nanoribbon, and nanoribbon with a hydrophobic coating) under constant flow rate conditions using water and water-glycerol mixtures. The results show that the superhydrophobic nanoribbon with a hydrophobic coating surface finish allows greater flow at low pressure differences but that the effect disappears as the pressure at the inlet of the tube is increased. The second experiment is a simple visual demonstration of the low-pressure behavior using two nominally identical tubes in terms of length and cross-section, but with one tube possessing a superhydrophobic internal surface finish. In this experiment a reservoir is allowed to feed the two tubes with open ends via a T-piece and it is observed that, once flow commences, it preferentially occurs down the superhydrophobic tube.

Transparent electrodes made with ultrasonic spray coating technique for flexible heaters

NASA Astrophysics Data System (ADS)

Wroblewski, G.; Krzemiński, J.; Janczak, D.; Sowiński, J.; Jakubowska, M.

2017-08-01

Transparent electrodes are one of the basic elements of various electronic components. The paper presents the preliminary results related to novel method of ultrasonic spray coating used for fabrication of transparent flexible electrodes. Experiments were conducted by means of specially made laboratory setup composed of ultrasonic spray generator and XYZ plotter. In the first part of the paper diverse solvents were used to determine the crucial technological parameters such as atomization voltage and fluid flow velocity. Afterwards paint containing carbon nanotubes suspended in the two solvent system was prepared and deposited on the polyethylene terephthalate foil. Thickness, roughness and electrical measurements were performed to designate the relations of technological parameters of ultrasonic spray coating on thickness, roughness, sheet resistance and optical transmission of fabricated samples.

Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping.

PubMed

Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

2015-12-21

Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species.

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.

Superhydrophilic Coatings for Improved Sonobuoy Performance

DTIC Science & Technology

2011-06-13

surface evenly with water. This effect is the exact opposite of superhydrophobicity . [0006] Superhydrophobicity has the requirement of a hydrophobic...the surface roughness is not critical; but to make a superhydrophobic surface then the correct degree of surface roughness is crucial. [0007] The...elastomer that is neither superhydrophilic nor superhydrophobic . Because of this coating, as soon as the device makes contact with the water, air

Salvinia-Effect-Inspired "Sticky" Superhydrophobic Surfaces by Meniscus-Confined Electrodeposition.

PubMed

Zheng, Deyin; Jiang, Youhua; Yu, Wentao; Jiang, Xiufen; Zhao, Xin; Choi, Chang-Hwan; Sun, Guangyi

2017-11-28

Inspired by the Salvinia effect, we report the fabrication and characterization of a novel "sticky" superhydrophobic surface sustaining a Cassie-Baxter wetting state for water droplets with high contact angles but strong solid-liquid retention. Unlike superhydrophobic surfaces mimicking the lotus or petal effect, whose hydrophobicity and droplet retention are typically regulated by hierarchical micro- and nanostructures made of a homogeneous material with the same surface energy, our superhydrophobic surface merely requires singular microstructures covered with a hydrophobic coating but creatively coupled with hydrophilic tips with different surface energy. Hydrophilic tips are selectively formed by meniscus-confined electrodeposition of a metal (e.g., nickel) layer on top of hydrophobic microstructures. During the electrodeposition process, the superhydrophobic surface retains its plastron so that the electrolyte cannot penetrate into the cavity of hydrophobic microstructures, consequently making the electrochemical reaction between solid and electrolyte occur only on the tip. In contrast to typical superhydrophobic surfaces where droplets are highly mobile, the "sticky" superhydrophobic surface allows a water droplet to have strong local pinning and solid-liquid retention on the hydrophilic tips, which is of great significance in many droplet behaviors such as evaporation.

Superhydrophobic, carbon-infiltrated carbon nanotubes on Si and 316L stainless steel with tunable geometry

NASA Astrophysics Data System (ADS)

Stevens, Kimberly A.; Esplin, Christian D.; Davis, Taylor M.; Butterfield, D. Jacob; Ng, Philip S.; Bowden, Anton E.; Jensen, Brian D.; Iverson, Brian D.

2018-05-01

The use of carbon nanotubes to create superhydrophobic coatings has been considered due to their ability to offer a relatively uniform nanostructure. However, carbon nanotubes (CNTs) may be considered delicate with a typical diameter of tens of nanometers for a multi-walled CNT; as-grown carbon nanotubes often require the addition of a thin-film hydrophobic coating to render them superhydrophobic. Furthermore, fine control over the diameter of the as-grown CNTs or the overall nanostructure is difficult. This work demonstrates the utility of using carbon infiltration to layer amorphous carbon on multi-walled nanotubes to improve structural integrity and achieve superhydrophobic behavior with tunable geometry. These carbon-infiltrated carbon nanotube (CICNT) surfaces exhibit an increased number of contact points between neighboring tubes, resulting in a composite structure with improved mechanical stability. Additionally, the native surface can be rendered superhydrophobic with a vacuum pyrolysis treatment, with contact angles as high as 160° and contact angle hysteresis on the order of 1°. The CICNT diameter, static contact angle, sliding angle, and contact angle hysteresis were examined for varying levels of carbon-infiltration to determine the effect of infiltration on superhydrophobicity. The same superhydrophobic behavior and tunable geometry were also observed with CICNTs grown directly on stainless steel without an additional catalyst layer. The ability to tune the geometry while maintaining superhydrophobic behavior offers significant potential in condensation heat transfer, anti-icing, microfluidics, anti-microbial surfaces, and other bio-applications where control over the nanostructure is beneficial.

Superhydrophobic-superhydrophilic binary micropatterns by localized thermal treatment of polyhedral oligomeric silsesquioxane (POSS)-silica films

NASA Astrophysics Data System (ADS)

Schutzius, Thomas M.; Bayer, Ilker S.; Jursich, Gregory M.; Das, Arindam; Megaridis, Constantine M.

2012-08-01

Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ~100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications.Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions

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

Schaeffer, Daniel A.; Polizos, Georgios; Smith, D. Barton

Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a self-cleaning effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 16≥0° to 175°. This result is remarkable because such behavior cannotmore » be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, surfaces exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the contact angle and optical transmission between 190 to 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents isopropyl alcohol and 4-chlorobenzotrifluoride (PCBTF) and a proprietary ceramic binder (Cerakote ). Finally, this solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 minutes, these coatings exhibited superhydrophobic behavior with a static CA ≥160°.« less

Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation.

PubMed

Li, Jian; Kang, Ruimei; Tang, Xiaohua; She, Houde; Yang, Yaoxia; Zha, Fei

2016-04-14

Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.

Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates.

PubMed

Ebert, Daniel; Bhushan, Bharat

2016-11-01

Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM). Copyright © 2016 Elsevier Inc. All rights reserved.

Super-Hydrophobic Surface Prepared by Lanthanide Oxide Ceramic Deposition Through PS-PVD Process

NASA Astrophysics Data System (ADS)

Li, Jie; Li, Cheng-Xin; Chen, Qing-Yu; Gao, Jiu-Tao; Wang, Jun; Yang, Guan-Jun; Li, Chang-Jiu

2017-02-01

Super-hydrophobic surface has received widespread attention in recent years. Both the surface morphology and chemical composition have significant impact on hydrophobic performance. A novel super-hydrophobic surface based on plasma spray-vapor deposition was introduced in the present paper. Samaria-doped ceria, which has been proved as an intrinsic hydrophobic material, was used as feedstock material. Additionally, in order to investigate the influence of surface free energy on the hydrophobicity, chemical modification by low surface free energy materials including stearic acid and 1,1,2,2-tetrahydroperfluorodecyltrimethoxysilane (FAS) was used on coating surface. Scanning electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the coating surface. The results show that the obtained surface has a hierarchical structure composed by island-like structures agglomerated with angular-like sub-micrometer-sized particles. Moreover, with the surface free energy decreases, the hydrophobic property of the surface improves gradually. The water contact angle of the as-sprayed coating surface increases from 110° to 148° after modification by stearic acid and up to 154° by FAS. Furthermore, the resultant surface with super-hydrophobicity exhibits an excellent stability.

Robust superhydrophobic surface on Al substrate with durability, corrosion resistance and ice-phobicity

PubMed Central

Wang, Guoyong; Liu, Shuai; Wei, Sufeng; Liu, Yan; Lian, Jianshe; Jiang, Qing

2016-01-01

Practical application of superhydrophobic surfaces is limited by the fragility of nanoscale asperities. Combining chemical etching and anodization, microscale pits and nanoscale pores, instead of the micro and nano protrusions on traditional superhydrophobic surfaces mimicking Lutos leaves, were fabricated on commercially pure aluminum surfaces. After modified by FDTS, the surfaces were superhydrophobic and self-cleaning. The ultrahigh hardness and electrochemical stability of Al2O3 coating endowed the surface excellent mechanical durability and good corrosion resistance. Because the method is scalable, it may find practical application on body panels of automobiles and aircrafts and so on. PMID:26853810

Super-hydrophobic coatings based on non-solvent induced phase separation during electro-spraying.

PubMed

Gao, Jiefeng; Huang, Xuewu; Wang, Ling; Zheng, Nan; Li, Wan; Xue, Huaiguo; Li, Robert K Y; Mai, Yiu-Wing

2017-11-15

The polymer solution concentration determines whether electrospinning or electro-spraying occurs, while the addition of the non-solvent into the polymer solution strongly influences the surface morphology of the obtained products. Both smooth and porous surfaces of the electro-sprayed microspheres can be harvested by choosing different non-solvent and its amount as well as incorporating polymeric additives. The influences of the solution concentration, weight ratio between the non-solvent and the copolymer, and the polymeric additives on the surface morphology and the wettability of the electro-sprayed products were systematically studied. Surface pores and/or asperities on the microsphere surface were mainly caused by the non-solvent induced phase separation (NIPS) and subsequent evaporation of the non-solvent during electro-spraying. With increasing polymer solution concentration, the microsphere was gradually changed to the bead-on-string geometry and finally to a nanofiber form, leading to a sustained decrease of the contact angle (CA). It was found that the substrate coatings derived from the microspheres possessing hierarchical surface pores or dense asperities had high surface roughness and super-hydrophobicity with CAs larger than 150° while sliding angles smaller than 10°; but coatings composed of microspheres with smooth surfaces gave relatively low CAs. Copyright © 2017 Elsevier Inc. All rights reserved.

Superhydrophobic to hydrophilic transition of multi-walled carbon nanotubes induced by Na+ ion irradiation

NASA Astrophysics Data System (ADS)

Das, Pritam; Dhal, Satyanarayan; Ghosh, Susanta; Chatterjee, Sriparna; Rout, Chandra S.; Ramgir, Niranjan; Chatterjee, Shyamal

2017-12-01

Multi-walled carbon nanotubes (MWCNT) having diameter in the range of 5-30 nm were coated on silicon wafer using spray coating technique. The coated film was irradiated with 5 keV Na+ at a fluence of 1 × 1016 ions·cm-2. A large-scale welding is observed in the post-irradiated nanotube assembly under scanning electron microscope. We have studied dynamic wetting properties of the nanotubes. While the pristine MWCNT shows superhydrophobic nature, the irradiated MWCNT turns into hydrophilic. Our simulation based on iradina and experimental evidences show defect formation in MWCNT due to ion irradiation. We have invoked mechanism based on defect mediated adsorption of water, which plays major role for transition from superhydrophobic to hydrophilic.

Enhanced Thermal Transport of Surfaces with Superhydrophobic Coatings

DTIC Science & Technology

2015-07-01

transport, superhydrophobic, jumping droplet, cooling, nanostructure, self - assembled monolayer 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...modified from a hydrophilic chemistry (oxide) to a hydrophobic surface using a fluorinated (or protonated) self - assembled monolayer (SAM). Chemical...seconds and dried with filtered nitrogen. 2.3 SAM Deposition The final step involved the deposition of a self - assembled monolayer onto the silvered

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity.

PubMed

Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

2017-01-01

Highly transparent, energy-saving, and superhydrophobic nanostructured SiO 2 /VO 2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO 2 layer and a top protective layer that consists of SiO 2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO 2 layer. The transmittance of the composite films in visible region ( T lum ) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO 2 films and tungsten-doped VO 2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO 2 /VO 2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW . cm -2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity

NASA Astrophysics Data System (ADS)

Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

2017-12-01

Highly transparent, energy-saving, and superhydrophobic nanostructured SiO2/VO2 composite films have been fabricated using a sol-gel method. These composite films are composed of an underlying infrared (IR)-regulating VO2 layer and a top protective layer that consists of SiO2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO2 layer. The transmittance of the composite films in visible region (Tlum) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO2 films and tungsten-doped VO2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO2/VO2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW.cm-2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.

Study on bouncing motion of a water drop collision on superhydrophobic surface under icing conditions

NASA Astrophysics Data System (ADS)

Maeda, Tetsuro; Morita, Katsuaki; Kimura, Shigeo

2017-11-01

When micro droplets in the air are supercooled and collide with the object, they froze on the surface at the time of a collision and can be defined as icing. If supercooled water droplets collide with an airfoil of an aircraft in flight and shape changes, there is a danger of losing lift and falling. Recently, the ice protection system using a heater and Anti- / Deicing (superhydrophobic) coating is focused. In this system, colliding water droplets are melted by the heat of the heater at the tip of the blade, and the water droplet is bounced by the aerodynamic force on the rear superhydrophobic coating. Thus, it prevents the phenomenon of icing again at the back of the wing (runback ice). Therefore, it is possible to suppress power consumption of the electric heater. In that system, it is important to withdraw water droplets at an extremely superhydrophobic surface at an early stage. However, research on bouncing phenomenon on superhydrophobic surface under icing conditions are not done much now. Therefore, in our research, we focus on one drop supercooled water droplet that collides with the superhydrophobic surface in the icing phenomenon, and aim to follow that phenomenon. In this report, the contact time is defined as the time from collision of a water droplet to bouncing from the superhydrophobic surface, and various parameters (temperature, speed, and diameter) on water droplets under icing conditions are set as the water drop bouncing time (contact time) of the product.

Bioinspired Antifreeze Secreting Frost-Responsive Pagophobic Coatings

NASA Astrophysics Data System (ADS)

Sun, Xiaoda; Damle, Viraj; Rykaczewski, Konrad

2014-11-01

Prevention of ice and frost accumulation is of interest to transportation, power generation, and agriculture industries. Superhydrophobic and lubricant impregnated pagophobic coatings have been proposed, however, they both fail in frosting conditions. Inspired by functional liquid secretion in natural systems, such as toxin secretion by poison dart frost in response to predator presence, we developed frost-responsive antifreeze secreting pagophobic coatings. These are bi-layered coatings with an inner superhydrophilic ``dermis'' infused with antifreeze and an outer permeable superhydrophobic ``epidermis.'' The superhydrophobic epidermis separates the antifreeze from the environment and prevents ice accumulation by repelling impinging water droplets. In frosting conditions, the antifreeze is secreted from the dermis through pores in the epidermis either due to contact with condensed droplets or temporary switch of the epidermis wettability from hydrophobic to hydrophilic caused by surface icing. Here we demonstrate superior performance of this multifunctional coating in simulated frosting, freezing mist/fog, and freezing spray/rain conditions. KR acknowledges startup funding from ASU.

Transparent nanocrystalline ZnO and ZnO:Al coatings obtained through ZnS sols

NASA Astrophysics Data System (ADS)

Kolobkova, E. V.; Evstropiev, S. K.; Nikonorov, N. V.; Vasilyev, V. N.; Evstropyev, K. S.

2017-11-01

Thin and uniform ZnO and ZnO:Al coatings were prepared on glass surfaces by using film-forming colloidal solutions containing small ZnS nanoparticles and polyvinylpyrrolidone as a polymer stabilizer. Film-forming ZnS sols were synthesized in the mixed water-propanol-2 solutions by chemical reaction between zinc nitrate and sodium sulfide. The addition of modifying component such as Al(NO3)3 into the film-forming solutions allows one to obtain thin and uniform ZnO:Al coatings. An increase in the sodium sulfide content in film-forming solutions leads to the growth of light absorption in the UV. The evolution of a coating material at all technological stages from the ZnS sols up to the transparent ZnO and ZnO:Al2O3 coatings (the latter kind being denoted further, in accord with a common practice, by ZnO:Al) was studied using the optical spectroscopy, XRD analysis, DSC-TGA, and SEM methods. The chemical processes of decomposing salts and the polymer occur by heating the intermediate composite ZnS/polyvinylpyrrolidone coatings in the 280-500 °C temperature range. Experimental data show that the ZnO and ZnO:Al coatings prepared consist of the slightly elongated oxide nanoparticles. These coatings fully cover the glass surface and demonstrate a high transparency in the UV and visible.

Development of high dispersed TiO2 paste for transparent screen-printable self-cleaning coatings on glass

NASA Astrophysics Data System (ADS)

Wang, Yuanhao; Lu, Lin; Yang, Hongxing; Che, Quande

2013-01-01

This paper reports a cheap and facile method to fabricate transparent self-cleaning coatings on glass by screen-printing high dispersed TiO2 paste. Three kinds of ZrO2 beads with diameter of 2, 1, and 0.1-0.2 mm were utilized to investigate their influence on the grinding and dispersion of the commercial TiO2 powder in the ball mill. From the SEM images, surface profiler and transmittance spectrum it could be demonstrated that the smallest ZrO2 bead with the diameter of 0.1-0.2 mm was the best candidate to disperse the TiO2 powder into nanoscale size to make the high dispersed TiO2 paste which was the key factor to achieve a smooth, high transparent TiO2 coating. The surface wettability measurement showed that all the screen-printed coatings had super hydrophilic surfaces, which was independent to the surface morphology. However, the coating with the highest transparency showed the lowest photocatalytic activity which is mainly due to the light loss.

Transparent, Conductive Coatings Developed for Arc-Proof Solar Arrays

NASA Technical Reports Server (NTRS)

1996-01-01

Transparent, conductive thin-film coatings have many potential applications where a surface must be able to dissipate electrical charges without sacrificing its optical properties. Such applications include automotive and aircraft windows, heat mirrors, optoelectronic devices, gas sensors, and solar cell array surfaces for space applications. Many spacecraft missions require that solar cell array surfaces dissipate charges in order to avoid damage such as electronic upsets, formation of pinholes in the protective coatings on solar array blankets, and contamination due to deposition of sputtered products. In tests at the NASA Lewis Research Center, mixed thin-films of sputter-deposited indium tin oxide (ITO) and magnesium fluoride (MgF2) that could be tailored to the desired sheet resistivity, showed transmittance values of greater than 90 percent. The samples evaluated were composed of mixed, thin-film ITO/MgF2 coatings, with a nominal thickness of 650 angstroms, deposited onto glass substrates. Preliminary results indicated that these coatings were durable to vacuum ultraviolet radiation and atomic oxygen. These coatings show promise for use on solar array surfaces in polar low-Earth-orbit environments, where a sheet resistivity of less than 10(exp 8)/square is required, and in geosynchronous orbit environments, where a resistivity of less than 10(exp 9)/square is required.

Facile synthesis of stable superhydrophobic nanocomposite based on multi-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Mokarian, Zahra; Rasuli, Reza; Abedini, Yousefali

2016-04-01

A facile approach to fabricate a stable superhydrophobic composite comprising multi-walled carbon nanotubes and silicone rubber has been reported. Contact angle of de-ionized water droplets on the prepared surface was measured with the value of near 159°; while water droplets easily rolled off and bounced on it. Surface free energy of the superhydrophobic coating was examined by three methods about 26 mJ/m2. The prepared film shows good stability under high stress conditions such as ultraviolet exposure, heating, pencil hardness test, attacking with different pH value and ionic-strength solutions. In addition, remarkable stability of the coating was observed after soaking in condensed hydrochloric acid, 5 wt.% NaCl aqueous solution, boiling water and tape test.

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance, solar modulation capability, and superhydrophobicity

PubMed Central

Wang, Chao; Zhao, Li; Liang, Zihui; Dong, Binghai; Wan, Li; Wang, Shimin

2017-01-01

Abstract Highly transparent, energy-saving, and superhydrophobic nanostructured SiO2/VO2 composite films have been fabricated using a sol–gel method. These composite films are composed of an underlying infrared (IR)-regulating VO2 layer and a top protective layer that consists of SiO2 nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO2 layer. The transmittance of the composite films in visible region (T lum) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO2 films and tungsten-doped VO2 film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO2/VO2 composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW.cm−2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications. PMID:28970866

Nano-engineering of superhydrophobic aluminum surfaces for anti-corrosion

NASA Astrophysics Data System (ADS)

Jeong, Chanyoung

Metal corrosion is a serious problem, both economically and operationally, for engineering systems such as aircraft, automobiles, pipelines, and naval vessels. In such engineering systems, aluminum is one of the primary materials of construction due to its light weight compared to steel and good general corrosion resistance. However, because of aluminum's relatively lower resistance to corrosion in salt water environments, protective measures such as thick coatings, paints, or cathodic protection must be used for satisfactory service life. Unfortunately, such anti-corrosion methods can create other concerns, such as environmental contamination, protection durability, and negative impact on hydrodynamic efficiency. Recently, a novel approach to preventing metal corrosion has emerged, using superhydrophobic surfaces. Superhydrophobic surfaces create a composite interface to liquid by retaining air within the surface structures, thus minimizing the direct contact of the liquid environment to the metal surface. The result is a highly non-wetting and anti-adherent surface that can offer other benefits such as biofouling resistance and hydrodynamic low friction. Prior research with superhydrophobic surfaces for corrosion applications was based on irregular surface roughening and/or chemical coatings, which resulted in random surface features, mostly on the micrometer scale. Such microscale surface roughness with poor controllability of structural dimensions and shapes has been a critical limitation to deeper understanding of the anti-corrosive effectiveness and optimized application of this approach. The research reported here provides a novel approach to producing controlled superhydrophobic nanostructures on aluminum that allows a systematic investigation of the superhydrophobic surface parameters on the corrosion resistance and hence can provide a route to optimization of the surface. Electrochemical anodization is used to controllably modulate the oxide layer

Effects of superhydrophobic surface on the propeller wake

NASA Astrophysics Data System (ADS)

Choi, Hongseok; Lee, Jungjin; Park, Hyungmin

2017-11-01

This study investigates the change in propeller wake when the superhydrophobic surface is applied on the propeller blade. The propeller rotates in a quiescent water tank, facing its bottom, with a rotational Reynolds number of 96000. To measure the three-dimensional flow fields, we use stereo PIV and a water prism is installed at the camera-side tank wall. Two cameras are tilted 30 degrees from the normal axis of the tank wall, satisfying schiempflug condition. Superhydrophobic surface is made by coating hydrophobic nanoparticles on the propeller blade. Measurements are done on two vertical planes (at the center of propeller hub and the blade tip), and are ensemble averaged being classified by blade phase of 0 and 90 degrees. Velocity fluctuation, turbulent kinetic energy, and vorticity are evaluated. With superhydrophobic surface, it is found that the turbulence level is significantly (20 - 30 %) reduced with a small penalty (less than 5%) in the streamwise momentum (i.e., thrust) generation. This is because the cone shaped propeller wake gets narrower and organized vortex structures are broken with the superhydrophobic surfaces. More detailed flow analysis will be given. Supported by NRF (NRF-2016R1C1B2012775, NRF-2016M2B2A9A02945068) programs of Korea government.

Electrical Properties and Manufacturability of ITO-MgF2 and Related Transparent Arcproof Spacecraft Coatings

NASA Technical Reports Server (NTRS)

Hambourger, Paul D.

2003-01-01

To investigate the applicability of co-deposited indium tin oxide and magnesium fluoride as a transparent arcproof coating on the exterior of PowerSphere microsatellites. This included testing coating performance after deposition on flexible polymeric substrates, determining whether ultraviolet (UV) radiation present during deposition might affect the UV-curing resin contained in the substrate, and preparation of coated polymeric samples for radiation damage studies by the PowerSphere team.

Transparent photocatalytic coatings on the surface of the tips of medical fibre-optic bundles

NASA Astrophysics Data System (ADS)

Evstropiev, S. K.; Volynkin, V. M.; Kiselev, V. M.; Dukelskii, K. V.; Evstropyev, K. S.; Demidov, V. V.; Gatchin, Yu. A.

2017-12-01

We report the results of the development of the sol - gel method for obtaining thin, transparent (in the visible part of the spectrum) TiO2/MgO coatings on the surfaces of the tips of medical fibre-optic bundles. Such coatings are capable of generating singlet oxygen under the action of UV radiation and are characterised by high antibacterial activity.

Plasmonic Three-Dimensional Transparent Conductor Based on Al-Doped Zinc Oxide-Coated Nanostructured Glass Using Atomic Layer Deposition

DOE PAGES

Malek, Gary A.; Aytug, Tolga; Liu, Qingfeng; ...

2015-04-02

Transparent nanostructured glass coatings, fabricated on glass substrates, with a unique three-dimensional (3D) architecture were utilized as the foundation for the design of plasmonic 3D transparent conductors. Transformation of the non-conducting 3D structure to a conducting 3D network was accomplished through atomic layer deposition of aluminum-doped zinc oxide (AZO). After AZO growth, gold nanoparticles (AuNPs) were deposited by electronbeam evaporation to enhance light trapping and decrease the overall sheet resistance. Field emission scanning electron microscopy and atomic force microcopy images revealed the highly porous, nanostructured morphology of the AZO coated glass surface along with the in-plane dimensions of the depositedmore » AuNPs. Sheet resistance measurements conducted on the coated samples verified that the electrical properties of the 3D network are comparable to that of the untextured two-dimensional AZO coated glass substrates. In addition, transmittance measurements of the glass samples coated with various AZO thicknesses showed preservation of the highly transparent nature of each sample, while the AuNPs demonstrated enhanced light scattering as well as light-trapping capability.« less

Plasmonic Three-Dimensional Transparent Conductor Based on Al-Doped Zinc Oxide-Coated Nanostructured Glass Using Atomic Layer Deposition

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

Malek, Gary A.; Aytug, Tolga; Liu, Qingfeng

Transparent nanostructured glass coatings, fabricated on glass substrates, with a unique three-dimensional (3D) architecture were utilized as the foundation for the design of plasmonic 3D transparent conductors. Transformation of the non-conducting 3D structure to a conducting 3D network was accomplished through atomic layer deposition of aluminum-doped zinc oxide (AZO). After AZO growth, gold nanoparticles (AuNPs) were deposited by electronbeam evaporation to enhance light trapping and decrease the overall sheet resistance. Field emission scanning electron microscopy and atomic force microcopy images revealed the highly porous, nanostructured morphology of the AZO coated glass surface along with the in-plane dimensions of the depositedmore » AuNPs. Sheet resistance measurements conducted on the coated samples verified that the electrical properties of the 3D network are comparable to that of the untextured two-dimensional AZO coated glass substrates. In addition, transmittance measurements of the glass samples coated with various AZO thicknesses showed preservation of the highly transparent nature of each sample, while the AuNPs demonstrated enhanced light scattering as well as light-trapping capability.« less

Coating-Free, Air-Stable Silver Nanowires for High-performance Transparent Conductive Film.

PubMed

Tang, Long; Zhang, Jiajia; Dong, Lei; Pan, Yunmei; Yang, Chongyang; Li, Mengxiong; Ruan, Yingbo; Ma, Jianhua; Lu, Hongbin

2018-06-21

Silver nanowires (Ag NWs) based films are considered as a promising alternative for traditional indium tin oxide (ITO) but still suffer from some limitations, including insufficient conductivity, transparency and environmental instability. We here report a novel etching synthesis strategy to improve the performance of Ag NW films. Different from the traditional methods to synthesize high aspect ratios of NWs or employ electrically conductive coatings, we find it effective to reduce the high-reactivity defects of NWs for optimizing the comprehensive performance of Ag NW films. In this strategy etching can suppress the generation of high-reactivity defects and meanwhile the etching growth of NWs can be accomplished in an uneven ligand distribution environment. The resulting Ag NWs are uniformly straight and sharp-edged structure. The transparent conductive film (TCF) obtained exhibits simultaneous improvements in electrical conductivity, transparency and air-stability. Even after exposure in air for 200 days and no any protective coatings, the film can still meet the highest requirement of practical applications, with a figure of merit 361 (i.e., FoM > 350). These results not only demonstrate the importance of defect control in the synthesis of Ag NWs, but also pave a way for further optimizing the performance of Ag NW-based films. © 2018 IOP Publishing Ltd.

Superhydrophobic polymeric films with hierarchical structures produced by nanoimprint (NIL) and plasma roughening

NASA Astrophysics Data System (ADS)

Durret, Jérôme; Szkutnik, Pierre-David; Frolet, Nathalie; Labau, Sebastien; Gourgon, Cécile

2018-07-01

The structuration of various polymeric films has been studied to create superhydrophobic surfaces. Nanoimprint lithography and/or plasma etching processes with CF4/Ar have been used on FEP, PMMA and PET polymer films. On the one hand, the effect of the CF4/Ar gases, the input power and the plasma treatment duration have been investigated in terms of etching and fluorination degree, and XPS analyses are precisely discussed. On the other hand, wettability performances were characterized. Relationships between the contact angle, the contact angle hysteresis and the surface structures have been investigated. The wetting behaviors and the transition between the Wenzel and the Cassie-Baxter states was discussed as a function of the roughness. We have prepared each studied polymer films in transparent and flexible superhydrophobic surfaces whose contact angle are ∼160° and hysteresis are ∼2°. A short plasma treatment time (10 s) is sufficient to obtain a superhydrophobic behavior on FEP and PMMA. Results indicate that hierarchical structures allow a more stable superhydrophobic state regarding inhomogeneities. Moreover, the use of plasma etching is suggested to overcome some limitations of the NIL in the case of structures with a high aspect ratio. Finally, a quick and large surface fabrication method for superhydrophobic films is detailed.

Superhydrophobic hybrid inorganic-organic thiol-ene surfaces fabricated via spray-deposition and photopolymerization.

PubMed

Sparks, Bradley J; Hoff, Ethan F T; Xiong, Li; Goetz, James T; Patton, Derek L

2013-03-13

We report a simple and versatile method for the fabrication of superhydrophobic inorganic-organic thiol-ene coatings via sequential spray-deposition and photopolymerization under ambient conditions. The coatings are obtained by spray-deposition of UV-curable hybrid inorganic-organic thiol-ene resins consisting of pentaerythritol tetra(3-mercaptopropionate) (PETMP), triallyl isocyanurate (TTT), 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (TMTVSi), and hydrophobic fumed silica nanoparticles. The spray-deposition process and nanoparticle agglomeration/dispersion provide surfaces with hierarchical morphologies exhibiting both micro- and nanoscale roughness. The wetting behavior, dependent on the concentration of TMTVSi and hydrophobic silica nanoparticles, can be varied over a broad range to ultimately provide coatings with high static water contact angles (>150°), low contact angle hysteresis, and low roll off angles (<5°). The cross-linked thiol-ene coatings are solvent resistant, stable at low and high pH, and maintain superhydrophobic wetting behavior after extended exposure to elevated temperatures. We demonstrate the versatility of the spray-deposition and UV-cure process on a variety of substrate surfaces including glass, paper, stone, and cotton fabric.

The one-step electroposition of superhydrophobic surface on AZ31 magnesium alloy and its time-dependence corrosion resistance in NaCl solution

NASA Astrophysics Data System (ADS)

Zhong, Yuxing; Hu, Jin; Zhang, Yufen; Tang, Shawei

2018-01-01

A calcium myristic superhydrophobicity coating with a hierarchical micro-nanostructure was fabricated on AZ31 magnesium alloy by one-step electroposition. The effects of deposition time on the coating structure, such as morphology, thickness, wettability and phase composition of the coating were studied. The corrosion behavior of the coated samples in 3.5% NaCl solution was also investigated and the corrosion mechanism was discussed. It was found that the deposition time has a visible effect on the morphology, thickness and wettability, which distinctly affects the corrosion resistance of coatings. The corrosion resistance of the coating gradually decreases with the increase in the immersion time due to the disappearance of the air layer which exists on the coating surface. The superhydrophobic surfaces present the temporal limitations to the corrosion resistance of AZ31 magnesium alloy.

Investigation on stability and moisture absorption of superhydrophobic wood under alternating humidity and temperature conditions

NASA Astrophysics Data System (ADS)

Qing, Yan; Liu, Ming; Wu, Yiqiang; Jia, Shanshan; Wang, Shuang; Li, Xingong

The application of superhydrophobic wood is majorly limited by its durability when subjected to natural conditions. Herein, the stability of two representative superhydrophobic woods (i.e., Poplar (Populus tomentosa) and Chinese fir (Cunninghamia lanceolata)), were prepared via a one-step hydrothermal process using tetrabutyltitanate (Ti(OC4H9)4, TBOT) and vinyltriethoxysilane (CH2CHSi(OC2H5)3, VTES) as a co-precursor and sequentially tested under different humidity and temperature conditions. The variables including morphology, water contact angle (WCA), color parameter, chemical components of the surface, and moisture absorption property were characterized using a scanning electron microscope (SEM), WCA measurement, a colorimeter, a Fourier transform infrared (FTIR) spectroscopy, and a moisture absorption test, respectively. It was found that initial static WCAs of superhydrophobic wood were larger than 150°. Micron-sized cracks were formed on the coatings after the alternating humidity and temperature aging cycles. This lowered the water repellency, but the WCA was still greater than 140°. There was nearly no chemical change of wood after the aging test; the color change between the same species of untreated and superhydrophobic wood was very small, only with a difference of 0.42 and 4.05 in overall color change ΔE∗ values for Chinese fir and poplar, respectively. The superhydrophobic coatings had a trivial influence on wood moisture absorption property, which only lowered 3% in poplar and 2% in Chinese fir, respectively.

Behavior of severely supercooled water drops impacting on superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Maitra, Tanmoy; Antonini, Carlo; Tiwari, Manish K.; Mularczyk, Adrian; Imeri, Zulkufli; Schoch, Philippe; Poulikakos, Dimos

2014-11-01

Surface icing, commonplace in nature and technology, has broad implications to daily life. To prevent surface icing, superhydrophobic surfaces/coatings with rationally controlled roughness features (both at micro and nano-scale) are considered to be a promising candidate. However, to fabricate/synthesize a high performance icephobic surface or coating, understanding the dynamic interaction between water and the surface during water drop impact in supercooled state is necessary. In this work, we investigate the water/substrate interaction using drop impact experiments down to -17°C. It is found that the resulting increased viscous effect of water at low temperature significantly affects all stages of drop dynamics such as maximum spreading, contact time and meniscus penetration into the superhydrophobic texture. Most interestingly, the viscous effect on the meniscus penetration into roughness feature leads to clear change in the velocity threshold for rebounding to sticking transition by 25% of supercooled drops. Swiss National Science Foundation (SNF) Grant 200021_135479.

Optically transparent and durable Al2O3 coatings for harsh environments by ultra short pulsed laser deposition

NASA Astrophysics Data System (ADS)

Korhonen, Hannu; Syväluoto, Aki; Leskinen, Jari T. T.; Lappalainen, Reijo

2018-01-01

Nowadays, an environmental protection is needed for a number of optical applications in conditions quickly impairing the clarity of optical surfaces. Abrasion resistant optical coatings applied onto plastics are usually based on alumina or polysiloxane technology. In many applications transparent glasses and ceramics need a combination of abrasive and chemically resistant shielding or other protective solutions like coatings. In this study, we intended to test our hypothesis that clear and pore free alumina coating can be uniformly distributed on glass prisms by ultra short pulsed laser deposition (USPLD) technique to protect the sensitive surfaces against abrasives. Abrasive wear tests were carried out by the use of SiC emery paper using specified standard procedures. After the wear tests the measured transparencies of coated prisms turned out to be close those of the prisms before coating. The coating on sensitive surfaces consistently displayed enhanced wear resistance exhibiting still high quality, even after severe wear testing. Furthermore, the coating modified the surface properties towards hydrophobic nature in contrast to untreated prisms, which became very hydrophilic especially due to wear.

Steady anti-icing coatings on weathering steel fabricated by HVOF spraying

NASA Astrophysics Data System (ADS)

Xi, Naiyuan; Liu, Yan; Zhang, Xiangning; Liu, Nan; Fu, Hao; Hang, Zongqiu; Yang, Guiying; Chen, Hui; Gao, Wei

2018-06-01

Super-hydrophobic surface has attracted much attention over the years due to their unique wettability and excellent performances like highly hydrophobic, ice-phobic, etc. A fast and straightforward fabrication method in this work was proposed to prepare super-hydrophobic coating on weathering steel substrate by high velocity oxygen-fuel (HVOF) spraying, which aimed to delay the beginning freezing time, decrease the ice accumulation amount and reduce the adhesion of ice. The resulting showed that the contact angle of the coatings was about 154.3 ± 3.0°, and the sliding angle was about 4.1 ± 0.1°. Moreover, compared with steel substrate, as-prepared super-hydrophobic coatings exhibit memorable promotion in reducing icing weight and repelling ice.

Robust Fluorine-Free Superhydrophobic Amino-Silicone Oil/SiO2 Modification of Electrospun Polyacrylonitrile Membranes for Waterproof-Breathable Application.

PubMed

Sheng, Junlu; Xu, Yue; Yu, Jianyong; Ding, Bin

2017-05-03

Superhydrophobic waterproof-breathable membranes have attracted considerable interest owing to their multifunctional applications in self-cleaning, anti-icing, anticorrosion, outdoor tents, and protective clothing. Despite the researches pertaning to the construction of superhydrophobic functional membranes by nanoparticle finishing have increased drastically, the disconnected particle component is easy to fall off from the membranes under deformation and wear conditions, which has restricted their wide use in practice. Here, robust superhydrophobic microporous membranes were prepared via a facile and environmentally friendly strategy by dip-coating amino-silicone oil (ASO) onto the electrospun polyacrylonitrile (PAN) membranes, followed by SiO 2 nanoparticles (SiO 2 NPs) blade coating. Compared with hydrophilic PAN membranes, the modified membranes exhibited superhydrophobic surface with an advancing water contact angle up to 156°, after introducing ASO as low surface energy substance and SiO 2 NPs as filler to reduce the pore size and construct the multihierarchical rough structure. Varying the concentrations of ASO and SiO 2 NPs systematically, the PAN electrospun membranes modified with 1 wt % ASO and 0.1 wt % SiO 2 NPs were endowed with good water-resistance (74.3 kPa), relative low thermal conductivity (0.0028 W m -1 K -1 ), modest vapor permeability (11.4 kg m -2 d -1 ), and air permeability (20.5 mm s -1 ). Besides, the inorganic-organic hybrid coating of ASO/SiO 2 NPs could maintain its superhydrophobicity even after 40 abrasion cycles. The resulting membranes were found to resist variations on the pH scale from 0 to 12, and retained their water repellent properties when exposed to harsh acidic and alkali conditions. This facile fabrication of durable fluorine-free superhydrophobic membranes simultaneous with good waterproof-breathable performance provides the advantages for potential applications in self-cleaning materials and versatile protective

TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

NASA Astrophysics Data System (ADS)

Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan; Xie, Xi

2017-12-01

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating

PubMed Central

Hang, Tian; Chen, Hui-Jiuan; Xiao, Shuai; Yang, Chengduan; Chen, Meiwan; Tao, Jun; Shieh, Han-ping; Yang, Bo-ru; Liu, Chuan

2017-01-01

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials. PMID:29308265

Facile preparation of high density polyethylene superhydrophobic/superoleophilic coatings on glass, copper and polyurethane sponge for self-cleaning, corrosion resistance and efficient oil/water separation.

PubMed

Cheng, Yuanyuan; Wu, Bei; Ma, Xiaofan; Lu, Shixiang; Xu, Wenguo; Szunerits, Sabine; Boukherroub, Rabah

2018-04-18

Inspired by the lotus effect and water-repellent properties of water striders' legs, superhydrophobic surfaces have been intensively investigated from both fundamental and applied perspectives for daily and industrial applications. Various techniques are available for the fabrication of artificial superoleophilic/superhydrophobic (SS). However, most of these techniques are tedious and often require hazardous or expensive equipment, which hampers their implementation for practical applications. In the present work, we used a versatile and straightforward technique based on polymer drop-casting for the preparation SS materials that can be implemented on any substrate. High density polyethylene (HDPE) SS coatings were prepared on different substrates (glass, copper mesh and polyurethane (PU) sponge) by drop casting the parent polymer xylene-ethanol solution at room temperature. All the substrates exhibited a superhydrophobic behavior with a water contact angle (WCA) greater than 150°. Furthermore, the corrosion resistance, stability, self-cleaning property, and water/oil separation of the developed materials were also assessed. While copper mesh and PU sponge exhibited good ability for oil and organic solvents separation from water, the HDPE-functionalized PU sponge displayed good adsorption capacity, 32-90 times the weight of adsorbed substance vs. the weight of adsorbent. Copyright © 2018 Elsevier Inc. All rights reserved.

Functionalized hexagonal boron nitride nano-coatings for protection of transparent plastics

NASA Astrophysics Data System (ADS)

Van Tran, Thu; Usta, Aybala; Asmatulu, Ramazan

2016-04-01

Nanocoating is the result of a coating application of nanomaterials to build a consistent network of molecules in a paint to protect the surfaces of various materials and devices. Hexagonal Boron Nitride (h-BN) is in two dimensional form with excellent thermal, mechanical and chemical properties. These BN nanocoatings are also a thermally insulating material for heat management. After adding functionalized h-BNs into paints or other coatings, they will absorb the harmful UV part of sunlight and prevent coating against the environmental degradations. The impacts of the environmental factors on the coatings can be substantially eliminated. In the present study, h-BNs were modified with [2-(2-Aminoethylamino) propyl] trimethoxysilane and uniformly dispersed into the polyurethane coatings with different amounts, such as 0.1, 0.2, 0.4, and 0.8wt% to increase hardness and water resistance, and decrease the UV degradation level of coatings and transparent plastics. The prepared samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, Scanning Electron Microscope (SEM), Water Contact Angle, and Differential Scanning Calorimeter (DSC). The test results showed that the nanocoatings with functionalized h-BN provided excellent physical and chemical behaviors against the UV and other physical degradations on the substrates.

Delayed condensation and frost formation on superhydrophobic carbon soot coatings by controlling the presence of hydrophilic active sites

NASA Astrophysics Data System (ADS)

Esmeryan, Karekin D.; Castano, Carlos E.; Mohammadi, Reza; Lazarov, Yuliyan; Radeva, Ekaterina I.

2018-02-01

Condensation frosting is an undesired natural phenomenon that could be impeded efficiently using appropriate wettability and morphologically patterned surfaces. The icephobic properties of carbon soot and the fabrication scalability of its synthesis method are a good foundation for anti-frosting applications; however, the fundamentals of frost growth and spreading on sooted surfaces have not been examined yet. In this study, we investigate the anti-frosting performance of three groups of superhydrophobic soot coatings by means of 16 MHz quartz crystal microbalances (QCMs). The analysis of the real-time sensor signal of each soot coated QCM pattern shows that frost formation and its propagation velocity depend on the quantity of oxygen functionalities and structural defects in the material. In turn, the reduction of both parameters shifts the onset of frost growth to temperatures below  -20 °C, whereas the interdroplet ice bridging is slowed by a factor of four. Moreover, high-resolution scanning electron micrographs of the samples imply delamination upon defrosting of the soot with spherical-like morphology via polar interactions driven mechanism. These results reveal an opportunity for control of frost incipiency on sooted surfaces by adjusting the synthesis conditions and depositing soot coatings with as low as possible content of hydrophilic active sites.

A versatile route to polymer-reinforced, broadband antireflective and superhydrophobic thin films without high-temperature treatment.

PubMed

Ren, Tingting; Geng, Zhi; He, Junhui; Zhang, Xiaojie; He, Jin

2017-01-15

Broadband high transmittance, good mechanical robustness as well as simple and low temperature fabrication are three important aspects that dictate the practical applications of superhydrophobic thin films, especially on organic substrates. However, it has proved difficult to meet these challenges. In the present work, superhydrophobic thin films were prepared by first dip-coating solid silica nanoparticles, then spray-coating hollow silica nanoparticles, followed by spray-coating mesoporous silica nanosheets & poly(vinyl alcohol) (PVA), and eventually chemical vapor deposition of 1H,1H,2H,2H-perflurooctyltriethoxysilane (POTS) at 90°C. The optimized thin film has a maximum transmittance of 96.0% in the wavelength range of 300-2500nm and a WCA of 164° and a RA of 1°. The thin film also shows good mechanical robustness toward water droplet impact test, sand impact abrasion test and tape adhesion tests, which results from PVA as a binder, the formation of covalent bond between the hydroxyl group of PVA and the ethoxy group of POTS and the chemical inertness of CC, CF bonds of POTS molecules. To our best knowledge, it is the first example where antireflective and superhydrophobic thin films of excellent mechanical robustness were realized at low temperature on organic substrates (PMMA, PC). The current work would provide a promising route to meet the challenges in practical applications simultaneously posed by the requirements of broadband antireflection, good mechanical robustness as well as simple and low temperature fabrication of superhydrophobic thin films. Copyright © 2016 Elsevier Inc. All rights reserved.

Free-surface liquid jet impingement on rib patterned superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Maynes, D.; Johnson, M.; Webb, B. W.

2011-05-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on hydrophilic, hydrophobic, and superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 1900. The superhydrophobic surfaces are fabricated with both hydrophobically coated silicon and polydimethylsiloxane that exhibit alternating microribs and cavities. For all surfaces a transition from a thin radially moving liquid sheet occurs. This takes the form of the classical hydraulic jump for the hydrophilic surfaces but is markedly different for the hydrophobic and superhydrophobic surfaces, where the transition is significantly influenced by surface tension and a break-up into droplets is observed at high Weber number. For the superhydrophobic surfaces, the transition exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. However, the total projected area of the ellipse exhibits a nearly linear dependence on the jet Weber number, and was nominally invariant with varying hydrophobicity and relative size of the ribs and cavities. For the hydrophobic and superhydrophobic scenarios, the local Weber number based on the local radial velocity and local depth of the radially moving liquid sheet is observed to be of order unity at the transition location. The results also reveal that for increasing relative size of the cavities, the ratio of the ellipse axis (major-to-minor) increases.

Improved attachment of mesenchymal stem cells on super-hydrophobic TiO2 nanotubes.

PubMed

Bauer, Sebastian; Park, Jung; von der Mark, Klaus; Schmuki, Patrik

2008-09-01

Self-organized layers of vertically orientated TiO(2) nanotubes providing defined diameters ranging from 15 up to 100nm were grown on titanium by anodic oxidation. These TiO(2) nanotube layers show super-hydrophilic behavior. After coating TiO(2) nanotube layers with a self-assembled monolayer (octadecylphosphonic acid) they showed a diameter-dependent wetting behavior ranging from hydrophobic (108+/-2 degrees ) up to super-hydrophobic (167+/-2 degrees ). Cell adhesion, spreading and growth of mesenchymal stem cells on the unmodified and modified nanotube layers were investigated and compared. We show that cell adhesion and proliferation are strongly affected in the super-hydrophobic range. Adsorption of extracellular matrix proteins as fibronectin, type I collagen and laminin, as well as bovine serum albumin, on the coated and uncoated surfaces showed a strong influence on wetting behavior and dependence on tube diameter.

Combating Frosting with Joule-Heated Liquid-Infused Superhydrophobic Coatings.

PubMed

Elsharkawy, Mohamed; Tortorella, Domenico; Kapatral, Shreyas; Megaridis, Constantine M

2016-05-03

Frost formation is omnipresent when suitable environmental conditions are met. A good portion of research on combating frost formation has revolved around the passive properties of superhydrophobic (SHPO) and slippery lubricant-impregnated porous (SLIP) surfaces. Despite much progress, the need for surfaces that can effectively combat frost formation over prolonged periods still remains. In this work, we report, for the first time, the use of electrically conductive SHPO/SLIP surfaces for active mitigation of frost formation. First, we demonstrate the failure of these surfaces to passively avert prolonged (several hours) frosting. Next, we make use of their electroconductive property for active Joule heating, which results in the removal of any formed frost. We study the role of the impregnating lubricant in the heat transfer across the interface, the surface, and the ambient. We show that, even though the thermal properties of the impregnating lubricant may vary drastically, the lubricant type does not noticeably affect the defrosting behavior of the surface. We attribute this outcome to the dominant thermal resistance of the thick frost layer formed on the cooled surface. We support this claim by drawing parallels between the present system and heat transfer through a one-dimensional (1D) composite medium, and solving the appropriate transient transport equations. Lastly, we propose periodic thermal defrosting for averting frost formation altogether. This methodology utilizes the coating's passive repellent capabilities, while eliminating the dominant effect of thick deposited frost layers. The periodic heating approach takes advantage of lubricants with higher thermal conductivities, which effectively enhance heat transfer through the porous multiphase surface that forms the first line of defense against frosting.

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.

Wetting, superhydrophobicity, and icephobicity in biomimetic composite materials

NASA Astrophysics Data System (ADS)

Hejazi, Vahid

Recent developments in nano- and bio-technology require new materials. Among these new classes of materials which have emerged in the recent years are biomimetic materials, which mimic structure and properties of materials found in living nature. There are a large number of biological objects including bacteria, animals and plants with properties of interest for engineers. Among these properties is the ability of the lotus leaf and other natural materials to repel water, which has inspired researchers to prepare similar surfaces. The Lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. The range of actual and potential applications of superhydrophobic surfaces is diverse including optical, building and architecture, textiles, solar panels, lab-on-a-chip, microfluidic devices, and applications requiring antifouling from biological and organic contaminants. In this thesis, in chapter one, we introduce the general concepts and definitions regarding the wetting properties of the surfaces. In chapter two, we develop novel models and conduct experiments on wetting of composite materials. To design sustainable superhydrophobic metal matrix composite (MMC) surfaces, we suggest using hydrophobic reinforcement in the bulk of the material, rather than only at its surface. We experimentally study the wetting properties of graphite-reinforced Al- and Cu-based composites and conclude that the Cu-based MMCs have the potential to be used in the future for the applications where the wear-resistant superhydrophobicity is required. In chapter three, we introduce hydrophobic coating at the surface of concrete materials making them waterproof to prevent material failure, because concretes and ceramics cannot stop water from seeping through them and forming cracks. We create water-repellant concretes with CA close to 160o using superhydrophobic coating. In chapter four, experimental

Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

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

Wang, Yang; Wei Liu, Xiao; Zhang, Hai Feng, E-mail: wy3121685@163.com

We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H{sub 2}O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

Superhydrophobic Surface Coatings for Microfluidics and MEMs.

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

Branson, Eric D.; Singh, Seema; Houston, Jack E.

2006-11-01

Low solid interfacial energy and fractally rough surface topography confer to Lotus plants superhydrophobic (SH) properties like high contact angles, rolling and bouncing of liquid droplets, and self-cleaning of particle contaminants. This project exploits the porous fractal structure of a novel, synthetic SH surface for aerosol collection, its self-cleaning properties for particle concentration, and its slippery nature 3 to enhance the performance of fluidic and MEMS devices. We propose to understand fundamentally the conditions needed to cause liquid droplets to roll rather than flow/slide on a surface and how this %22rolling transition%22 influences the boundary condition describing fluid flow inmore » a pipe or micro-channel. Rolling of droplets is important for aerosol collection strategies because it allows trapped particles to be concentrated and transported in liquid droplets with no need for a pre-defined/micromachined fluidic architecture. The fluid/solid boundary condition is important because it governs flow resistance and rheology and establishes the fluid velocity profile. Although many research groups are exploring SH surfaces, our team is the first to unambiguously determine their effects on fluid flow and rheology. SH surfaces could impact all future SNL designs of collectors, fluidic devices, MEMS, and NEMS. Interfaced with inertial focusing aerosol collectors, SH surfaces would allow size-specific particle populations to be collected, concentrated, and transported to a fluidic interface without loss. In microfluidic systems, we expect to reduce the energy/power required to pump fluids and actuate MEMS. Plug-like (rather than parabolic) velocity profiles can greatly improve resolution of chip-based separations and enable unprecedented control of concentration profiles and residence times in fluidic-based micro-reactors. Patterned SH/hydrophilic channels could induce mixing in microchannels and enable development of microflow control elements

Robust Superhydrophobic Carbon Nanotube Film with Lotus Leaf Mimetic Multiscale Hierarchical Structures.

PubMed

Wang, Pengwei; Zhao, Tianyi; Bian, Ruixin; Wang, Guangyan; Liu, Huan

2017-12-26

Superhydrophobic carbon nanotube (CNT) films have demonstrated many fascinating performances in versatile applications, especially for those involving solid/liquid interfacial processes, because of their ability to affect the material/energy transfer at interfaces. Thus, developing superhydrophobic CNTs has attracted extensive research interests in the past decades, and it could be achieved either by surface coating of low-free energy materials or by constructing micro/nanohierarchical structures via various complicated processes. So far, developing a simple approach to fabricate stable superhydrophobic CNTs remains a challenge because the capillary force induced coalescence frequently happens when interacting with liquid. Herein, drawing inspirations from the lotus leaf, we proposed a simple one-step chemical vapor deposition approach with programmable controlled gas flow to directly fabricate a CNT film with rather stable superhydrophobicity, which can effectively prevent even small water droplets from permeating into the film. The robust superhydrophobicity was attributable to typical lotus-leaf-like micro/nanoscale hierarchical surface structures of the CNT film, where many microscale clusters composed of entangled nanotubes randomly protrude out of the under-layer aligned nanotubes. Consequently, dual-scale air pockets were trapped within each microscale CNT cluster and between, which could largely reduce the liquid/solid interface, leading to a Cassie state. Moreover, the superhydrophobicity of the CNT film showed excellent durability after long time exposure to air and even to corrosive liquids with a wide range of pH values. We envision that the approach developed is advantageous for versatile physicochemical interfacial processes, such as drag reduction, electrochemical catalysis, anti-icing, and biosensors.

Robust Hydrophobic Surfaces from Suspension HVOF Thermal Sprayed Rare-Earth Oxide Ceramics Coatings.

PubMed

Bai, M; Kazi, H; Zhang, X; Liu, J; Hussain, T

2018-05-03

This study has presented an efficient coating method, namely suspension high velocity oxy-fuel (SHVOF) thermal spraying, to produce large super-hydrophobic ceramic surfaces with a unique micro- and nano-scale hierarchical structures to mimic natural super-hydrophobic surfaces. CeO 2 was selected as coatings material, one of a group of rare-earth oxide (REO) ceramics that have recently been found to exhibit intrinsic hydrophobicity, even after exposure to high temperatures and abrasive wear. Robust hydrophobic REO ceramic surfaces were obtained from the deposition of thin CeO 2 coatings (3-5 μm) using an aqueous suspension with a solid concentration of 30 wt.% sub-micron CeO 2 particles (50-200 nm) on a selection of metallic substrates. It was found that the coatings' hydrophobicity, microstructure, surface morphology, and deposition efficiency were all determined by the metallic substrates underneath. More importantly, it was demonstrated that the near super-hydrophobicity of SHVOF sprayed CeO 2 coatings was achieved not only by the intrinsic hydrophobicity of REO but also their unique hierarchically structure. In addition, the coatings' surface hydrophobicity was sensitive to the O/Ce ratio, which could explain the 'delayed' hydrophobicity of REO coatings.

Superhydrophobic, Biomimetic Surfaces with High and Low Adhesion, Optical Transmittance, and Nanoscale Mechanical Wear Resistance

NASA Astrophysics Data System (ADS)

Ebert, Daniel R.

Superhydrophobic surfaces (defined as surfaces having water contact angle greater than 150°) show great promise for use in a rapidly growing number of engineering applications, ranging from biomedical devices to fluid drag reduction in pipelines. In nature, the surfaces of many organisms, such as certain plant leaves, are known to exhibit superhydrophobicity. In some cases, droplet adhesion is very low (droplet rolls away easily), while in other cases adhesion is high (droplet remains adhered when surface is inverted). The recent advent and development of microscopes with resolution down to a few nanometers (such as atomic force microscopes and scanning electron microscopes) has allowed for in-depth understanding of the micro- and nanoscale mechanisms employed by these plant leaves and other natural surfaces to achieve their particular wetting properties. Biomimetics (or "mimicking nature") is therefore a very promising approach for the development of engineering surfaces with desired wetting characteristics. However, research in creating biomimetic surfaces is still in its early stages, and many of the surfaces created thus far are not mechanically robust, which is required for many potential real-world applications. In addition, for applications such as self-cleaning windows and solar panels, optical transparency is required. In this thesis, a set of original studies are presented in which superhydrophobic surfaces were designed based on biomimetics and fabricated using a wide of variety of techniques. The surfaces were characterized with regard to wetting characteristics such as water contact angle and contact angle hysteresis, micro- and nanoscale mechanical durability, and in some cases optical transmittance. Theoretical wetting models served as guides both in the design and in the understanding of experimental results, especially in regard to different wetting regime and regime transition. This work provides important conclusions and valuable insight for

Wettability of natural superhydrophobic surfaces.

PubMed

Webb, Hayden K; Crawford, Russell J; Ivanova, Elena P

2014-08-01

Since the description of the 'Lotus Effect' by Barthlott and Neinhuis in 1997, the existence of superhydrophobic surfaces in the natural world has become common knowledge. Superhydrophobicity is associated with a number of possible evolutionary benefits that may be bestowed upon an organism, ranging from the ease of dewetting of their surfaces and therefore prevention of encumbrance by water droplets, self-cleaning and removal of particulates and potential pathogens, and even to antimicrobial activity. The superhydrophobic properties of natural surfaces have been attributed to the presence of hierarchical microscale (>1 μm) and nanoscale (typically below 200 nm) structures on the surface, and as a result, the generation of topographical hierarchy is usually considered of high importance in the fabrication of synthetic superhydrophobic surfaces. When one surveys the breadth of data available on naturally existing superhydrophobic surfaces, however, it can be observed that topographical hierarchy is not present on all naturally superhydrophobic surfaces; in fact, the only universal feature of these surfaces is the presence of a sophisticated nanoscale structure. Additionally, several natural surfaces, e.g. those present on rose petals and gecko feet, display high water contact angles and high adhesion of droplets, due to the pinning effect. These surfaces are not truly superhydrophobic, and lack significant degrees of nanoscale roughness. Here, we discuss the phenomena of superhydrophobicity and pseudo-superhydrophobicity in nature, and present an argument that while hierarchical surface roughness may aid in the stability of the superhydrophobic effect, it is nanoscale surface architecture alone that is the true determinant of superhydrophobicity. Copyright © 2014 Elsevier B.V. All rights reserved.

Drag crisis moderation by thin air layers sustained on superhydrophobic spheres falling in water.

PubMed

Jetly, Aditya; Vakarelski, Ivan U; Thoroddsen, Sigurdur T

2018-02-28

We investigate the effect of thin air layers naturally sustained on superhydrophobic surfaces on the terminal velocity and drag force of metallic spheres free falling in water. The surface of 20 mm to 60 mm steel or tungsten-carbide spheres is rendered superhydrophobic by a simple coating process that uses a commercially available hydrophobic agent. By comparing the free fall of unmodified spheres and superhydrophobic spheres in a 2.5 meter tall water tank, it is demonstrated that even a very thin air layer (∼1-2 μm) that covers the freshly dipped superhydrophobic sphere can reduce the drag force on the spheres by up to 80%, at Reynolds numbers from 10 5 to 3 × 10 5 , owing to an early drag crisis transition. This study complements prior investigations on the drag reduction efficiency of model gas layers sustained on heated metal spheres falling in liquid by the Leidenfrost effect. The drag reduction effects are expected to have significant implications for the development of sustainable air-layer-based energy saving technologies.

Adhesion behaviors on superhydrophobic surfaces.

PubMed

Zhu, Huan; Guo, Zhiguang; Liu, Weimin

2014-04-18

The adhesion behaviors of superhydrophobic surfaces have become an emerging topic to researchers in various fields as a vital step in the interactions between materials and organisms/materials. Controlling the chemical compositions and topological structures via various methods or technologies is essential to fabricate and modulate different adhesion properties, such as low-adhesion, high-adhesion and anisotropic adhesion on superhydrophobic surfaces. We summarize the recent developments in both natural superhydrophobic surfaces and artificial superhydrophobic surfaces with various adhesions and also pay attention to superhydrophobic surfaces switching between low- and high-adhesion. The methods to regulate or translate the adhesion of superhydrophobic surfaces can be considered from two perspectives. One is to control the chemical composition and change the surface geometric structure on the surfaces, respectively or simultaneously. The other is to provide external stimulations to induce transitions, which is the most common method for obtaining switchable adhesions. Additionally, adhesion behaviors on solid-solid interfaces, such as the behaviors of cells, bacteria, biomolecules and icing on superhydrophobic surfaces are also noticeable and controversial. This review is aimed at giving a brief and crucial overview of adhesion behaviors on superhydrophobic surfaces.

Enhanced Corrosion Resistance of Superhydrophobic Layered Double Hydroxide Films with Long-Term Stability on Al Substrate.

PubMed

Cao, Yanhui; Zheng, Dajiang; Li, Xueliang; Lin, Jinyan; Wang, Cheng; Dong, Shigang; Lin, Changjian

2018-05-02

A superhydrophobic ZnAl-layered double hydroxide (LDH)-La film was prepared by a hydrothermal method and further modification by laurate anions in this work. Comprehensive characterizations of this film were performed in terms of morphology, composition, structure, roughness, and wettability by scanning electronic microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, three-dimensional laser scanning confocal microscopy. The long-term corrosion protection effect of this superhydrophobic film was investigated deeply by monitoring the changes of the electrochemical impedance spectra for a long time of up to a month in 3.5 wt % NaCl solution. In the meantime, the changes of the contact angle were also recorded with the evolution of the immersion time. The result indicated that the stable superhydrophobic ZnAl-LDH-La film was able to provide efficient protection for the underlying Al substrate for a long time. In addition, the capability of the superhydrophobic surface against harsh conditions, including chemical damages and physical damages, was emphatically investigated. It was found that the superhydrophobic surface was chemically stable toward acid (pH ≥ 3), alkali, and heating, and it also exhibited high ultraviolet (UV) radiation resistance. This superhydrophobic coating maintained superhydrophobicity for 7 days of radiation in an UV chamber equipped with a 40 W UV lamp (λ = 254 nm), indicating superior ability of adapting to outdoor environment. This comprehensive investigation of the superhydrophobic ZnAl-LDH-La film is considerably helpful for researchers and engineers to get deep insight into its potential for practical applications in the field of corrosion and protection.

Durable polyorganosiloxane superhydrophobic films with a hierarchical structure by sol-gel and heat treatment method

NASA Astrophysics Data System (ADS)

Jiang, Zhenlin; Fang, Shuying; Wang, Chaosheng; Wang, Huaping; Ji, Chengchang

2016-12-01

For a surface to be superhydrophobic a combination of surface roughness and low surface energy is required. In this study, polyorganosiloxane superhydrophobic surfaces were fabricated using a sol-gel and heat treatment process followed by coating with a nanosilica (SiO2) sol and organosiloxane 1, 1, 1, 3, 5, 5, 5-heptamethyl-3-[2-(trimethoxysilyl)ethyl]-trisiloxane (β-HPEOs). The nano-structure was superimposed using self-assembled, surface-modified silica nanoparticles, forming two-dimensional hierarchical structures. The water contact angle (WCA) of polyorganosiloxane superhydrophobic surface was 143.7 ± 0.6°, which was further increased to 156.7 ± 1.1° with water angle hysteresis of 2.5 ± 0.6° by superimposing nanoparticles using a heat treatment process. An analytical characterization of the surface revealed that the nano-silica and polyorganosiloxane formed a micro/nano structure on the films and the wetting behaviour of the films changed from hydrophilic to superhydrophobic. The WCA of these films were 143.7 ± 0.6° and at heat treatment temperatures of less than 400 °C, the WCA increased from 144.5 ± 0.7° to 156.7 ± 1.1°. The prepared superhydrophobic films were stable even after heat treatment at 430 °C for 30 min and their superhydrophobicity was durable for more than 120 days. The effects of heat treatment process on the surface chemistry structure, wettability and morphology of the polyorganosiloxane superhydrophobic films were investigated in detail. The results indicated that the stability of the chemical structure was required to yield a thermally-stable superhydrophobic surface.

Superhydrophobic Surface Based on a Coral-Like Hierarchical Structure of ZnO

PubMed Central

Wu, Jun; Xia, Jun; Lei, Wei; Wang, Baoping

2010-01-01

Background Fabrication of superhydrophobic surfaces has attracted much interest in the past decade. The fabrication methods that have been studied are chemical vapour deposition, the sol-gel method, etching technique, electrochemical deposition, the layer-by-layer deposition, and so on. Simple and inexpensive methods for manufacturing environmentally stable superhydrophobic surfaces have also been proposed lately. However, work referring to the influence of special structures on the wettability, such as hierarchical ZnO nanostructures, is rare. Methodology This study presents a simple and reproducible method to fabricate a superhydrophobic surface with micro-scale roughness based on zinc oxide (ZnO) hierarchical structure, which is grown by the hydrothermal method with an alkaline aqueous solution. Coral-like structures of ZnO were fabricated on a glass substrate with a micro-scale roughness, while the antennas of the coral formed the nano-scale roughness. The fresh ZnO films exhibited excellent superhydrophilicity (the apparent contact angle for water droplet was about 0°), while the ability to be wet could be changed to superhydrophobicity after spin-coating Teflon (the apparent contact angle greater than 168°). The procedure reported here can be applied to substrates consisting of other materials and having various shapes. Results The new process is convenient and environmentally friendly compared to conventional methods. Furthermore, the hierarchical structure generates the extraordinary solid/gas/liquid three-phase contact interface, which is the essential characteristic for a superhydrophobic surface. PMID:21209931

Structurally colored films with superhydrophobicity and wide viewing angles based on bumpy melanin-like particles

NASA Astrophysics Data System (ADS)

Yi, Bo; Shen, Huifang

2018-01-01

Non-iridescent structural colors and lotus effect universally existing in the nature provide a great inspiration for artificially developing angle-independent and high hydrophobic structurally colored films. To this end, a facile strategy is put forward for achieving superhydrophobic structurally colored films with wide viewing angles and high visibility based on bumpy melanin-like polydopamine-coated polystyrene particles. Here, hierarchical and amorphous structures are assembled in a self-driven manner due to particles' protrusive surfaces. The superhydrophobicity of the structurally colored films, with water contact angle up to 151°, is realized by combining the hierarchical surface roughness with a dip-coating process of polydimethylsiloxane-hexane solution, while angle-independence revealed in the films is ascribed to amorphous arrays. In addition, benefited from an essential light-absorbing property and high refractive index of polydopamine, the visibility of as-prepared colored films is fundamentally enhanced. Moreover, the mechanical robustness of the films is considerably boosted by inletting 3-aminopropyltriethoxysilane. This fabrication strategy might provide an opportunity for promoting the open-air application of structurally colored coatings.

Hydraulic Jumps on Superhydrophobic Surfaces Exhibiting Ribs and Cavities

NASA Astrophysics Data System (ADS)

Johnson, Michael; Russell, Benton; Maynes, Daniel; Webb, Brent

2009-11-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 1400. The superhydrophobic surfaces are fabricated with both silicon and PDMS surfaces and exhibit micro-ribs and cavities coated with a hydrophobic coating. In general, the hydraulic jump exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. When the water depth downstream of the jump was imposed at a predetermined value, the major and minor axis of the jump increased with decreasing water depth, following classical hydraulic jump behavior. When no water depth was imposed, however, the total projected area of the ellipse exhibited a nearly linear dependence on the jet Weber number, and was nominally invariant with varying hydrophobicity and relative size of the ribs and cavities. For this scenario the Weber number (based on the local radial velocity and water depth prior to the jump) was of order unity at the jump location. The results also reveal that for increasing relative size of the cavities, the ratio of the ellipse axis (major-to-minor) increases.

Superhydrophobic films and methods for making superhydrophobic films

DOEpatents

Aytug, Tolga; Paranthaman, Mariappan Parans; Simpson, John T.; Bogorin, Daniela Florentina

2017-09-26

This disclosure relates to methods that include depositing a first component and a second component to form a film including a plurality of nanostructures, and coating the nanostructures with a hydrophobic layer to render the film superhydrophobic. The first component and the second component can be immiscible and phase-separated during the depositing step. The first component and the second component can be independently selected from the group consisting of a metal oxide, a metal nitride, a metal oxynitride, a metal, and combinations thereof. The films can have a thickness greater than or equal to 5 nm; an average surface roughness (Ra) of from 90 to 120 nm, as measured on a 5 .mu.m.times.5 .mu.m area; a surface area of at least 20 m.sup.2/g; a contact angle with a drop of water of at least 120 degrees; and can maintain the contact angle when exposed to harsh conditions.

Hybrid surface design for robust superhydrophobicity.

PubMed

Dash, Susmita; Alt, Marie T; Garimella, Suresh V

2012-06-26

Surfaces may be rendered superhydrophobic by engineering the surface morphology to control the extent of the liquid-air interface and by the use of low-surface-energy coatings. The droplet state on a superhydrophobic surface under static and dynamic conditions may be explained in terms of the relative magnitudes of the wetting and antiwetting pressures acting at the liquid-air interface on the substrate. In this paper, we discuss the design and fabrication of hollow hybrid superhydrophobic surfaces which incorporate both communicating and noncommunicating air gaps. The surface design is analytically shown to exhibit higher capillary (or nonwetting) pressure compared to solid pillars with only communicating air gaps. Six hybrid surfaces are fabricated with different surface parameters selected such that the Cassie state of a droplet is energetically favorable. The robustness of the surfaces is tested under dynamic impingement conditions, and droplet dynamics are explained using pressure-based transitions between Cassie and Wenzel states. During droplet impingement, the effective water hammer pressure acting due to the sudden change in the velocity of the droplet is determined experimentally and is found to be at least 2 orders of magnitude less than values reported in the literature. The experiments show that the water hammer pressure depends on the surface morphology and capillary pressure of the surface. We propose that the observed reduction in shock pressure may be attributed to the presence of air gaps in the substrate. This feature allows liquid deformation and hence avoids the sudden stoppage of the droplet motion as opposed to droplet behavior on smooth surfaces.

Super-Hydrophobic/Icephobic Coatings Based on Silica Nanoparticles Modified by Self-Assembled Monolayers.

PubMed

Liu, Junpeng; Janjua, Zaid A; Roe, Martin; Xu, Fang; Turnbull, Barbara; Choi, Kwing-So; Hou, Xianghui

2016-12-02

A super-hydrophobic surface has been obtained from nanocomposite materials based on silica nanoparticles and self-assembled monolayers of 1 H ,1 H ,2 H ,2 H -perfluorooctyltriethoxysilane (POTS) using spin coating and chemical vapor deposition methods. Scanning electron microscope images reveal the porous structure of the silica nanoparticles, which can trap small-scale air pockets. An average water contact angle of 163° and bouncing off of incoming water droplets suggest that a super-hydrophobic surface has been obtained based on the silica nanoparticles and POTS coating. The monitored water droplet icing test results show that icing is significantly delayed by silica-based nano-coatings compared with bare substrates and commercial icephobic products. Ice adhesion test results show that the ice adhesion strength is reduced remarkably by silica-based nano-coatings. The bouncing phenomenon of water droplets, the icing delay performance and the lower ice adhesion strength suggest that the super-hydrophobic coatings based on a combination of silica and POTS also show icephobicity. An erosion test rig based on pressurized pneumatic water impinging impact was used to evaluate the durability of the super-hydrophobic/icephobic coatings. The results show that durable coatings have been obtained, although improvement will be needed in future work aiming for applications in aerospace.

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.

Cutting a Drop of Water Pinned by Wire Loops Using a Superhydrophobic Surface and Knife

PubMed Central

Yanashima, Ryan; García, Antonio A.; Aldridge, James; Weiss, Noah; Hayes, Mark A.; Andrews, James H.

2012-01-01

A water drop on a superhydrophobic surface that is pinned by wire loops can be reproducibly cut without formation of satellite droplets. Drops placed on low-density polyethylene surfaces and Teflon-coated glass slides were cut with superhydrophobic knives of low-density polyethylene and treated copper or zinc sheets, respectively. Distortion of drop shape by the superhydrophobic knife enables a clean break. The driving force for droplet formation arises from the lower surface free energy for two separate drops, and it is modeled as a 2-D system. An estimate of the free energy change serves to guide when droplets will form based on the variation of drop volume, loop spacing and knife depth. Combining the cutting process with an electrofocusing driving force could enable a reproducible biomolecular separation without troubling satellite drop formation. PMID:23029297

Robust and Superhydrophobic Surface Modification by a "Paint + Adhesive" Method: Applications in Self-Cleaning after Oil Contamination and Oil-Water Separation.

PubMed

Chen, Baiyi; Qiu, Jianhui; Sakai, Eiichi; Kanazawa, Nobuhiro; Liang, Ruilu; Feng, Huixia

2016-07-13

Conventional superhydrophobic surfaces have always depended on expensive, sophisticated, and fragile roughness structures. Therefore, poor robustness has turned into the bottleneck for large-scale industrial applications of the superhydrophobic surfaces. To handle this problem, a superhydrophobic surface with firm robustness urgently needs to be developed. In this work, we created a versatile strategy to fabricate robust, self-cleaning, and superhydrophobic surfaces for both soft and hard substrates. We created an ethanol based suspension of perfluorooctyltriethoxysilane-mdodified calcium carbonate nanoparticles which can be sprayed onto both hard and soft substrates to form superhydrophobic surfaces. For all kinds of substrates, spray adhesive was directly coated onto abluent substrate surfaces to promote the robustness. These superhydrophobic surfaces showed remarkable robustness against knife scratch and sandpaper abrasion, while retaining its superhydrophobicity even after 30 abrasion cycles with sandpaper. What is more, the superhydrophobic surfaces have shown promising potential applications in self-cleaning and oil-water separation. The surfaces retained their self-cleaning property even immersed in oil. In addition to oil-water separation, the water contents in oil after separation of various mixtures were all below 150 ppm, and for toluene even as low as 55 ppm. Furthermore, the as-prepared device for oil-water separation could be cycled 6 times and still retained excellent oil-water separation efficiency.

Transparent Pullulan/Mica Nanocomposite Coatings with Outstanding Oxygen Barrier Properties

PubMed Central

Boyacı, Derya; Trabattoni, Silvia; Tavazzi, Silvia

2017-01-01

This study presents a new bionanocomposite coating on poly(ethylene terephthalate) (PET) made of pullulan and synthetic mica. Mica nanolayers have a very high aspect ratio (α), at levels much greater than that of conventional exfoliated clay layers (e.g., montmorillonite). A very small amount of mica (0.02 wt %, which is ϕ ≈ 0.00008) in pullulan coatings dramatically improved the oxygen barrier performance of the nanocomposite films under dry conditions, however, this performance was partly lost as the environmental relative humidity (RH) increased. This outcome was explained in terms of the perturbation of the spatial ordering of mica sheets within the main pullulan phase, because of RH fluctuations. This was confirmed by modelling of the experimental oxygen transmission rate (OTR) data according to Cussler’s model. The presence of the synthetic nanobuilding block (NBB) led to a decrease in both static and kinetic coefficients of friction, compared with neat PET (≈12% and 23%, respectively) and PET coated with unloaded pullulan (≈26% reduction in both coefficients). In spite of the presence of the filler, all of the coating formulations did not significantly impair the overall optical properties of the final material, which exhibited haze values below 3% and transmittance above 85%. The only exception to this was represented by the formulation with the highest loading of mica (1.5 wt %, which is ϕ ≈ 0.01). These findings revealed, for the first time, the potential of the NBB mica to produce nanocomposite coatings in combination with biopolymers for the generation of new functional features, such as transparent high oxygen barrier materials. PMID:28925951

Optical phenomena and antifrosting property on biomimetics slippery fluid-infused antireflective films via layer-by-layer comparison with superhydrophobic and antireflective films.

PubMed

Manabe, Kengo; Nishizawa, Shingo; Kyung, Kyu-Hong; Shiratori, Seimei

2014-08-27

Sophisticated material interfaces generated by natural life forms such as lotus leaves and Nepenthes pitcher plants have exceptional abilities to resolve challenges in wide areas of industry and medicine. The nano- and microstructures inspired by these natural materials can repel various liquids and form self-cleaning coatings. In particular, slippery liquid-infused surfaces are receiving remarkable interest as transparent, nonfouling, and antifrosting synthetic surfaces for solar cells and optical devices. Here we focus on the transparency of lubricant-infused texture on antireflective films fabricated by layer-by-layer self-assembly that decrease light scattering, which is important to maintain device properties. A slippery fluid-infused antireflective film composed of chitin nanofibers less than 50 nm in diameter prevented light scattering at the long-wavelength side by Rayleigh scattering to achieve 97.2% transmittance. Moreover, films composed of the same materials demonstrated three different morphologies: superhydrophilicity with antireflection, superhydrophobicity, and omniphobicity, mimicking the biological structures of moth eyes, lotus leaves, and pitcher plants, respectively. The effect of thermal changes on the ability of each film to prevent frost formation was investigated. The slippery fluid-infused antireflective film showed effective antifrosting behavior.

"Shrink-to-fit" superhydrophobicity: thermally-induced microscale wrinkling of thin hydrophobic multilayers fabricated on flexible shrink-wrap substrates.

PubMed

Manna, Uttam; Carter, Matthew C D; Lynn, David M

2013-06-11

An approach to the design of flexible superhydrophobic surfaces based on thermally induced wrinkling of thin, hydrophobic polymer multilayers on heat-shrinkable polymer films is reported. This approach exploits shrinking processes common to "heat-shrink" plastics, and can thus be used to create "shrink-to-fit" superhydrophobic coatings on complex surfaces, manipulate the dimensions and densities of patterned features, and promote heat-activated repair of full-thickness defects. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacing superhydrophobic silica nanoparticle films with graphene and thermoplastic polyurethane for wear/abrasion resistance.

PubMed

Naderizadeh, Sara; Athanassiou, Athanassia; Bayer, Ilker S

2018-06-01

Nanoparticle films are one of the most suitable platforms for obtaining sub-micrometer and nanometer dual-scale surface texture required for liquid repellency. The assembly of superhydrophobic nanoparticles into conformal and strongly adherent films having abrasion-induced wear resistance still poses a significant challenge. Various techniques have been developed over the years to render nanoparticle films with good liquid repellent properties and transparency. However, forming abrasion resistant superhydrophobic nanoparticle films on hard surfaces is challenging. One possibility is to partially embed or weld nanoparticles in thin thermoplastic primers applied over metals. Hexamethyldisilazane-functionalized fumed silica nanoparticle films spray deposited on aluminum surfaces were rendered abrasion resistant by thermally welding them into thermoplastic polyurethane (TPU) primer applied a priori over aluminum. Different solvents, nanoparticle concentrations and annealing temperatures were studied to optimize nanoparticle film morphology and hydrophobicity. Thermal annealing at 150 °C enhanced stability and wear resistance of nanoparticle films. A thin thermal interface layer of graphene nanoplatelets (GnPs) between the primer and the nanoparticle film significantly improved superhydrophobic wear resistance after annealing. As such, superhydrophobic nanocomposite films with the GnPs thermal interface layer displayed superior abrasion-induced wear resistance under 20 kPa compared to films having no GnPs-based thermal interface. Copyright © 2018 Elsevier Inc. All rights reserved.

Fabrication of surface micro- and nanostructures for superhydrophobic surfaces in electric and electronic applications

NASA Astrophysics Data System (ADS)

Xiu, Yonghao

our understanding of the roughness effect on superhydrophobicity (both contact angle and hysteresis), structured surfaces from polybutadiene, polyurethane, silica, and Si etc. were successfully prepared. For engineering applications of superhydrophobic surfaces, stability issues regarding UV, mechanical robustness and humid environment need to be investigated. Among these factors, UV stability is the first one to be studied. However, most polymer surfaces we prepared failed the purpose. Silica surfaces with excellent UV stability were prepared. This method consists of preparation of rough silica surfaces, thermal treatment and the following surface hydrophobization by fluoroalkyl silane treatment. Fluoroalkyl groups are UV stable and the underlying species are silica which is also UV stable (UV transparent). UV stability on the surface currently is 5,500 h according the standard test method of ASTM D 4329. No degradation on surface superhydrophobicity was observed. New methods for preparing superhydrophobic and transparent silica surfaces were investigated using urea-choline chloride eutectic liquid to generate fine roughness and reduce the cost for preparation of surface structures. Another possible application for self-cleaning in photovoltaic panels was investigated on Si surfaces by construction of the two-scale rough structures followed by fluoroalkyl silane treatment. Metal (Au) assisted etching was employed to fabricate nanostructures on micrometer pyramid surfaces. The light reflection on the prepared surfaces was investigated. After surface texturing using KOH etching for micrometer pyramids and the following nanostructure using metal assisted etching, surface light reflection reduced to a minimum value which shows that this surface texturing technique is highly promising for improving the photovoltaic efficiency while imparting photovoltaics the self-cleaning feature. This surface is also expected to be UV stable due to the same fluoroalkyl silane used

Preparation and properties of ZnS superhydrophobic surface with hierarchical structure

NASA Astrophysics Data System (ADS)

Yao, Lujun; Zheng, Maojun; He, Shuanghu; Ma, Li; Li, Mei; Shen, Wenzhong

2011-01-01

A novel ZnS hierarchical structure composed of nanorod arrays with branched nanosheets and nanowires grown on their upside walls, was synthesized over Au-coated silicon substrate via chemical vapor deposition technique. Contact angle and sliding angle of this hierarchical film with no surface modification were measured to be about 153.8° and 9.1° for 5 μl water droplets. Self-cleaning behavior and dynamic water-repelling performance were clearly demonstrated. In addition, electrowetting transition phenomenon from superhydrophobic to hydrophilic state happened when a critical bias ∼7.0 V was applied. Below this threshold voltage, the contact angle change is little. This work for the first time reports the creation of ZnS superhydrophobic surface and could enrich its research field as surface functional materials.

Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

NASA Astrophysics Data System (ADS)

Ngo, Chi-Vinh; Chun, Doo-Man

2017-07-01

Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100 °C was applied. The effect of 100-500 μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500 μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.

Superhydrophobic powder additives to enhance chemical agent resistant coating systems for military equipment for the U.S. Marine Corps (USMC) Corrosion Prevention and Control (CPAC) Program

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

Pawel, Steven J.; Armstrong, Beth L.; Haynes, James A.

The primary goal of the CPAC program at ORNL was to explore the feasibility of introducing various silica-based superhydrophobic (SH) powder additives as a way to improve the corrosion resistance of US Department of Defense (DOD) military-grade chemical agent resistant coating (CARC) systems. ORNL had previously developed and patented several SH technologies of interest to the USMC, and one of the objectives of this program was to identify methods to incorporate these technologies into the USMC’s corrosion-resistance strategy. This report discusses findings of the CPAC and their application.

Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation.

PubMed

Mondal, Bikash; Mac Giolla Eain, Marc; Xu, QianFeng; Egan, Vanessa M; Punch, Jeff; Lyons, Alan M

2015-10-28

Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces. Numerous efforts have been made to create surfaces which can promote dropwise condensation, including superhydrophobic surfaces on which water droplets are highly mobile. However, the challenge with using such surfaces in condensing environments is that hydrophobic coatings can degrade and/or water droplets on superhydrophobic surfaces transition from the mobile Cassie to the wetted Wenzel state over time and condensation shifts to a less-effective filmwise mechanism. To meet the need for a heat-transfer surface that can maintain stable dropwise condensation, we designed and fabricated a hybrid superhydrophobic-hydrophilic surface. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values, and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for silanized silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles is low-cost, robust, and scalable and so could be used for heat

Development of a highly transparent superamphiphobic plastic sheet by nanoparticle and chemical coating.

PubMed

Wong, Ten It; Wang, Hao; Wang, Fuke; Sin, Sau Leng; Quan, Cheng Gen; Wang, Shi Jie; Zhou, Xiaodong

2016-04-01

A highly transparent superamphiphobic plastic sheet was developed. The plastic sheet polymethyl methacrylate (PMMA) was spin-coated on a glass substrate. Synthesized silica nanoparticles were sprayed on PMMA, followed by fluorosilane drop-coating. The results of contact angle measurements show that the developed PMMA sheet has superamphiphobic properties with high advancing contact angles for water (154°), toluene (139°), and silicone oil (132.9°). The amphiphobicity of the plastic sheet can be tuned by the surface coverage of the silica nanoparticles distributed on the PMMA surface. The surface coverage of the nanoparticles on our PMMA sheet is about 20%, and it agrees with our contact angle calculations for the sheet with and without nanoparticles. Copyright © 2016 Elsevier Inc. All rights reserved.

Color properties of transparent and heat-reflecting MgF2-coated indium-tin-oxide films.

PubMed

Hamberg, I; Granqvist, C G

1983-02-15

The visual appearance of antireflection-coated transparent and heat-reflecting indium-tin-oxide (ITO) films on glass was studied by a colorimetric analysis in which the chromaticity coordinates for transmitted and reflected daylight were evaluated for various film thicknesses. A color purity of <1% in normal transmission and <10% in normal reflection could be achieved with ITO thicknesses in the 220-260- or 335-365-nm ranges and MgF2 thicknesses in the 90-105-nm range. These design criteria yield very efficient window coatings with high visual transmittance, low thermal emittance, and little or no perceived color.

Superhydrophobic Superoleophobic Woven Fabrics (Preprint)

DTIC Science & Technology

2011-06-01

AFRL-RX-TY-TP-2011-0050 SUPERHYDROPHOBIC SUPEROLEOPHOBIC WOVEN FABRICS (PREPRINT) Hoonjoo Lee Department of Textile and Apparel...RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (Include area code) JUN 2011 Book Chapter 20-JUN-2008 -- 30-APR-2011 Superhydrophobic Superoleophobic Woven Fabrics...roll-off angles are analyzed, and finally superhydrophobic , superoleophobic, woven fabric is designed and developed using chemical and geometrical

Combination of Functional Nanoengineering and Nanosecond Laser Texturing for Design of Superhydrophobic Aluminum Alloy with Exceptional Mechanical and Chemical Properties.

PubMed

Boinovich, Ludmila B; Modin, Evgeny B; Sayfutdinova, Adeliya R; Emelyanenko, Kirill A; Vasiliev, Alexander L; Emelyanenko, Alexandre M

2017-10-24

Industrial application of metallic materials is hindered by several shortcomings, such as proneness to corrosion, erosion under abrasive loads, damage due to poor cold resistance, or weak resistance to thermal shock stresses, etc. In this study, using the aluminum-magnesium alloy as an example of widely spread metallic materials, we show that a combination of functional nanoengineering and nanosecond laser texturing with the appropriate treatment regimes can be successfully used to transform a metal into a superhydrophobic material with exceptional mechanical and chemical properties. It is demonstrated that laser chemical processing of the surface may be simultaneously used to impart multimodal roughness and to modify the composition and physicochemical properties of a thick surface layer of the substrate itself. Such integration of topographical and physicochemical modification leads to specific surface nanostructures such as nanocavities filled with hydrophobic agent and hard oxynitride nanoinclusions. The combination of superhydrophobic state, nano- and micro features of the hierarchical surface, and the appropriate composition of the surface textured layer allowed us to provide the surface with the outstanding level of resistance of superhydrophobic coatings to external chemical and mechanical impacts. In particular, experimental data presented in this study indicate high resistance of the fabricated coatings to pitting corrosion, superheated water vapor, sand abrasive wear, and rapid temperature cycling from liquid nitrogen to room temperatures, without notable degradation of superhydrophobic performance.

Flexure Strength and Optical Transparency of Magnesium-Aluminate Spinel (MgAlO4): Influence of Polishing and Glass Coating

DTIC Science & Technology

2016-12-01

resulting from the addition of a sodium aluminosilicate ( SiO2 -BaO- Na2O-B2O3-Al2O3) glass coating on coarse-grained transparent spinel having 3...MgAlO4): Influence of Polishing and Glass Coating by Steve M Kilczewski, Robert J Pavlacka, Jeffrey J Swab, Jane W Adams, and Jared C Wright...Magnesium–Aluminate Spinel (MgAlO4): Influence of Polishing and Glass Coating by Steve M Kilczewski and Jared C Wright TKC Global, Herndon, VA

Transparent conductive carbon nanotubes coated flexible substrate and its application for electronic devices

NASA Astrophysics Data System (ADS)

Rahy, Abdelaziz

The primary goal of this project was to develop a flexible transparent conductor with 100 O/sq with 90% transmittance in the wavelength range of 400-700nm on a flexible substrate. A second objective was to simplify the coating process to be commercially viable. The best result achieved so far was 110 O/sq at 88% transmittance using purified single walled nanotubes (SWNTs) coated on a polyethylene naphthalate (PEN) substrate on both sides. The SWNT sample used was purchased from Carbon Nanotechnologies Inc (CNI). Proper sonication of the single walled nanotubes (SWNTs) with a proper solvent selection with no use of surfactant simplified the overall coating procedure from five steps (prior art method) to three steps utilizing a dip coating method. We also found that the use of metallic SWNTs can significantly improve the conductivity and transmittance compared with the use of mixed SWNTs, i.e., unseparated SWNTs We also studied a possible adhesion mechanism between SWNTs and the surface of PEN; we concluded that pi - pi stacking effect and hydrophobic-to-hydrophobic interaction are the major contributing factors to have CNTs adhere on the surface of the PEN substrate. Working devices of polymer light emitting diodes (PLEDs) and solar cell were successfully fabricated using SWNT coated substrates. A no optimized PLEDs device exhibited low turn-on voltage (˜5V), and the fabricated solar cell functioned. The devices have demonstrated the coated film can be used for potential electronic devices.

Superhydrophobic surfaces for applications in seawater.

PubMed

Ferrari, Michele; Benedetti, Alessandro

2015-08-01

Technological fields in which seawater is implied are numerorus, working in seawater (shipping, oil industry, marine aquaculture,..), and exploiting seawater in plants (cooling heat-exchange, desalination, power plants,..). All suffer from detrimental effects induced by biofouling mainly enhancing material failures and limiting energetic efficiencies. Among the remediation solutions, technologies coniugating economical, green and efficiency criteria should represent the direction. With the aim to meet these criteria, superhydrophobic (SH) technology attracted many researches for the protection of materials operating in contact with seawater. In this work, the literature focusing on such technology for the protection of surfaces in contact with seawater has been reviewed, mainly focusing on boat and ship hull protection. Despite the growing interest around SH technology in seawater for fouling control and friction drag reduction of hulls, to date literature shows that superhydrophobicity in seawater is still limited if compared with a time window compatible with technological needs (set on years). An evaluation of the causes of early superhydrophobicity loss under operative conditions clearly indicates that, to the best of present knowledge, a SH surface cannot preserve this feature by itself alone (especially in real seawater). Hence, we have considered to highlight the behaviour of SH surfaces in seawater in relation to early stages of biocolonization (conditioning film and pioneering bioslime formation). Considering the annual costs sustained for the biofouling impact control, advantages coming from SH surfaces, in terms of foul control and friction drag reduction, would allow economical savings allowing to cover both the appliance of longevity keeping strategies of the SH surfaces and investments in green technologies of SH coating life cycle (production, storing). In addition a brief outlook is provided on technological fields exploiting seawater in pipelines

Synthesis and characterization of transparent conductive zinc oxide thin films by sol-gel spin coating method

NASA Astrophysics Data System (ADS)

Winarski, David

Zinc oxide has been given much attention recently as it is promising for various semiconductor device applications. ZnO has a direct band gap of 3.3 eV, high exciton binding energy of 60 meV and can exist in various bulk powder and thin film forms for different applications. ZnO is naturally n-type with various structural defects, which sparks further investigation into the material properties. Although there are many potential applications for this ZnO, an overall lack of understand and control of intrinsic defects has proven difficult to obtain consistent, repeatable results. This work studies both synthesis and characterization of zinc oxide in an effort to produce high quality transparent conductive oxides. The sol-gel spin coating method was used to obtain highly transparent ZnO thin films with high UV absorbance. This research develops a new more consistent method for synthesis of these thin films, providing insight for maintaining quality control for each step in the procedure. A sol-gel spin coating technique is optimized, yielding highly transparent polycrystalline ZnO thin films with tunable electrical properties. Annealing treatment in hydrogen and zinc atmospheres is researched in an effort to increase electrical conductivity and better understand intrinsic properties of the material. These treatment have shown significant effects on the properties of ZnO. Characterization of doped and undoped ZnO synthesized by the sol-gel spin coating method was carried out using scanning electron microscopy, UV-Visible range absorbance, X-ray diffraction, and the Hall Effect. Treatment in hydrogen shows an overall decrease in the number of crystal phases and visible absorbance while zinc seems to have the opposite effect. The Hall Effect has shown that both annealing environments increase the n-type conductivity, yielding a ZnO thin film with a carrier concentration as high as 3.001 x 1021 cm-3.

Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant.

PubMed

Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

2017-03-01

Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface.

Controlling liquid splash on superhydrophobic surfaces by a vesicle surfactant

PubMed Central

Song, Meirong; Ju, Jie; Luo, Siqi; Han, Yuchun; Dong, Zhichao; Wang, Yilin; Gu, Zhen; Zhang, Lingjuan; Hao, Ruiran; Jiang, Lei

2017-01-01

Deposition of liquid droplets on solid surfaces is of great importance to many fundamental scientific principles and technological applications, such as spraying, coating, and printing. For example, during the process of pesticide spraying, more than 50% of agrochemicals are lost because of the undesired bouncing and splashing behaviors on hydrophobic or superhydrophobic leaves. We show that this kind of splashing on superhydrophobic surfaces can be greatly inhibited by adding a small amount of a vesicular surfactant, Aerosol OT. Rather than reducing splashing by increasing the viscosity via polymer additives, the vesicular surfactant confines the motion of liquid with the help of wettability transition and thus inhibits the splash. Significantly, the vesicular surfactant exhibits a distinguished ability to alter the surface wettability during the first inertial spreading stage of ~2 ms because of its dense aggregates at the air/water interface. A comprehensive model proposed by this idea could help in understanding the complex interfacial interactions at the solid/liquid/air interface. PMID:28275735

Metallic superhydrophobic surfaces via thermal sensitization

NASA Astrophysics Data System (ADS)

Vahabi, Hamed; Wang, Wei; Popat, Ketul C.; Kwon, Gibum; Holland, Troy B.; Kota, Arun K.

2017-06-01

Superhydrophobic surfaces (i.e., surfaces extremely repellent to water) allow water droplets to bead up and easily roll off from the surface. While a few methods have been developed to fabricate metallic superhydrophobic surfaces, these methods typically involve expensive equipment, environmental hazards, or multi-step processes. In this work, we developed a universal, scalable, solvent-free, one-step methodology based on thermal sensitization to create appropriate surface texture and fabricate metallic superhydrophobic surfaces. To demonstrate the feasibility of our methodology and elucidate the underlying mechanism, we fabricated superhydrophobic surfaces using ferritic (430) and austenitic (316) stainless steels (representative alloys) with roll off angles as low as 4° and 7°, respectively. We envision that our approach will enable the fabrication of superhydrophobic metal alloys for a wide range of civilian and military applications.

Robotic Patterning a Superhydrophobic Surface for Collective Cell Migration Screening.

PubMed

Pang, Yonggang; Yang, Jing; Hui, Zhixin; Grottkau, Brian E

2018-04-01

Collective cell migration, in which cells migrate as a group, is fundamental in many biological and pathological processes. There is increasing interest in studying the collective cell migration in high throughput. Cell scratching, insertion blocker, and gel-dissolving techniques are some methodologies used previously. However, these methods have the drawbacks of cell damage, substrate surface alteration, limitation in medium exchange, and solvent interference. The superhydrophobic surface, on which the water contact angle is greater than 150 degrees, has been recently utilized to generate patterned arrays. Independent cell culture areas can be generated on a substrate that functions the same as a conventional multiple well plate. However, so far there has been no report on superhydrophobic patterning for the study of cell migration. In this study, we report on the successful development of a robotically patterned superhydrophobic array for studying collective cell migration in high throughput. The array was developed on a rectangular single-well cell culture plate consisting of hydrophilic flat microwells separated by the superhydrophobic surface. The manufacturing process is robotic and includes patterning discrete protective masks to the substrate using 3D printing, robotic spray coating of silica nanoparticles, robotic mask removal, robotic mini silicone blocker patterning, automatic cell seeding, and liquid handling. Compared with a standard 96-well plate, our system increases the throughput by 2.25-fold and generates a cell-free area in each well non-destructively. Our system also demonstrates higher efficiency than conventional way of liquid handling using microwell plates, and shorter processing time than manual operating in migration assays. The superhydrophobic surface had no negative impact on cell viability. Using our system, we studied the collective migration of human umbilical vein endothelial cells and cancer cells using assays of endpoint

High-capacity ice-recrystallization endpoint assay employing superhydrophobic coatings that is equivalent to the 'splat' assay.

PubMed

Graham, Laurie A; Agrawal, Prashant; Oleschuk, Richard D; Davies, Peter L

2018-04-01

We have developed an ice recrystallization inhibition (IRI) assay system that allows the side-by-side comparison of up to a dozen samples treated in an identical manner. This system is ideal for determining, by serial dilution, the IRI 'endpoint' where the concentration of a sample is reached that can no longer inhibit recrystallization. Samples can be an order of magnitude smaller in volume (<1 μL) than those used for the conventional 'splat' assay. The samples are pipetted into wells cut out of a superhydrophobic coating on sapphire slides that are covered with a second slide and then snap-frozen in liquid nitrogen. Sapphire is greatly superior to glass in its ability to cool quickly without cracking. As a consequence, the samples freeze evenly as a multi-crystalline mass. The ice grain size is slightly larger than that obtained by the 'splat' assay but can be followed sufficiently well to assess IRI activity by changes in mean grain boundary size. The slides can be washed in detergent and reused with no carryover of IRI activity even from the highest protein concentrations. Copyright © 2018 Elsevier Inc. All rights reserved.

Wettability Switching Techniques on Superhydrophobic Surfaces

PubMed Central

2007-01-01

The wetting properties of superhydrophobic surfaces have generated worldwide research interest. A water drop on these surfaces forms a nearly perfect spherical pearl. Superhydrophobic materials hold considerable promise for potential applications ranging from self cleaning surfaces, completely water impermeable textiles to low cost energy displacement of liquids in lab-on-chip devices. However, the dynamic modification of the liquid droplets behavior and in particular of their wetting properties on these surfaces is still a challenging issue. In this review, after a brief overview on superhydrophobic states definition, the techniques leading to the modification of wettability behavior on superhydrophobic surfaces under specific conditions: optical, magnetic, mechanical, chemical, thermal are discussed. Finally, a focus on electrowetting is made from historical phenomenon pointed out some decades ago on classical planar hydrophobic surfaces to recent breakthrough obtained on superhydrophobic surfaces.

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

Swarctz, Christopher; Alijallis, Elias; Hunter, Scott Robert

In this study, a closed loop low-temperature wind tunnel was custom-built and uniquely used to investigate the anti-icing mechanism of superhydrophobic surfaces in regulated flow velocities, temperatures, humidity, and water moisture particle sizes. Silica nanoparticle-based hydrophobic coatings were tested as superhydrophobic surface models. During tests, images of ice formation were captured by a camera and used for analysis of ice morphology. Prior to and after wind tunnel testing, apparent contact angles of water sessile droplets on samples were measured by a contact angle meter to check degradation of surface superhydrophobicity. A simple peel test was also performed to estimate adhesionmore » of ice on the surfaces. When compared to an untreated sample, superhydrophobic surfaces inhibited initial ice formation. After a period of time, random droplet strikes attached to the superhydrophobic surfaces and started to coalesce with previously deposited ice droplets. These sites appear as mounds of accreted ice across the surface. The appearance of the ice formations on the superhydrophobic samples is white rather than transparent, and is due to trapped air. These ice formations resemble soft rime ice rather than the transparent glaze ice seen on the untreated sample. Compared to untreated surfaces, the icing film formed on superhydrophobic surfaces was easy to peel off by shear flows.« less

Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating

NASA Astrophysics Data System (ADS)

Liang, Qijie; Yan, Xiaoqin; Gu, Yousong; Zhang, Kui; Liang, Mengyuan; Lu, Shengnan; Zheng, Xin; Zhang, Yue

2015-03-01

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m2. Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system.

Highly transparent triboelectric nanogenerator for harvesting water-related energy reinforced by antireflection coating.

PubMed

Liang, Qijie; Yan, Xiaoqin; Gu, Yousong; Zhang, Kui; Liang, Mengyuan; Lu, Shengnan; Zheng, Xin; Zhang, Yue

2015-03-13

Water-related energy is an inexhaustible and renewable energy resource in our environment, which has huge amount of energy and is not largely dictated by daytime and sunlight. The transparent characteristic plays a key role in practical applications for some devices designed for harvesting water-related energy. In this paper, a highly transparent triboelectric nanogenerator (T-TENG) was designed to harvest the electrostatic energy from flowing water. The instantaneous output power density of the T-TENG is 11.56 mW/m(2). Moreover, with the PTFE film acting as an antireflection coating, the maximum transmittance of the fabricated T-TENG is 87.4%, which is larger than that of individual glass substrate. The T-TENG can be integrated with silicon-based solar cell, building glass and car glass, which demonstrates its potential applications for harvesting waste water energy in our living environment and on smart home system and smart car system.

Resistance of superhydrophobic and oleophobic surfaces to varied temperature applications on 316L SS

NASA Astrophysics Data System (ADS)

Shams, Hamza; Basit, Kanza; Saleem, Sajid; Siddiqui, Bilal A.

316L SS also called Marine Stainless Steel is an important material for structural and marine applications. When superhydrophobic and oleophobic coatings are applied on 316L SS it shows significant resistance to wear and corrosion. This paper aims to validate the coatings manufacturer's information on optimal temperature range and test the viability of coating against multiple oil based cleaning agents. 316L SS was coated with multiple superhydrophic and oleohobic coatings and observed under SEM for validity of adhesion and thickness and then scanned under FFM to validate the tribological information. The samples were then dipped into multiple cleaning agents maintained at the range of operating temperatures specified by the manufacturer. Coating was observed for deterioration over a fixed time intervals through SEM and FFM. A comparison was drawn to validate the most critical cleaning agent and the most critical temperature at which the coating fails to leave the base substrate exposed to the environment.

Nanotexturing of polystyrene surface in fluorocarbon plasmas: from sticky to slippery superhydrophobicity.

PubMed

Mundo, Rosa Di; Palumbo, Fabio; d'Agostino, Riccardo

2008-05-06

In this work plasma etching processes have been studied to roughen and fluorinate polystyrene surface as an easy method to achieve a superhydrophobic slippery character. Radiofrequency discharges have been fed with CF(4)/O(2) mixtures and the effect of the O(2):CF(4) ratio, the input power, and the treatment duration have been investigated in terms of wettability, with focus on sliding performances. For this purpose, surface morphological variations, evaluated by means of scanning electron microscopy and atomic force microscopy, together with the chemical assessment by X-ray photoelectron spectroscopy, have been correlated with water contact angle hysteresis and volume resolved sliding angle measurements. Results indicate that by increasing the height and decreasing the density of the structures formed by etching, within a tailored range, a transition from sticky to slippery superhydrophobicity occurs. A short treatment time (5 min) is sufficient to obtain such an effect, provided that a high power input is utilized. Optimized surfaces show a unaltered transparency to visible light according to the low roughness produced.

Hydrophobic and superhydrophobic surfaces fabricated using atmospheric pressure cold plasma technology: A review.

PubMed

Dimitrakellis, Panagiotis; Gogolides, Evangelos

2018-04-01

Hydrophobic surfaces are often used to reduce wetting of surfaces by water. In particular, superhydrophobic surfaces are highly desired for several applications due to their exceptional properties such as self-cleaning, anti-icing, anti-friction and others. Such surfaces can be prepared via numerous methods including plasma technology, a dry technique with low environmental impact. Atmospheric pressure plasma (APP) has recently attracted significant attention as lower-cost alternative to low-pressure plasmas, and as a candidate for continuous rather than batch processing. Although there are many reviews on water-repellent surfaces, and a few reviews on APP technology, there are hardly any review works on APP processing for hydrophobic and superhydrohobic surface fabrication, a topic of high importance in nanotechnology and interface science. Herein, we critically review the advances on hydrophobic and superhydrophobic surface fabrication using APP technology, trying also to give some perspectives in the field. After a short introduction to superhydrophobicity of nanostructured surfaces and to APPs we focus this review on three different aspects: (1) The atmospheric plasma reactor technology used for fabrication of (super)hydrophobic surfaces. (2) The APP process for hydrophobic surface preparation. The hydrophobic surface preparation processes are categorized methodologically as: a) activation, b) grafting, c) polymerization, d) roughening and hydrophobization. Each category includes subcategories related to different precursors used. (3) One of the most important sections of this review concerns superhydrophobic surfaces fabricated using APP. These are methodologically characterized as follows: a) single step processes where micro-nano textured topography and low surface energy coating are created at the same time, or b) multiple step processes, where these steps occur sequentially in or out of the plasma. We end the review with some perspectives in the field. We

Are superhydrophobic surfaces best for icephobicity?

PubMed

Jung, Stefan; Dorrestijn, Marko; Raps, Dominik; Das, Arindam; Megaridis, Constantine M; Poulikakos, Dimos

2011-03-15

Ice formation can have catastrophic consequences for human activity on the ground and in the air. Here we investigate water freezing delays on untreated and coated surfaces ranging from hydrophilic to superhydrophobic and use these delays to evaluate icephobicity. Supercooled water microdroplets are inkjet-deposited and coalesce until spontaneous freezing of the accumulated mass occurs. Surfaces with nanometer-scale roughness and higher wettability display unexpectedly long freezing delays, at least 1 order of magnitude longer than typical superhydrophobic surfaces with larger hierarchical roughness and low wettability. Directly related to the main focus on heterogeneous nucleation and freezing delay of supercooled water droplets, the observed ensuing crystallization process consisted of two distinct phases: one very rapid recalescent partial solidification phase and a subsequent slower phase. Observations of the droplet collision process employed for the continuous liquid mass accumulation up to the point of ice formation reveal a previously unseen atmospheric-pressure, subfreezing-temperature regime for liquid-on-liquid bounce. On the basis of the entropy reduction of water near a solid surface, we formulate a modification to the classical heterogeneous nucleation theory, which predicts the observed freezing delay trends. Our results bring to question recent emphasis on super water-repellent surface formulations for ice formation retardation and suggest that anti-icing design must optimize the competing influences of both wettability and roughness.

Transition Regimes of Jet Impingement on Rib and Cavity Superhydrophobic Surfaces

NASA Astrophysics Data System (ADS)

Johnson, Michael; Maynes, Daniel; Webb, Brent

2010-11-01

We report experimental results characterizing the dynamics of a liquid jet impinging normally on superhydrophobic surfaces spanning the Weber number (based on the jet velocity and diameter) range from 100 to 2000.The superhydrophobic surfaces are fabricated with both silicon and PDMS surfaces and exhibit micro-ribs and cavities coated with a hydrophobic coating. In general, the hydraulic jump exhibits an elliptical shape with the major axis being aligned parallel to the ribs, concomitant with the frictional resistance being smaller in the parallel direction than in the transverse direction. When the water depth downstream of the jump was imposed at a predetermined value, the major and minor axis of the jump increased with decreasing water depth, following classical hydraulic jump behavior. When no water depth was imposed, a regime change was observed within the Weber number range explained. For We < 1200, the flow forms a filament at the edge of the ellipse, where the flow moves along the rim of the ellipse toward the major axis. The filaments then join and continue to move parallel to the ribs. For 1200 < We < 1800, the filaments beyond the ellipse break into multiple streams and droplets and begin to take on a component perpendicular to the ribs. For We > 1800 a small amount of water flows purely in the transverse direction.

Flexible Superhydrophobic and Superoleophilic MoS2 Sponge for Highly Efficient Oil-Water Separation.

PubMed

Gao, Xiaojia; Wang, Xiufeng; Ouyang, Xiaoping; Wen, Cuie

2016-06-02

Removal of oils and organic solvents from water is an important global challenge for energy conservation and environmental protection. Advanced sorbent materials with excellent sorption capacity need to be developed. Here we report on a superhydrophobic and superoleophilic MoS2 nanosheet sponge (SMS) for highly efficient separation and absorption of oils or organic solvents from water. This novel sponge exhibits excellent absorption performance through a combination of superhydrophobicity, high porosity, robust stability in harsh conditions (including flame retardance and inertness to corrosive and different temperature environments) and excellent mechanical properties. The dip-coating strategy proposed for the fabrication of the SMS, which does not require a complicated process or sophisticated equipment, is very straightforward and easy to scale up. This finding shows promise for water remediation and oil recovery.

Laser synthesized super-hydrophobic conducting carbon with broccoli-type morphology as a counter-electrode for dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Gokhale, Rohan; Agarkar, Shruti; Debgupta, Joyashish; Shinde, Deodatta; Lefez, Benoit; Banerjee, Abhik; Jog, Jyoti; More, Mahendra; Hannoyer, Beatrice; Ogale, Satishchandra

2012-10-01

A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode.A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode. Electronic supplementary information (ESI) available: Materials and equipment details, solar cell fabrication protocol, electrolyte spreading time measurement details, XPS spectra, electronic study, film adhesion test detailed analysis and field emission results. See DOI: 10.1039/c2nr32082g

Constructing superhydrophobic WO3@TiO2 nanoflake surface beyond amorphous alloy against electrochemical corrosion on iron steel

NASA Astrophysics Data System (ADS)

Yu, S. Q.; Ling, Y. H.; Wang, R. G.; Zhang, J.; Qin, F.; Zhang, Z. J.

2018-04-01

To eliminate harmful localized corrosion, a new approach by constructing superhydrophobic WO3@TiO2 hierarchical nanoflake surface beyond FeW amorphous alloy formed on stainless steel was proposed. Facile dealloying and liquid deposition was employed at low temperature to form a nanostructured layer composing inner WO3 nanoflakes coated with TiO2 nanoparticles (NPs) layer. After further deposition of PFDS on nanoflakes, the contact angle reached 162° while the corrosion potential showed a negative shift of 230 mV under illumination, resulting in high corrosion resistance in 3.5 wt% NaCl solution. The tradeoff between superhydrophobic surface and photo-electro response was investigated. It was found that this surface feature makes 316 SS be immune to localized corrosion and a pronounced photo-induced process of electron storage/release as well as the stability of the functional layer were detected with or without illumination, and the mechanism behind this may be related to the increase of surface potential due to water repellence and the delayed cathodic protection of semiconducting coating derived mainly from the valence state changes of WO3. This study demonstrates a simple and low-cost electrochemical approach for protection of steel and novel means to produce superhydrophobic surface and cathodic protection with controllable electron storage/release on engineering scale.

Streaming potential of superhydrophobic microchannels.

PubMed

Park, Hung Mok; Kim, Damoa; Kim, Se Young

2017-03-01

For the purpose of gaining larger streaming potential, it has been suggested to employ superhydrophobic microchannels with a large velocity slip. There are two kinds of superhydrophobic surfaces, one having a smooth wall with a large Navier slip coefficient caused by the hydrophobicity of the wall material, and the other having a periodic array of no- shear slots of air pockets embedded in a nonslip wall. The electrokinetic flows over these two superhydrophobic surfaces are modelled using the Navier-Stokes equation and convection-diffusion equations of the ionic species. The Navier slip coefficient of the first kind surfaces and the no-shear slot ratio of the second kind surfaces are similar in the sense that the volumetric flow rate increases as these parameter values increase. However, although the streaming potential increases monotonically with respect to the Navier slip coefficient, it reaches a maximum and afterward decreases as the no-shear ratio increases. The results of the present investigation imply that the characterization of superhydrophobic surfaces employing only the measurement of volumetric flow rate against pressure drop is not appropriate and the fine structure of the superhydrophobic surfaces must be verified before predicting the streaming potential and electrokinetic flows accurately. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Turbulent Boundary Layer Flow over Superhydrophobic Surfaces

DTIC Science & Technology

2013-05-10

DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Turbulent Boundary Layer Flow over Superhydrophobic ...modified surfaces. This study encompassed the testing of four different surfaces: 1) Teflon SLIP, 2) Aluminum SLIP, 3) Honeycomb Superhydrophobic and 4...Polydimethylsiloxane elastomer (PDMSe) Superhydrophobic . Each of these surfaces uses specific geometrical surface features to modify the original

Fabrication of ZIF-8@SiO2 Micro/Nano Hierarchical Superhydrophobic Surface on AZ31 Magnesium Alloy with Impressive Corrosion Resistance and Abrasion Resistance.

PubMed

Wu, Cuiqing; Liu, Qi; Chen, Rongrong; Liu, Jingyuan; Zhang, Hongsen; Li, Rumin; Takahashi, Kazunobu; Liu, Peili; Wang, Jun

2017-03-29

Superhydrophobic coatings are highly promising for protecting material surfaces and for wide applications. In this study, superhydrophobic composites, comprising a rhombic-dodecahedral zeolitic imidazolate framework (ZIF-8@SiO 2 ), have been manufactured onto AZ31 magnesium alloy via chemical etching and dip-coating methods to enhance stability and corrosion resistance. Herein, we report on a simple strategy to modify hydrophobic hexadecyltrimethoxysilan (HDTMS) on ZIF-8@SiO 2 to significantly improve the property of repelling water. We show that various liquids can be stable on its surface and maintain a contact angle higher than 150°. The morphologies and chemical composition were characterized by means of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FI-IR). In addition, the anticorrosion and antiattrition properties of the film were assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization and HT, respectively. Such a coating shows promising potential as a material for large-scale fabrication.

Magnetically Responsive Superhydrophobic Surface: In Situ Reversible Switching of Water Droplet Wettability and Adhesion for Droplet Manipulation.

PubMed

Yang, Chao; Wu, Lei; Li, Gang

2018-06-13

A smart, magnetically responsive superhydrophobic surface was facilely prepared by combining spray coating and magnetic-field-directed self-assembly. The surface comprised a dense array of magnetorheological elastomer micropillars (MREMPs). Benefitting from the magnetic field-stiffening effect of the MREMPs, the surface exhibited reversible switching of the wettability and adhesion that was responsive to an on/off magnetic field. The wettability and adhesion properties of the surfaces with MREMPs were investigated under different magnetic fields. The results revealed that the adhesion force and sliding behaviors of these surfaces were strongly dependent on the intensity of the applied magnetic field and the mixing ratio of poly(dimethylsiloxane) (PDMS), iron particles, and solvent (in solution) used for preparation of the magnetically responsive superhydrophobic surfaces. The adhesion transition was attributed to the tunable mechanical properties of the MREMPs, which was easily controlled by an external magnetic field. It was also demonstrated that the magnetically responsive superhydrophobic surface can be used as a "mechanical hand" for no-loss liquid droplet transportation. This magnetically responsive superhydrophobic surface not only provides a novel interface for microfluidic control and droplet transportation, but also opens up new avenues for achieving smart liquid-repellent skin, programmable fluid collection and transport, and smart microfluidic devices.

Robust superhydrophobic surface by nature-inspired polyphenol chemistry for effective oil-water separation

NASA Astrophysics Data System (ADS)

Bu, Yiming; Huang, Jingjing; Zhang, Shiyu; Wang, Yinghua; Gu, Shaojin; Cao, Genyang; Yang, Hongjun; Ye, Dezhan; Zhou, Yingshan; Xu, Weilin

2018-05-01

With the ever-increasing oil spillages, oil-water separation has attracted widespread concern in recent years. In this work, a nature-inspired polyphenol method has been developed to fabricate the durable superhydrophobic surfaces for the oil-water separation. Inspiring from the adhesion of polyphenol and reducing capacity of free catechol/pyrogallol groups in polyphenol, firstly, the simple immersion of commercial materials (melamine sponge, PET, and nonwoven cotton fabrics) in tannic acid (TA) solution allows to form a multifunctional coating on the surface of sponge or fabrics, which was used as reducing reagent to generate Ag nanoparticles (NPs). Then, decoration of 1H, 1H, 2H, 2H-perfluorodecanethiol (PFDT) molecules produced superhydrophobic surfaces. The surface topological structure, chemical composition, and superhydrophobic property of the as-prepared surface are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), and water contact angle (WCA) measurements. The WCAs of as-prepared sponge and fabrics were higher than 150°. The stability, absorption capacity, and recyclability of as-prepared sponge and fabrics were investigated. The as-prepared sponge demonstrates high oil/water selectivity and high absorption capacity (66-150 g/g) for a broad variety of oils and organic solvents, and was chemically resistant, robust against abrasion, and long-term durability in harsh environments. Most important of all, it can continuously separate various kinds of oils or organic pollutants from the surface of water. This study presents a facile strategy to fabricate superhydrophobic materials for continuous oil-water separation, displaying great potential in large-scale practical application.

Surface modification of blood-contacting biomaterials by plasma-polymerized superhydrophobic films using hexamethyldisiloxane and tetrafluoromethane as precursors

NASA Astrophysics Data System (ADS)

Hsiao, Chaio-Ru; Lin, Cheng-Wei; Chou, Chia-Man; Chung, Chi-Jen; He, Ju-Liang

2015-08-01

This paper proposes a plasma polymerization system that can be used to modify the surface of the widely used biomaterial, polyurethane (PU), by employing low-cost hexamethyldisiloxane (HMDSO) and tetrafluoromethane (CF4) as precursors; this system features a pulsed-dc power supply. Plasma-polymerized HMDSO/CF4 (pp-HC) with coexisting micro- and nanoscale morphology was obtained as a superhydrophobic coating material by controlling the HMDSO/CF4 (fH) monomer flow ratio. The developed surface modification technology can be applied to medical devices, because it is non-cytotoxic and has favorable hemocompatibility, and no blood clots form when the device surface direct contacts. Experimental results reveal that the obtained pp-HC films contained SiOx nanoparticles randomly dispersed on the micron-scale three-dimensional network film surface. The sbnd CF functional group, sbnd CF2 bonding, and SiOx were detected on the film surface. The maximal water contact angle of the pp-HC coating was 161.2°, apparently attributable to the synergistic effect of the coexisting micro- and nanoscale surface morphology featuring a low surface-energy layer. The superhydrophobic and antifouling characteristics of the coating were retained even after it was rubbed 20 times with a steel wool tester. Results of in vitro cytotoxicity, fibrinogen adsorption, and platelet adhesion tests revealed favorable myoblast cell proliferation and the virtual absence of fibrinogen adsorption and platelet adhesion on the pp-HC coated specimens. These quantitative findings imply that the pp-HC coating can potentially prevent the formation of thrombi and provide an alternative means of modifying the surfaces of blood-contacting biomaterials.

Effect of substrate roughness on the apparent surface free energy of sputter deposited superhydrophobic polytetrafluoroethylene coatings: A comparison of experimental data with different theoretical models

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

Selvakumar, N.; Barshilia, Harish C.; Rajam, K. S.

2010-07-15

We have studied the effect of substrate roughness on the wettability and the apparent surface free energy (SFE) of sputter deposited polytetrafluoroethylene (PTFE) coatings deposited on untreated glass (average roughness, R{sub a}=2.0 nm), plasma etched glass (R{sub a}=7.4 nm), and sandblasted glass (R{sub a}=4500 nm) substrates. The wettability of the PTFE coatings deposited on substrates with varying roughnesses was evaluated by measuring the apparent contact angle (CA) using a series of probe liquids from nonpolar aprotic to polar protic. The wettability measurements indicate that an apparent water CA of 152 deg. with a sliding angle of 8 deg. was achievedmore » for PTFE coatings deposited on a substrate with R{sub a}=4500 nm. The superhydrophobicity observed in these coatings is attributed to the presence of dual scale roughness, densely packed microstructure and the presence of CF{sub 3} groups. Unlike the bulk PTFE which is mainly dispersive, the sputter deposited PTFE coatings are expected to have some degree of polar component due to the plasma treatment. In order to calculate the dispersive SFE of PTFE coatings, we have used the Girifalco-Good-Fowkes (GGF) method and validated it with the Zisman model. Furthermore, the Owens-Wendt model has been used to calculate the dispersive and the polar components of the apparent SFE of the PTFE coatings. These results are further corroborated using the Fowkes method. Finally, an ''equation of state'' theory proposed by Neumann has been used to calculate the apparent SFE values of the PTFE coatings. The results indicate that the apparent SFE values of the PTFE coatings obtained from the Owens-Wendt and the Fowkes methods are comparable to those obtained from the Neumann's method. The analyses further demonstrate that the GGF and the Zisman methods underestimate the apparent SFE values of the sputter deposited PTFE coatings.« less

Super-hydrophobic bandages and method of making the same

DOEpatents

Simpson, John T [Clinton, TN; D'Urso, Brian R [Pittsburgh, PA

2012-06-05

A bandage that includes a material, which can be breathable, having a first surface, and a plurality of superhydrophobic particles attached to the first surface. The plurality of superhydrophobic particles ranging in size from about 100 nanometers to about 10 micrometers. The superhydrophobic particles including a protrusive material defining a plurality of nanopores and a plurality of spaced apart nanostructures that define an external boundary of the hydrophobic particles. The nanopores providing a flow through porosity. The first surface can be rendered superhydrophobic by the attached superhydrophobic particles. The material can have a second surface opposite the first surface that is hydrophilic. The superhydrophobic particles can be adhered to the first surface by a binder. Also included is a method of making the bandages described herein.

Ultra-high mobility transparent organic thin film transistors grown by an off-centre spin-coating method.

PubMed

Yuan, Yongbo; Giri, Gaurav; Ayzner, Alexander L; Zoombelt, Arjan P; Mannsfeld, Stefan C B; Chen, Jihua; Nordlund, Dennis; Toney, Michael F; Huang, Jinsong; Bao, Zhenan

2014-01-01

Organic semiconductors with higher carrier mobility and better transparency have been actively pursued for numerous applications, such as flat-panel display backplane and sensor arrays. The carrier mobility is an important figure of merit and is sensitively influenced by the crystallinity and the molecular arrangement in a crystal lattice. Here we describe the growth of a highly aligned meta-stable structure of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from a blended solution of C8-BTBT and polystyrene by using a novel off-centre spin-coating method. Combined with a vertical phase separation of the blend, the highly aligned, meta-stable C8-BTBT films provide a significantly increased thin film transistor hole mobility up to 43 cm(2) Vs(-1) (25 cm(2) Vs(-1) on average), which is the highest value reported to date for all organic molecules. The resulting transistors show high transparency of >90% over the visible spectrum, indicating their potential for transparent, high-performance organic electronics.

Superhydrophobic materials for biomedical applications.

PubMed

Falde, Eric J; Yohe, Stefan T; Colson, Yolonda L; Grinstaff, Mark W

2016-10-01

Superhydrophobic surfaces are actively studied across a wide range of applications and industries, and are now finding increased use in the biomedical arena as substrates to control protein adsorption, cellular interaction, and bacterial growth, as well as platforms for drug delivery devices and for diagnostic tools. The commonality in the design of these materials is to create a stable or metastable air layer at the material surface, which lends itself to a number of unique properties. These activities are catalyzing the development of new materials, applications, and fabrication techniques, as well as collaborations across material science, chemistry, engineering, and medicine given the interdisciplinary nature of this work. The review begins with a discussion of superhydrophobicity, and then explores biomedical applications that are utilizing superhydrophobicity in depth including material selection characteristics, in vitro performance, and in vivo performance. General trends are offered for each application in addition to discussion of conflicting data in the literature, and the review concludes with the authors' future perspectives on the utility of superhydrophobic biomaterials for medical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Superhydrophobic Materials for Biomedical Applications

PubMed Central

Colson, Yolonda L.; Grinstaff, Mark W.

2016-01-01

Superhydrophobic surfaces are actively studied across a wide range of applications and industries, and are now finding increased use in the biomedical arena as substrates to control protein adsorption, cellular interaction, and bacterial growth, as well as platforms for drug delivery devices and for diagnostic tools. The commonality in the design of these materials is to create a stable or metastable air state at the material surface, which lends itself to a number of unique properties. These activities are catalyzing the development of new materials, applications, and fabrication techniques, as well as collaborations across material science, chemistry, engineering, and medicine given the interdisciplinary nature of this work. The review begins with a discussion of superhydrophobicity, and then explores biomedical applications that are utilizing superhydrophobicity in depth including material selection characteristics, in vitro performance, and in vivo performance. General trends are offered for each application in addition to discussion of conflicting data in the literature, and the review concludes with the authors’ future perspectives on the utility of superhydrophobic surfaces for biomedical applications. PMID:27449946

Stable biomimetic super-hydrophobic engineering materials.

PubMed

Guo, Zhiguang; Zhou, Feng; Hao, Jingcheng; Liu, Weimin

2005-11-16

We describe a simple and inexpensive method to produce super-hydrophobic surfaces on aluminum and its alloy by oxidation and chemical modification. Water or aqueous solutions (pH = 1-14) have contact angles of 168 +/- 2 and 161 +/- 2 degrees on the treated surfaces of Al and Al alloy, respectively. The super-hydrophobic surfaces are produced by the cooperation of binary structures at micro- and nanometer scales, thus reducing the energies of the surfaces. Such super-hydrophobic properties will greatly extend the applications of aluminum and its alloy as lubricating materials.

Novel fabrication of a robust superhydrophobic PU@ZnO@Fe3O4@SA sponge and its application in oil-water separations.

PubMed

Tran, Viet-Ha Thi; Lee, Byeong-Kyu

2017-12-13

We report a novel superhydrophobic material based on commercially available polyurethane (PU) sponge with high porosity, low density and good elasticity. The fabrication of a superhydrophobic sponge capable of efficiently separating oil from water was achieved by imitating or mimicking nature's designs. The original PU sponge was coated with zinc oxide (ZnO), stearic acid (SA) and iron oxide particles (Fe 3 O 4 ) via a facile and environmentally friendly method. After each treatment, the properties of the modified sponge were characterized, and the changes in wettability were examined. Water contact angle (WCA) measurements confirmed the excellent superhydrophobicity of the material withhigh static WCA of 161° andlow dynamic WCA (sliding WCA of 7° and shedding WCA of 8°). The fabricated sponge showed high efficiency in separation (over 99%) of different oils from water. Additionally, the fabricated PU@ZnO@Fe 3 O 4 @SA sponge could be magnetically guided to quickly absorb oil floating on the water surface. Moreover, the fabricated sponge showed excellent stability and reusability in terms of superhydrophobicity and oil absorption capacity. The durable, magnetic and superhydrophobic properties of the fabricated sponge render it applicable to the cleanup of marine oil spills and other oil-water separation issues, with eco-friendly recovery of the oil by simple squeezing process.

Uniting Superhydrophobic, Superoleophobic and Lubricant Infused Slippery Behavior on Copper Oxide Nano-structured Substrates

NASA Astrophysics Data System (ADS)

Ujjain, Sanjeev Kumar; Roy, Pritam Kumar; Kumar, Sumana; Singha, Subhash; Khare, Krishnacharya

2016-10-01

Alloys, specifically steel, are considered as the workhorse of our society and are inimitable engineering materials in the field of infrastructure, industry and possesses significant applications in our daily life. However, creating a robust synthetic metallic surface that repels various liquids has remained extremely challenging. The wettability of a solid surface is known to be governed by its geometric nano-/micro structure and the chemical composition. Here, we are demonstrating a facile and economical way to generate copper oxide micro-nano structures with spherical (0D), needle (1D) and hierarchical cauliflower (3D) morphologies on galvanized steel substrates using a simple chemical bath deposition method. These nano/micro textured steel surfaces, on subsequent coating of a low surface energy material display excellent superhydrophobic, superoleophobic and slippery behavior. Polydimethylsiloxane coated textured surfaces illustrate superhydrophobicity with water contact angle about 160°(2) and critical sliding angle ~2°. When functionalized with low-surface energy perfluoroalkylsilane, these surfaces display high repellency for low surface tension oils as well as hydrocarbons. Among them, the hierarchical cauliflower morphology exhibits re-entrant structure thereby showing the best superoleophobicity with contact angle 149° for dodecane. Once infused with a lubricant like silicone oil, they show excellent slippery behavior with low contact angle hysteresis (~ 2°) for water drops.

Meltwater Evolution during Defrosting on Superhydrophobic Surfaces.

PubMed

Chu, Fuqiang; Wu, Xiaomin; Wang, Lingli

2018-01-10

Defrosting is essential for removing frost from engineering surfaces, but some fundamental issues are still unclear, especially for defrosting on superhydrophobic surfaces. Here, defrosting experiments on prepared superhydrophobic surfaces were conducted along with the investigation on meltwater evolution characteristics. According to the experiments, the typical meltwater evolution process on superhydrophobic surfaces can be divided into two stages: dewetting by edge curling and dewetting by shrinkage. The edge curling of a meltwater film is a distinct phenomenon and has been first reported in this work. Profiting from the ultralow adhesion of the superhydrophobic surface, edge curling is mainly attributed to two unbalanced forces (one at the interface between the ice slurry layer and pure water layer and the other in the triple phase line area) acting on the layered meltwater film. During the multi-meltwater evolution process, the nonbreaking of chained droplets on superhydrophobic surfaces is also an interesting phenomenon, which is controlled by the interaction between the surface tension and the retentive force because of contact angle hysteresis. An approximate criterion was then developed to explain and determine the status of chained droplets, and experimental data from various surfaces have validated the effectiveness of this criterion. This work may deepen the understanding of defrosting on superhydrophobic surfaces and promote antifrosting/icing applications in engineering.

Shear driven droplet shedding and coalescence on a superhydrophobic surface

NASA Astrophysics Data System (ADS)

Moghtadernejad, S.; Tembely, M.; Jadidi, M.; Esmail, N.; Dolatabadi, A.

2015-03-01

The interest on shedding and coalescence of sessile droplets arises from the importance of these phenomena in various scientific problems and industrial applications such as ice formation on wind turbine blades, power lines, nacelles, and aircraft wings. It is shown recently that one of the ways to reduce the probability of ice accretion on industrial components is using superhydrophobic coatings due to their low adhesion to water droplets. In this study, a combined experimental and numerical approach is used to investigate droplet shedding and coalescence phenomena under the influence of air shear flow on a superhydrophobic surface. Droplets with a size of 2 mm are subjected to various air speeds ranging from 5 to 90 m/s. A numerical simulation based on the Volume of Fluid method coupled with the Large Eddy Simulation turbulent model is carried out in conjunction with the validating experiments to shed more light on the coalescence of droplets and detachment phenomena through a detailed analysis of the aerodynamics forces and velocity vectors on the droplet and the streamlines around it. The results indicate a contrast in the mechanism of two-droplet coalescence and subsequent detachment with those related to the case of a single droplet shedding. At lower speeds, the two droplets coalesce by attracting each other with successive rebounds of the merged droplet on the substrate, while at higher speeds, the detachment occurs almost instantly after coalescence, with a detachment time decreasing exponentially with the air speed. It is shown that coalescence phenomenon assists droplet detachment from the superhydrophobic substrate at lower air speeds.

Flexible Transparent Supercapacitors Based on Hierarchical Nanocomposite Films.

PubMed

Chen, Fanhong; Wan, Pengbo; Xu, Haijun; Sun, Xiaoming

2017-05-31

Flexible transparent electronic devices have recently gained immense popularity in smart wearable electronics and touch screen devices, which accelerates the development of the portable power sources with reliable flexibility, robust transparency and integration to couple these electronic devices. For potentially coupled as energy storage modules in various flexible, transparent and portable electronics, the flexible transparent supercapacitors are developed and assembled from hierarchical nanocomposite films of reduced graphene oxide (rGO) and aligned polyaniline (PANI) nanoarrays upon their synergistic advantages. The nanocomposite films are fabricated from in situ PANI nanoarrays preparation in a blended solution of aniline monomers and rGO onto the flexible, transparent, and stably conducting film (FTCF) substrate, which is obtained by coating silver nanowires (Ag NWs) layer with Meyer rod and then coating of rGO layer on polyethylene terephthalate (PET) substrate. Optimization of the transparency, the specific capacitance, and the flexibility resulted in the obtained all-solid state nanocomposite supercapacitors exhibiting enhanced capacitance performance, good cycling stability, excellent flexibility, and superior transparency. It provides promising application prospects for exploiting flexible, low-cost, transparent, and high-performance energy storage devices to be coupled into various flexible, transparent, and wearable electronic devices.

Durable polymer-aerogel based superhydrophobic coatings, a composite material

DOEpatents

Kissel, David J; Brinker, Charles Jeffrey

2014-03-04

Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

Durable polymer-aerogel based superhydrophobic coatings: a composite material

DOEpatents

Kissel, David J.; Brinker, Charles Jeffrey

2016-02-02

Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

Superhydrophobic Blood-Repellent Surfaces.

PubMed

Jokinen, Ville; Kankuri, Esko; Hoshian, Sasha; Franssila, Sami; Ras, Robin H A

2018-06-01

Superhydrophobic surfaces repel water and, in some cases, other liquids as well. The repellency is caused by topographical features at the nano-/microscale and low surface energy. Blood is a challenging liquid to repel due to its high propensity for activation of intrinsic hemostatic mechanisms, induction of coagulation, and platelet activation upon contact with foreign surfaces. Imbalanced activation of coagulation drives thrombogenesis or formation of blood clots that can occlude the blood flow either on-site or further downstream as emboli, exposing tissues to ischemia and infarction. Blood-repellent superhydrophobic surfaces aim toward reducing the thrombogenicity of surfaces of blood-contacting devices and implants. Several mechanisms that lead to blood repellency are proposed, focusing mainly on platelet antiadhesion. Structured surfaces can: (i) reduce the effective area exposed to platelets, (ii) reduce the adhesion area available to individual platelets, (iii) cause hydrodynamic effects that reduce platelet adhesion, and (iv) reduce or alter protein adsorption in a way that is not conducive to thrombus formation. These mechanisms benefit from the superhydrophobic Cassie state, in which a thin layer of air is trapped between the solid surface and the liquid. The connections between water- and blood repellency are discussed and several recent examples of blood-repellent superhydrophobic surfaces are highlighted. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanofibers-based nanoweb promise superhydrophobic polyaniline: from star-shaped to leaf-shaped structures.

PubMed

Fan, Haosen; Wang, Hao; Guo, Jing; Zhao, Ning; Xu, Jian

2013-11-01

Star-shaped and leaf-shaped polyaniline (PANI) hierarchical structures with interlaced nanofibers on the surface were successfully prepared by chemical polymerization of aniline in the presence of lithium triflate (LT). Chemical structure and composition of the star-like PANI obtained were characterized by FTIR and UV-vis spectra. PANI 2D architectures can be tailored from star-shaped to leaf-shaped structures by change the concentration of LT. The synthesized star-like and leaf-like polyaniline show good superhydrophobicity with water contact angles of both above 150° due to the combination of the rough nanoweb structure and the low surface tension of fluorinated chain of dopant. This method is a facile and applicable strategy for a large-scale fabrication of 2D PANI micro/nanostructures. Many potential applications such as self-cleaning and antifouling coating can be expected based on the superhydrophobic PANI micro/nanostructures. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Recent Advances in Superhydrophobic Electrodeposits

PubMed Central

Tam, Jason; Palumbo, Gino; Erb, Uwe

2016-01-01

In this review, we present an extensive summary of research on superhydrophobic electrodeposits reported in the literature over the past decade. As a synthesis technique, electrodeposition is a simple and scalable process to produce non-wetting metal surfaces. There are three main categories of superhydrophobic surfaces made by electrodeposition: (i) electrodeposits that are inherently non-wetting due to hierarchical roughness generated from the process; (ii) electrodeposits with plated surface roughness that are further modified with low surface energy material; (iii) composite electrodeposits with co-deposited inert and hydrophobic particles. A recently developed strategy to improve the durability during the application of superhydrophobic electrodeposits by controlling the microstructure of the metal matrix and the co-deposition of hydrophobic ceramic particles will also be addressed. PMID:28773278

Recent Advances in Superhydrophobic Electrodeposits.

PubMed

Tam, Jason; Palumbo, Gino; Erb, Uwe

2016-03-03

In this review, we present an extensive summary of research on superhydrophobic electrodeposits reported in the literature over the past decade. As a synthesis technique, electrodeposition is a simple and scalable process to produce non-wetting metal surfaces. There are three main categories of superhydrophobic surfaces made by electrodeposition: (i) electrodeposits that are inherently non-wetting due to hierarchical roughness generated from the process; (ii) electrodeposits with plated surface roughness that are further modified with low surface energy material; (iii) composite electrodeposits with co-deposited inert and hydrophobic particles. A recently developed strategy to improve the durability during the application of superhydrophobic electrodeposits by controlling the microstructure of the metal matrix and the co-deposition of hydrophobic ceramic particles will also be addressed.

High gain durable anti-reflective coating with oblate voids

DOEpatents

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev

2016-06-28

Disclosed herein are single layer transparent coatings with an anti-reflective property, a hydrophobic property, and that are highly abrasion resistant. The single layer transparent coatings contain a plurality of oblate voids. At least 1% of the oblate voids are open to a surface of the single layer transparent coatings.

A large-scale superhydrophobic surface-enhanced Raman scattering (SERS) platform fabricated via capillary force lithography and assembly of Ag nanocubes for ultratrace molecular sensing.

PubMed

Tan, Joel Ming Rui; Ruan, Justina Jiexin; Lee, Hiang Kwee; Phang, In Yee; Ling, Xing Yi

2014-12-28

An analytical platform with an ultratrace detection limit in the atto-molar (aM) concentration range is vital for forensic, industrial and environmental sectors that handle scarce/highly toxic samples. Superhydrophobic surface-enhanced Raman scattering (SERS) platforms serve as ideal platforms to enhance detection sensitivity by reducing the random spreading of aqueous solution. However, the fabrication of superhydrophobic SERS platforms is generally limited due to the use of sophisticated and expensive protocols and/or suffers structural and signal inconsistency. Herein, we demonstrate a high-throughput fabrication of a stable and uniform superhydrophobic SERS platform for ultratrace molecular sensing. Large-area box-like micropatterns of the polymeric surface are first fabricated using capillary force lithography (CFL). Subsequently, plasmonic properties are incorporated into the patterned surfaces by decorating with Ag nanocubes using the Langmuir-Schaefer technique. To create a stable superhydrophobic SERS platform, an additional 25 nm Ag film is coated over the Ag nanocube-decorated patterned template followed by chemical functionalization with perfluorodecanethiol. Our resulting superhydrophobic SERS platform demonstrates excellent water-repellency with a static contact angle of 165° ± 9° and a consequent analyte concentration factor of 59-fold, as compared to its hydrophilic counterpart. By combining the analyte concentration effect of superhydrophobic surfaces with the intense electromagnetic "hot spots" of Ag nanocubes, our superhydrophobic SERS platform achieves an ultra-low detection limit of 10(-17) M (10 aM) for rhodamine 6G using just 4 μL of analyte solutions, corresponding to an analytical SERS enhancement factor of 10(13). Our fabrication protocol demonstrates a simple, cost- and time-effective approach for the large-scale fabrication of a superhydrophobic SERS platform for ultratrace molecular detection.

Laser synthesized super-hydrophobic conducting carbon with broccoli-type morphology as a counter-electrode for dye sensitized solar cells.

PubMed

Gokhale, Rohan; Agarkar, Shruti; Debgupta, Joyashish; Shinde, Deodatta; Lefez, Benoit; Banerjee, Abhik; Jog, Jyoti; More, Mahendra; Hannoyer, Beatrice; Ogale, Satishchandra

2012-11-07

A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode.

Rational strategy for the atmospheric icing prevention based on chemically functionalized carbon soot coatings

NASA Astrophysics Data System (ADS)

Esmeryan, Karekin D.; Bressler, Ashton H.; Castano, Carlos E.; Fergusson, Christian P.; Mohammadi, Reza

2016-12-01

Although the superhydrophobic surfaces are preferable for passive anti-icing systems, as they provide water shedding before initiation of ice nucleation, their practical usage is still under debate. This is so, as the superhydrophobic materials are not necessarily icephobic and most of the synthesis techniques are characterized with low fabrication scalability. Here, we describe a rational strategy for the atmospheric icing prevention, based on chemically functionalized carbon soot, suitable for large-scale fabrication of superhydrophobic coatings that exhibit and retain icephobicity in harsh operational conditions. This is achieved through a secondary treatment with ethanol and aqueous fluorocarbon solution, which improves the coating's mechanical strength without altering its water repellency. Subsequent experimental analyses on the impact dynamics of icy water droplets on soot coated aluminum and steel sheets show that these surfaces remain icephobic in condensate environments and substrate temperatures down to -35 °C. Furthermore, the soot's icephobicity and non-wettability are retained in multiple icing/de-icing cycles and upon compressed air scavenging, spinning and water jetting with impact velocity of ∼25 m/s. Finally, on frosted soot surfaces, the droplets freeze in a spherical shape and are entirely detached by adding small amount of thermal energy, indicating lower ice adhesion compared to the uncoated metal substrates.

Fabrication of Slippery Lubricant-Infused Porous Surface with High Underwater Transparency for the Control of Marine Biofouling.

PubMed

Wang, Peng; Zhang, Dun; Sun, Shimei; Li, Tianping; Sun, Yan

2017-01-11

Marine optical instruments are bearing serious biofouling problem, which affects the accuracy of data collected. To solve the biofouling problem of marine optical instruments, a novel instance of slippery lubricant-infused porous surface (SLIPS) with high underwater-transparency was designed over glass substrate via infusing lubricant into its porous microstructure fabricated with hydrothermal method. The advantage of SLIPS as antibiofouling strategy to marine optical instruments was proven by comparing its underwater optical and antibiofouling performances with three kinds of samples (hydrophilic glass sample, textured hydrophilic glass sample, and superhydrophobic glass sample). The modification of SLIPS enhances the underwater-transparency of glass sample within the wavelength of 500-800 nm, for the infusion of lubricant with lower refractive index than glass substrate. In contrast with hydrophilic surface, textured hydrophilic surface and superhydrophobic surface, SLIPS can significantly inhibit bacterial and algal settlements, thereby maintaining high underwater-transparency in both dynamic and static seawater. The inhibition of bacterial and algal settlements over SLIPS results from its liquid-like property. The contact angle hysteresis of water over SLIPS increases with immersion time in seawater under different conditions (static, dynamic, and vibration conditions). Both dynamic and vibration conditions accelerate the failure of SLIPS exposed in seawater. This research provides valuable information for solving biofouling problem of marine optical instruments with SLIPS.

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.

Fabrication of superhydrophobic film by microcellular plastic foaming method

NASA Astrophysics Data System (ADS)

Zhang, Zhen Xiu; Li, Ya Nan; Xia, Lin; Ma, Zhen Guo; Xin, Zhen Xiang; Kim, Jin Kuk

2014-08-01

To solve the complicated manufacturing operation and the usage of toxic solvent problems, a simple and novel method to fabricate superhydrophobic film by surface foaming method was introduced in this paper. The superhydrophobic property of the foamed material was obtained at a contact angle >150° and a rolling angle about 8°. The foamed material can instantly generate its superhydrophobicity via peeling process. The effects of blowing agent content, foaming time and peeling rate on the foam structure and superhydrophobicity were studied.

Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

PubMed

Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

2015-01-28

The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

Designing robust alumina nanowires-on-nanopores structures: superhydrophobic surfaces with slippery or sticky water adhesion.

PubMed

Peng, Shan; Tian, Dong; Miao, Xinrui; Yang, Xiaojun; Deng, Wenli

2013-11-01

Hierarchical alumina surfaces with different morphologies were fabricated by a simple one-step anodization method. These alumina films were fabricated by a new raw material: silica gel plate (aluminum foil with a low purity of 97.17%). The modulation of anodizing time enabled the formation of nanowires-on-nanopores hybrid nanostructures having controllable nanowires topographies through a self-assembly process. The resultant structures were demonstrated to be able to achieve superhydrophobicity without any hydrophobic coating layer. More interestingly, it is found that the as-prepared superhydrophobic alumina surfaces exhibited high contrast water adhesion. Hierarchical alumina film with nanowire bunches-on-nanopores (WBOP) morphology presents extremely slippery property which can obtain a sliding angle (SA) as low as 1°, nanowire pyramids-on-nanopores (WPOP) structure shows strongly sticky water adhesion with the adhesive ability to support 15 μL inverted water droplet at most. The obtained superhydrophobic alumina surfaces show remarkable mechanical durability even treated by crimping or pressing without impact on the water-repellent performance. Moreover, the created surfaces also show excellent resistivity to ice water, boiling water, high temperature, organic solvent and oil contamination, which could expand their usefulness and efficacy in harsh conditions. Copyright © 2013 Elsevier Inc. All rights reserved.

Effect of texture randomization on the slip and interfacial robustness in turbulent flows over superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Seo, Jongmin; Mani, Ali

2018-04-01

Superhydrophobic surfaces demonstrate promising potential for skin friction reduction in naval and hydrodynamic applications. Recent developments of superhydrophobic surfaces aiming for scalable applications use random distribution of roughness, such as spray coating and etched process. However, most previous analyses of the interaction between flows and superhydrophobic surfaces studied periodic geometries that are economically feasible only in laboratory-scale experiments. In order to assess the drag reduction effectiveness as well as interfacial robustness of superhydrophobic surfaces with randomly distributed textures, we conduct direct numerical simulations of turbulent flows over randomly patterned interfaces considering a range of texture widths w+≈4 -26 , and solid fractions ϕs=11 %-25 % . Slip and no-slip boundary conditions are implemented in a pattern, modeling the presence of gas-liquid interfaces and solid elements. Our results indicate that slip of randomly distributed textures under turbulent flows is about 30 % less than those of surfaces with aligned features of the same size. In the small texture size limit w+≈4 , the slip length of the randomly distributed textures in turbulent flows is well described by a previously introduced Stokes flow solution of randomly distributed shear-free holes. By comparing DNS results for patterned slip and no-slip boundary against the corresponding homogenized slip length boundary conditions, we show that turbulent flows over randomly distributed posts can be represented by an isotropic slip length in streamwise and spanwise direction. The average pressure fluctuation on a gas pocket is similar to that of the aligned features with the same texture size and gas fraction, but the maximum interface deformation at the leading edge of the roughness element is about twice as large when the textures are randomly distributed. The presented analyses provide insights on implications of texture randomness on drag

Templated biomimetic multifunctional coatings

NASA Astrophysics Data System (ADS)

Sun, Chih-Hung; Gonzalez, Adriel; Linn, Nicholas C.; Jiang, Peng; Jiang, Bin

2008-02-01

We report a bioinspired templating technique for fabricating multifunctional optical coatings that mimic both unique functionalities of antireflective moth eyes and superhydrophobic cicada wings. Subwavelength-structured fluoropolymer nipple arrays are created by a soft-lithography-like process. The utilization of fluoropolymers simultaneously enhances the antireflective performance and the hydrophobicity of the replicated films. The specular reflectivity matches the optical simulation using a thin-film multilayer model. The dependence of the size and the crystalline ordering of the replicated nipples on the resulting antireflective properties have also been investigated by experiment and modeling. These biomimetic materials may find important technological application in self-cleaning antireflection coatings.

Testing the performance of superhydrophobic aluminum surfaces.

PubMed

Ruiz-Cabello, F Javier Montes; Ibáñez-Ibáñez, Pablo F; Gómez-Lopera, J Francisco; Martínez-Aroza, José; Cabrerizo-Vílchez, Miguel; Rodríguez-Valverde, Miguel A

2017-12-15

The analysis of wetting properties of superhydrophobic surfaces may be a difficult task due to the restless behavior of drops on this type of surfaces and the limitations of goniometry for high contact angles. A method to validate the performance of superhydrophobic surfaces, rather than standard goniometry, is required. In this work, we used bouncing drop dynamics as a useful tool to predict the water repellency of different superhydrophobic surfaces. From bouncing drop experiments conducted over a wide range of superhydrophobic surfaces, we found that those surfaces with a proper roughness degree and homogeneous chemical composition showed higher water-repellency. We also conducted a drop condensation study at saturating conditions aimed to determine whether there is direct correlation between water repellency and condensation delay. We found that the drop condensation process is strongly related to the surface topography, as well as the intrinsic wettability. The condensation is promoted on rough surfaces but it is delayed on intrinsically hydrophobic surfaces. However, the differences found in condensation delay between the superhydrophobic surfaces explored in this study cannot be justified by their chemical homogeneity nor their efficiency as water repellent surfaces, separately. Copyright © 2017 Elsevier Inc. All rights reserved.

Effects of alpha-zirconium phosphate on thermal degradation and flame retardancy of transparent intumescent fire protective coating

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

Xing, Weiyi; Zhang, Ping; Song, Lei

2014-01-01

Graphical abstract: - Highlights: • A transparent intumescent fire protective coating was obtained by UV-cured technology. • OZrP could enhance the thermal stability and anti-oxidation of the coating. • OZrP could reduce the combustion properties of the coatings. - Abstract: Organophilic alpha-zirconium phosphate (OZrP) was used to improve the thermal and fire retardant behaviors of the phenyl di(acryloyloxyethyl)phosphate (PDHA)-triglycidyl isocyanurate acrylate (TGICA)-2-phenoxyethyl acrylate (PHEA) (PDHA-TGICA-PHEA) coating. The morphology of nanocomposite coating was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of OZrP on the flame retardancy, thermal stability, fireproofing time and char formation of the coatingsmore » was investigated by microscale combustion calorimeter (MCC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), laser Raman spectroscopy (LRS) and scanning electric microscope (SEM). The results showed that by adding OZrP, the peak heat release rate and total heat of combustion were significantly reduced. The highest improvement was achieved with 0.5 wt% OZrP. XPS analysis indicated that the performance of anti-oxidation of the coating was improved with the addition of OZrP, and SEM images showed that a good synergistic effect was obtained through a ceramic-like layer produced by OZrP covered on the surface of char.« less

Dictating anisotropic electric conductivity of a transparent copper nanowire coating by the surface structure of wood.

PubMed

Guo, Huizhang; Büchel, Martin; Li, Xing; Wäckerlin, Aneliia; Chen, Qing; Burgert, Ingo

2018-05-01

In this article, a robust, air-stable, flexible and transparent copper (Cu) nanowire (NW) network coating on the surface of the wood is presented, based on a fusion welding of the Cu NWs by photonic curing. Thereby, an anisotropic conductivity can be achieved, which is originating from the structural organization of the wood body and its surface. Furthermore, the Cu NWs are protected from oxidation or wear by a commercially available paraffin wax-polyolefin, which also results in surface water repellency. The developed processing steps present a facile and flexible routine for applying Cu NW transparent conductors to abundant biomaterials and solve current manufacturing obstacles for corrosion-resistant circuits while keeping the natural appearance of the substrate. It may open a venue for more extensive utilization of materials from renewable resources such as wood for electronic devices in smart buildings or mobility applications. © 2018 The Author(s).

A Highly Stretchable and Robust Non-fluorinated Superhydrophobic Surface.

PubMed

Ju, Jie; Yao, Xi; Hou, Xu; Liu, Qihan; Zhang, Yu Shrike; Khademhosseini, Ali

2017-08-21

Superhydrophobic surface simultaneously possessing exceptional stretchability, robustness, and non-fluorination is highly desirable in applications ranging from wearable devices to artificial skins. While conventional superhydrophobic surfaces typically feature stretchability, robustness, or non-fluorination individually, co-existence of all these features still remains a great challenge. Here we report a multi-performance superhydrophobic surface achieved through incorporating hydrophilic micro-sized particles with pre-stretched silicone elastomer. The commercial silicone elastomer (Ecoflex) endowed the resulting surface with high stretchability; the densely packed micro-sized particles in multi-layers contributed to the preservation of the large surface roughness even under large strains; and the physical encapsulation of the microparticles by silicone elastomer due to the capillary dragging effect and the chemical interaction between the hydrophilic silica and the elastomer gave rise to the robust and non-fluorinated superhydrophobicity. It was demonstrated that the as-prepared fluorine-free surface could preserve the superhydrophobicity under repeated stretching-relaxing cycles. Most importantly, the surface's superhydrophobicity can be well maintained after severe rubbing process, indicating wear-resistance. Our novel superhydrophobic surface integrating multiple key properties, i.e. stretchability, robustness, and non-fluorination, is expected to provide unique advantages for a wide range of applications in biomedicine, energy, and electronics.

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

Uniting Superhydrophobic, Superoleophobic and Lubricant Infused Slippery Behavior on Copper Oxide Nano-structured Substrates

PubMed Central

Ujjain, Sanjeev Kumar; Roy, Pritam Kumar; Kumar, Sumana; Singha, Subhash; Khare, Krishnacharya

2016-01-01

Alloys, specifically steel, are considered as the workhorse of our society and are inimitable engineering materials in the field of infrastructure, industry and possesses significant applications in our daily life. However, creating a robust synthetic metallic surface that repels various liquids has remained extremely challenging. The wettability of a solid surface is known to be governed by its geometric nano-/micro structure and the chemical composition. Here, we are demonstrating a facile and economical way to generate copper oxide micro-nano structures with spherical (0D), needle (1D) and hierarchical cauliflower (3D) morphologies on galvanized steel substrates using a simple chemical bath deposition method. These nano/micro textured steel surfaces, on subsequent coating of a low surface energy material display excellent superhydrophobic, superoleophobic and slippery behavior. Polydimethylsiloxane coated textured surfaces illustrate superhydrophobicity with water contact angle about 160°(2) and critical sliding angle ~2°. When functionalized with low-surface energy perfluoroalkylsilane, these surfaces display high repellency for low surface tension oils as well as hydrocarbons. Among them, the hierarchical cauliflower morphology exhibits re-entrant structure thereby showing the best superoleophobicity with contact angle 149° for dodecane. Once infused with a lubricant like silicone oil, they show excellent slippery behavior with low contact angle hysteresis (~ 2°) for water drops. PMID:27752098

Large-area fabrication of superhydrophobic surfaces for practical applications: an overview

PubMed Central

Xue, Chao-Hua; Jia, Shun-Tian; Zhang, Jing; Ma, Jian-Zhong

2010-01-01

This review summarizes the key topics in the field of large-area fabrication of superhydrophobic surfaces, concentrating on substrates that have been used in commercial applications. Practical approaches to superhydrophobic surface construction and hydrophobization are discussed. Applications of superhydrophobic surfaces are described and future trends in superhydrophobic surfaces are predicted. PMID:27877336

Flow condensation on copper-based nanotextured superhydrophobic surfaces.

PubMed

Torresin, Daniele; Tiwari, Manish K; Del Col, Davide; Poulikakos, Dimos

2013-01-15

Superhydrophobic surfaces have shown excellent ability to promote dropwise condensation with high droplet mobility, leading to enhanced surface thermal transport. To date, however, it is unclear how superhydrophobic surfaces would perform under the stringent flow condensation conditions of saturated vapor at high temperature, which can affect superhydrophobicity. Here, we investigate this issue employing "all-copper" superhydrophobic surfaces with controlled nanostructuring for minimal thermal resistance. Flow condensation tests performed with saturated vapor at a high temperature (110 °C) showed the condensing drops penetrate the surface texture (i.e., attain the Wenzel state with lower droplet mobility). At the same time, the vapor shear helped ameliorate the mobility and enhanced the thermal transport. At the high end of the examined vapor velocity range, a heat flux of ~600 kW m(-2) was measured at 10 K subcooling and 18 m s(-1) vapor velocity. This clearly highlights the excellent potential of a nanostructured superhydrophobic surface in flow condensation applications. The surfaces sustained dropwise condensation and vapor shear for five days, following which mechanical degradation caused a transition to filmwise condensation. Overall, our results underscore the need to investigate superhydrophobic surfaces under stringent and realistic flow condensation conditions before drawing conclusions regarding their performance in practically relevant condensation applications.

Water Penetration through a Superhydrophobic Mesh During a Drop Impact.

PubMed

Ryu, Seunggeol; Sen, Prosenjit; Nam, Youngsuk; Lee, Choongyeop

2017-01-06

When a water drop impacts a mesh having submillimeter pores, a part of the drop penetrates through the mesh if the impact velocity is sufficiently large. Here we show that different surface wettability, i.e., hydrophobicity and superhydrophobicity, leads to different water penetration dynamics on a mesh during drop impact. We show, despite the water repellence of a superhydrophobic surface, that water can penetrate a superhydrophobic mesh more easily (i.e., at a lower impact velocity) over a hydrophobic mesh via a penetration mechanism unique to a superhydrophobic mesh. On a superhydrophobic mesh, the water penetration can occur during the drop recoil stage, which appears at a lower impact velocity than the critical impact velocity for water penetration right upon impact. We propose that this unique water penetration on a superhydrophobic mesh can be attributed to the combination of the hydrodynamic focusing and the momentum transfer from the water drop when it is about to bounce off the surface, at which point the water drop retrieves most of its kinetic energy due to the negligible friction on superhydrophobic surfaces.

Water Penetration through a Superhydrophobic Mesh During a Drop Impact

NASA Astrophysics Data System (ADS)

Ryu, Seunggeol; Sen, Prosenjit; Nam, Youngsuk; Lee, Choongyeop

2017-01-01

When a water drop impacts a mesh having submillimeter pores, a part of the drop penetrates through the mesh if the impact velocity is sufficiently large. Here we show that different surface wettability, i.e., hydrophobicity and superhydrophobicity, leads to different water penetration dynamics on a mesh during drop impact. We show, despite the water repellence of a superhydrophobic surface, that water can penetrate a superhydrophobic mesh more easily (i.e., at a lower impact velocity) over a hydrophobic mesh via a penetration mechanism unique to a superhydrophobic mesh. On a superhydrophobic mesh, the water penetration can occur during the drop recoil stage, which appears at a lower impact velocity than the critical impact velocity for water penetration right upon impact. We propose that this unique water penetration on a superhydrophobic mesh can be attributed to the combination of the hydrodynamic focusing and the momentum transfer from the water drop when it is about to bounce off the surface, at which point the water drop retrieves most of its kinetic energy due to the negligible friction on superhydrophobic surfaces.

Silver nanowire-based transparent, flexible, and conductive thin film

PubMed Central

2011-01-01

The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl) vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles. PMID:21711602

The Anti-Biofouling Properties of Superhydrophobic Surfaces are Short-Lived.

PubMed

Hwang, Gi Byoung; Page, Kristopher; Patir, Adnan; Nair, Sean P; Allan, Elaine; Parkin, Ivan P

2018-06-12

Superhydrophobic surfaces are present in nature on the leaves of many plant species. Water rolls on these surfaces, and the rolling motion picks up particles including bacteria and viruses. Man-made superhydrophobic surfaces have been made in an effort to reduce biofouling. We show here that the anti-biofouling property of a superhydrophobic surface is due to an entrapped air-bubble layer that reduces contact between the bacteria and the surface. Further, we showed that prolonged immersion of superhydrophobic surfaces in water led to loss of the bubble-layer and subsequent bacterial adhesion that unexpectedly exceeded that of the control materials. This behavior was not restricted to one particular type of material but was evident on different types of superhydrophobic surfaces. This work is important in that it suggests that superhydrophobic surfaces may actually encourage bacterial adhesion during longer term exposure.

Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device

PubMed Central

Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

2016-01-01

We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal. PMID:26932470

Superhydrophobic surfaces

DOEpatents

Wang, Evelyn N; McCarthy, Matthew; Enright, Ryan; Culver, James N; Gerasopoulos, Konstantinos; Ghodssi, Reza

2015-03-24

Surfaces having a hierarchical structure--having features of both microscale and nanoscale dimensions--can exhibit superhydrophobic properties and advantageous condensation and heat transfer properties. The hierarchical surfaces can be fabricated using biological nanostructures, such as viruses as a self-assembled nanoscale template.

Variable-transparency wall regulates temperatures of structures

NASA Technical Reports Server (NTRS)

Osullivan, W. J., Jr.

1964-01-01

An effective temperature regulating wall consists of one layer /e.g., one of the paraffins/ relatively opaque to thermal radiation in the solid state and transparent to it in the molten state and placed between two transparent layers. A mirror coating is applied to back layer.

Dynamic Defrosting on Scalable Superhydrophobic Surfaces.

PubMed

Murphy, Kevin R; McClintic, William T; Lester, Kevin C; Collier, C Patrick; Boreyko, Jonathan B

2017-07-19

Recent studies have shown that frost can grow in a suspended Cassie state on nanostructured superhydrophobic surfaces. During defrosting, the melting sheet of Cassie frost spontaneously dewets into quasi-spherical slush droplets that are highly mobile. Promoting Cassie frost would therefore seem advantageous from a defrosting standpoint; however, nobody has systematically compared the efficiency of defrosting Cassie ice versus defrosting conventional surfaces. Here, we characterize the defrosting of an aluminum plate, one-half of which exhibits a superhydrophobic nanostructure while the other half is smooth and hydrophobic. For thick frost sheets (>1 mm), the superhydrophobic surface was able to dynamically shed the meltwater, even at very low tilt angles. In contrast, the hydrophobic surface was unable to shed any appreciable meltwater even at a 90° tilt angle. For thin frost layers (≲1 mm), not even the superhydrophobic surface could mobilize the meltwater. We attribute this to the large apparent contact angle of the meltwater, which for small amounts of frost serves to minimize coalescence events and prevent droplets from approaching the capillary length. Finally, we demonstrate a new mode of dynamic defrosting using an upside-down surface orientation, where the melting frost was able to uniformly detach from the superhydrophobic side and subsequently pull the frost from the hydrophobic side in a chain reaction. Treating surfaces to enable Cassie frost is therefore very desirable for enabling rapid and low-energy thermal defrosting, but only for frost sheets that are sufficiently thick.

Multifunctional transparent ZnO nanorod films.

PubMed

Kwak, Geunjae; Jung, Sungmook; Yong, Kijung

2011-03-18

Transparent ZnO nanorod (NR) films that exhibit extreme wetting states (either superhydrophilicity or superhydrophobicity through surface chemical modification), high transmittance, UV protection and antireflection have been prepared via the facile ammonia hydrothermal method. The periodic 1D ZnO NR arrays showed extreme wetting states as well as antireflection properties due to their unique surface structure and prevented the UVA region from penetrating the substrate due to the unique material property of ZnO. Because of the simple, time-efficient and low temperature preparation process, ZnO NR films with useful functionalities are promising for fabrication of highly light transmissive, antireflective, UV protective, antifogging and self-cleaning optical materials to be used for optical devices and photovoltaic energy devices.

Biomimetic polymeric superhydrophobic surfaces and nanostructures: from fabrication to applications.

PubMed

Wen, Gang; Guo, ZhiGuang; Liu, Weimin

2017-03-09

Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil-water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world

Solving the Controversy on the Wetting Transparency of Graphene.

PubMed

Kim, Donggyu; Pugno, Nicola M; Buehler, Markus J; Ryu, Seunghwa

2015-10-26

Since its discovery, the wetting transparency of graphene, the transmission of the substrate wetting property over graphene coating, has gained significant attention due to its versatility for potential applications. Yet, there have been debates on the interpretation and validity of the wetting transparency. Here, we present a theory taking two previously disregarded factors into account and elucidate the origin of the partial wetting transparency. We show that the liquid bulk modulus is crucial to accurately calculate the van der Waals interactions between the liquid and the surface, and that various wetting states on rough surfaces must be considered to understand a wide range of contact angle measurements that cannot be fitted with a theory considering the flat surface. In addition, we reveal that the wetting characteristic of the substrate almost vanishes when covered by any coating as thick as graphene double layers. Our findings reveal a more complete picture of the wetting transparency of graphene as well as other atomically thin coatings, and can be applied to study various surface engineering problems requiring wettability-tuning.

Solving the Controversy on the Wetting Transparency of Graphene

PubMed Central

Kim, Donggyu; Pugno, Nicola M.; Buehler, Markus J.; Ryu, Seunghwa

2015-01-01

Since its discovery, the wetting transparency of graphene, the transmission of the substrate wetting property over graphene coating, has gained significant attention due to its versatility for potential applications. Yet, there have been debates on the interpretation and validity of the wetting transparency. Here, we present a theory taking two previously disregarded factors into account and elucidate the origin of the partial wetting transparency. We show that the liquid bulk modulus is crucial to accurately calculate the van der Waals interactions between the liquid and the surface, and that various wetting states on rough surfaces must be considered to understand a wide range of contact angle measurements that cannot be fitted with a theory considering the flat surface. In addition, we reveal that the wetting characteristic of the substrate almost vanishes when covered by any coating as thick as graphene double layers. Our findings reveal a more complete picture of the wetting transparency of graphene as well as other atomically thin coatings, and can be applied to study various surface engineering problems requiring wettability-tuning. PMID:26496835

Low temperature self-cleaning properties of superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Wang, Fajun; Shen, Taohua; Li, Changquan; Li, Wen; Yan, Guilong

2014-10-01

Outdoor surfaces are usually dirty surfaces. Ice accretion on outdoor surfaces could lead to serious accidents. In the present work, the superhydrophobic surface based on 1H, 1H, 2H, 2H-Perfluorodecanethiol (PFDT) modified Ag/PDMS composite was prepared to investigate the anti-icing property and self-cleaning property at temperatures below freezing point. The superhydrophobic surface was deliberately polluted with activated carbon before testing. It was observed that water droplet picked up dusts on the cold superhydrophobic surface and took it away without freezing at a measuring temperature of -10 °C. While on a smooth PFDT surface and a rough surface base on Ag/PDMS composite without PFDT modification, water droplets accumulated and then froze quickly at the same temperature. However, at even lower temperature of -12 °C, the superhydrophobic surface could not prevent the surface water from icing. In addition, it was observed that the frost layer condensed from the moisture pay an important role in determining the low temperature self-cleaning properties of a superhydrophobic surface.

Transparent binary-thickness coatings on metal substrates that produce binary patterns of orthogonal elliptical polarization states in reflected light

NASA Astrophysics Data System (ADS)

Azzam, Rasheed M. A.; Angel, Wade W.

1992-12-01

A reflective division-of-wavefront polarizing beam splitter is described that uses a dual- thickness transparent thin-film coating on a metal substrate. A previous design that used a partially clad substrate at the principal angle of the metal [Azzam, JOSA A 5, 1576 (1988)] is replaced by a more general one in which the substrate is coated throughout and the film thickness alternates between two non-zero levels. The incident linear polarization azimuth is chosen near, but not restricted to, 45 degree(s) (measured from the plane of incidence), and the angle of incidence may be selected over a range of values. The design procedure, which uses the two-dimensional Newton-Raphson method, is applied to the SiO2-Au film- substrate system at 633 nm wavelength, as an example, and the characteristics of the various possible coatings are presented.

Delayed frost growth on jumping-drop superhydrophobic surfaces.

PubMed

Boreyko, Jonathan B; Collier, C Patrick

2013-02-26

Self-propelled jumping drops are continuously removed from a condensing superhydrophobic surface to enable a micrometric steady-state drop size. Here, we report that subcooled condensate on a chilled superhydrophobic surface are able to repeatedly jump off the surface before heterogeneous ice nucleation occurs. Frost still forms on the superhydrophobic surface due to ice nucleation at neighboring edge defects, which eventually spreads over the entire surface via an interdrop frost wave. The growth of this interdrop frost front is shown to be up to 3 times slower on the superhydrophobic surface compared to a control hydrophobic surface, due to the jumping-drop effect dynamically minimizing the average drop size and surface coverage of the condensate. A simple scaling model is developed to relate the success and speed of interdrop ice bridging to the drop size distribution. While other reports of condensation frosting on superhydrophobic surfaces have focused exclusively on liquid-solid ice nucleation for isolated drops, these findings reveal that the growth of frost is an interdrop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser minimized frost formation relative to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by limiting the success of interdrop ice bridge formation.

Bio-inspired Edible Superhydrophobic Interface for Reducing Residual Liquid Food.

PubMed

Li, Yao; Bi, Jingran; Wang, Siqi; Zhang, Tan; Xu, Xiaomeng; Wang, Haitao; Cheng, Shasha; Zhu, Bei-Wei; Tan, Mingqian

2018-03-07

Significant wastage of residual liquid food, such as milk, yogurt, and honey, in food containers has attracted great attention. In this work, a bio-inspired edible superhydrophobic interface was fabricated using U.S. Food and Drug Administration-approved and edible honeycomb wax, arabic gum, and gelatin by a simple and low-cost method. The bio-inspired edible superhydrophobic interface showed multiscale structures, which were similar to that of a lotus leaf surface. This bio-inspired edible superhydrophobic interface displayed high contact angles for a variety of liquid foods, and the residue of liquid foods could be effectively reduced using the bio-inspired interface. To improve the adhesive force of the superhydrophobic interface, a flexible edible elastic film was fabricated between the interface and substrate material. After repeated folding and flushing for a long time, the interface still maintained excellent superhydrophobic property. The bio-inspired edible superhydrophobic interface showed good biocompatibility, which may have potential applications as a functional packaging interface material.

Superhydrophobic Ag nanostructures on polyaniline membranes with strong SERS enhancement.

PubMed

Liu, Weiyu; Miao, Peng; Xiong, Lu; Du, Yunchen; Han, Xijiang; Xu, Ping

2014-11-07

We demonstrate here a facile fabrication of n-dodecyl mercaptan-modified superhydrophobic Ag nanostructures on polyaniline membranes for molecular detection based on SERS technique, which combines the superhydrophobic condensation effect and the high enhancement factor. It is calculated that the as-fabricated superhydrophobic substrate can exhibit a 21-fold stronger molecular condensation, and thus further amplifies the SERS signal to achieve more sensitive detection. The detection limit of the target molecule, methylene blue (MB), on this superhydrophobic substrate can be 1 order of magnitude higher than that on the hydrophilic substrate. With high reproducibility, the feasibility of using this SERS-active superhydrophobic substrate for quantitative molecular detection is explored. A partial least squares (PLS) model was established for the quantification of MB by SERS, with correlation coefficient R(2) = 95.1% and root-mean-squared error of prediction (RMSEP) = 0.226. We believe this superhydrophobic SERS substrate can be widely used in trace analysis due to its facile fabrication, high signal reproducibility and promising SERS performance.

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.

Fabrics coated with lubricated nanostructures display robust omniphobicity

DOE PAGES

Shillingford, Cicely; MacCallum, Noah; Wong, Tak -Sing; ...

2013-12-11

The development of a stain-resistant and pressure-stable textile is desirable for consumer and industrial applications alike, yet it remains a challenge that current technologies have been unable to fully address. Traditional superhydrophobic surfaces, inspired by the lotus plant, are characterized by two main components: hydrophobic chemical functionalization and surface roughness. While this approach produces water-resistant surfaces, these materials have critical weaknesses that hinder their practical utility, in particular as robust stain-free fabrics. For example, traditional superhydrophobic surfaces fail (i.e., become stained) when exposed to low-surface-tension liquids, under pressure when impacted by a high-velocity stream of water (e.g., rain), and whenmore » exposed to physical forces such as abrasion and twisting. We have recently introduced slippery lubricant-infused porous surfaces (SLIPS), a self-healing, pressure-tolerant and omniphobic surface, to address these issues. However we present the rational design and optimization of nanostructured lubricant-infused fabrics and demonstrate markedly improved performance over traditional superhydrophobic textile treatments: SLIPS-functionalized cotton and polyester fabrics exhibit decreased contact angle hysteresis and sliding angles, omni-repellent properties against various fluids including polar and nonpolar liquids, pressure tolerance and mechanical robustness, all of which are not readily achievable with the state-of-the-art superhydrophobic coatings.« less

Fabrics coated with lubricated nanostructures display robust omniphobicity

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

Shillingford, C; MacCallum, N; Wong, TS

2013-12-11

The development of a stain-resistant and pressure-stable textile is desirable for consumer and industrial applications alike, yet it remains a challenge that current technologies have been unable to fully address. Traditional superhydrophobic surfaces, inspired by the lotus plant, are characterized by two main components: hydrophobic chemical functionalization and surface roughness. While this approach produces water-resistant surfaces, these materials have critical weaknesses that hinder their practical utility, in particular as robust stain-free fabrics. For example, traditional superhydrophobic surfaces fail (i.e., become stained) when exposed to low-surface-tension liquids, under pressure when impacted by a high-velocity stream of water (e. g., rain), andmore » when exposed to physical forces such as abrasion and twisting. We have recently introduced slippery lubricant-infused porous surfaces (SLIPS), a self-healing, pressure-tolerant and omniphobic surface, to address these issues. Herein we present the rational design and optimization of nanostructured lubricant-infused fabrics and demonstrate markedly improved performance over traditional superhydrophobic textile treatments: SLIPS-functionalized cotton and polyester fabrics exhibit decreased contact angle hysteresis and sliding angles, omni-repellent properties against various fluids including polar and nonpolar liquids, pressure tolerance and mechanical robustness, all of which are not readily achievable with the state-of-the-art superhydrophobic coatings.« less

Fabrics coated with lubricated nanostructures display robust omniphobicity.

PubMed

Shillingford, Cicely; MacCallum, Noah; Wong, Tak-Sing; Kim, Philseok; Aizenberg, Joanna

2014-01-10

The development of a stain-resistant and pressure-stable textile is desirable for consumer and industrial applications alike, yet it remains a challenge that current technologies have been unable to fully address. Traditional superhydrophobic surfaces, inspired by the lotus plant, are characterized by two main components: hydrophobic chemical functionalization and surface roughness. While this approach produces water-resistant surfaces, these materials have critical weaknesses that hinder their practical utility, in particular as robust stain-free fabrics. For example, traditional superhydrophobic surfaces fail (i.e., become stained) when exposed to low-surface-tension liquids, under pressure when impacted by a high-velocity stream of water (e.g., rain), and when exposed to physical forces such as abrasion and twisting. We have recently introduced slippery lubricant-infused porous surfaces (SLIPS), a self-healing, pressure-tolerant and omniphobic surface, to address these issues. Herein we present the rational design and optimization of nanostructured lubricant-infused fabrics and demonstrate markedly improved performance over traditional superhydrophobic textile treatments: SLIPS-functionalized cotton and polyester fabrics exhibit decreased contact angle hysteresis and sliding angles, omni-repellent properties against various fluids including polar and nonpolar liquids, pressure tolerance and mechanical robustness, all of which are not readily achievable with the state-of-the-art superhydrophobic coatings.

Fabrics coated with lubricated nanostructures display robust omniphobicity

NASA Astrophysics Data System (ADS)

Shillingford, Cicely; MacCallum, Noah; Wong, Tak-Sing; Kim, Philseok; Aizenberg, Joanna

2014-01-01

The development of a stain-resistant and pressure-stable textile is desirable for consumer and industrial applications alike, yet it remains a challenge that current technologies have been unable to fully address. Traditional superhydrophobic surfaces, inspired by the lotus plant, are characterized by two main components: hydrophobic chemical functionalization and surface roughness. While this approach produces water-resistant surfaces, these materials have critical weaknesses that hinder their practical utility, in particular as robust stain-free fabrics. For example, traditional superhydrophobic surfaces fail (i.e., become stained) when exposed to low-surface-tension liquids, under pressure when impacted by a high-velocity stream of water (e.g., rain), and when exposed to physical forces such as abrasion and twisting. We have recently introduced slippery lubricant-infused porous surfaces (SLIPS), a self-healing, pressure-tolerant and omniphobic surface, to address these issues. Herein we present the rational design and optimization of nanostructured lubricant-infused fabrics and demonstrate markedly improved performance over traditional superhydrophobic textile treatments: SLIPS-functionalized cotton and polyester fabrics exhibit decreased contact angle hysteresis and sliding angles, omni-repellent properties against various fluids including polar and nonpolar liquids, pressure tolerance and mechanical robustness, all of which are not readily achievable with the state-of-the-art superhydrophobic coatings.

Dynamic Defrosting on Scalable Superhydrophobic Surfaces

DOE PAGES

Murphy, Kevin R.; McClintic, William T.; Lester, Kevin C.; ...

2017-06-27

Recent studies have shown that frost can grow in a suspended Cassie state on nanostructured superhydrophobic surfaces. During defrosting, the melting sheet of Cassie frost spontaneously dewets into quasi-spherical slush droplets that are highly mobile. Promoting Cassie frost would therefore seem advantageous from a defrosting standpoint; however, nobody has systematically compared the efficiency of defrosting Cassie ice versus defrosting conventional surfaces. Here, we characterize the defrosting of an aluminum plate, one-half of which exhibits a superhydrophobic nanostructure while the other half is smooth and hydrophobic. For thick frost sheets (>1 mm), the superhydrophobic surface was able to dynamically shed themore » meltwater, even at very low tilt angles. In contrast, the hydrophobic surface was unable to shed any appreciable meltwater even at a 90° tilt angle. For thin frost layers (≲1 mm), not even the superhydrophobic surface could mobilize the meltwater. We attribute this to the large apparent contact angle of the meltwater, which for small amounts of frost serves to minimize coalescence events and prevent droplets from approaching the capillary length. Finally, we demonstrate a new mode of dynamic defrosting using an upside-down surface orientation, where the melting frost was able to uniformly detach from the superhydrophobic side and subsequently pull the frost from the hydrophobic side in a chain reaction. Treating surfaces to enable Cassie frost is therefore very desirable for enabling rapid and low-energy thermal defrosting, but only for frost sheets that are sufficiently thick.« less

Dynamic Defrosting on Scalable Superhydrophobic Surfaces

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

Murphy, Kevin R.; McClintic, William T.; Lester, Kevin C.

Recent studies have shown that frost can grow in a suspended Cassie state on nanostructured superhydrophobic surfaces. During defrosting, the melting sheet of Cassie frost spontaneously dewets into quasi-spherical slush droplets that are highly mobile. Promoting Cassie frost would therefore seem advantageous from a defrosting standpoint; however, nobody has systematically compared the efficiency of defrosting Cassie ice versus defrosting conventional surfaces. Here, we characterize the defrosting of an aluminum plate, one-half of which exhibits a superhydrophobic nanostructure while the other half is smooth and hydrophobic. For thick frost sheets (>1 mm), the superhydrophobic surface was able to dynamically shed themore » meltwater, even at very low tilt angles. In contrast, the hydrophobic surface was unable to shed any appreciable meltwater even at a 90° tilt angle. For thin frost layers (≲1 mm), not even the superhydrophobic surface could mobilize the meltwater. We attribute this to the large apparent contact angle of the meltwater, which for small amounts of frost serves to minimize coalescence events and prevent droplets from approaching the capillary length. Finally, we demonstrate a new mode of dynamic defrosting using an upside-down surface orientation, where the melting frost was able to uniformly detach from the superhydrophobic side and subsequently pull the frost from the hydrophobic side in a chain reaction. Treating surfaces to enable Cassie frost is therefore very desirable for enabling rapid and low-energy thermal defrosting, but only for frost sheets that are sufficiently thick.« less

Surface Nanostructures Formed by Phase Separation of Metal Salt-Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications

NASA Astrophysics Data System (ADS)

Con, Celal; Cui, Bo

2017-12-01

This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt-polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.

Surface Nanostructures Formed by Phase Separation of Metal Salt-Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications.

PubMed

Con, Celal; Cui, Bo

2017-12-16

This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt-polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.

Superhydrophobic nanostructured Kapton® surfaces fabricated through Ar + O2 plasma treatment: Effects of different environments on wetting behaviour

NASA Astrophysics Data System (ADS)

Barshilia, Harish C.; Ananth, A.; Gupta, Nitant; Anandan, C.

2013-03-01

Kapton® [poly (4,4'-oxy diphenylene pyromellitimide)] polyimides have widespread usage in semiconductor devices, solar arrays, protective coatings and space applications, due to their excellent chemical and physical properties. In addition to their inherent properties, imparting superhydrophobicity on these surfaces will be an added advantage. Present work describes the usage of Ar + O2 plasma treatment for the preparation of superhydrophobic Kapton® surfaces. Immediately after the plasma treatment, the surfaces showed superhydrophilicity as a result of high energy dangling bonds and polar group concentration. But the samples kept in low vacuum for 48 h exhibited superhydrophobicity with high water contact angles (>150°). It is found that the post plasma treatment process, called ageing, especially in low vacuum plays an important role in delivering superhydrophobic property to Kapton®. Field emission scanning electron microscopy and atomic force microscopy were used to probe the physical changes in the surface of the Kapton®. The surfaces showed formation of nano-feathers and nano-tussock microstructures with variation in surface roughness against plasma treatment time. A thorough chemical investigation was performed using Fourier transform infrared spectroscopy and micro-Raman spectroscopy, which revealed changes in the surface of the Ar + O2 plasma treated Kapton®. Surface chemical species of Kapton® were confirmed again by X-ray photoelectron spectroscopy spectra for untreated surfaces whereas Ar + O2 plasma treated samples showed the de-bonding and re-organization of structural elements. Creation of surface roughness plays a dominant role in the contribution of superhydrophobicity to Kapton® apart from the surface modifications due to Ar + O2 plasma treatment and ageing in low vacuum.

Superhydrophobic hierarchical structure carbon mesh films for oil/water separation application

NASA Astrophysics Data System (ADS)

Lu, Zhaoxia; Huang, Xing; Wang, Lisheng

2017-08-01

In this study, we showed that a superoleophobic mesh with the self-cleaning ability could be readily prepared by a facile spray-coating method on stainless steel mesh. Poly(methyl methacrylate) was employed to provide a stable strength between carbon nanotubes and steel mesh surface. The effect of opening size of these steel meshes on surface wetting has been investigated. The dynamics of liquid droplets was investigated as well. The as-prepared meshes exhibited both superhydrophobicity and superoleophilicity and could effectively separate water from the oil and water mixture. The present study contributes to the development of oil and water separation materials for marine industrial application.

Electrospun superhydrophobic membranes with unique structures for membrane distillation.

PubMed

Liao, Yuan; Loh, Chun-Heng; Wang, Rong; Fane, Anthony G

2014-09-24

With modest temperature demand, low operating pressure, and high solute rejection, membrane distillation (MD) is an attractive option for desalination, waste treatment, and food and pharmaceutical processing. However, large-scale practical applications of MD are still hindered by the absence of effective membranes with high hydrophobicity, high porosity, and adequate mechanical strength, which are important properties for MD permeation fluxes, stable long-term performance, and effective packing in modules without damage. This study describes novel design strategies for highly robust superhydrophobic dual-layer membranes for MD via electrospinning. One of the newly developed membranes comprises a durable and ultrathin 3-dimensional (3D) superhydrophobic skin and porous nanofibrous support whereas another was fabricated by electrospinning 3D superhydrophobic layers on a nonwoven support. These membranes exhibit superhydrophobicity toward distilled water, salty water, oil-in-water emulsion, and beverages, which enables them to be used not only for desalination but also for other processes. The superhydrophobic dual-layer membrane #3S-N with nanofibrous support has a competitive permeation flux of 24.6 ± 1.2 kg m(-2) h(-1) in MD (feed and permeate temperate were set as 333 and 293 K, respectively) due to the higher porosity of the nanofibrous scaffold. Meanwhile, the membranes with the nonwoven support exhibit greater mechanical strength due to this support combined with better long-term performance because of the thicker 3D superhydrophobic layers. The morphology, pore size, porosity, mechanical properties, and liquid enter pressure of water of these superhydrophobic composite membranes with two different structures are reported and compared with commercial polyvinylidene fluoride membranes.

Highly transparent and flexible circuits through patterning silver nanowires into microfluidic channels.

PubMed

Sun, Jing; Zhou, Wenhui; Yang, Haibo; Zhen, Xue; Ma, Longfei; Williams, Dirk; Sun, Xudong; Lang, Ming-Fei

2018-05-10

The development of flexible and transparent devices requires completely transparent and flexible circuits (TFCs). To overcome the disadvantages of the previously reported TFCs that are partially transparent, lacking pattern control, or labor consuming, we achieve true TFCs via a facile process with precise pattern control, exhibiting concurrent high transparency, conductivity, flexibility, stretchability, and robustness. A highly transparent and flexible conductive film is first made through spin coating silver nanowires (AgNWs) onto polydimethylsiloxane (PDMS), and demonstrates simultaneous high transparency (90.86%) and low sheet resistance (3.22 Ω sq-1). Taking advantage of microfluidic technology, circuits with ultraprecise and complex patterns from the microscale to milliscale are obtained through spin coating of AgNWs into microfluidic channels on PDMS. Without elaborate processing, this method may be suitable for mass production, which would contribute enormously to potential applications in wearable medical equipment and transparent electronic devices.

Drop impact on inclined superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Choi, Wonjae; Leclear, Sani; Leclear, Johnathon; Abhijeet, .; Park, Kyoo-Chul

We report an empirical study and dimensional analysis on the impact patterns of water drops on inclined superhydrophobic surfaces. While the classic Weber number determines the spreading and recoiling dynamics of a water drop on a horizontal / smooth surface, for a superhydrophobic surface, the dynamics depends on two distinct Weber numbers, each calculated using the length scale of the drop or of the pores on the surface. Impact on an inclined superhydrophobic surface is even more complicated, as the velocity that determines the Weber number is not necessarily the absolute speed of the drop but the velocity components normal and tangential to the surface. We define six different Weber numbers, using three different velocities (absolute, normal and tangential velocities) and two different length scales (size of the drop and of the texture). We investigate the impact patterns on inclined superhydrophobic surfaces with three different types of surface texture: (i) posts, (ii) ridges aligned with and (iii) ridges perpendicular to the impact direction. Results suggest that all six Weber numbers matter, but affect different parts of the impact dynamics, ranging from the Cassie-Wenzel transition, maximum spreading, to anisotropic deformation. We acknowledge financial support from the Office of Naval Research (ONR) through Contract 3002453812.

Environmentally Benign Production of Stretchable and Robust Superhydrophobic Silicone Monoliths.

PubMed

Davis, Alexander; Surdo, Salvatore; Caputo, Gianvito; Bayer, Ilker S; Athanassiou, Athanassia

2018-01-24

Superhydrophobic materials hold an enormous potential in sectors as important as aerospace, food industries, or biomedicine. Despite this great promise, the lack of environmentally friendly production methods and limited robustness remain the two most pertinent barriers to the scalability, large-area production, and widespread use of superhydrophobic materials. In this work, highly robust superhydrophobic silicone monoliths are produced through a scalable and environmentally friendly emulsion technique. It is first found that stable and surfactantless water-in-polydimethylsiloxane (PDMS) emulsions can be formed through mechanical mixing. Increasing the internal phase fraction of the precursor emulsion is found to increase porosity and microtexture of the final monoliths, rendering them superhydrophobic. Silica nanoparticles can also be dispersed in the aqueous internal phase to create micro/nanotextured monoliths, giving further improvements in superhydrophobicity. Due to the elastomeric nature of PDMS, superhydrophobicity can be maintained even while the material is mechanically strained or compressed. In addition, because of their self-similarity, the monoliths show outstanding robustness to knife-scratch, tape-peel, and finger-wipe tests, as well as rigorous sandpaper abrasion. Superhydrophobicity was also unchanged when exposed to adverse environmental conditions including corrosive solutions, UV light, extreme temperatures, and high-energy droplet impact. Finally, important properties for eventual adoption in real-world applications including self-cleaning, stain-repellence, and blood-repellence are demonstrated.

Spontaneous recovery of superhydrophobicity on nanotextured surfaces

PubMed Central

Prakash, Suruchi; Xi, Erte; Patel, Amish J.

2016-01-01

Rough or textured hydrophobic surfaces are dubbed “superhydrophobic” due to their numerous desirable properties, such as water repellency and interfacial slip. Superhydrophobicity stems from an aversion of water for the hydrophobic surface texture, so that a water droplet in the superhydrophobic “Cassie state” contacts only the tips of the rough surface. However, superhydrophobicity is remarkably fragile and can break down due to the wetting of the surface texture to yield the “Wenzel state” under various conditions, such as elevated pressures or droplet impact. Moreover, due to large energetic barriers that impede the reverse transition (dewetting), this breakdown in superhydrophobicity is widely believed to be irreversible. Using molecular simulations in conjunction with enhanced sampling techniques, here we show that on surfaces with nanoscale texture, water density fluctuations can lead to a reduction in the free energetic barriers to dewetting by circumventing the classical dewetting pathways. In particular, the fluctuation-mediated dewetting pathway involves a number of transitions between distinct dewetted morphologies, with each transition lowering the resistance to dewetting. Importantly, an understanding of the mechanistic pathways to dewetting and their dependence on pressure allows us to augment the surface texture design, so that the barriers to dewetting are eliminated altogether and the Wenzel state becomes unstable at ambient conditions. Such robust surfaces, which defy classical expectations and can spontaneously recover their superhydrophobicity, could have widespread importance, from underwater operation to phase-change heat transfer applications. PMID:27140619

Method of forming macro-structured high surface area transparent conductive oxide electrodes

DOEpatents

Forman, Arnold J.; Chen, Zhebo; Jaramillo, Thomas F.

2016-01-05

A method of forming a high surface area transparent conducting electrode is provided that includes depositing a transparent conducting thin film on a conductive substrate, where the transparent conducting thin film includes transparent conductive particles and a solution-based transparent conducting adhesive layer which serves to coat and bind together the transparent conducting particles, and heat treating the transparent conducting adhesion layer on the conductive substrate, where an increased surface area transparent conducting electrode is formed.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling

PubMed Central

Bayer, Ilker S.; Krishnan, K. Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H.; Farrell, Thomas E.; Crouch, Jeffrey D.

2016-01-01

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests. PMID:27924913

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling.

PubMed

Bayer, Ilker S; Krishnan, K Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H; Farrell, Thomas E; Crouch, Jeffrey D

2016-12-07

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling

NASA Astrophysics Data System (ADS)

Bayer, Ilker S.; Krishnan, K. Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H.; Farrell, Thomas E.; Crouch, Jeffrey D.

2016-12-01

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests.

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.

Interaction between Air Bubbles and Superhydrophobic Surfaces in Aqueous Solutions.

PubMed

Shi, Chen; Cui, Xin; Zhang, Xurui; Tchoukov, Plamen; Liu, Qingxia; Encinas, Noemi; Paven, Maxime; Geyer, Florian; Vollmer, Doris; Xu, Zhenghe; Butt, Hans-Jürgen; Zeng, Hongbo

2015-07-07

Superhydrophobic surfaces are usually characterized by a high apparent contact angle of water drops in air. Here we analyze the inverse situation: Rather than focusing on water repellency in air, we measure the attractive interaction of air bubbles and superhydrophobic surfaces in water. Forces were measured between microbubbles with radii R of 40-90 μm attached to an atomic force microscope cantilever and submerged superhydrophobic surfaces. In addition, forces between macroscopic bubbles (R = 1.2 mm) at the end of capillaries and superhydrophobic surfaces were measured. As superhydrophobic surfaces we applied soot-templated surfaces, nanofilament surfaces, micropillar arrays with flat top faces, and decorated micropillars. Depending on the specific structure of the superhydrophobic surfaces and the presence and amount of entrapped air, different interactions were observed. Soot-templated surfaces in the Cassie state showed superaerophilic behavior: Once the electrostatic double-layer force and a hydrodynamic repulsion were overcome, bubbles jumped onto the surface and fully merged with the entrapped air. On nanofilaments and micropillar arrays we observed in addition the formation of sessile bubbles with finite contact angles below 90° or the attachment of bubbles, which retained their spherical shape.

Transparent optically vanadium dioxide thermochromic smart film fabricated via electrospinning technique

NASA Astrophysics Data System (ADS)

Lu, Yuan; Xiao, Xiudi; Cao, Ziyi; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

2017-12-01

The monoclinic phase vanadium dioxide VO2 (M) based transparent thermochromic smart films were firstly fabricated through heat treatment of opaque VO2-based composite nanofibrous mats, which were deposited on the glass substrate via electrospinning technique. Noteworthily, the anti-oxidation property of VO2 smart film was improved due to inner distribution of VO2 in the polymethylmethacrylate (PMMA) nanofibers, and the composite mats having water contact angle of 165° determined itself good superhydrophobic property. Besides, PMMA nanofibrous mats with different polymer concentrations demonstrated changeable morphology and fiber diameter. The VO2 nanoparticles having diameter of 30-50 nm gathered and exhibited ellipse-like or belt-like structure. Additionally, the solar modulation ability of PMMA-VO2 composite smart film was 6.88% according to UV-Vis-NIR spectra. The research offered a new notion for fabricating transparent VO2 thermochromic material.

Superhydrophobic surfaces’ influence on streaming current based energy harvester

NASA Astrophysics Data System (ADS)

Fouché, Florent; Dargent, Thomas; Coffinier, Yannick; Treizebré, Anthony; Vlandas, Alexis; Senez, Vincent

2016-11-01

The purpose of this paper is to report the design, fabrication and characterization of silicon-based microfluidic channels with superhydrophobic walls for energy harvesting. We present the fabrication step of silicon based streaming current energy harvester and the nanostructuration of the microchannel walls. We characterize the superhydrophobic properties of the surface in a closed system. Our preliminary results on the electrical characterization of the device show a 43% increase of power harvested with our superhydrophobic surface compared to a planar hydrophobic surface.

Super-hydrophobic, highly adhesive, polydimethylsiloxane (PDMS) surfaces.

PubMed

Stanton, Morgan M; Ducker, Robert E; MacDonald, John C; Lambert, Christopher R; McGimpsey, W Grant

2012-02-01

Super-hydrophobic surfaces have been fabricated by casting polydimethylsiloxane (PDMS) on a textured substrate of known surface topography, and were characterized using contact angle, atomic force microscopy, surface free energy calculations, and adhesion measurements. The resulting PDMS has a micro-textured surface with a static contact angle of 153.5° and a hysteresis of 27° when using de-ionized water. Unlike many super-hydrophobic materials, the textured PDMS is highly adhesive, allowing water drops as large as 25.0 μL to be inverted. This high adhesion, super-hydrophobic behavior is an illustration of the "petal effect". This rapid, reproducible technique has promising applications in transport and analysis of microvolume samples. Copyright © 2011 Elsevier Inc. All rights reserved.

Superhydrophobic and polymer drag reduction in turbulent Taylor-Couette flow

NASA Astrophysics Data System (ADS)

Rajappan, Anoop; McKinley, Gareth H.

2017-11-01

We use a custom-built Taylor-Couette apparatus (radius ratio η = 0.75) to study frictional drag reduction by dilute polymer solutions and superhydrophobic (SH) surfaces in turbulent flows for 15000 < Re < 86000 . By monitoring the torque-speed scaling we show that the swirling flow becomes fully turbulent above Re = 15000 and we focus on measurements in this regime. By applying SH coatings on the inner cylinder, we can evaluate the drag reducing performance of the coating and calculate the effective slip length in turbulent flow using a suitably modified Prandtl-von Kármán analysis. We also investigate drag reduction by dilute polymer solutions, and show that natural biopolymers from plant mucilage can be an inexpensive and effective alternative to synthetic polymers in drag reduction applications, approaching the same maximum drag reduction asymptote. Finally we explore combinations of the two methods - one arising from wall slip and the other due to changes in turbulence dynamics in the bulk flow - and find that the two effects are not additive; interestingly, the effectiveness of polymer drag reduction is drastically reduced in the presence of an SH coating on the wall. This study was financially supported by the Office of Naval Research (ONR) through Contract No. 3002453814.

Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve

PubMed Central

Bark, David L.; Vahabi, Hamed; Bui, Hieu; Movafaghi, Sanli; Moore, Brandon; Kota, Arun K.; Popat, Ketul; Dasi, Lakshmi P.

2016-01-01

In this study, we explore how blood-material interactions and hemodynamics are impacted by rendering a clinical quality 25 mm St. Jude Medical Bileaflet mechanical heart valve (BMHV) superhydrophobic (SH) with the aim of reducing thrombo-embolic complications associated with BMHVs. Basic cell adhesion is evaluated to assess blood-material interactions, while hemodynamic performance is analyzed with and without the SH coating. Results show that a SH coating with a receding contact angle (CA) of 160º strikingly eliminates platelet and leukocyte adhesion to the surface. Alternatively, many platelets attach to and activate on pyrolytic carbon (receding CA=47), the base material for BMHVs. We further show that the performance index increases by 2.5% for coated valve relative to an uncoated valve, with a maximum possible improved performance of 5%. Both valves exhibit instantaneous shear stress below 10 N/m2 and Reynolds Shear Stress below 100 N/m2. Therefore, a SH BMHV has the potential to relax the requirement for antiplatelet and anticoagulant drug regimens typically required for patients receiving MHVs by minimizing blood-material interactions, while having a minimal impact on hemodynamics. We show for the first time that SH-coated surfaces may be a promising direction to minimize thrombotic complications in complex devices such as heart valves. PMID:27098219

Bioinspired superhydrophobic surfaces, fabricated through simple and scalable roll-to-roll processing

PubMed Central

Park, Sung-Hoon; Lee, Sangeui; Moreira, David; Bandaru, Prabhakar R.; Han, InTaek; Yun, Dong-Jin

2015-01-01

A simple, scalable, non-lithographic, technique for fabricating durable superhydrophobic (SH) surfaces, based on the fingering instabilities associated with non-Newtonian flow and shear tearing, has been developed. The high viscosity of the nanotube/elastomer paste has been exploited for the fabrication. The fabricated SH surfaces had the appearance of bristled shark skin and were robust with respect to mechanical forces. While flow instability is regarded as adverse to roll-coating processes for fabricating uniform films, we especially use the effect to create the SH surface. Along with their durability and self-cleaning capabilities, we have demonstrated drag reduction effects of the fabricated films through dynamic flow measurements. PMID:26490133

Bioinspired superhydrophobic surfaces, fabricated through simple and scalable roll-to-roll processing.

PubMed

Park, Sung-Hoon; Lee, Sangeui; Moreira, David; Bandaru, Prabhakar R; Han, InTaek; Yun, Dong-Jin

2015-10-22

A simple, scalable, non-lithographic, technique for fabricating durable superhydrophobic (SH) surfaces, based on the fingering instabilities associated with non-Newtonian flow and shear tearing, has been developed. The high viscosity of the nanotube/elastomer paste has been exploited for the fabrication. The fabricated SH surfaces had the appearance of bristled shark skin and were robust with respect to mechanical forces. While flow instability is regarded as adverse to roll-coating processes for fabricating uniform films, we especially use the effect to create the SH surface. Along with their durability and self-cleaning capabilities, we have demonstrated drag reduction effects of the fabricated films through dynamic flow measurements.

Visibly transparent polymer solar cells produced by solution processing.

PubMed

Chen, Chun-Chao; Dou, Letian; Zhu, Rui; Chung, Choong-Heui; Song, Tze-Bin; Zheng, Yue Bing; Hawks, Steve; Li, Gang; Weiss, Paul S; Yang, Yang

2012-08-28

Visibly transparent photovoltaic devices can open photovoltaic applications in many areas, such as building-integrated photovoltaics or integrated photovoltaic chargers for portable electronics. We demonstrate high-performance, visibly transparent polymer solar cells fabricated via solution processing. The photoactive layer of these visibly transparent polymer solar cells harvests solar energy from the near-infrared region while being less sensitive to visible photons. The top transparent electrode employs a highly transparent silver nanowire-metal oxide composite conducting film, which is coated through mild solution processes. With this combination, we have achieved 4% power-conversion efficiency for solution-processed and visibly transparent polymer solar cells. The optimized devices have a maximum transparency of 66% at 550 nm.

Fabrication of Superhydrophobic Surfaces with Controllable Electrical Conductivity and Water Adhesion.

PubMed

Ye, Lijun; Guan, Jipeng; Li, Zhixiang; Zhao, Jingxin; Ye, Cuicui; You, Jichun; Li, Yongjin

2017-02-14

A facile and versatile strategy for fabricating superhydrophobic surfaces with controllable electrical conductivity and water adhesion is reported. "Vine-on-fence"-structured and cerebral cortex-like superhydrophobic surfaces are constructed by filtering a suspension of multiwalled carbon nanotubes (MWCNTs), using polyoxymethylene nonwovens as the filter paper. The nonwovens with micro- and nanoporous two-tier structures act as the skeleton, introducing a microscale structure. The MWCNTs act as nanoscale structures, creating hierarchical surface roughness. The surface topography and the electrical conductivity of the superhydrophobic surfaces are controlled by varying the MWCNT loading. The vine-on-fence-structured surfaces exhibit "sticky" superhydrophobicity with high water adhesion. The cerebral cortex-like surfaces exhibit self-cleaning properties with low water adhesion. The as-prepared superhydrophobic surfaces are chemically resistant to acidic and alkaline environments of pH 2-12. They therefore have potential in applications such as droplet-based microreactors and thin-film microextraction. These findings aid our understanding of the role that surface topography plays in the design and fabrication of superhydrophobic surfaces with different water-adhesion properties.

Icephobicity and the effect of water condensation on the superhydrophobic low-density polyethylene surface

NASA Astrophysics Data System (ADS)

Yuan, Zhiqing; Wang, Menglei; Huang, Juan; Wang, Xian; Bin, Jiping; Peng, Chaoyi; Xing, Suli; Xiao, Jiayu; Zeng, Jingcheng; Xiao, Ximei; Fu, Xin; Gong, Huifang; Zhao, Dejian; Chen, Hong

2015-06-01

A superhydrophobic surface was obtained on a low-density polyethylene (LDPE) substrate using a facile method. The water contact angle and the sliding angle of the superhydrophobic LDPE surface were 155 ± 2° and 4°, respectively. The ice shear stress of the superhydrophobic LDPE surface was 2.08 times smaller than that of the flat LDPE surface. The superhydrophobic surface still showed excellent icephobicity and superhydrophobicity after undergoing a circulatory icing/deicing procedure five times. In addition, water condensation and its effect on the icephobicity of the as-prepared superhydrophobic surface were also studied.

Zinc oxyfluoride transparent conductor

DOEpatents

Gordon, Roy G.

1991-02-05

Transparent, electrically conductive and infrared-reflective films of zinc oxyfluoride are produced by chemical vapor deposition from vapor mixtures of zinc, oxygen and fluorine-containing compounds. The substitution of fluorine for some of the oxygen in zinc oxide results in dramatic increases in the electrical conductivity. For example, diethyl zinc, ethyl alcohol and hexafluoropropene vapors are reacted over a glass surface at 400.degree. C. to form a visibly transparent, electrically conductive, infrared reflective and ultraviolet absorptive film of zinc oxyfluoride. Such films are useful in liquid crystal display devices, solar cells, electrochromic absorbers and reflectors, energy-conserving heat mirrors, and antistatic coatings.

Wetting and Dewetting Transitions on Submerged Superhydrophobic Surfaces with Hierarchical Structures.

PubMed

Wu, Huaping; Yang, Zhe; Cao, Binbin; Zhang, Zheng; Zhu, Kai; Wu, Bingbing; Jiang, Shaofei; Chai, Guozhong

2017-01-10

The wetting transition on submersed superhydrophobic surfaces with hierarchical structures and the influence of trapped air on superhydrophobic stability are predicted based on the thermodynamics and mechanical analyses. The dewetting transition on the hierarchically structured surfaces is investigated, and two necessary thermodynamic conditions and a mechanical balance condition for dewetting transition are proposed. The corresponding thermodynamic phase diagram of reversible transition and the critical reversed pressure well explain the experimental results reported previously. Our theory provides a useful guideline for precise controlling of breaking down and recovering of superhydrophobicity by designing superhydrophobic surfaces with hierarchical structures under water.

An atomistic-continuum hybrid simulation of fluid flows over superhydrophobic surfaces

PubMed Central

Li, Qiang; He, Guo-Wei

2009-01-01

Recent experiments have found that slip length could be as large as on the order of 1 μm for fluid flows over superhydrophobic surfaces. Superhydrophobic surfaces can be achieved by patterning roughness on hydrophobic surfaces. In the present paper, an atomistic-continuum hybrid approach is developed to simulate the Couette flows over superhydrophobic surfaces, in which a molecular dynamics simulation is used in a small region near the superhydrophobic surface where the continuum assumption is not valid and the Navier-Stokes equations are used in a large region for bulk flows where the continuum assumption does hold. These two descriptions are coupled using the dynamic coupling model in the overlap region to ensure momentum continuity. The hybrid simulation predicts a superhydrophobic state with large slip lengths, which cannot be obtained by molecular dynamics simulation alone. PMID:19693344

Wetting, adhesion and friction of superhydrophobic and hydrophilic leaves and fabricated micro/nanopatterned surfaces

NASA Astrophysics Data System (ADS)

Bhushan, Bharat; Jung, Yong Chae

2008-06-01

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water-repellent properties. When two hydrophilic bodies are brought into contact, any liquid present at the interface forms menisci, which increases adhesion/friction and the magnitude is dependent upon the contact angle. Certain plant leaves are known to be superhydrophobic in nature due to their roughness and the presence of a thin wax film on the leaf surface. Various leaf surfaces on the microscale and nanoscale have been characterized in order to separate out the effects of the microbumps and nanobumps and the wax on the hydrophobicity. The next logical step in realizing superhydrophobic surfaces that can be produced is to design surfaces based on understanding of the leaves. The effect of micropatterning and nanopatterning on the hydrophobicity was investigated for two different polymers with micropatterns and nanopatterns. Scale dependence on adhesion was also studied using atomic force microscope tips of various radii. Studies on silicon surfaces patterned with pillars of varying diameter, height and pitch values and deposited with a hydrophobic coating were performed to demonstrate how the contact angles vary with the pitch. The effect of droplet size on contact angle was studied by droplet evaporation and a transition criterion was developed to predict when air pockets cease to exist. Finally, an environmental scanning electron microscope study on the effect of droplet size of about 20 µm radius on the contact angle of patterned surfaces is presented. The importance of hierarchical roughness structure on destabilization of air pockets is discussed.

Multi-layer coatings

DOEpatents

Maghsoodi, Sina; Brophy, Brenor L.; Abrams, Ze'ev R.; Gonsalves, Peter R.

2016-06-28

Disclosed herein are coating materials and methods for applying a top-layer coating that is durable, abrasion resistant, highly transparent, hydrophobic, low-friction, moisture-sealing, anti-soiling, and self-cleaning to an existing conventional high temperature anti-reflective coating. The top coat imparts superior durability performance and new properties to the under-laying conventional high temperature anti-reflective coating without reducing the anti-reflectiveness of the coating. Methods and data for optimizing the relative thickness of the under-layer high temperature anti-reflective coating and the top-layer thickness for optimizing optical performance are also disclosed.

Self-healing of the superhydrophobicity by ironing for the abrasion durable superhydrophobic cotton fabrics

PubMed Central

Wu, Jingxia; Li, Jingye; Deng, Bo; Jiang, Haiqing; Wang, Ziqiang; Yu, Ming; Li, Linfan; Xing, Chenyang; Li, Yongjin

2013-01-01

Self-healing of the superhydrophobic cotton fabric (SCF) obtained by the radiation-induced graft polymerization of lauryl methacrylate (LMA) and n-hexyl methacrylate (HMA), can be achieved by ironing. Through the steam ironing process, the superhydrophobicity of the SCFs will be regenerated even after the yarns are ruptured during the abrasion test under a load pressure of 44.8 kPa. SCFs made from LMA grafted cotton fabric can ultimately withstand at least 24,000 cycles of abrasion with periodic steam ironing. The FT-IR microscope results show that the migration of the polymethacrylates graft chains from the interior to the surface is responsible for the self-healing effect. PMID:24135813

Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

PubMed Central

Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

2015-01-01

Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications. PMID:26250403

Polyurethane-acrylate-based hydrophobic film: Facile fabrication, characterization, and application

NASA Astrophysics Data System (ADS)

Park, Jongsung; Nguyen, Bui Quoc Huy; Kim, Ji-Kwan; Shanmugasundaram, Arunkumar; Lee, Dong-Weon

2018-06-01

Polyurethane-acrylate (PUA) is a versatile UV-curable polymer with a short curing time at room temperature, whose surface structure can be flexibly modified by applying various micropatterns. In this paper, we propose a facile and cost-effective fabrication method for the continuous production of an optically transparent PUA-based superhydrophobic thin film. Poly(dimethylsiloxane) (PDMS) was employed as a soft mold for the fabrication of PUA films through the roll-to-roll technique. In addition, nanosilica was spray-coated onto the PUA surface to further improve the hydrophobicity. The fabricated PUA thin film showed the highest static water contact angle (WCA) of ∼140°. The high durability of the PUA film was also demonstrated through mechanical impacting tests. Furthermore, only ∼2% of voltage loss was observed in the solar panel covered with the PUA-based superhydrophobic film. These obtained results indicate the feasibility of applying the film as a protective layer in applications requiring a high transparency and a self-cleaning effect.

Superhydrophobic/Superhydrophilic Janus Fabrics Reducing Blood Loss.

PubMed

Zhu, Tang; Wu, Junrong; Zhao, Ning; Cai, Chao; Qian, Zhenchao; Si, Fangfang; Luo, Heng; Guo, Jing; Lai, Xuan; Shao, Longquan; Xu, Jian

2018-04-01

Hemostatic fabrics are most commonly used in baseline emergency treatment; however, the unnecessary blood loss due to the excessive blood absorption by traditional superhydrophilic fabrics is overlooked. Herein, for the first time, superhydrophobic/superhydrophilic Janus fabrics (superhydrophobic on one side and superhydrophilic on the other) are proposed: the superhydrophilic part absorbs water in the blood to expedite the clotting while the superhydrophobic part prevents blood from further permeating. Compared with the common counterparts, effective bleeding control with reducing blood loss more than 50% can be achieved while the breathability largely remain by using Janus fabrics. The proposed prototypes can even prolong the survival time in the rat model with serious bleeding. This strategy for reducing blood loss via simply tuning wettability is promising for the practical applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible transparent electrode

NASA Astrophysics Data System (ADS)

Demiryont, Hulya; Shannon, Kenneth C., III; Moorehead, David; Bratcher, Matthew

2011-06-01

This paper presents the properties of the EclipseTECTM transparent conductor. EclipseTECTM is a room temperature deposited nanostructured thin film coating system comprised of metal-oxide semiconductor elements. The system possesses metal-like conductivity and glass-like transparency in the visible region. These highly conductive TEC films exhibit high shielding efficiency (35dB at 1 to 100GHz). EclipseTECTM can be deposited on rigid or flexible substrates. For example, EclipseTECTM deposited on polyethylene terephthalate (PET) is extremely flexible that can be rolled around a 9mm diameter cylinder with little or no reduction in electrical conductivity and that can assume pre-extension states after an applied stress is relieved. The TEC is colorless and has been tailored to have high visible transmittance which matches the eye sensitivity curve and allows the viewing of true background colors through the coating. EclipseTECTM is flexible, durable and can be tailored at the interface for applications such as electron- or hole-injecting OLED electrodes as well as electrodes in flexible displays. Tunable work function and optical design flexibility also make EclipseTECTM well-suited as a candidate for grid electrode replacement in next-generation photovoltaic cells.

Deforming water droplets with a superhydrophobic silica coating.

PubMed

Li, Xiaoguang; Shen, Jun

2013-11-04

The surface liquidity of a water droplet is eliminated by rubbing hydrophobic particles onto the droplet surface using a sol-gel silica coating with extremely weak binding force, which results in solid-like deformability of a liquid drop.

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

A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties

PubMed Central

Ramakrishna, S.; Santhosh Kumar, K. S.; Mathew, Dona; Reghunadhan Nair, C. P.

2015-01-01

Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings. PMID:26679096

Fabricating Superhydrophobic and Superoleophobic Surfaces with Multiscale Roughness Using Airbrush and Electrospray

NASA Astrophysics Data System (ADS)

AL-Milaji, Karam N.

Examples of superhydrophobic surfaces found in nature such as self-cleaning property of lotus leaf and walking on water ability of water strider have led to an extensive investigation in this area over the past few decades. When a water droplet rests on a textured surface, it may either form a liquid-solid-vapor composite interface by which the liquid droplet partially sits on air pockets or it may wet the surface in which the water replaces the trapped air depending on the surface roughness and the surface chemistry. Super water repellent surfaces have numerous applications in our daily life such as drag reduction, anti-icing, anti-fogging, energy conservation, noise reduction, and self-cleaning. In fact, the same concept could be applied in designing and producing surfaces that repel organic contaminations (e.g. low surface tension liquids). However, superoleophobic surfaces are more challenging to fabricate than superhydrophobic surfaces since the combination of multiscale roughness with re-entrant or overhang structure and surface chemistry must be provided. In this study, simple, cost-effective and potentially scalable techniques, i.e., airbrush and electrospray, were employed for the sake of making superhydrophobic and superoleophobic coatings with random and patterned multiscale surface roughness. Different types of silicon dioxide were utilized in this work to in order to study and to characterize the effect of surface morphology and surface roughness on surface wettability. The experimental findings indicated that super liquid repellent surfaces with high apparent contact angles and extremely low sliding angles were successfully fabricated by combining re-entrant structure, multiscale surface roughness, and low surface energy obtained from chemically treating the fabricated surfaces. In addition to that, the experimental observations regarding producing textured surfaces in mask-assisted electrospray were further validated by simulating the actual working

Transparent conductive graphene textile fibers

PubMed Central

Neves, A. I. S.; Bointon, T. H.; Melo, L. V.; Russo, S.; de Schrijver, I.; Craciun, M. F.; Alves, H.

2015-01-01

Transparent and flexible electrodes are widely used on a variety of substrates such as plastics and glass. Yet, to date, transparent electrodes on a textile substrate have not been explored. The exceptional electrical, mechanical and optical properties of monolayer graphene make it highly attractive as a transparent electrode for applications in wearable electronics. Here, we report the transfer of monolayer graphene, grown by chemical vapor deposition on copper foil, to fibers commonly used by the textile industry. The graphene-coated fibers have a sheet resistance as low as ~1 kΩ per square, an equivalent value to the one obtained by the same transfer process onto a Si substrate, with a reduction of only 2.3 per cent in optical transparency while keeping high stability under mechanical stress. With this approach, we successfully achieved the first example of a textile electrode, flexible and truly embedded in a yarn. PMID:25952133

Effect of superhydrophobic surfaces on the flow over a hydrofoil at low Reynolds number

NASA Astrophysics Data System (ADS)

Kim, Hyunseok; Kim, Nayoung; Park, Hyungmin

2014-11-01

In the present study, we experimentally investigate the effect of superhydrophobic surface on the flow over a hydrofoil at low Rec <104 , where c is the chord length of a hydrofoil. As a hydrofoil, we consider the cross-sections typically used for airfoils like NACA0012, NACA0024, and NACA4412, which stand for thin, thick and cambered hydrofoils, respectively. Spray-coating of hydrophobic nanoparticles are applied onto the hydrofoil surface and subsequent velocity fields are measured in a water tunnel using two-dimensional particle image velocimetry at different angles of attack, α =0° -20° . At small α's (for example, less than 10°), it is found that the surface slip tends to affect the flow separation slightly and also modify the size of recirculation region in the wake. Since a massive separation occurs at the leading edge at larger α's, however, the effect of superhydrophobic surface becomes diminished. In the talk, the dependence of the hydrodynamic role of surface slip on the hydrofoil shape and Rec will be presented. Supported by the NRF Programs (NRF-2012M2A8A4055647, NRF-2013R1A1A1008373) of Korean government.

Robust superhydrophobic diamond microspheres for no-loss transport of corrosive liquid microdroplets.

PubMed

Wang, Qiang; Bai, Jie; Dai, Bing; Yang, Zhenhuai; Guo, Shuai; Yang, Lei; He, Yurong; Han, Jiecai; Zhu, Jiaqi

2017-02-16

Superhydrophobic surfaces usually lose their characteristics when exposed to a corrosive environment. To solve this issue, we synthesized superhydrophobic diamond microspheres by microwave-plasma-assisted chemical vapor deposition. Commercial epoxy glue was used to bond the microspheres to various substrates. The thus-synthesized composite films exhibited robust superhydrophobicity and an ultrahigh adhesive force.

One-step fabrication of biomimetic superhydrophobic surface by electrodeposition on magnesium alloy and its corrosion inhibition.

PubMed

Liu, Yan; Xue, Jingze; Luo, Dan; Wang, Huiyuan; Gong, Xu; Han, Zhiwu; Ren, Luquan

2017-04-01

A facile, rapid and one-step electrodeposition process has been employed to construct a superhydrophobic surface with micro/nano scale structure on a Mg-Sn-Zn (TZ51) alloy, which is expected to be applied as a biodegradable biomedical implant materials. By changing the electrodeposition time, the maximum contact angle of the droplet was observed as high as 160.4°±0.7°. The characteristics of the as-prepared surface were conducted by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR). Besides, the anti-corrosion performance of the coatings in stimulated body fluid (SBF) solution were investigated by electrochemical measurement. The results demonstrated that the anti-corrosion property of superhydrophobic surface was greatly improved. This method show beneficial effects on the wettability and corrosion behavior, and therefore provides a efficient route to mitigate the undesirable rapid corrosion of magnesium alloy in favor of application for clinical field. Copyright © 2016 Elsevier Inc. All rights reserved.

An all-water-based system for robust superhydrophobic surfaces.

PubMed

Liu, Mingming; Hou, Yuanyuan; Li, Jing; Tie, Lu; Guo, Zhiguang

2018-06-01

Superhydrophobic surfaces with micro-/nanohierarchical structures are mechanically weak. Generally, organic solvents are used to dissolve or disperse organic adhesives and modifiers to enhance the mechanical strength of superhydrophobic surfaces. In this work, an all-water-based spraying solution is developed for the preparation of robust superhydrophobic surfaces, which contains ZnO nanoparticles, aluminum phosphate as an inorganic adhesive, and polytetrafluoroethylene with low surface energy. The all-water-based system is appreciated for low price and less pollution. Importantly, the prepared superhydrophobic surfaces are durable enough against various harsh conditions (such as UV irradiation for 12 h, pH values from 1 to 13, and temperatures from -10 to 300 °C for 12 h) and physical damages (including sandpaper abrasion and sand impact tests for 50 cycles). In addition, the obtained interfacial materials show promise for practical applications such as anti-icing and oil-water separation. Copyright © 2018 Elsevier Inc. All rights reserved.

Superhydrophobic, diatomaceous earth comprising bandages and method of making the same

DOEpatents

Simpson, John T.; D'Urso, Brian R.

2017-01-10

A bandage comprising a substrate having a first surface with a plurality of superhydrophobic particles attached to the first surface. The plurality of superhydrophobic particles can be porous diatomaceous earth particles having a hydrophobic layer conforming to the surfaces of the DE particles, where the hydrophobic layer is bound to the DE particles. The plurality of attached superhydrophobic particles can render the first surface superhydrophobic, while a second surface opposite the first surface can be hydrophilic or hydrophobic. The substrate can be breathable in order to maintain skin health for the tissue underlying the bandage. The substrate can be selected from porous films, apertured films, textiles, nonwoven materials, impregnated composites thereof, and combinations thereof.

Transparent, flexible surface enhanced Raman scattering substrates based on Ag-coated structured PET (polyethylene terephthalate) for in-situ detection

NASA Astrophysics Data System (ADS)

Zuo, Zewen; Zhu, Kai; Gu, Chuan; Wen, Yibing; Cui, Guanglei; Qu, Jun

2016-08-01

Transparent, flexible surface-enhanced Raman scattering (SERS) substrates were fabricated by metalization of structured polyethylene terephthalate (PET) sheets. The resultant Ag-coated structured PET SERS substrates were revealed to be highly sensitive with good reproducibility and stability, an enhancement factor of 3 × 106 was acquired, which can be attributed mainly to the presence of plentiful multiple-type hot spots within the quasi-three-dimensional surface of the structured PET obtained by oxygen plasma etching. In addition, detections of model molecules on fruit skin were also carried out, demonstrating the great potential of the Ag-coated structured PET in in-situ detection of analyte on irregular objects. Importantly, the technique used for the preparation of such substrate is completely compatible with well-established silicon device technologies, and large-area fabrication with low cost can be readily realized.

Multiphase Combustion of Metalized Nanocomposite Energetic Materials

DTIC Science & Technology

2014-12-19

Materials, Energy & Fuels (01 2011) Eric Nixon, Michelle Pantoya, Ganapathy Sivakumar, Ashwin Vijayasai, Tim Dallas. Superhydrophobic Coatings for... Superhydrophobic Coatings for Nanoenergetic Material Combustion, Surface Coatings and Technology205, 5103-5108, 2011. 4. Dikici, B., Shaw, B...A., Dallas, T., Superhydrophobic Coatings for Nanoenergetic Material Combustion, Surface Coatings and Technology 205, 5103-5108, 2011. (3

A High-Efficiency Superhydrophobic Plasma Separator

PubMed Central

Liu, Changchun; Liao, Shih-Chuan; Song, Jinzhao; Mauk, Michael G.; Li, Xuanwen; Wu, Gaoxiang; Ge, Dengteng; Greenberg, Robert M.; Yang, Shu; Bau, Haim H.

2016-01-01

To meet stringent limit-of-detection specifications for low abundance target molecules, a relatively large volume of plasma is needed for many blood-based clinical diagnostics. Conventional centrifugation methods for plasma separation are not suitable for on-site testing or bedside diagnostics. Here, we report a simple, yet high-efficiency, clamshell-style, superhydrophobic plasma separator that is capable of separating a relatively large volume of plasma from several hundred microliters of whole blood (finger-prick blood volume). The plasma separator consists of a superhydrophobic top cover with a separation membrane and a superhydrophobic bottom substrate. Unlike previously reported membrane-based plasma separators, the separation membrane in our device is positioned at the top of the sandwiched whole blood film to increase the membrane separation capacity and plasma yield. In addition, the device’s superhydrophobic characteristics (i) facilitates the formation of well-defined, contracted, thin blood film with a high contact angle; (ii) minimizes biomolecular adhesion to surfaces; (iii) increases blood clotting time; and (iv) reduces blood cell hemolysis. The device demonstrated a “blood in-plasma out” capability, consistently extracting 65±21.5 μL of plasma from 200 μL of whole blood in less than 10 min without electrical power. The device was used to separate plasma from Schistosoma mansoni genomic DNA-spiked whole blood with a recovery efficiency of > 84.5 ± 25.8 %. The S. mansoni genomic DNA in the separated plasma was successfully tested on our custom-made microfluidic chip by using loop mediated isothermal amplification (LAMP) method. PMID:26732765

Superhydrophobic Silicon Nanocrystal-Silica Aerogel Hybrid Materials: Synthesis, Properties, and Sensing Application.

PubMed

Kehrle, Julian; Purkait, Tapas K; Kaiser, Simon; Raftopoulos, Konstantinos N; Winnacker, Malte; Ludwig, Theresa; Aghajamali, Maryam; Hanzlik, Marianne; Rodewald, Katia; Helbich, Tobias; Papadakis, Christine M; Veinot, Jonathan G C; Rieger, Bernhard

2018-04-24

Silicon nanocrystals (SiNCs) are abundant and exhibit exquisitely tailorable optoelectronic properties. The incorporation of SiNCs into highly porous and lightweight substrates such as aerogels leads to hybrid materials possessing the attractive features of both materials. This study describes the covalent deposition of SiNCs on and intercalation into silica aerogels, explores the properties, and demonstrates a prototype sensing application of the composite material. SiNCs of different sizes were functionalized with triethoxyvinylsilane (TEVS) via a radical grafting approach and subsequently used for the synthesis of photoluminescent silica hybrids. The resulting SiNC-containing aerogels possess high porosities, SiNC-based size-dependent photoluminescence, transparency, and a superhydrophobic macroscopic surface. The materials were used to examine the photoluminescence response toward low concentrations of 3-nitrotoluene (270 μM), demonstrating their potential as a sensing platform for high-energy materials.

Fabrication of superhydrophobic polyaniline films with rapidly switchable wettability

NASA Astrophysics Data System (ADS)

Zhou, Xiaoyan; Zhang, Zhaozhu; Men, Xuehu; Yang, Jin; Xu, Xianghui; Zhu, Xiaotao; Xue, Qunji

2011-10-01

A superhydrophobic polyaniline (PANI) film has been fabricated by using a facile one-step spraying method. The PANI was synthesized via in situ doping polymerization in the presence of perfluorooctanoic acid (PFOA) as the dopant. The water contact angle of this superhydrophobic surface reaches to 156°. Both the surface chemical compositions and morphological structures were analyzed. A granular morphology of PANI with a moderate amount of nanofibers was obtained. Moreover, a rapid surface wettability transition between superhydrophobicity and superhydrophilicity can be observed when it is doped with PFOA and de-doped with base. The mechanism for this tunable wettability has been discussed in detail.

Stability of plasma treated superhydrophobic surfaces under different ambient conditions.

PubMed

Chen, Faze; Liu, Jiyu; Cui, Yao; Huang, Shuai; Song, Jinlong; Sun, Jing; Xu, Wenji; Liu, Xin

2016-05-15

Plasma hydrophilizing of superhydrophobic substrates has become an important area of research, for example, superhydrophobic-(super)hydrophilic patterned surfaces have significant practical applications such as lab-on-chip systems, cell adhesion, and control of liquid transport. However, the stability of plasma-induced hydrophilicity is always considered as a key issue since the wettability tends to revert back to the untreated state (i.e. aging behavior). This paper focuses on the stability of plasma treated superhydrophobic surface under different ambient conditions (e.g. temperature and relative humidity). Water contact angle measurement and X-ray photoelectron spectroscopy are used to monitor the aging process. Results show that low temperature and low relative humidity are favorable to retard the aging process and that pre-storage at low temperature (-10°C) disables the treated surface to recover superhydrophobicity. When the aging is performed in water, a long-lasting hydropholicity is obtained. As the stability of plasma-induced hydrophilcity over a desired period of time is a very important issue, this work will contribute to the optimization of storage conditions of plasma treated superhydrophobic surfaces. Copyright © 2016 Elsevier Inc. All rights reserved.

Self-cleaning of superhydrophobic surfaces by self-propelled jumping condensate

PubMed Central

Wisdom, Katrina M.; Qu, Xiaopeng; Liu, Fangjie; Watson, Gregory S.; Chen, Chuan-Hua

2013-01-01

The self-cleaning function of superhydrophobic surfaces is conventionally attributed to the removal of contaminating particles by impacting or rolling water droplets, which implies the action of external forces such as gravity. Here, we demonstrate a unique self-cleaning mechanism whereby the contaminated superhydrophobic surface is exposed to condensing water vapor, and the contaminants are autonomously removed by the self-propelled jumping motion of the resulting liquid condensate, which partially covers or fully encloses the contaminating particles. The jumping motion off the superhydrophobic surface is powered by the surface energy released upon coalescence of the condensed water phase around the contaminants. The jumping-condensate mechanism is shown to spontaneously clean superhydrophobic cicada wings, where the contaminating particles cannot be removed by gravity, wing vibration, or wind flow. Our findings offer insights for the development of self-cleaning materials. PMID:23630277

Exploiting both optical and electrical anisotropy in nanowire electrodes for higher transparency.

PubMed

Dong, Jianjin; Goldthorpe, Irene A

2018-01-26

Transparent electrodes such as indium tin oxide and random meshes of silver nanowires (AgNWs) have isotropic in-plane properties. However, we show that imparting some alignment to AgNWs can create anisotropic transparency and electrical conductivity characteristics that may benefit many applications. For example, liquid crystal displays and the touch sensors on top of them often only need to be transparent to one type of polarized light as well as predominantly conductive in only one direction. Herein, AgNWs are slightly preferentially aligned during their deposition by rod coating. Compared to randomly oriented AgNW films, the alignment boosts the transparency to perpendicularly polarized light, as well as achieves a higher transparency for a given sheet resistance in one direction compared to randomly oriented AgNWs films. These factors together increase the transparency of a 16 Ω/sq electrode by 7.3 percentage points. The alignment technique is cheap and scalable, compatible with roll-to-roll processes, and most importantly does not require extra processing steps, as rod coating is already a standard process for AgNW electrode fabrication.

Exploiting both optical and electrical anisotropy in nanowire electrodes for higher transparency

NASA Astrophysics Data System (ADS)

Dong, Jianjin; Goldthorpe, Irene A.

2018-01-01

Transparent electrodes such as indium tin oxide and random meshes of silver nanowires (AgNWs) have isotropic in-plane properties. However, we show that imparting some alignment to AgNWs can create anisotropic transparency and electrical conductivity characteristics that may benefit many applications. For example, liquid crystal displays and the touch sensors on top of them often only need to be transparent to one type of polarized light as well as predominantly conductive in only one direction. Herein, AgNWs are slightly preferentially aligned during their deposition by rod coating. Compared to randomly oriented AgNW films, the alignment boosts the transparency to perpendicularly polarized light, as well as achieves a higher transparency for a given sheet resistance in one direction compared to randomly oriented AgNWs films. These factors together increase the transparency of a 16 Ω/sq electrode by 7.3 percentage points. The alignment technique is cheap and scalable, compatible with roll-to-roll processes, and most importantly does not require extra processing steps, as rod coating is already a standard process for AgNW electrode fabrication.

Comparison of Three Methods for Generating Superhydrophobic, Superoleophobic Nylon Nonwoven Surfaces (Postprint)

DTIC Science & Technology

2011-04-01

AFRL-RX-TY-TP-2010-0076 COMPARISON OF THREE METHODS FOR GENERATING SUPERHYDROPHOBIC , SUPEROLEOPHOBIC NYLON NONWOVEN SURFACES Rahul Saraf...Generating Superhydrophobic , Superoleophobic Nylon Nonwoven Surfaces (POSTPRINT) FA8650-07-1-5916 0602102F GOVT L0 QL102006 ^Saraf, Rahul,; ^Lee, Hoon...Document contains color images. This research deals with creating a superhydrophobic /superoleophobic surface by preparing a metastable Cassie

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

Aytug, Tolga

Maintaining clarity and avoiding the accumulation of water and dirt on optically transparent surfaces such as US military vehicle windshields, viewports, periscope optical head windows, and electronic equipment cover glasses are critical to providing a high level of visibility, improved survivability, and much-needed safety for warfighters in the field. Through a combination of physical vapor deposition techniques and the exploitation of metastable phase separation in low-alkali borosilicate, a novel technology was developed for the fabrication of optically transparent, porous nanostructured silica thin film coatings that are strongly bonded to glass platforms. The nanotextured films, initially structurally superhydrophilic, exhibit superior superhydrophobicity,more » hence antisoiling ability, following a simple but robust modification in surface chemistry. The surfaces yield water droplet contact angles as high as 172°. Moreover, the nanostructured nature of these coatings provides increased light scattering in the UV regime and reduced reflectivity (i.e., enhanced transmission) over a broad range of the visible spectrum. In addition to these functionalities, the coatings exhibit superior mechanical resistance to abrasion and are thermally stable to temperatures approaching 500°C. The overall process technology relies on industry standard equipment and inherently scalable manufacturing processes and demands only nontoxic, naturally abundant, and inexpensive base materials. Such coatings, applied to the optical components of current and future combat equipment and military vehicles will provide a significant strategic advantage for warfighters. The inherent self-cleaning properties of such superhydrophobic coatings will also mitigate biofouling of optical windows exposed to high-humidity conditions and can help decrease repair/replacement costs, reduce maintenance, and increase readiness by limiting equipment downtime.« less

Preparation and wettability examinations of transparent SiO2 binder-added MgF2 nanoparticle coatings covered with fluoro-alkyl silane self-assembled monolayer.

PubMed

Murata, Tsuyoshi; Hieda, Junko; Saito, Nagahiro; Takai, Osamu

2012-05-01

SiO2-added MgF2 nanoparticle coatings with various surface roughness properties were formed on fused silica-glass substrates from autoclaved sols prepared at 100-180 °C. To give it hydrophobicity, we treated the samples with fluoro-alkyl silane (FAS) vapor to form self-assembled monolayers on the nanoparticle coating and we examined the wettability of the samples. The samples preserved good transparency even after the FAS treatment. The wettability examination revealed that higher autoclave temperatures produced a larger average MgF2 nanoparticle particle size, a larger surface roughness, and a higher contact angle and the roll-off angle.

Water droplet evaporation from sticky superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Lee, Moonchan; Kim, Wuseok; Lee, Sanghee; Baek, Seunghyeon; Yong, Kijung; Jeon, Sangmin

2017-07-01

The evaporation dynamics of water from sticky superhydrophobic surfaces was investigated using a quartz crystal microresonator and an optical microscope. Anodic aluminum oxide (AAO) layers with different pore sizes were directly fabricated onto quartz crystal substrates and hydrophobized via chemical modification. The resulting AAO layers exhibited hydrophobic or superhydrophobic characteristics with strong adhesion to water due to the presence of sealed air pockets inside the nanopores. After placing a water droplet on the AAO membranes, variations in the resonance frequency and Q-factor were measured throughout the evaporation process, which were related to changes in mass and viscous damping, respectively. It was found that droplet evaporation from a sticky superhydrophobic surface followed a constant contact radius (CCR) mode in the early stage of evaporation and a combination of CCR and constant contact angle modes without a Cassie-Wenzel transition in the final stage. Furthermore, AAO membranes with larger pore sizes exhibited longer evaporation times, which were attributed to evaporative cooling at the droplet interface.

Single-step direct fabrication of pillar-on-pore hybrid nanostructures in anodizing aluminum for superior superhydrophobic efficiency.

PubMed

Jeong, Chanyoung; Choi, Chang-Hwan

2012-02-01

Conventional electrochemical anodizing processes of metals such as aluminum typically produce planar and homogeneous nanopore structures. If hydrophobically treated, such 2D planar and interconnected pore structures typically result in lower contact angle and larger contact angle hysteresis than 3D disconnected pillar structures and, hence, exhibit inferior superhydrophobic efficiency. In this study, we demonstrate for the first time that the anodizing parameters can be engineered to design novel pillar-on-pore (POP) hybrid nanostructures directly in a simple one-step fabrication process so that superior surface superhydrophobicity can also be realized effectively from the electrochemical anodization process. On the basis of the characteristic of forming a self-ordered porous morphology in a hexagonal array, the modulation of anodizing voltage and duration enabled the formulation of the hybrid-type nanostructures having controlled pillar morphology on top of a porous layer in both mild and hard anodization modes. The hybrid nanostructures of the anodized metal oxide layer initially enhanced the surface hydrophilicity significantly (i.e., superhydrophilic). However, after a hydrophobic monolayer coating, such hybrid nanostructures then showed superior superhydrophobic nonwetting properties not attainable by the plain nanoporous surfaces produced by conventional anodization conditions. The well-regulated anodization process suggests that electrochemical anodizing can expand its usefulness and efficacy to render various metallic substrates with great superhydrophilicity or -hydrophobicity by directly realizing pillar-like structures on top of a self-ordered nanoporous array through a simple one-step fabrication procedure.

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.

Laser-induced superhydrophobic grid patterns on PDMS for droplet arrays formation

NASA Astrophysics Data System (ADS)

Farshchian, Bahador; Gatabi, Javad R.; Bernick, Steven M.; Park, Sooyeon; Lee, Gwan-Hyoung; Droopad, Ravindranath; Kim, Namwon

2017-02-01

We demonstrate a facile single step laser treatment process to render a polydimethylsiloxane (PDMS) surface superhydrophobic. By synchronizing a pulsed nanosecond laser source with a motorized stage, superhydrophobic grid patterns were written on the surface of PDMS. Hierarchical micro and nanostructures were formed in the irradiated areas while non-irradiated areas were covered by nanostructures due to deposition of ablated particles. Arrays of droplets form spontaneously on the laser-patterned PDMS with superhydrophobic grid pattern when the PDMS sample is simply immersed in and withdrawn from water due to different wetting properties of the irradiated and non-irradiated areas. The effects of withdrawal speed and pitch size of superhydrophobic grid on the size of formed droplets were investigated experimentally. The droplet size increases initially with increasing the withdrawal speed and then does not change significantly beyond certain points. Moreover, larger droplets are formed by increasing the pitch size of the superhydrophobic grid. The droplet arrays formed on the laser-patterned PDMS with wettability contrast can be used potentially for patterning of particles, chemicals, and bio-molecules and also for cell screening applications.

A review on the mechanical and thermodynamic robustness of superhydrophobic surfaces.

PubMed

Scarratt, Liam R J; Steiner, Ullrich; Neto, Chiara

2017-08-01

Advancements in the fabrication and study of superhydrophobic surfaces have been significant over the past 10years, and some 20years after the discovery of the lotus effect, the study of special wettability surfaces can be considered mainstream. While the fabrication of superhydrophobic surfaces is well advanced and the physical properties of superhydrophobic surfaces well-understood, the robustness of these surfaces, both in terms of mechanical and thermodynamic properties, are only recently getting attention in the literature. In this review we cover publications that appeared over the past ten years on the thermodynamic and mechanical robustness of superhydrophobic surfaces, by which we mean the long term stability under conditions of wear, shear and pressure. The review is divided into two parts, the first dedicated to thermodynamic robustness and the second dedicated to mechanical robustness of these complex surfaces. Our work is intended as an introductory review for researchers interested in addressing longevity and stability of superhydrophobic surfaces, and provides an outlook on outstanding aspects of investigation. Copyright © 2017 Elsevier B.V. All rights reserved.

Laser Printing of Superhydrophobic Patterns from Mixtures of Hydrophobic Silica Nanoparticles and Toner Powder.

PubMed

Ngo, Chi-Vinh; Chun, Doo-Man

2016-11-08

In this work, a new and facile dry printing method was developed for the direct fabrication of superhydrophobic patterns based on silica nanoparticles. Mixtures of hydrophobic fumed silica nanoparticles and toner powder were printed on paper and polymer sheets using a commercial laser printer to produce the superhydrophobic patterns. The mixing ratio of the toner powder (for the laser printer) to hydrophobic silica was also investigated to optimize both the printing quality and the superhydrophobicity of the printed areas. The proper mixing ratio was then used to print various superhydrophobic patterns, including triangular, square, circular, and complex arrangements, to demonstrate that superhydrophobic surfaces with different patterns can be fabricated in a few seconds without any post-processing. The superhydrophobicity of each sample was evaluated by contact angle measurements, and all printed areas showed contact angles greater than 150°. The research described here opens the possibility of rapid production of superhydrophobic surfaces with various patterns. Ultimately, the obtained findings may have a significant impact on applications related to self-cleaning, control of water geometry and position, fluid mixing and fluid transport.

Laser Printing of Superhydrophobic Patterns from Mixtures of Hydrophobic Silica Nanoparticles and Toner Powder

PubMed Central

Ngo, Chi-Vinh; Chun, Doo-Man

2016-01-01

In this work, a new and facile dry printing method was developed for the direct fabrication of superhydrophobic patterns based on silica nanoparticles. Mixtures of hydrophobic fumed silica nanoparticles and toner powder were printed on paper and polymer sheets using a commercial laser printer to produce the superhydrophobic patterns. The mixing ratio of the toner powder (for the laser printer) to hydrophobic silica was also investigated to optimize both the printing quality and the superhydrophobicity of the printed areas. The proper mixing ratio was then used to print various superhydrophobic patterns, including triangular, square, circular, and complex arrangements, to demonstrate that superhydrophobic surfaces with different patterns can be fabricated in a few seconds without any post-processing. The superhydrophobicity of each sample was evaluated by contact angle measurements, and all printed areas showed contact angles greater than 150°. The research described here opens the possibility of rapid production of superhydrophobic surfaces with various patterns. Ultimately, the obtained findings may have a significant impact on applications related to self-cleaning, control of water geometry and position, fluid mixing and fluid transport. PMID:27824132

Tunable Droplet Breakup Dynamics on Micropillared Superhydrophobic Surfaces.

PubMed

Zhang, Rui; Hao, Pengfei; Zhang, Xiwen; Niu, Fenglei; He, Feng

2018-06-22

Functional materials with controllable droplet breakup properties have extensive application prospects in aircraft anti-icing, spraying cooling, surface coating, and so on. Here we show that introducing micropillar arrays with various morphologies to fabricate superhydrophobic surfaces could either facilitate or suppress droplet splitting. The spacing and height of micropillars play an essential role in tuning the splitting patterns. Delayed splashing occurs on dense pillars which support the liquid lamella and provide channels for air to escape. A novel droplet breakup mechanism is found on sparse tall pillars, which rises from the instability of lateral liquid jets and significantly reduces the droplet breakup threshold. The critical Weber number of the rupture of low-viscous liquid is solely determined by the geometric parameters of micropillars and droplets. This work unveils the impact of ordered microstructures on the droplet breakup dynamics and provides a quantitative analysis of the geometric parameters in revising the breakup criteria.

Effect of superhydrophobicity on surface damage of silicone rubber under AC voltage

NASA Astrophysics Data System (ADS)

Li, Yufeng; Jin, Haiyun; Nie, Shichao; Tong, Cheng; Gao, Naikui

2018-03-01

In this paper, the influence of superhydrophobicity on the surface damage of silicone rubber is studied. On a common silicone rubber surface, a droplet can become elongated, and arc discharge induced by the droplet can cause tracking on the silicone rubber surface. However, for a superhydrophobic silicone rubber surface, a droplet can leave the silicone rubber due to the low adhesion of the superhydrophobic surface. Accordingly, arc discharge caused by the droplet does not occur, and the surface of the silicone rubber is not affected. Results demonstrate that using a superhydrophobic surface has a significant effect on limiting the surface damage of silicone rubber.

Electrokinetic energy conversion in a finite length superhydrophobic microchannel

NASA Astrophysics Data System (ADS)

Malekidelarestaqi, M.; Mansouri, A.; Chini, S. F.

2018-07-01

We investigated the effect of superhydrophobic walls on electrokinetics phenomena in a finite-length microchannel with superhydrophobic walls (in both transient and steady-state). We implemented the effect of superhydrophobicity using Navier's slip-length. To include the importance of the electric double-layer, we scaled the slip-length with respect to Debye-length (κ-1). By increasing the slip-length from 0 to 144 nm (1.5κ-1), streaming-current, streaming-potential, flow-rate and electrokinetic energy conversion increased by 2.55, 2.44, 1.8, and 3.4 folds, accordingly. The electrokinetic energy conversion of each microchannel was in the order of picowatt. To produce more energy, an array of microchannels should be used.

Influence of hydrophobic and superhydrophobic surfaces on reducing aerodynamic insect residues

NASA Astrophysics Data System (ADS)

Krishnan, K. Ghokulla; Milionis, Athanasios; Loth, Eric; Farrell, Thomas E.; Crouch, Jeffrey D.; Berry, Douglas H.

2017-01-01

Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircrafts with laminar-flow surfaces. This study investigates the effectiveness of various hydrophobic and superhydrophobic surfaces in reducing residue of insects on an aerodynamic surface at relatively high impact speeds (about 45 m/s). An experimental setup consisting of a wind tunnel and a method to inject live flightless fruit flies was used to test the effectiveness of various surfaces against insect fouling. Insect fouling was analyzed based on residue area and height from multiple impacts. In general most of the residue area was due to the hemolymph spreading while most of the residue height was due to adhesion of exoskeleton parts. Hydrophobic and especially superhydrophobic surfaces performed better than a hydrophilic aluminum surface in terms of minimizing the residue area of various insect components (exoskeleton, hemolymph, and red fluid). Surfaces with reduced wettability and short lateral length scales tended to have the smallest residue area. Residue height was not as strongly influenced by surface wettability since even a single exoskeleton adhered to the surface upon impact was enough to produce a residue height of the order of one mm. In general, the results indicate that hemolymph spread needs to be avoided (e.g. by having reduced wettability and short lateral correlation lengths) in order to minimize the residue area, while exoskeleton adherence needs to be avoided (e.g. by having oleophobic properties and micro/nano roughness) in order to minimize the residue height. In particular, two of the superhydrophobic coatings produced substantial reduction in residue height and area, relative to the baseline surface of aluminum. However, the surfaces also showed poor mechanical durability on the high-speed insect impact location. This suggests that although low wettability materials show great insect anti-fouling behavior, their durability needs to

Nearly Perfect Durable Superhydrophobic Surfaces Fabricated by a Simple One-Step Plasma Treatment.

PubMed

Ryu, Jeongeun; Kim, Kiwoong; Park, JooYoung; Hwang, Bae Geun; Ko, YoungChul; Kim, HyunJoo; Han, JeongSu; Seo, EungRyeol; Park, YongJong; Lee, Sang Joon

2017-05-16

Fabrication of superhydrophobic surfaces is an area of great interest because it can be applicable to various engineering fields. A simple, safe and inexpensive fabrication process is required to fabricate applicable superhydrophobic surfaces. In this study, we developed a facile fabrication method of nearly perfect superhydrophobic surfaces through plasma treatment with argon and oxygen gases. A polytetrafluoroethylene (PTFE) sheet was selected as a substrate material. We optimized the fabrication parameters to produce superhydrophobic surfaces of superior performance using the Taguchi method. The contact angle of the pristine PTFE surface is approximately 111.0° ± 2.4°, with a sliding angle of 12.3° ± 6.4°. After the plasma treatment, nano-sized spherical tips, which looked like crown-structures, were created. This PTFE sheet exhibits the maximum contact angle of 178.9°, with a sliding angle less than 1°. As a result, this superhydrophobic surface requires a small external force to detach water droplets dripped on the surface. The contact angle of the fabricated superhydrophobic surface is almost retained, even after performing an air-aging test for 80 days and a droplet impacting test for 6 h. This fabrication method can provide superb superhydrophobic surface using simple one-step plasma etching.

Shear-Sensitive Liquid Crystal Coating Method Applied Through Transparent Test Surfaces

NASA Technical Reports Server (NTRS)

Reda, Daniel C.; Wilder, Michael C.

1999-01-01

Research conducted at NASA Ames Research Center has shown that the color-change response of a shear-sensitive liquid crystal coating (SSLCC) to aerodynamic shear depends on both the magnitude of the local shear vector and its direction relative to the observer's in-plane line of sight. In conventional applications, the surface of the SSLCC exposed to aerodynamic shear is illuminated with white light from the normal direction and observed from an oblique above-plane view angle of order 30 deg. In this top-light/top-view mode, shear vectors with components directed away from the observer cause the SSLCC to exhibit color-change responses. At any surface point, the maximum color change (measured from the no-shear red or orange color) always occurs when the local vector is aligned with, and directed away from, the observer. The magnitude of the color change at this vector-observer-aligned orientation scales directly with shear stress magnitude. Conversely, any surface point exposed to a shear vector with a component directed toward the observer exhibits a non-color-change response, always characterized by a rusty-red or brown color, independent of both shear magnitude and direction. These unique, highly directional color-change responses of SSLCCs to aerodynamic shear allow for the full-surface visualization and measurement of continuous shear stress vector distributions. The objective of the present research was to investigate application of the SSLCC method through a transparent test surface. In this new back-light/back-view mode, the exposed surface of the SSLCC would be subjected to aerodynamic shear stress while the contact surface between the SSLCC and the solid, transparent wall would be illuminated and viewed in the same geometrical arrangement as applied in conventional applications. It was unknown at the outset whether or not color-change responses would be observable from the contact surface of the SSLCC, and, if seen, how these color-change responses might

Self-cleaning of superhydrophobic surfaces by spontaneously jumping condensate drops

NASA Astrophysics Data System (ADS)

Wisdom, Katrina; Watson, Jolanta; Watson, Gregory; Chen, Chuan-Hua

2012-11-01

The self-cleaning function of superhydrophobic surfaces is conventionally attributed to the removal of contaminating particles by impacting or rolling water droplets, which implies the action of external forces such as gravity. Here, we demonstrate a new self-cleaning mechanism, whereby condensate drops spontaneously jump upon coalescence on a superhydrophobic surface, and the merged drop self-propels away from the surface along with the contaminants. The jumping-condensate mechanism is shown to autonomously clean superhydrophobic cicada wings, where the contaminating particles cannot be removed by external wind flow. Our findings offer new insights for the development of self-cleaning materials.

Drag Reduction On Multiscale Superhydrophobic Surfaces

NASA Astrophysics Data System (ADS)

Jenner, Elliot; Barbier, Charlotte; D'Urso, Brian

2013-11-01

Fluid drag reduction is of great interest in a variety of fields, including hull engineering, microfluidics, and drug delivery. We fabricated samples with multi-scale superhydrophobic surfaces, which consist of hexagonally self-ordered microscopic spikes grown via anodization on macroscopic grooves cut in aluminum. The hydrodynamic drag properties were studied with a cone-and-plate rheometer, showing significant drag reduction near 15% in turbulent flow and near 30% in laminar flow. In addition to these experiments, numerical simulations were performed in order to estimate the slip length at high speeds. Furthermore, we will report on the progress of experiments with a new type of surface combining superhydrophobic surfaces like those discussed above with Slippery Liquid Infused Porous Surfaces (SLIPS), which utilize an oil layer to create a hydrophobic self-repairing surface. These ``Super-SLIPS'' may combine the best properties of both superhydrophobic surfaces and SLIPS, by combining a drag reducing air-layer and an oil layer which may improve durability and biofouling resistance. This research was supported by the ORNL Seed Money Program. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725.

Predictive model for ice formation on superhydrophobic surfaces.

PubMed

Bahadur, Vaibhav; Mishchenko, Lidiya; Hatton, Benjamin; Taylor, J Ashley; Aizenberg, Joanna; Krupenkin, Tom

2011-12-06

The prevention and control of ice accumulation has important applications in aviation, building construction, and energy conversion devices. One area of active research concerns the use of superhydrophobic surfaces for preventing ice formation. The present work develops a physics-based modeling framework to predict ice formation on cooled superhydrophobic surfaces resulting from the impact of supercooled water droplets. This modeling approach analyzes the multiple phenomena influencing ice formation on superhydrophobic surfaces through the development of submodels describing droplet impact dynamics, heat transfer, and heterogeneous ice nucleation. These models are then integrated together to achieve a comprehensive understanding of ice formation upon impact of liquid droplets at freezing conditions. The accuracy of this model is validated by its successful prediction of the experimental findings that demonstrate that superhydrophobic surfaces can fully prevent the freezing of impacting water droplets down to surface temperatures of as low as -20 to -25 °C. The model can be used to study the influence of surface morphology, surface chemistry, and fluid and thermal properties on dynamic ice formation and identify parameters critical to achieving icephobic surfaces. The framework of the present work is the first detailed modeling tool developed for the design and analysis of surfaces for various ice prevention/reduction strategies. © 2011 American Chemical Society

Hot water-repellent and mechanically durable superhydrophobic mesh for oil/water separation.

PubMed

Cao, Min; Luo, Xiaomin; Ren, Huijun; Feng, Jianyan

2018-02-15

The leakage of oil or organic pollutants into the ocean arouses a global catastrophe. The superhydrophobic materials have offered a new idea for the efficient, thorough and automated oil/water separation. However, most of such materials lose superhydrophobicity when exposed to hot water (e.g. >55 °C). In this study, a hot water-repellent superhydrophobic mesh used for oil/water separation was prepared with one-step spray of modified polyurethane and hydrophobic silica nanoparticles on the copper mesh. The as-prepared superhydrophobic mesh could be applied as the effective materials for the separation of oil/water mixture with a temperature up to 100 °C. In addition, the obtained mesh could selectively remove a wide range of organic solvents from water with high absorption capacity and good recyclability. Moreover, the as-prepared superhydrophobic mesh shows excellent mechanical durability, which makes it a promising material for practical oil/water separation. Copyright © 2017 Elsevier Inc. All rights reserved.

Transparent, Weakly Conductive Films for Space Applications

NASA Technical Reports Server (NTRS)

Griffin, John; Morgan, Ashraf; Hambourger, Paul D.

2004-01-01

Electrically insulating spacecraft surfaces are vulnerable to nonuniform charge buildup due to particles emitted by the sun. On Mars, insulating surfaces of exploration vehicles and structures will be affected by dust coatings possibly held in place by triboelectric surface charge. Application of a conductive film may be a solution to the charging problem, but the coating must be highly transparent if used on solar panels, lenses, etc. Sheet resistivity requirements depend on the application and are in the range 10(exp 2) - 10(exp 8) ohms/square. Co-deposited indium tin oxide (ITO) and MgF2 is promising, with high transparency, tailorable electrical properties, and durability to atomic oxygen. Due to ITO's relatively narrow bandgap (approximately 3.5 eV), the film might absorb enough ultraviolet to protect polymeric substrates. Recent work on dual-magnetron-sputtered ITO-MgF2 showed that a variety of polymeric substrates can be coated at room temperature. However, the sheet resistivity is very sensitive to composition, suggestive of a percolation transition. This could be a serious problem for large-scale coating production. We will report on attempts to control film composition by plasma emission monitoring of the ITO and MgF2 guns.

Anticorrosion Coatings Based on Assemblies of Superhydrophobic Particles Impregnated with Conductive Oil

DTIC Science & Technology

2016-05-13