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1

Nanostructures increase water droplet adhesion on hierarchically rough superhydrophobic surfaces.  

PubMed

Hierarchical roughness is known to effectively reduce the liquid-solid contact area and water droplet adhesion on superhydrophobic surfaces, which can be seen for example in the combination of submicrometer and micrometer scale structures on the lotus leaf. The submicrometer scale fine structures, which are often referred to as nanostructures in the literature, have an important role in the phenomenon of superhydrophobicity and low water droplet adhesion. Although the fine structures are generally termed as nanostructures, their actual dimensions are often at the submicrometer scale of hundreds of nanometers. Here we demonstrate that small nanometric structures can have very different effect on surface wetting compared to the large submicrometer scale structures. Hierarchically rough superhydrophobic TiO(2) nanoparticle surfaces generated by the liquid flame spray (LFS) on board and paper substrates revealed that the nanoscale surface structures have the opposite effect on the droplet adhesion compared to the larger submicrometer and micrometer scale structures. Variation in the hierarchical structure of the nanoparticle surfaces contributed to varying droplet adhesion between the high- and low-adhesive superhydrophobic states. Nanoscale structures did not contribute to superhydrophobicity, and there was no evidence of the formation of the liquid-solid-air composite interface around the nanostructures. Therefore, larger submicrometer and micrometer scale structures were needed to decrease the liquid-solid contact area and to cause the superhydrophobicity. Our study suggests that a drastic wetting transition occurs on superhydrophobic surfaces at the nanometre scale; i.e., the transition between the Cassie-Baxter and Wenzel wetting states will occur as the liquid-solid-air composite interface collapses around nanoscale structures. Consequently, water adheres tightly to the surface by penetrating into the nanostructure. The droplet adhesion mechanism presented in this paper gives valuable insight into a phenomenon of simultaneous superhydrophobicity and high water droplet adhesion and contributes to a more detailed comprehension of superhydrophobicity overall. PMID:22263866

Teisala, Hannu; Tuominen, Mikko; Aromaa, Mikko; Stepien, Milena; Mäkelä, Jyrki M; Saarinen, Jarkko J; Toivakka, Martti; Kuusipalo, Jurkka

2012-02-03

2

Jumping-Droplet-Enhanced Condensation on Scalable Superhydrophobic Nanostructured Surfaces  

SciTech Connect

When droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump from the surface due to the release of excess surface energy. If designed properly, these superhydrophobic nanostructured surfaces can not only allow for easy droplet removal at micrometric length scales during condensation but also promise to enhance heat transfer performance. However, the rationale for the design of an ideal nanostructured surface as well as heat transfer experiments demonstrating the advantage of this jumping behavior are lacking. Here, we show that silanized copper oxide surfaces created via a simple fabrication method can achieve highly efficient jumping-droplet condensation heat transfer. We experimentally demonstrated a 25% higher overall heat flux and 30% higher condensation heat transfer coefficient compared to state-of-the-art hydrophobic condensing surfaces at low supersaturations (<1.12). This work not only shows significant condensation heat transfer enhancement but also promises a low cost and scalable approach to increase efficiency for applications such as atmospheric water harvesting and dehumidification. Furthermore, the results offer insights and an avenue to achieve high flux superhydrophobic condensation.

Miljkovic, N; Enright, R; Nam, Y; Lopez, K; Dou, N; Sack, J; Wang, E

2012-01-01

3

Jumping-Droplet-Enhanced Condensation on Scalable Superhydrophobic Nanostructured Surfaces  

NASA Astrophysics Data System (ADS)

When droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump from the surface due to the release of excess surface energy. If designed properly, these superhydrophobic nanostructured surfaces can not only allow for easy droplet removal at micrometric length scales during condensation but promise to enhance heat transfer performance. However, the rationale for the design of an ideal nanostructured surface, as well as heat transfer experiments demonstrating the advantage of this jumping behavior are lacking. Here, we show that silanized copper oxide surfaces created via a simple fabrication method can achieve highly efficient jumping-droplet condensation heat transfer. We experimentally demonstrated a 25% higher overall heat flux and 30% higher condensation heat transfer coefficient compared to state-of-the-art hydrophobic condensing surfaces at low supersaturations. This work not only shows significant condensation heat transfer enhancement, but promises a low cost and scalable approach to increase efficiency for applications such as atmospheric water harvesting and dehumidification. Furthermore, the results offer insights and an avenue to achieve high flux superhydrophobic condensation.

Miljkovic, Nenad; Enright, Ryan; Nam, Youngsuk; Lopez, Ken; Dou, Nicholas; Sack, Jean; Wang, Evelyn

2013-03-01

4

Jumping-droplet-enhanced condensation on scalable superhydrophobic nanostructured surfaces.  

PubMed

When droplets coalesce on a superhydrophobic nanostructured surface, the resulting droplet can jump from the surface due to the release of excess surface energy. If designed properly, these superhydrophobic nanostructured surfaces can not only allow for easy droplet removal at micrometric length scales during condensation but also promise to enhance heat transfer performance. However, the rationale for the design of an ideal nanostructured surface as well as heat transfer experiments demonstrating the advantage of this jumping behavior are lacking. Here, we show that silanized copper oxide surfaces created via a simple fabrication method can achieve highly efficient jumping-droplet condensation heat transfer. We experimentally demonstrated a 25% higher overall heat flux and 30% higher condensation heat transfer coefficient compared to state-of-the-art hydrophobic condensing surfaces at low supersaturations (<1.12). This work not only shows significant condensation heat transfer enhancement but also promises a low cost and scalable approach to increase efficiency for applications such as atmospheric water harvesting and dehumidification. Furthermore, the results offer insights and an avenue to achieve high flux superhydrophobic condensation. PMID:23190055

Miljkovic, Nenad; Enright, Ryan; Nam, Youngsuk; Lopez, Ken; Dou, Nicholas; Sack, Jean; Wang, Evelyn N

2012-12-17

5

UVO Tunable Superhydrophobic to Superhydrophilic Wetting Transition on Biomimetic Nanostructured Surfaces  

Microsoft Academic Search

A novel strategy for a tunable sigmoidal wetting transition from superhydrophobicity to superhydrophilicity on a continuous nanostructured hybrid film via gradient UV-ozone (UVO) exposure is presented. Along a single wetting gradient surface (40 mm), we could visualize the superhydrophobic (thetaH2O> 165^o and low contact angle hysteresis), transition (165^ o > thetaH2O> 10^ o) and superhydrophilic (thetaH2O< 10^o within 0.5 s

Alamgir Karim; Joong Tark Han; Sangcheol Kim

2007-01-01

6

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

NASA Astrophysics Data System (ADS)

In our study, the superhydrophobic surface based on biomimetic lotus leave is explored to maintain the desired properties for self-cleaning. Parameters in controlling bead-up and roll-off characteristics of water droplets were investigated on different model surfaces. The governing equations were proposed. Heuristic study is performed. First, the fundamental understanding of the effect of roughness on superhydrophobicity is performed. The effect of hierarchical roughness, i.e., two scale roughness effect on roughness is investigated using systems of (1) monodisperse colloidal silica sphere (submicron) arrays and Au nanoparticle on top and (2) Si micrometer pyramids and Si nanostructures on top from KOH etching and metal assisted etching of Si. The relation between the contact area fraction and water droplet contact angles are derived based on Wenzel and Cassie-Baxter equation for the systems and the two scale effect is explained regarding the synergistic combination of two scales. Previously the microscopic three-phase-contact line is thought to be the key factor in determining contact angles and hystereses. In our study, Laplace pressure was brought up and related to the three-phase-contact line and taken as a key figure of merit in determining superhydrophobicity. In addition, we are one of the first to study the effect of tapered structures (wall inclination). Combining with a second scale roughness on the tapered structures, stable Cassie state for both water and low surface energy oil may be achieved. This is of great significance for designing both superhydrophobicity and superoleophobicity. Regarding the origin of contact angle hysteresis, study of superhydrophobicity on micrometer Si pillars was performed. The relation between the interface work of function and contact angle hysteresis was proposed and derived mathematically based on the Young-Dupre equation. The three-phase-contact line was further related to a secondary scale roughness induced. Based on 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. Regarding the mechanical robustness, epoxy-silica superhydrophobic surfaces were prepared by O2 plas

Xiu, Yonghao

7

Superhydrophobic surfaces  

Microsoft Academic Search

Non-wettable surfaces with high water contact angles (WCAs) and facile sliding of drops, called superhydrophobic or ultrahydrophobic, have received tremendous attention in recent years. New publications have appeared in the last year documenting many new ways to prepare such surfaces—ranging from application driven work to make robust self-cleaning surfaces to careful model studies of patterned surfaces seeking to understand the

Minglin Ma; Randal M. Hill

2006-01-01

8

Extremely superhydrophobic surfaces with micro- and nanostructures fabricated by copper catalytic etching.  

PubMed

We demonstrate a simple method for the fabrication of rough silicon surfaces with micro- and nanostructures, which exhibited superhydrophobic behaviors. Hierarchically rough silicon surfaces were prepared by copper (Cu)-assisted chemical etching process where Cu nanoparticles having particle size of 10-30 nm were deposited on silicon surface, depending on the period of time of electroless Cu plating. Surface roughness was controlled by both the size of Cu nanoparticles and etching conditions. As-synthesized rough silicon surfaces showed water contact angles ranging from 93° to 149°. Moreover, the hierarchically rough silicon surfaces were chemically modified by spin-coating of a thin layer of Teflon precursor with low surface energy. And thus it exhibited nonsticky and enhanced hydrophobic properties with extremely high contact angle of nearly 180°. PMID:21162520

Lee, Jung-Pil; Choi, Sinho; Park, Soojin

2010-12-16

9

Optically Transparent, Mechanically Durable, Nanostructured Superhydrophobic Surfaces Enabled by Spinodally Phase-Separated Glass Thin Films  

SciTech Connect

Inspired by highly non-wetting natural biological surfaces (e.g., lotus leaves and water strider legs), artificial superhydrophobic surfaces that exhibit water droplet contact angles exceeding 150o have previously been constructed by utilizing various synthesis strategies.[ , , ] Such bio-inspired, water-repellent surfaces offer significant potential for numerous uses ranging from marine applications (e.g., anti-biofouling, anti-corrosion), anti-condensation (e.g., anti-icing, anti-fogging), membranes for selective separation (e.g., oil-water, gas-liquid), microfluidic systems, surfaces requiring reduced maintenance and cleaning, to applications involving glasses and optical materials.[ ] In addition to superhydrophobic attributes, for integration into device systems that have extended operational limits and overall improved performance, surfaces that also possess multifunctional characteristics are desired, where the functionality should match to the application-specific requirements.

Aytug, Tolga [ORNL; Christen, David K [ORNL; Hillesheim, Daniel A [ORNL; Hunter, Scott Robert [ORNL; Ivanov, Ilia N [ORNL; Jellison Jr, Gerald Earle [ORNL; Lupini, Andrew R [ORNL; Pennycook, Stephen J [ORNL; Trejo, Rosa M [ORNL; Winters, Kyle O. [University of Tennessee, Knoxville (UTK); Haynes, James A [ORNL; Simpson, John T [ORNL

2013-01-01

10

Recent advances in designing superhydrophobic surfaces.  

PubMed

The interest in superhydrophobic surfaces has grown exponentially over recent decades. Since the lotus leaf dual hierarchical structure was discovered, researchers have investigated the foundations of self-cleaning behavior. Generally, surface micro/nanostructuring combined with low surface energy of materials leads to extreme anti-wetting properties. The great number of papers on this subject attests the efforts of scientists in mimicking nature to generate superhydrophobicity. Besides the thirst for knowledge, scientists have been driven by the many possible industrial applications of superhydrophobic materials in several fields. Many methods and techniques have been developed to fabricate superhydrophobic surfaces, and the aim of this paper is to review the recent progresses in preparing manmade superhydrophobic surfaces. PMID:23647693

Celia, Elena; Darmanin, Thierry; Taffin de Givenchy, Elisabeth; Amigoni, Sonia; Guittard, Frédéric

2013-04-10

11

Electrokinetics on superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

On a superhydrophobic surface a liquid is exposed to a large air-water interface. The reduced wall friction is expected to cause a higher electro-osmotic mobility. On the other hand, the low charge density of a superhydrophobic surface reduces the electro-osmotic mobility. Due to a lack of experimental data it has not been clear so far whether the reduced wall friction or the reduced charge density dominate the electrokinetic mobilities. To separate the relative contributions of electrophoresis and electro-osmosis, the mobilities of colloids on a negatively charged hydrophilic, a superhydrophobic (Cassie) and a partially hydrophilized superhydrophobic (Cassie composite) coating were measured. To vary the charge density as well as its sign with respect to those of the colloids the partially hydrophilized surfaces were coated with polyelectrolytes. We analyzed the electrokinetic mobilities of negatively charged polystyrene colloids dispersed in aqueous medium on porous hydrophilic and superhydrophobic surfaces by confocal laser scanning electron microscopy. In all cases, the external electric field was parallel to the surface. The total electrokinetic mobilities on the superhydrophobic (Cassie) and negatively charged partially hydrophilized (Cassie composite) surfaces were similar, showing that electro-osmosis is small compared to electrophoresis. The positively charged Cassie composite surfaces tend to ‘trap’ the colloids due to attracting electrostatic interactions and rough morphology, reducing the mobility. Thus, either the charge density of the coatings in the Cassie composite state or its slip length is too low to enhance electro-osmosis.

Papadopoulos, Periklis; Deng, Xu; Vollmer, Doris; Butt, Hans-Jürgen

2012-11-01

12

Electrokinetics on superhydrophobic surfaces.  

PubMed

On a superhydrophobic surface a liquid is exposed to a large air-water interface. The reduced wall friction is expected to cause a higher electro-osmotic mobility. On the other hand, the low charge density of a superhydrophobic surface reduces the electro-osmotic mobility. Due to a lack of experimental data it has not been clear so far whether the reduced wall friction or the reduced charge density dominate the electrokinetic mobilities. To separate the relative contributions of electrophoresis and electro-osmosis, the mobilities of colloids on a negatively charged hydrophilic, a superhydrophobic (Cassie) and a partially hydrophilized superhydrophobic (Cassie composite) coating were measured. To vary the charge density as well as its sign with respect to those of the colloids the partially hydrophilized surfaces were coated with polyelectrolytes. We analyzed the electrokinetic mobilities of negatively charged polystyrene colloids dispersed in aqueous medium on porous hydrophilic and superhydrophobic surfaces by confocal laser scanning electron microscopy. In all cases, the external electric field was parallel to the surface. The total electrokinetic mobilities on the superhydrophobic (Cassie) and negatively charged partially hydrophilized (Cassie composite) surfaces were similar, showing that electro-osmosis is small compared to electrophoresis. The positively charged Cassie composite surfaces tend to 'trap' the colloids due to attracting electrostatic interactions and rough morphology, reducing the mobility. Thus, either the charge density of the coatings in the Cassie composite state or its slip length is too low to enhance electro-osmosis. PMID:23113983

Papadopoulos, Periklis; Deng, Xu; Vollmer, Doris; Butt, Hans-Jürgen

2012-10-31

13

Facile Synthesis of Three-Dimensional ZnO Nanostructure: Realization of a Multifunctional Stable Superhydrophobic Surface  

PubMed Central

Background After comprehensive study of various superhydrophobic phenomena in nature, it is no longer a puzzle for researchers to realize such fetching surfaces. However, the different types of artificial surfaces may get wetted and lose its water repellence if there exist defects or the liquid is under pressure. With respect to the industry applications, in which the resistance of wetting transition is critical important, new nanostructure satisfied a certain geometric criterion should be designed to hold a stable gas film at the base area to avoid the wet transition. Methodology A thermal deposition method was utilized to produce a thin ZnO seeds membrane on the aluminum foil. And then a chemical self-assemble technology was developed in present work to fabricate three-dimensional (3D) hierarchical dune-like ZnO architecture based on the prepared seeds membrane. Results Hierarchical ZnO with micro scale dune-like structure and core-sharing nanosheets was generated. The characterization results showed that there exist plenty of gaps and interfaces among the micro-dune and nanosheets, and thus the surface area was enlarged by such a unique morphology. Benefited from this unique 3D ZnO hierarchical nanostructure, the obtained surface exhibited stable water repellency after modification with Teflon, and furthermore, based on solid theory analysis, such 3D ZnO nanostructure would exhibit excellent sensing performance.

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

2011-01-01

14

Superhydrophobic thin films with nanostructured surface prepared with Au nanoparticle masks.  

PubMed

The hydrophobicity of a perfluoropolyether bisurethane methacrylate polymer film was investigated along with the formation of nano-hairs on its surface through reactive ion etching using gold nanoparticles (Au NPs) as masks. It was found that the hydrophobicity of the polymer film was strongly dependent on the number density of the nano-hairs which was determined by that of the Au NPs. The superhydrophobic surface was obtained when the number density was higher than 250 microm(-2). The effects of surface functionalization, Au NP immobilization, and etching time on the hydrophobicity of the polymer film were also examined extensively and discussed based on the results of the contact angle measurements and the scanning electron microscopy. PMID:22121761

Lee, Cho Yeon; Yoon, Suk Bon; Jang, Gun-Eik; Yun, Wan Soo

2011-07-01

15

Superhydrophobic nanostructures based on porous alumina  

Microsoft Academic Search

Superhydrophobic polytetrafluoroethylene (Teflon®, DuPont) sub-micro and nanostructures were fabricated by the dipping method, based on anodization process in oxalic acid. The polymer sticking phenomenon during the replication creates the sub-microstructures on the negative polytetrafluoroethylene nanostructure replica. This process gives a hierarchical structure with nanostructures on sub-microstructures, which looks like the same structures as lotus leaf and enables commercialization. The diameter

D. Kim; W. Hwang; H. C. Park; K.-H. Lee

2008-01-01

16

Mechanically durable superhydrophobic surfaces.  

PubMed

Development of durable non-wetting surfaces is hindered by the fragility of the microscopic roughness features that are necessary for superhydrophobicity. Mechanical wear on superhydrophobic surfaces usually shows as increased sticking of water, leading to loss of non-wettability. Increased wear resistance has been demonstrated by exploiting hierarchical roughness where nanoscale roughness is protected to some degree by large scale features, and avoiding the use of hydrophilic bulk materials is shown to help prevent the formation of hydrophilic defects as a result of wear. Additionally, self-healing hydrophobic layers and roughness patterns have been suggested and demonstrated. Nevertheless, mechanical contact not only causes damage to roughness patterns but also surface contamination, which shortens the lifetime of superhydrophobic surfaces in spite of the self-cleaning effect. The use of photocatalytic effect and reduced electric resistance have been suggested to prevent the accumulation of surface contaminants. Resistance to organic contaminants is more challenging, however, oleophobic surface patterns which are non-wetting to organic liquids have been demonstrated. While the fragility of superhydrophobic surfaces currently limits their applicability, development of mechanically durable surfaces will enable a wide range of new applications in the future. PMID:21274919

Verho, Tuukka; Bower, Chris; Andrew, Piers; Franssila, Sami; Ikkala, Olli; Ras, Robin H A

2010-12-09

17

Nanowetting of rough superhydrophobic surfaces  

SciTech Connect

Small angle x-ray scattering has been used to investigate the in situ immersive wetting of ultrarough surfaces which exhibit superhydrophobicity with extreme water contact angle ({theta}{sub A} = 169{sup o}). Reduced scattering contrast observed from rough surfaces when partially or totally wetted reveals significant physical differences between superhydrophobic surfaces not otherwise apparent from conventional contact angle measurements.

Zhang, H.; Lamb, R.N.; Cookson, D.J. (ASRP); (New South); (Melbourne)

2008-11-03

18

Facile Synthesis of Three-Dimensional ZnO Nanostructure: Realization of a Multifunctional Stable Superhydrophobic Surface  

Microsoft Academic Search

BackgroundAfter comprehensive study of various superhydrophobic phenomena in nature, it is no longer a puzzle for researchers to realize such fetching surfaces. However, the different types of artificial surfaces may get wetted and lose its water repellence if there exist defects or the liquid is under pressure. With respect to the industry applications, in which the resistance of wetting transition

Jun Wu; Jun Xia; Wei Lei; Baoping Wang

2011-01-01

19

Superhydrophobic surfaces fabricated by surface modification of alumina particles  

NASA Astrophysics Data System (ADS)

The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of <2°. Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

2012-10-01

20

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

21

Progess in superhydrophobic surface development  

Microsoft Academic Search

Research into extreme water-repellent surfaces began many decades ago, although it was only relatively recently that the term superhydrophobicity appeared in literature. Here we review the work on the preparation of superhydrophobic surfaces, with focus on the different techniques used and how they have developed over the years, with particular focus on the last two years. We discuss the origins

Paul Roach; Neil J. Shirtcliffe; Michael I. Newton

2008-01-01

22

The synthesis of superhydrophobic Bi2S3 complex nanostructures  

NASA Astrophysics Data System (ADS)

In this paper, we report a biomolecule-assisted soft chemistry route for constructing complex Bi2S3 nanostructures that exhibit controlled wetting behavior. The as-synthesized sample was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), field emission SEM (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FT-IR), Raman, x-ray photoelectron (XPS) and photoluminescence (PL). The Raman spectra indicate that the surface optical (SO) phonon mode occurs in Bi2S3 nanoparticles. The SO phonon mode is attributed to the defects on the surface of Bi2S3 nanoparticles. In addition, the possible formation mechanism of the self-assembled urchin-like Bi2S3 complex nanostructures is discussed. The established complex nanostructure can control the surface topology of a membrane to create a superhydrophobic surface. A water contact angle (CA) of > 150° of the as-synthesized Bi2S3 complex nanostructures can be obtained, which may find potential application in environmental chemistry.

Xiao, Yujiang; Cao, Huaqiang; Liu, Kaiyu; Zhang, Sichun; Chernow, Victoria

2010-04-01

23

An easy route to make superhydrophobic surface  

NASA Astrophysics Data System (ADS)

Superhydrophobic films with excellent flexibility have been fabricated on silicon surface, generated by means of a chemical galvanic cell route, within a short span of 10 sec. The results show a water contact angle of 155° (superhydrophobic) for the chemically modified silicon surface while it is 63° (hydrophilic) in pure silicon substrate. The surface roughness increases with well ordered protrusions after the chemical treatment. Surface roughness and low surface energy are ascribed for the superhydrophobic behavior of these chemically modified silicon surfaces.

Panda, Kalpataru; Kumar, N.; Polaki, S. R.; Panigrahi, B. K.

2012-06-01

24

Effective slip on textured superhydrophobic surfaces  

Microsoft Academic Search

We study fluid flow in the vicinity of textured and superhydrophobically coated surfaces with characteristic texture sizes on the order of 10 mum. Both for droplets moving down an inclined surface and for an external flow near the surface (hydrofoil), there is evidence of appreciable drag reduction in the presence of surface texture combined with superhydrophobic coating. On textured inclined

Salil Gogte; Peter Vorobieff; Richard Truesdell; Andrea Mammoli; Frank van Swol; Pratik Shah; C. Jeffrey Brinker

2005-01-01

25

Influence of Surface Roughness on Superhydrophobicity  

Microsoft Academic Search

Superhydrophobic surfaces, with a liquid contact angle theta greater than 150°, have important practical applications ranging from self-cleaning window glasses, paints, and fabrics to low-friction surfaces. Many biological surfaces, such as the lotus leaf, have a hierarchically structured surface roughness which is optimized for superhydrophobicity through natural selection. Here we present a molecular dynamics study of liquid droplets in contact

C. Yang; U. Tartaglino; B. N. J. Persson

2006-01-01

26

Shear Flow on Super-Hydrophobic Surfaces  

Microsoft Academic Search

Super-hydrophobic surfaces, which exhibit large contact angles, can give rise to slip flow of aqueous fluids. We present our work on shear flow of atomistic fluids over simple super-hydrophobic surfaces. Molecular dynamic simulations are employed to investigate the flow field of fluid between two parallel surfaces, one of which is moving. Exploring a range of fluid thermodynamic state points, we

Sivakumar R. Challa; Richard Truesdell; Peter Vorobieff; Andrea Mammoli; Frank van Swol

2008-01-01

27

Shear flow on super-hydrophobic surfaces  

Microsoft Academic Search

Super-hydrophobic surfaces, which exhibit large contact angles, can give rise to slip flow of aqueous fluids. We present our work on shear flow of atomistic fluids over simple super-hydrophobic surfaces. Molecular dynamic simulations are employed to investigate the flow field of fluid between two parallel surfaces, one of which is moving. Exploring a range of fluid thermodynamic state points, we

Frank B. van Swol; Richard Truesdell; Peter V. Vorobieff; Sivakumar R. Challa; Andrea A. Mammoli

2007-01-01

28

Wettability Switching Techniques on Superhydrophobic Surfaces  

PubMed Central

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.

2007-01-01

29

Fabrication of Novel Superhydrophobic Surfaces and Water Droplet Bouncing Behavior — Part 1: Stable ZnO–PDMS Superhydrophobic Surface with Low Hysteresis Constructed Using ZnO Nanoparticles  

Microsoft Academic Search

A superhydrophobic surface has many advantages in micro\\/nanomechanical applications, such as low adhesion, low friction and high restitution coefficient, etc. In this paper, we introduce a novel and simple route to fabricate superhydrophobic surfaces using ZnO nanocrystals. First, tetrapod-like ZnO nanocrystals were prepared via a one-step, direct chemical vapor deposition (CVD) approach. The nanostructured ZnO material was characterized by scanning

Bin-Bin Wang; Jiang-Tao Feng; Ya-Pu Zhao; T. X. Yu

2010-01-01

30

Shear flow on super-hydrophobic surfaces.  

SciTech Connect

Super-hydrophobic surfaces, which exhibit large contact angles, can give rise to slip flow of aqueous fluids. We present our work on shear flow of atomistic fluids over simple super-hydrophobic surfaces. Molecular dynamic simulations are employed to investigate the flow field of fluid between two parallel surfaces, one of which is moving. Exploring a range of fluid thermodynamic state points, we demonstrate the influence of fluid phase and structure near the surfaces on prevalence, and degree, of slip at the super-hydrophobic surface.

van Swol, Frank B.; Truesdell, Richard; Vorobieff, Peter V.; Challa, Sivakumar R.; Mammoli, Andrea A.

2007-10-01

31

Slip on Superhydrophobic Surfaces  

Microsoft Academic Search

This review discusses the use of the combination of surface roughness and hy- drophobicity for engineering large slip at the fluid-solid interface. These su- perhydrophobic surfaces were initially inspired by the unique water-repellent properties of the lotus leaf and can be employed to produce drag reduction in both laminar and turbulent flows, enhance mixing in laminar flows, and amplify diffusion-osmotic

Jonathan P. Rothstein

2010-01-01

32

Unidirectional superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

It has long been known that the hairy, waxy cuticle of water-walking insects renders them water-repellent; they thus exhibit high static contact angles. We have recently demonstrated that by the virtue of the geometry and flexibility of the hair, the integument is also directionally anisotropic and so plays a key propulsive role. We here report our attempts to design and implement an analogous synthetic surface that exhibits unidirectional adhesion. The surface effectively acts like a fluidic-diode; allowing contact lines to advance in only one direction. When vibrated randomly, drops suspended on the surface advance in only one direction. Applications in valve-less pumps and drop transport in microfluidic devices are discussed.

Prakash, Manu; Bush, John

2007-11-01

33

Mechanically durable superhydrophobic surfaces prepared by abrading  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces with both excellent mechanical durability and easy reparability based on polytetrafluoroethylene/room temperature vulcanized silicone rubber (PTFE/RTVSR) composites were prepared by a simple abrading method. The surface energy of RTVSR matrix decreased with the increasing volume fraction of PTFE particles, and the surface rough microstructures of the composites were created by abrading. A water droplet on the surface exhibited a contact angle of about 165° +/- 3.4° and a sliding angle of about 7.3° +/- 1.9°. Such superhydrophobic surfaces showed strong mechanical durability against sandpaper because the surfaces were prepared in the way of mechanical abrasion, and the fresh exposed surfaces were still superhydrophobic. In addition, the micro-structures on the elastic surface of the composite will be compressed by elastic deformation to avoid being broken during the friction cycles when cotton fabric was used as an abrasion surface. The deformation will rebound to renew the original surface structures when the load is withdrawn. Therefore, the elastic PTFE/RTVSR composites are of advantage to construct superhydrophobic surfaces with better abrasion resistance. More importantly, such superhydrophobicity can be repaired by a simple abrading regeneration process within a few minutes when the surface is damaged or polluted by organic contaminant.

Wang, Fajun; Yu, Shan; Ou, Junfei; Xue, Mingshan; Li, Wen

2013-09-01

34

Wetting study of patterned surfaces for superhydrophobicity  

Microsoft Academic Search

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water-repellent properties. A number of studies have been carried out to produce artificial biomimetic roughness-induced hydrophobic surfaces. In general, both homogeneous and composite interfaces are possible on the produced surface. Silicon surfaces patterned with pillars of two different diameters and heights with varying pitch values were fabricated.

Bharat Bhushan; Yong Chae Jung

2007-01-01

35

Drag Reduction on a Patterned Superhydrophobic Surface  

Microsoft Academic Search

We present an experimental study of a low-Reynolds number shear flow between two surfaces, one of which has a regular grooved texture augmented with a superhydrophobic coating. The combination reduces the effective fluid-surface contact area, thereby appreciably decreasing the drag on the surface and effectively changing the macroscopic boundary condition on the surface from no slip to limited slip. We

Richard Truesdell; Andrea Mammoli; Peter Vorobieff; Frank van Swol; C. Jeffrey Brinker

2006-01-01

36

Superhydrophobic surfaces with nanofibers or nanorods based on thiophene derivatives  

NASA Astrophysics Data System (ADS)

Fabricating superhydrophobic surfaces via self-assembly of organic conjugated small molecules is realized by spray-drying the thiophene derivates organic solutions. Formation of microsized pores and arrayed nanofibers or nanorods on the surfaces is responsible for the superhydrophobicity of the coatings. This technique can be applied for fabrication of large area superhydrophobic surfaces with conjugated molecules on different substrates.

Jia, Zhixin; Liu, Mingxian; Liu, Fang; Luo, Yuanfang; Jia, Demin; Guo, Baochun

2010-01-01

37

Large Slip of Aqueous Liquid Flow over a Nanoengineered Superhydrophobic Surface  

Microsoft Academic Search

While many recent studies have confirmed the existence of liquid slip over certain solid surfaces, there has not been a deliberate effort to design and fabricate a surface that would maximize the slip under practical conditions. Here, we have engineered a nanostructured superhydrophobic surface that minimizes the liquid-solid contact area so that the liquid flows predominantly over a layer of

Chang-Hwan Choi; Chang-Jin Kim

2006-01-01

38

Microdroplet growth mechanism during water condensation on superhydrophobic surfaces.  

PubMed

By promoting dropwise condensation of water, nanostructured superhydrophobic coatings have the potential to dramatically increase the heat transfer rate during this phase change process. As a consequence, these coatings may be a facile method of enhancing the efficiency of power generation and water desalination systems. However, the microdroplet growth mechanism on surfaces which evince superhydrophobic characteristics during condensation is not well understood. In this work, the sub-10 ?m dynamics of droplet formation on nanostructured superhydrophobic surfaces are studied experimentally and theoretically. A quantitative model for droplet growth in the constant base (CB) area mode is developed. The model is validated using optimized environmental scanning electron microscopy (ESEM) imaging of microdroplet growth on a superhydrophobic surface consisting of immobilized alumina nanoparticles modified with a hydrophobic promoter. The optimized ESEM imaging procedure increases the image acquisition rate by a factor of 10-50 as compared to previous research. With the improved imaging temporal resolution, it is demonstrated that nucleating nanodroplets coalesce to create a wetted flat spot with a diameter of a few micrometers from which the microdroplet emerges in purely CB mode. After the droplet reaches a contact angle of 130-150°, its base diameter increases in a discrete steplike fashion. The droplet height does not change appreciably during this steplike base diameter increase, leading to a small decrease of the contact angle. Subsequently, the drop grows in CB mode until it again reaches the maximum contact angle and increases its base diameter in a steplike fashion. This microscopic stick-and-slip motion can occur up to four times prior to the droplet coalescence with neighboring drops. Lastly, the constant contact angle (CCA) and the CB growth models are used to show that modeling formation of a droplet with a 150° contact angle in the CCA mode rather than in the CB mode severely underpredicts both the drop formation time and the average heat transfer rate through the drop. PMID:22548441

Rykaczewski, Konrad

2012-05-10

39

Electrostatically driven droplets deposited on superhydrophobic surfaces  

Microsoft Academic Search

The behavior of dielectric droplets deposited on a superhydrophobic surface and exposed to a constant and uniform electric field is investigated. The change in the droplet shape is described by a linear dependence of its eccentricity on the applied electric field. The proposed control of the droplet shape with the electric field may serve as an alternative to electrowetting technologies.

Edward Bormashenko; Roman Pogreb; Tamir Stein; Gene Whyman; Mordechai Hakham-Itzhaq

2009-01-01

40

Fabrication of superhydrophobic polymethylsilsesquioxane nanostructures on cotton textiles by a solution–immersion process  

Microsoft Academic Search

Superhydrophobic cotton textiles are prepared by a simple, one-step and inexpensive phase separation method under ambient conditions by which a layer of polymethylsilsesquioxane (PMSQ) nanostructures is covered onto the cellulose fibers. By changing the silane precursor concentration, PMSQ nanostructures with various shapes, morphologies and sizes were fabricated. Nanostructures were characterized using SEM, EDS, and attenuated total reflectance FTIR. The wettability

Mohammad A. Shirgholami; Mohammad Shateri Khalil-Abad; Ramin Khajavi; Mohammad E. Yazdanshenas

2011-01-01

41

High strain sustaining, nitrile rubber based, large-area, superhydrophobic, nanostructured composite coatings  

Microsoft Academic Search

Elastomeric superhydrophobic nanostructured composite coatings scalable to large areas are prepared by spray casting particle-polymer dispersions. The dispersions consist of nanostructured carbon black particles along with submicrometer-sized poly(tetrafluoroethylene) particles dispersed in nitrile rubber solution in acetone, with the goal to attain superhydrophobicity with minimal content of particle fillers. The coatings are applied on various flexible substrates, which are subsequently stretched

Thomas M. Schutzius; Manish K. Tiwari; Ilker S. Bayer; Constantine M. Megaridis

2011-01-01

42

Creation of a Superhydrophobic Surface from an Amphiphilic Polymer  

Microsoft Academic Search

Superhydrophobic surfaces, with a water contact angle (CA) greater than 1508, have attracted great interest for both fundamental research and practical applications.(1) Conven- tionally, superhydrophobic surfaces are fabricated by com- bining appropriate surface roughness with low-surface-energy materials (hydrophobic materials, CA greater than 908).(2-18) It has been commonly acknowledged that it is impossible to obtain superhydrophobic surfaces from amphiphilic materi- als.

Lin Feng; Yanlin Song; Jin Zhai; Biqian Liu; Jian Xu; Lei Jiang; Daoben Zhu

2003-01-01

43

Preparation of superhydrophobic surfaces on cotton textiles  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces were fabricated by the complex coating of silica nanoparticles with functional groups onto cotton textiles to generate a dual-size surface roughness, followed by hydrophobization with stearic acid, 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane or their combination. The wettability and morphology of the as-fabricated surfaces were investigated by contact angle measurement and scanning electron microscopy. Characterizations by transmission electron microscopy, Fourier transformation infrared spectroscopy, and thermal gravimetric analysis were also conducted.

Xue, Chao-Hua; Jia, Shun-Tian; Zhang, Jing; Tian, Li-Qiang; Chen, Hong-Zheng; Wang, Mang

2008-07-01

44

Formation of superhydrophobic/superhydrophilic patterns by combination of nanostructure-imprinted perfluoropolymer and nanostructured silicon oxide for biological droplet generation  

NASA Astrophysics Data System (ADS)

In this letter, we report a technology for fabricating superhydrophobic/superhydrophilic patterns using a combination of a nanostructure-imprinted perfluoropolymer and nanostructured silicon oxide. In our previous study, we used a combination of hydrophobic and superhydrophilic materials. However, it was difficult to split low-surface-tension liquids such as biological liquids into droplets solely using hydrophobic/hydrophilic patterns. In this study, the contact angle of the hydrophobic region was enhanced from 109.3° to 155.6° by performing nanostructure imprinting on a damage-reduced perfluoropolymer. The developed superhydrophobic/superhydrophilic patterns allowed the splitting of even those media that contained fetal bovine serum into droplets of a desired shape.

Kobayashi, Taizo; Shimizu, Kazunori; Kaizuma, Yoshihiro; Konishi, Satoshi

2011-03-01

45

Single-step direct fabrication of pillar-on-pore hybrid nanostructures in anodizing aluminum for superior superhydrophobic efficiency.  

PubMed

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. PMID:22201335

Jeong, Chanyoung; Choi, Chang-Hwan

2012-01-18

46

Wettability influences cell behavior on superhydrophobic surfaces with different topographies  

Microsoft Academic Search

Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavior on superhydrophobic surfaces is influenced by surface topography and polymer type. Biomimetic superhydrophobic rough surfaces of

B. N. Lourenco; G. Marchioli; W Song; R. L. Reis; Blitterswijk van C. A; H. B. J. Karperien; Apeldoorn van A. A; J. F. Mano

2012-01-01

47

Composite, Nanostructured, Super-Hydrophobic Material.  

National Technical Information Service (NTIS)

A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite materia...

B. R. D'Urso J. T. Simpson

2005-01-01

48

Impalement transitions in droplets impacting microstructured superhydrophobic surfaces  

Microsoft Academic Search

Liquid droplets impacting a superhydrophobic surface decorated with micron-scale posts often bounce off the surface. However, by decreasing the impact velocity, droplets may land on the surface in a fakir state, and by increasing it, posts may impale droplets that are then stuck on the surface. We use a two-phase lattice Boltzmann model to simulate droplet impact on superhydrophobic surfaces,

J. Hyväluoma; J. Timonen

2008-01-01

49

Superhydrophobic surfaces: from natural to biomimetic to functional.  

PubMed

Nature is the creation of aesthetic functional systems, in which many natural materials have vagarious structures. Inspired from nature, such as lotus leaf, butterfly' wings, showing excellent superhydrophobicity, scientists have recently fabricated a lot of biomimetic superhydrophobic surfaces by virtue of various smart and easy routes. Whilst, many examples, such as lotus effect, clearly tell us that biomimicry is dissimilar to a simple copying or duplicating of biological structures. In this feature article, we review the recent studies in both natural superhydrophobic surfaces and biomimetic superhydrophobic surfaces, and highlight some of the recent advances in the last four years, including the various smart routes to construct rough surfaces, and a lot of chemical modifications which lead to superhydrophobicity. We also review their functions and applications to date. Finally, the promising routes from biomimetic superhydrophobic surfaces in the next are proposed. PMID:20846662

Guo, Zhiguang; Liu, Weimin; Su, Bao-Lian

2010-08-24

50

Drag reduction on a patterned superhydrophobic surface.  

PubMed

We present an experimental study of a low-Reynolds number shear flow between two surfaces, one of which has a regular grooved texture augmented with a superhydrophobic coating. The combination reduces the effective fluid-surface contact area, thereby appreciably decreasing the drag on the surface and effectively changing the macroscopic boundary condition on the surface from no slip to limited slip. We measure the force on the surface and the velocity field in the immediate vicinity on the surface (and thus the wall shear) simultaneously. The latter facilitates a direct assessment of the effective slip length associated with the drag reduction. PMID:16907578

Truesdell, Richard; Mammoli, Andrea; Vorobieff, Peter; van Swol, Frank; Brinker, C Jeffrey

2006-07-26

51

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

52

Effect of electro-osmotic flow on energy conversion on superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

It has been suggested that superhydrophobic surfaces, due to the presence of a no-shear zone, can greatly enhance transport of surface charges, leading to a considerable increase in the streaming potential. This could find potential use in micro-energy harvesting devices. In this paper, we show using analytical and numerical methods, that when a streaming potential is generated in such superhydrophobic geometries, the reverse electro-osmotic flow and hence current generated by this, is significant. A decrease in streaming potential compared to what was earlier predicted is expected. We also show that, due to the electro-osmotic streaming-current, a saturation in both the power extracted and efficiency of energy conversion is achieved in such systems for large values of the free surface charge densities. Nevertheless, under realistic conditions, such microstructured devices with superhydrophobic surfaces have the potential to even reach energy conversion efficiencies only achieved in nanostructured devices so far.

Seshadri, Gowrishankar; Baier, Tobias

2013-04-01

53

Hybrid surface design for robust superhydrophobicity.  

PubMed

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. PMID:22630787

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

2012-06-06

54

A simple approach to fabricate stable superhydrophobic glass surfaces  

NASA Astrophysics Data System (ADS)

We present a facile method to fabricate superhydrophobic glass surface via one-step hydrothermal method and chemical modification. The etched glass surface shows the hierarchical textured morphology as well as the multiple scales of roughness and large numbers of nanorods and pores. The formation mechanism of the hierarchically structured surface is discussed in detail. After surface modification with vinyltriethoxysilane, the glass surface exhibits stable superhydrophobicity with a high contact angle of 155° and a low sliding angle of 5°. A water droplet of 10 ?L can bounce away from the surface when it vertically hit the superhydrophobic glass surface. Moreover, the contact angle of the superhydrophobic glass surface under different pH values and storage time are measured to study the stability of the superhydrophobic property.

Ji, Haiyan; Chen, Gang; Yang, Jin; Hu, Jie; Song, Haojie; Zhao, Yutao

2013-02-01

55

Why superhydrophobic surfaces are not always icephobic.  

PubMed

We discuss mechanical forces that act upon a water droplet and a piece of ice on a rough solid surface and the difference between dewetting and ice fracture. The force needed to detach a water droplet depends on contact angle (CA) hysteresis and can be reduced significantly in the case of a superhydrophobic surface. The force needed to detach a piece of ice depends on the receding CA and the initial size of interfacial cracks. Therefore, even surfaces with very high receding CA may have strong adhesion to ice if the size of the cracks is small. PMID:23009385

Nosonovsky, Michael; Hejazi, Vahid

2012-09-25

56

Motion of Liquid Droplets on a Superhydrophobic Oleophobic Surface (Postprint).  

National Technical Information Service (NTIS)

Developing a superhydrophobic oleophobic material is achieved by two criteria: low surface energy and properly designed surface morphology. The relationships among surface tensions, contact angles, contact angle hystereses, roll-off angles, and surface mo...

H. J. Lee J. R. Owens

2010-01-01

57

Superhydrophobic surfaces fabricated from nano- and microstructured cellulose stearoyl esters.  

PubMed

Robust, superhydrophobic and self-cleaning films were fabricated using nano- or microstructured cellulose fatty acid esters, which were prepared via nanoprecipitation. The superhydrophobic films could be coated on diverse surfaces with non-uniform shapes by distinct coating techniques. PMID:23609473

Geissler, Andreas; Chen, Longquan; Zhang, Kai; Bonaccurso, Elmar; Biesalski, Markus

2013-05-28

58

Superhydrophobic surfaces: From natural to biomimetic to functional  

Microsoft Academic Search

Nature is the creation of aesthetic functional systems, in which many natural materials have vagarious structures. Inspired from nature, such as lotus leaf, butterfly’ wings, showing excellent superhydrophobicity, scientists have recently fabricated a lot of biomimetic superhydrophobic surfaces by virtue of various smart and easy routes. Whilst, many examples, such as lotus effect, clearly tell us that biomimicry is dissimilar

Zhiguang Guo; Weimin Liu; Bao-Lian Su

2011-01-01

59

Drying of colloidal droplets on superhydrophobic surfaces.  

PubMed

Recent research on the flow patterns during the drying of droplets of solutions or suspensions has revealed a characteristic flow of dissolved or suspended material to the droplet periphery to produce the 'coffee ring' phenomenon. This effect was used to make ceramic well-plates by spontaneous manufacturing. Here we demonstrate that when a colloidal droplet dries on a superhydrophobic surface, the effect is rather different. Evaporation from the region adjacent to the three phase line becomes so restricted that the interior flows, and hence the final destination of particles, changes and the characteristic bowl-shape becomes inverted. PMID:20692671

Chen, Lifeng; Evans, Julian R G

2010-07-21

60

Surface-initiated polymerization of superhydrophobic polymethylene.  

PubMed

We report a new surface-initiated polymerization strategy that yields superhydrophobic polymethylene (PM) films from initially smooth substrates of gold and silicon. The films are prepared by assembling a vinyl-terminated self-assembled monolayer, followed by exposure of the surface to a 0.1 M solution of borane, and polymerizing from the borane sites upon exposure to a solution of diazomethane at -17 degrees C. Surface-initiated polymethylenation (SIPM) presents rapid growth in relation to other surface-initiated reactions, producing PM films thicker than 500 nm after 2 min of reaction and 3 microm after 24 h of reaction. AFM and SEM images show the presence of micro- and nanoscale features that enable the entrapment of air when exposed to water. Consistent with this result, these films exhibit advancing water contact angles greater than 160 degrees, dramatically different than 103 degrees measured for smooth PM films, and hysteresis values ranging from 2 degrees to 40 degrees, depending on the substrate and polymerization time. The superhydrophobic character of the films results in the entrapment of air at the polymer/solution interface to provide remarkable resistances greater than 10(10) Omega x cm(2) against the transport of aqueous redox probes and cause the film to behave as a "perfect" capacitor. PMID:20359210

Tuberquia, Juan C; Nizamidin, Nabijan; Harl, Robert R; Albert, Jake; Hunter, Jason; Rogers, Bridget R; Jennings, G Kane

2010-04-28

61

Superhydrophobic surfaces with excellent mechanical durability and easy repairability  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces with both excellent mechanical durability and easy repairability based on polytetrafluoroethylene/polyvinylidene fluoride (PTFE/PVDF) composites were prepared by a facile method. The surface energy of PVDF matrix was lowered by the incorporation of PTFE particles, and the rough micro textures on the surfaces of the composites were created by abrading. A water droplet on the surface exhibited a contact angle of about 163.5°, and a sliding angle lower than 5°. Such superhydrophobic surfaces showed strong mechanical durability because the surfaces were prepared in the way of mechanical abrasion. The scratch tests indicated that the surface micro textures were retained after the abrasion cycles, and the fresh exposed surfaces were still superhydrophobic. More importantly, such superhydrophobicity can be repaired by a simple abrading regeneration process within a few minutes when the surface is polluted by dust or organic contaminant.

Wang, F. J.; Lei, S.; Ou, J. F.; Xue, M. S.; Li, W.

2013-07-01

62

Motion of liquid droplets on a superhydrophobic oleophobic surface  

Microsoft Academic Search

Developing a superhydrophobic oleophobic material is achieved by two criteria: low surface energy and properly designed surface\\u000a morphology. The relationships among surface tensions, contact angles, contact angle hystereses, roll-off angles, and surface\\u000a morphologies of such materials are studied. Numerical formulae related to the surface energy of liquids and solids are used\\u000a to predict the wetting behavior of superhydrophobic and oleophobic

Hoon Joo Lee; Jeffery R. Owens

2011-01-01

63

Stable superhydrophobic surfaces over a wide pH range  

NASA Astrophysics Data System (ADS)

A stable superhydrophobic surface was fabricated by solidifying poly(epoxy-terminated polydimethylsiloxane- co-bisphenol A) [P(ETPDMS- co-BPA)] copolymer on a rough substrate. The low surface energy of the copolymer and the geometric structure at micrometer scale of the surface contribute to the superhydrophobic property. The as-prepared surface shows stable superhydrophobicity over a wide pH range (1-14) and the wettability is excellent stable to heating, water, corrosive solution and organic solvent treatments. The procedure is simple and time-saving as well as utilizing non-fluorine-containing compounds.

Guo, Li; Yuan, Wenfang; Li, Junping; Zhang, Zhijie; Xie, Zemin

2008-01-01

64

Superhydrophobic graphene-based materials: surface construction and functional applications.  

PubMed

Many naturally occurring surfaces have superhydrophobicity that fulfils their functional demands, which has inspired considerable interest to develop similar artificial superhydrophobic surfaces with a variety of functionalities. Graphene is an ideal candidate for functional superhydrophobic surfaces due to its exceptional physicochemical properties. The recent advances in this emerging field are summarized, including the wetting behavior of water on graphene and the formation of crumpling/nanoparticle/foam-induced hierarchical structures, with emphasis on fundamental understanding for related processes. The potential applications in energy, environmental remediation, and thermal management are also discussed. PMID:24089354

Chen, Zhongxin; Dong, Lei; Yang, Dong; Lu, Hongbin

2013-09-02

65

Solvothermal synthesis of nanoporous polymer chalk for painting superhydrophobic surfaces.  

PubMed

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. PMID:21875116

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

2011-09-13

66

Delayed Frost Growth on Jumping-Drop Superhydrophobic Surfaces  

SciTech Connect

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 inter-drop frost wave. The growth of this inter-drop frost front is shown to be up to three 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 inter-drop 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 inter-drop phenomenon that is strongly coupled to the wettability and drop size distribution of the surface. A jumping-drop superhydrophobic condenser was found to be superior to a conventional dropwise condenser in two respects: preventing heterogeneous ice nucleation by continuously removing subcooled condensate, and delaying frost growth by minimizing the success of interdrop ice bridge formation.

Boreyko, Jonathan B [ORNL; Collier, Pat [ORNL

2013-01-01

67

Electro-osmosis on Anisotropic Superhydrophobic Surfaces  

NASA Astrophysics Data System (ADS)

We give a general theoretical description of electro-osmotic flow at striped superhydrophobic surfaces in a thin double layer limit, and derive a relation between the electro-osmotic mobility and hydrodynamic slip-length tensors. Our analysis demonstrates that electro-osmotic flow shows a very rich behavior controlled by slip length and charge at the gas sectors. In the case of an uncharged liquid-gas interface, the flow is the same or inhibited relative to the flow in a homogeneous channel with a zero interfacial slip. By contrast, it can be amplified by several orders of magnitude provided slip regions are uniformly charged. When gas and solid regions are oppositely charged, we predict a flow reversal, which suggests the possibility of a huge electro-osmotic slip even for electroneutral surfaces. On the basis of these observations we suggest strategies for practical microfluidic devices.

Belyaev, Aleksey V.; Vinogradova, Olga I.

2011-08-01

68

Effects of Contact Angle Hysteresis on Ice Adhesion and Growth over Superhydrophobic Surfaces under Dynamic Flow Conditions  

SciTech Connect

In this paper, the iceophobic properties of superhydrophobic surfaces are investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared by coating the substrates of aluminum and steel plates with nano-structured hydrophobic particles. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20 F accompanying micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by high-resolution CCD cameras. Results show that the superhydrophobic coatings significantly delay the ice formation and accretion even under the dynamic flow condition of the highly energetic impingement of accelerated super-cooled water droplets. It is found that there is a time scale for this phenomenon (delay of the ice formation) which has a clear correlation with the contact angle hysteresis and the length scale of surface roughness of the superhydrophobic surface samples, being the highest for the plate with the lowest contact angle hysteresis and finer surface roughness. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis (dynamic property) and the non-wetting superhydrophobic state under the hydrodynamic pressure of impinging droplets, rather than to only have a high contact angle (static property), in order to result in efficient anti-icing properties under dynamic conditions such as forced flows.

Sarshar, Mohammad Amin [Stevens Institute of Technology, Hoboken, New Jersey; Swarctz, Christopher [Stevens Institute of Technology, Hoboken, New Jersey; Hunter, Scott Robert [ORNL; Simpson, John T [ORNL; Choi, Chang-Hwan [Stevens Institute of Technology, Hoboken, New Jersey

2012-01-01

69

A novel fabrication of superhydrophobic surfaces for universal applicability  

NASA Astrophysics Data System (ADS)

The present work reports a novel and facile approach to fabricate stable superhydrophobic surfaces for universal applicability in practice. Poly(furfuryl alcohol)/copper composite coatings were prepared on substrates via a brush-painting method; after being immersed in a stearic acid solution, the superhydrophobic surfaces were obtained due to the formation of copper stearate on the substrates. These products were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectrometry, X-ray powder diffraction and the X-ray photoelectron spectrum. Results demonstrate that the superhydrophobic surfaces formed originally on copper substrates can also be generated on other substrates without the copper element. Furthermore, this work will provide a simple and universal method to create large-scale superhydrophobic surfaces on various substrates.

Chen, Su-Wen; Guo, Bo-Long; Wu, Wang-Suo

2011-12-01

70

Facile fabrication of transparent superhydrophobic surfaces by spray deposition.  

PubMed

Herein, we present a one-step facile spray-deposition process for fabricating a new superhydrophobic surface with a novel statistical copolymer. The polymeric material is relatively inexpensive, easily prepared, transparent, solvent-processable, very simple, and applicable to rugged substrates. The materials presented herein also feature a near-perfect superhydrophobic surface with a static water contact angle of 178° and a transmittance of higher than 75% at 550 nm wavelength. PMID:21728363

Hwang, Ha Soo; Kim, Nam Hyun; Lee, Seung Goo; Lee, Dong Yun; Cho, Kilwon; Park, In

2011-07-08

71

Silicon nanowire and polyethylene superhydrophobic surfaces for discrete magnetic microfluidics  

Microsoft Academic Search

A microfluidic method to manipulate small drops of water is studied on two different superhydrophobic surfaces. Using this digital magnetofluidic method, water drops containing paramagnetic carbonyl-iron microparticles were displaced on silicon nanowire (Si NW) and low-density polyethylene (LDPE) superhydrophobic surfaces using magnetic fields. Horizontal, vertical, or upside-down drop movement is made possible by the action of capillary forces induced by

Ana Egatz-Gómez; John Schneider; P. Aella; Dongqing Yang; P. Domínguez-García; Solitaire Lindsay; S. T. Picraux; Miguel A. Rubio; Sonia Melle; Manuel Marquez; Antonio A. García

2007-01-01

72

Superhydrophobic nanostructured coating for anti-icing applications  

NASA Astrophysics Data System (ADS)

In this work, anti-icing superhydrophobic (SHP) tungsten nanorod (WNR) surfaces were fabricated. The fabrication of WNR surfaces as rough surfaces was carried out using the Glancing Angle Deposition (GLAD) technique. Using the magnetron-sputtering deposition method, the deposition Ar pressure, Ar flow rate, and substrate tilting angle were varied to fabricate WNRs with different surface morphologies and porosities. The surface energy of the WNR films was lowered by coating them with a nano-layer (10-15nm) of Teflon AF2400 using an effusion cell. Static contact angle (SCA) measurements of the sessile water droplet gently dispensed on surfaces were used to characterize the static wetting properties of those surfaces. After surface treatment of the fabricated WNRs with different spacing, heights, and nanorod natural pyramidal tips, surfaces with tunable hydrophobic properties with SCAs ranging from 120° to 160° were obtained. The well-known classical Wenzel and Cassie models were used to predict the observed CAs. The proposed geometrically modified Cassie model showed consistent agreement with the observed high SCAs. The dynamic study of the wetting properties of the fabricated surfaces was carried out using water droplet evaporation on the surfaces. The kinetics of water droplet evaporation showed a significant influence of surface wetting properties, morphology, and porosity on the three modes of evaporation. Moreover, the contact angle hysteresis (CAH) of the surfaces was measured by the dynamic approach of adding/withdrawing water to/from the surfaces, respectively. The SHP-WNR films maintained a relatively low CAH of 30 degrees. The CAHs obtained by both kinetics of evaporation and the dynamic approach were consistent. Finally, the ability of the supercooled SHP-WNRs, kept at a temperature of -10 °C, to repel supercooled water droplets with a subzero temperature as low as -10 °C was tested. The SHP-WNRs' surfaces were able to repel supercooled water droplets released from a height of 15 mm with an impact velocity of 0.54 m/s. Calculations of energy dissipation in the course of bouncing due to the water droplets' physical properties and the surface wetting properties were performed. In addition to surface CAH and water droplet vibration, a significant energy loss due to an increase in supercooled water droplet viscosity as a function of its temperature was observed.

Khedir, Khedir R.

73

What do we need for a superhydrophobic surface? A review on the recent progress in the preparation of superhydrophobic surfaces  

Microsoft Academic Search

Superhydrophobic surfaces have drawn a lot of interest both in academia and in industry because of the self-cleaning properties. This critical review focuses on the recent progress (within the last three years) in the preparation, theoretical modeling, and applications of superhydrophobic surfaces. The preparation approaches are reviewed according to categorized approaches such as bottom-up, top-down, and combination approaches. The advantages

Xue-Mei Li; David N. Reinhoudt; Mercedes Crego-Calama

2007-01-01

74

Nanotextured silica surfaces with robust superhydrophobicity and omnidirectional broadband supertransmissivity.  

PubMed

Designing multifunctional surfaces that have user-specified interactions with impacting liquids and with incident light is a topic of both fundamental and practical significance. Taking cues from nature, we use tapered conical nanotextures to fabricate the multifunctional surfaces; the slender conical features result in large topographic roughness, while the axial gradient in the effective refractive index minimizes reflection through adiabatic index-matching between air and the substrate. Precise geometric control of the conical shape and slenderness of the features as well as periodicity at the nanoscale are all keys to optimizing the multifunctionality of the textured surface, but at the same time, these demands pose the toughest fabrication challenges. Here we report a systematic approach to concurrent design of optimal structures in the fluidic and optical domains and a fabrication procedure that achieves the desired aspect ratios and periodicities with few defects and large pattern area. Our fabricated nanostructures demonstrate structural superhydrophilicity or, in combination with a suitable chemical coating, robust superhydrophobicity. Enhanced polarization-independent optical transmission exceeding 98% has also been achieved over a broad range of bandwidth and incident angles. These nanotextured surfaces are also robustly antifogging or self-cleaning, offering potential benefits for applications such as photovoltaic solar cells. PMID:22482937

Park, Kyoo-Chul; Choi, Hyungryul J; Chang, Chih-Hao; Cohen, Robert E; McKinley, Gareth H; Barbastathis, George

2012-05-01

75

Femtosecond laser irradiation of metallic surfaces: effects of laser parameters on superhydrophobicity.  

PubMed

This work studies in detail the effect of femtosecond laser irradiation process parameters (fluence and scanning speed) on the hydrophobicity of the resulting micro/nano-patterned morphologies on stainless steel. Depending on the laser parameters, four distinctly different nano-patterns were produced, namely nano-rippled, parabolic-pillared, elongated sinusoidal-pillared and triple roughness nano-structures. All of the produced structures were classified according to a newly defined parameter, the laser intensity factor (LIF); by increasing the LIF, the ablation rate and periodicity of the asperities increase. In order to decrease the surface energy, all of the surfaces were coated with a fluoroalkylsilane agent. Analysis of the wettability revealed enhanced superhydrophobicity for most of these structures, particularly those possessing the triple roughness pattern that also exhibited low contact angle hysteresis. The high permanent superhydrophobicity of this pattern is due to the special micro/nano-structure of the surface that facilitates the Cassie-Baxter state. PMID:24045766

Moradi, Sona; Kamal, Saeid; Englezos, Peter; Hatzikiriakos, Savvas G

2013-09-17

76

Femtosecond laser irradiation of metallic surfaces: effects of laser parameters on superhydrophobicity  

NASA Astrophysics Data System (ADS)

This work studies in detail the effect of femtosecond laser irradiation process parameters (fluence and scanning speed) on the hydrophobicity of the resulting micro/nano-patterned morphologies on stainless steel. Depending on the laser parameters, four distinctly different nano-patterns were produced, namely nano-rippled, parabolic-pillared, elongated sinusoidal-pillared and triple roughness nano-structures. All of the produced structures were classified according to a newly defined parameter, the laser intensity factor (LIF); by increasing the LIF, the ablation rate and periodicity of the asperities increase. In order to decrease the surface energy, all of the surfaces were coated with a fluoroalkylsilane agent. Analysis of the wettability revealed enhanced superhydrophobicity for most of these structures, particularly those possessing the triple roughness pattern that also exhibited low contact angle hysteresis. The high permanent superhydrophobicity of this pattern is due to the special micro/nano-structure of the surface that facilitates the Cassie-Baxter state.

Moradi, Sona; Kamal, Saeid; Englezos, Peter; Hatzikiriakos, Savvas G.

2013-10-01

77

Velocity-field measurements near surfaces with superhydrophobic coating  

Microsoft Academic Search

An experimental study of the flow near a surface with a recently developed superhydrophobic (SH) coating employs particle-tracking techniques to reconstruct the velocity field adjacent to the surface. Visualization in the immediate vicinity of the surface is facilitated by matching the refractive index of the base surface material with the refractive index of the fluid. The results of the experiments

Peter Vorobieff; C. Jeff Brinker; Pratik Shah; Richard Truesdell; Andrea Mammoli; Frank van Swol

2003-01-01

78

Superhydrophobic surfaces: are they really ice-repellent?  

PubMed

This work investigates the anti-ice performance of various superhydrophobic surfaces under different conditions. The adhesion strength of glaze ice (similar to that deposited during "freezing rain") is used as a measure of ice-releasing properties. The results show that the ice-repellent properties of the materials deteriorate during icing/deicing cycles, as surface asperities appear to be gradually damaged. It is also shown that the anti-icing efficiency of superhydrophobic surfaces is significantly lower in a humid atmosphere, as water condensation both on top of and between surface asperities takes place, leading to significantly larger values of ice adhesion strength. This work thus shows that superhydrophobic surfaces are not always ice-repellent and their use as anti-ice materials may therefore be limited. PMID:21141839

Kulinich, S A; Farhadi, S; Nose, K; Du, X W

2010-12-08

79

Wettability influences cell behavior on superhydrophobic surfaces with different topographies.  

PubMed

Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavior on superhydrophobic surfaces is influenced by surface topography and polymer type. Biomimetic superhydrophobic rough surfaces of polystyrene and poly(L-lactic acid) with different micro/nanotopographies were obtained from smooth surfaces using a simple phase-separation based method. Total protein was quantified and showed a less adsorption of bovine serum albumin onto rough surfaces as compared to smooth surfaces of the same material. The mouse osteoblastic MC3T3-E1 cell line and primary bovine articular chondrocytes were used to study cell attachment and proliferation. Cells attached and proliferate better in the smooth surfaces. The superhydrophobic surfaces allowed cells to adhere but inhibited their proliferation. This study indicates that surface wettability, rather than polymer type or the topography of the superhydrophobic surfaces, is a critical factor in determining cell behavior. PMID:22833364

Lourenço, Bianca N; Marchioli, Giulia; Song, Welong; Reis, Rui L; van Blitterswijk, Clemens A; Karperien, Marcel; van Apeldoorn, Aart; Mano, João F

2012-07-26

80

Reversible switching between superhydrophobic states on a hierarchically structured surface  

PubMed Central

Nature offers exciting examples for functional wetting properties based on superhydrophobicity, such as the self-cleaning surfaces on plant leaves and trapped air on immersed insect surfaces allowing underwater breathing. They inspire biomimetic approaches in science and technology. Superhydrophobicity relies on the Cassie wetting state where air is trapped within the surface topography. Pressure can trigger an irreversible transition from the Cassie state to the Wenzel state with no trapped air—this transition is usually detrimental for nonwetting functionality and is to be avoided. Here we present a new type of reversible, localized and instantaneous transition between two Cassie wetting states, enabled by two-level (dual-scale) topography of a superhydrophobic surface, that allows writing, erasing, rewriting and storing of optically displayed information in plastrons related to different length scales.

Verho, Tuukka; Korhonen, Juuso T.; Sainiemi, Lauri; Jokinen, Ville; Bower, Chris; Franze, Kristian; Franssila, Sami; Andrew, Piers; Ikkala, Olli; Ras, Robin H. A.

2012-01-01

81

Controllable adhesive superhydrophobic surfaces based on PDMS microwell arrays.  

PubMed

This paper presents a one-step method to fabricate superhydrophobic surfaces with extremely controllable adhesion based on PDMS microwell arrays. The microwell array structures are rapidly produced on PDMS films by a point-by-point femtosecond laser scanning process. The as-prepared superhydrophobic surfaces show water controllable adhesion that ranges from ultrahigh to ultralow by adjusting the extent of overlap of the adjacent microwells, on which the sliding angle can be controlled from 180° (a water droplet can not slide down even when the as-prepared surface is turned upside down) to 3°. A "micro-airbag effect" is introduced to explain the adhesion transition phenomenon of the microwell array structures. This work provides a facile and promising strategy to fabricate superhydrophobic surfaces with controllable adhesion. PMID:23391207

Yong, Jiale; Chen, Feng; Yang, Qing; Zhang, Dongshi; Bian, Hao; Du, Guangqing; Si, Jinhai; Meng, Xiangwei; Hou, Xun

2013-02-25

82

A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces  

NASA Astrophysics Data System (ADS)

A simple immersion approach for fabricating superhydrophobic Mg alloy surfaces is present here. Micro/nanometer-scale rough structures composed of micrometer-scale island-like rough structures and nanometer-scale sheets are generated on the Mg alloy surfaces after immersion in the aqueous CuSO4 solution. After ultrasonic cleaning, the micro/nanometer-scale rough structures are disappeared, whereas the lump-like rough structures appear on the Mg alloy surfaces. After modification with stearic acid, the as-prepared micro/nanometer-scale rough structures and the micrometer-scale lump-like rough structures all show superhydrophobicity. The contact angles of the water droplet on the aforementioned two structures are respectively 151.3° and 161.8°. The rolling angles are respectively 3° and 13°. The results indicate that the cooperation of suitable rough structures and stearic acid modification is responsible for the obtained superhydrophobicity on the Mg alloy surfaces.

Song, Jinlong; Lu, Yao; Huang, Shuai; Liu, Xin; Wu, Libo; Xu, Wenji

2013-02-01

83

Patterned superhydrophobic surface based on Pd-based metallic glass  

NASA Astrophysics Data System (ADS)

Without any modification or post-treatment, superhydrophobic surfaces with good stability were fabricated by hot-embossing honeycomb patterns on Pd40Cu30Ni10P20 bulk metallic glass (BMG). The water contact angle reaches above 150° when the pitch between adjacent cells is larger than the critical size of 115.5 ?m. The wetting behavior on the patterned BMG can be well rationalized in terms of the modified Cassie-Baxter theory [A. B. D. Cassie and S. Baxter, Trans. Faraday Soc. 40, 546 (1944)] by considering surface energy gradient. The achievement of the superhydrophobicity on BMG surface opens a window for the functional applications of metallic glasses.

Xia, Ting; Li, Ning; Wu, Yue; Liu, Lin

2012-08-01

84

Superhydrophobic surface supported bioassay--an application in blood typing.  

PubMed

This study presents a new application of superhydrophobic surfaces in conducting biological assays for human blood typing using a liquid drop micro reactor. The superhydrophobic substrate was fabricated by a simple printing technique with Teflon powder. The non-wetting and weak hysteresis characteristics of superhydrophobic surfaces enable the blood and antibody droplets to have a near-spherical shape, making it easy for the haemagglutination reaction inside the droplet to be photographed or recorded by a digital camera and then analyzed by image analysis software. This novel blood typing method requires only a small amount of blood sample. The evaluation of assay results using image analysis techniques offers potential to develop high throughput operations of rapid blood typing assays for pathological laboratories. With the capability of identifying detailed red blood cell agglutination patterns and intensities, this method is also useful for confirming blood samples that have weak red blood cell antigens. PMID:23434709

Li, Lizi; Tian, Junfei; Li, Miaosi; Shen, Wei

2013-01-30

85

Ag dendrites with rod-like tips: synthesis, characterization and fabrication of superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

A facile, low-cost and templateless wet-chemical method was reported for the mass synthesis of Ag dendrites with rod-like tips which were characterized by various methods. The columniform tips protruded in random directions, of which the diameters were similar. A series of experiments were carried out to explore the effect of sodium citrate on the morphology of the obtained Ag nanostructures, and it was demonstrated that the concentration of sodium citrate was important for the formation of the cylindrical tips on the Ag dendrites. A possible mechanism was proposed to explain the role of sodium citrate in the synthesis of Ag dendrites with rod-like tips. Based on the roughness caused by the Ag dendrites, a superhydrophobic surface was fabricated in a simple procedure on a glass substrate, and the contact angle of the surface was as high as 156.4°. According to similar procedures, superhydrophobic surfaces were easily attained on a DVD disc and commercial aluminium foil, indicating the as-prepared Ag dendrites can be used to fabricate superhydrophobic surfaces on various smooth substrates.

Ren, Wen; Guo, Shaojun; Dong, Shaojun; Wang, Erkang

2011-05-01

86

Electrostatic transportation of water droplets on superhydrophobic surfaces  

Microsoft Academic Search

This article reports electrostatic transportation of water droplets on superhydrophobic alkylketene dimer (AKD) and Teflon AFR surfaces. The actuation is based on electrostatic forces generated by metal electrodes placed underneath the surface. By switching the electrode voltages, the droplets moved stepwise along the electrode paths. The lowest voltage which resulted continuous movement was 124 VAC (rms) and the maximum speed

Altti Torkkeli; Jaakko Saarilahti; Ari Haara; Harri Harma; Tero Soukka; Pertti Tolonen

2001-01-01

87

Patterning and impregnation of superhydrophobic surfaces using aqueous solutions.  

PubMed

We report a solvent-assisted approach to the patterning and impregnation of porous superhydrophobic coatings that permits the use of entirely aqueous solutions. This approach permits immobilization of proteins and enzymes, creating opportunities to decorate superhydrophobic surfaces with hydrophilic domains and channels that can capture aliquots of aqueous media, guide and mix aqueous solutions, and chemically process streams of organic molecules. Because this approach does not require destruction of non-wetting features, it can also be used to transfer highly water-soluble polymers and small molecules without compromising superhydrophobicity, providing methods for post-fabrication loading of water-soluble agents into protective non-wetting coatings that are difficult to achieve using other approaches. PMID:23931600

Manna, Uttam; Lynn, David M

2013-08-19

88

Superhydrophobic surface as a fluid enhancement material in engineering applications  

NASA Astrophysics Data System (ADS)

In this study, a superhydrophobic surface and its relation to the enhancement of the droplet fluid dynamics to the surface of the object materials was investigated. As the comparison, hydrophilic and uncoated surface of an object also investigated. The investigations used height of impact at 89 mm. The high quality speed camera is employed to investigate the droplet dynamic on a copper foil and a calcium fluoride surfaces. Both of the materials are coated with superhydrophobic and hydrophilic surfaces separately. The droplet diameter was analyzed using the program PHANTOM. The droplet contact angle was analyzed by the Goniometry method. The water was dropped on the calcium fluoride and the copper foil using a syringe (sharp tip) with initial droplet diameter of 1.9 mm. To record the droplet fluid shape, the photo micro sensor was placed inside the trigger box below the syringe. The results showed that the superhydrophobic surface both on copper foil and calcium fluoride enhanced the mobility of a droplet compared to the hydrophilic and the uncoated surfaces. The results showed that the maximum droplet diameter on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 4.7, 5.0, 5.2 mm, respectively; and for the calcium fluoride are 4.5, 5.1 and 5.5 mm, respectively. Meanwhile, the results for the droplet contact angle on the copper foil coated by the superhydrophobic, the hydrophilic and the uncoated surfaces are 20°, 90°, 160°, respectively; and for the calcium fluoride are 25°, 95°, 165°, respectively.

Tetuko, Anggito P.; Khaerudini, Deni S.; Sardjono, Priyo; Sebayang, Perdamean; Rosengarten, Gary

2013-09-01

89

Investigating the Interface of Superhydrophobic Surfaces in Contact With Water.  

National Technical Information Service (NTIS)

Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film...

A. P. Malanoski D. A. Doshi E. D. Branson P. B. Shah S. Singh

2005-01-01

90

Drag reduction in turbulent flows over superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate that periodic, micropatterned superhydrophobic surfaces, previously noted for their ability to provide laminar flow drag reduction, are capable of reducing drag in the turbulent flow regime. Superhydrophobic surfaces contain micro- or nanoscale hydrophobic features which can support a shear-free air-water interface between peaks in the surface topology. Particle image velocimetry and pressure drop measurements were used to observe significant slip velocities, shear stress, and pressure drop reductions corresponding to drag reductions approaching 50%. At a given Reynolds number, drag reduction is found to increase with increasing feature size and spacing, as in laminar flows. No observable drag reduction was noted in the laminar regime, consistent with previous experimental results for the channel geometry considered. The onset of drag reduction occurs at a critical Reynolds number where the viscous sublayer thickness approaches the scale of the superhydrophobic microfeatures and performance is seen to increase with further reduction in viscous sublayer height. These results indicate superhydrophobic surfaces may provide a significant drag reducing mechanism for marine vessels.

Daniello, Robert J.; Waterhouse, Nicholas E.; Rothstein, Jonathan P.

2009-08-01

91

Tens of centimeter-scale flexible superhydrophobic nanofiber structures through curing process.  

PubMed

Superhydrophobic surfaces have been fabricated for many biological and engineering applications. However, due to the delamination of the nanostructured layer from a handling layer during the fabrication process, we could not have obtained uniform nanostructured surfaces in large areas. Here, we first report tens of centimeter-scale superhydrophobic nanostructures with flexibility, cost-effective, no aging degradation and drag reduction by adopting curing processes, which have uniform superhydrophobic nanostructured surfaces on the size of 30x14 cm2. Such a nanostructure could be a potential platform for many applications such as microfluidic devices for biological studies, and industrial self-cleaning products for automobiles, ships, and houses. PMID:19606302

Lee, Sangmin; Kang, Jong Hoon; Lee, Sang Joon; Hwang, Woonbong

2009-04-21

92

Micro to nano: Surface size scale and superhydrophobicity  

PubMed Central

Summary This work looks at the fundamental question of how the surface mobility of drops in the composite state is related to the size scale of the roughness features of the surface. To this end, relevant literature is first reviewed and the important terms are clarified. We then describe and discuss contact and roll-off angle measurements on a set of hydrophobicized silicon post surfaces for which all parameters except for the surface size scale were held constant. It was found that a critical transition from “sticky superhydrophobic” (composite state with large contact angle hysteresis) to “truly superhydrophobic” (composite state with low hysteresis) takes place as the size of the surface features reaches 1 ?m.

Dorrer, Christian

2011-01-01

93

Modeling drag reduction and meniscus stability of superhydrophobic surfaces comprised of random roughness  

Microsoft Academic Search

Previous studies dedicated to modeling drag reduction and stability of the air-water interface on superhydrophobic surfaces were conducted for microfabricated coatings produced by placing hydrophobic microposts\\/microridges arranged on a flat surface in aligned or staggered configurations. In this paper, we model the performance of superhydrophobic surfaces comprised of randomly distributed roughness (e.g., particles or microposts) that resembles natural superhydrophobic surfaces,

Mohamed A. Samaha; Hooman Vahedi Tafreshi; Mohamed Gad-el-Hak

2011-01-01

94

One-step process for the fabrication of superhydrophobic surfaces with easy repairability  

NASA Astrophysics Data System (ADS)

A simple technique for fabrication of superhydrophobic surfaces was developed by spraying copper stearate suspension on various substrates. The copper stearate suspension is prepared by the reaction of copper acetate and stearic acid in ethanol solution. The as-prepared surfaces exhibit both superhydrophobicity and self-cleaning properties. When the superhydrophobic surfaces were destroyed, the damaged surfaces could be easily repaired by spraying the copper stearate suspension on the wrecked surfaces again, and the superhydrophobicity of the surfaces was regenerated at the same time.

Li, Jian; Wan, Hongqi; Ye, Yinping; Zhou, Huidi; Chen, Jianmin

2012-01-01

95

Dual-scaled stable superhydrophobic nano-flower surfaces  

Microsoft Academic Search

Novel dual-scaled superhydrophobic nano-flower surfaces were fabricated by 1-mask photolithography, DRIE and carbon nanotube (CNT) microwave plasma enhanced CVD (MPCVD). Patterned structure was characterized by SEM, TEM and AFM techniques. With the additional petal-like CNT structure, the apparent contact angle (ACA) increased dramatically compared with silicon (~140%) and parylene-coated (~78%) micropillar surfaces and resulted in a small sliding angle (around

Longquan Chen; Zhiyong Xiao; P. C. H. Chan; Yi-Kuen Lee

2009-01-01

96

Preparation and characterization of super-hydrophobic and oleophobic surface  

Microsoft Academic Search

A novel method for preparing and characterizing super-hydrophobic and oleophobic surface is presented. Aluminum (Al) substrate\\u000a was roughened by sandblasting and electrolytic etching to obtain micro- and nano-sized complex morphologies. Then, its substrate\\u000a was covered by a chemically adsorbed monolayer (CAM) containing a fluorocarbon group. The surface of Al substrate roughened\\u000a and covered with CAM was observed by scanning electron

Yuji OhkuboIssei TsujiShogo Onishi; Issei Tsuji; Shogo Onishi; Kazufumi Ogawa

2010-01-01

97

Droplet detachment by air flow for microstructured superhydrophobic surfaces.  

PubMed

Quantitative correlation between critical air velocity and roughness of microstructured surface has still not been established systematically until the present; the dynamics of water droplet detachment by air flow from micropillar-like superhydrophobic surfaces is investigated by combining experiments and simulation comparisons. Experimental evidence demonstrates that the onset of water droplet detachment from horizontal micropillar-like superhydrophobic surfaces under air flow always starts with detachment of the rear contact lines of the droplets from the pillar tops, which exhibits a similar dynamic mechanism for water droplet motion under a gravity field. On the basis of theoretical analysis and numerical simulation, an explicit analytical model is proposed for investigating the detaching mechanism, in which the critical air velocity can be fully determined by several intrinsic parameters: water-solid interface area fraction, droplet volume, and Young's contact angle. This model gives predictions of the critical detachment velocity of air flow that agree well with the experimental measurements. PMID:23557076

Hao, Pengfei; Lv, Cunjing; Yao, Zhaohui

2013-04-17

98

Bioinspired superhydrophobic, self-cleaning and low drag surfaces  

NASA Astrophysics Data System (ADS)

Nature has evolved objects with desired functionality using commonly found materials. Nature capitalizes on hierarchical structures to achieve functionality. The understanding of the functions provided by objects and processes found in nature can guide us to produce nanomaterials, nanodevices, and processes with desirable functionality. This article provides an overview of four topics: (1) Lotus Effect used to develop superhydrophobic and self-cleaning/antifouling surfaces with low adhesion, (2) Shark Skin Effect to develop surfaces with low fluid drag and anti-fouling characteristics, and (3-4) Rice Leaf and Butterfly Wing Effect to develop superhydrophobic and self-cleaning surfaces with low drag. Rice Leaf and Butterfly Wings combine the Shark Skin and Lotus Effects.

Bhushan, Bharat

2013-09-01

99

Stable superhydrophobic surface: fabrication of interstitial cottonlike structure of copper nanocrystals by magnetron sputtering  

NASA Astrophysics Data System (ADS)

A stable superhydrophobic copper surface was obtained by radio-frequency magnetic sputtering on Si (100) and quartz substrates. The water contact angle and sliding angle of the superhydrophobic copper surface were 160.5° and 3±1.9°, respectively. Scanning electron microscopy (SEM) photos show that the superhydrophobic surface structure comprises many uniform nanocrystals with a diameter of about 100 nm. A brief explanation of the formation of this special microstructure and the mechanism of its wettability were proposed.

Li, Guoxing; Wang, Bo; Liu, Yi; Tan, Tian; Song, Xuemei; Li, Er; Yan, Hui

2008-04-01

100

Induced detachment of coalescing droplets on superhydrophobic surfaces.  

PubMed

Coalescence of a falling droplet with a stationary sessile droplet on a superhydrophobic surface is investigated by a combined experimental and numerical study. In the experiments, the droplet diameter, the impact velocity, and the distance between the impacting droplets were controlled. The evolution of surface shape during the coalescence of two droplets on the superhydrophobic surface is captured using high speed imaging and compared with numerical results. A two-phase volume of fluid (VOF) method is used to determine the dynamics of droplet coalescence, shape evaluation, and contact line movement. The spread length of two coalesced droplets along their original center is also predicted by the model and compared well with the experimental results. The effect of different parameters such as impact velocity, center to center distance, and droplet size on contact time and restitution coefficient are studied and compared to the experimental results. Finally, the wetting and the self-cleaning properties of superhydrophobic surfaces have been investigated. It has been found that impinging water drops with very small amount of kinetic impact energy were able to thoroughly clean these surfaces. PMID:22171956

Farhangi, Mehran M; Graham, Percival J; Choudhury, N Roy; Dolatabadi, Ali

2012-01-06

101

The synthesis of superhydrophobic Bi2S3 complex nanostructures  

Microsoft Academic Search

In this paper, we report a biomolecule-assisted soft chemistry route for constructing complex Bi2S3 nanostructures that exhibit controlled wetting behavior. The as-synthesized sample was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), field emission SEM (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FT-IR), Raman, x-ray photoelectron (XPS) and photoluminescence (PL). The Raman spectra indicate that

Yujiang Xiao; Huaqiang Cao; Kaiyu Liu; Sichun Zhang; Victoria Chernow

2010-01-01

102

Superhydrophobic/superhydrophilic surfaces from a carbon nanotube based composite coating  

NASA Astrophysics Data System (ADS)

A facile method for forming a MWNT-based composite coating with behavior of the superhydrophilic/superhydrophobic transition is demonstrated. The change of the surface microstructure and the surface chemical composition arising from increasing temperatures determines the surface wettability of the resulting composite coating. The coating surface shows the superhydrophobic property at 150, 200, and 360°, and displays superhydrophilic performance at 300°C.

Men, Xue-Hu; Zhang, Zhao-Zhu; Yang, Jin; Wang, Kun; Jiang, Wei

2010-02-01

103

Modeling Droplets on Superhydrophobic Surfaces:  Equilibrium States and Transitions  

Microsoft Academic Search

We present a lattice Boltzmann solution of the equations of motion describing\\u000athe spreading of droplets on topologically patterned substrates. We apply it to\\u000amodel superhydrophobic behaviour on surfaces covered by an array of\\u000amicron-scale posts. We find that the patterning results in a substantial\\u000aincrease in contact angle, from $110^o$ to $156^o$. The dynamics of the\\u000atransition from drops

A. Dupuis; J. M. Yeomans

2005-01-01

104

Programming nanostructured soft biological surfaces by atomic layer deposition.  

PubMed

Here, we present the first successful attempt to programme the surface properties of nanostructured soft biological tissues by atomic layer deposition (ALD). The nanopatterned surface of lotus leaf was tuned by 3-125 nm TiO2 thin films. The lotus/TiO2 composites were studied by SEM-EDX, XPS, Raman, TG-DTA, XRR, water contact angle and photocatalysis measurements. While we could preserve the superhydrophobic feature of lotus, we managed to add a new property, i.e. photocatalytic activity. We also explored how surface passivation treatments and various ALD precursors affect the stability of the sensitive soft biological tissues. As we were able to gradually change the number of nanopatterns of lotus, we gained new insight into how the hollow organic nanotubes on the surface of lotus influence its superhydrophobic feature. PMID:23680967

Szilágyi, Imre Miklós; Teucher, Georg; Härkönen, Emma; Färm, Elina; Hatanpää, Timo; Nikitin, Timur; Khriachtchev, Leonid; Räsänen, Markku; Ritala, Mikko; Leskelä, Markku

2013-05-16

105

Programming nanostructured soft biological surfaces by atomic layer deposition  

NASA Astrophysics Data System (ADS)

Here, we present the first successful attempt to programme the surface properties of nanostructured soft biological tissues by atomic layer deposition (ALD). The nanopatterned surface of lotus leaf was tuned by 3-125 nm TiO2 thin films. The lotus/TiO2 composites were studied by SEM-EDX, XPS, Raman, TG-DTA, XRR, water contact angle and photocatalysis measurements. While we could preserve the superhydrophobic feature of lotus, we managed to add a new property, i.e. photocatalytic activity. We also explored how surface passivation treatments and various ALD precursors affect the stability of the sensitive soft biological tissues. As we were able to gradually change the number of nanopatterns of lotus, we gained new insight into how the hollow organic nanotubes on the surface of lotus influence its superhydrophobic feature.

Miklós Szilágyi, Imre; Teucher, Georg; Härkönen, Emma; Färm, Elina; Hatanpää, Timo; Nikitin, Timur; Khriachtchev, Leonid; Räsänen, Markku; Ritala, Mikko; Leskelä, Markku

2013-06-01

106

PREFACE: Nanostructured surfaces  

NASA Astrophysics Data System (ADS)

We can define nanostructured surfaces as well-defined surfaces which contain lateral features of size 1-100 nm. This length range lies well below the micron regime but equally above the Ångstrom regime, which corresponds to the interatomic distances on single-crystal surfaces. This special issue of Journal of Physics: Condensed Matter presents a collection of twelve papers which together address the fabrication, characterization, properties and applications of such nanostructured surfaces. Taken together they represent, in effect, a status report on the rapid progress taking place in this burgeoning area. The first four papers in this special issue have been contributed by members of the European Research Training Network ‘NanoCluster’, which is concerned with the deposition, growth and characterization of nanometre-scale clusters on solid surfaces—prototypical examples of nanoscale surface features. The paper by Vandamme is concerned with the fundamentals of the cluster-surface interaction; the papers by Gonzalo and Moisala address, respectively, the optical and catalytic properties of deposited clusters; and the paper by van Tendeloo reports the application of transmission electron microscopy (TEM) to elucidate the surface structure of spherical particles in a catalyst support. The fifth paper, by Mendes, is also the fruit of a European Research Training Network (‘Micro-Nano’) and is jointly contributed by three research groups; it reviews the creation of nanostructured surface architectures from chemically-synthesized nanoparticles. The next five papers in this special issue are all concerned with the characterization of nanostructured surfaces with scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). The papers by Bolotov, Hamilton and Dunstan demonstrate that the STM can be employed for local electrical measurements as well as imaging, as illustrated by the examples of deposited clusters, model semiconductor structures and real devices, respectively, while the papers by Ledieu and Guo report the structural characterization of novel surface systems—quasicrystal surfaces and supramolecular monolayers, respectively. The final two papers, by Bennett and Smith, demonstrate the positive interplay between experimental measurements and theoretical modelling in the investigation of nanostructured surfaces. The examples discussed include, respectively, the growth of metal clusters on oxide surfaces and the deposition of fullerenes and energetic clusters from the gas phase. We note finally that the last six papers in this special issue have been contributed by members of the Committee of the newly-formed Nanoscale Physics and Technology Group of the Institute of Physics. The Group shares with this special issue the aim of promoting and disseminating exciting advances in the flourishing field of nanoscale physics.

Palmer, Richard E.

2003-10-01

107

Frost formation on a super-hydrophobic surface under natural convection conditions  

Microsoft Academic Search

In this paper, the frost deposition phenomena on a cold super-hydrophobic surface whose contact angle with water is 162° were observed of the formation of water droplets, the freezing process, the formation of initial frost crystals and the frost layer structure. The frost layer structure formed on the super-hydrophobic surface shows remarkable differences to that on a plain copper surface:

Zhongliang Liu; Yunjun Gou; Jieteng Wang; Shuiyuan Cheng

2008-01-01

108

Comparison of Three Methods for Generating Superhydrophobic, Superoleophobic Nylon Nonwoven Surfaces (Postprint).  

National Technical Information Service (NTIS)

This research deals with creating a superhydrophobic/superoleophobic surface by preparing a metastable Cassie -Baxter (CB) surface. To create a CB surface it is essential to have low surface energy and properly constructed surface morphology. We have expl...

C. Willis H. J. Lee J. R. Owens R. Saraf S. Michielsen

2011-01-01

109

Fabrication of super-hydrophobic channels  

Microsoft Academic Search

A new approach was developed in this work to create channels which had not only super-hydrophobic bottom surfaces but also super-hydrophobic sidewalls. Researchers have demonstrated that a flow experienced less drag forces and thus required smaller driving pressure in a channel of micro\\/nanostructure-formed top and bottom surfaces. The drag forces should be further reduced in a channel which has not

Xinchuan Liu; Cheng Luo

2010-01-01

110

Contact angle, adhesion and friction properties of micro-and nanopatterned polymers for superhydrophobicity  

Microsoft Academic Search

Superhydrophobic surfaces have considerable technological potential for various applications due to their extreme water-repellent properties. A number of studies have been carried out to produce artificial biomimetic roughness-induced hydrophobic surfaces. It is not clear whether microstructures or nanostructures or their certain combination on the surface, are required for superhydrophobicity. A variety of micro- and nanopatterned surfaces of two different polymers,

Yong Chae Jung; Bharat Bhushan

2006-01-01

111

Spectral tuning of liquid microdroplets standing on a superhydrophobic surface using electrowetting  

Microsoft Academic Search

Using electrowetting, we demonstrate reversible spectral tuning of the whispering gallery modes of glycerol\\/water microdroplets standing on a superhydrophobic surface by up to 4.7 nm at 400 V. Our results can inspire electrically tunable optical switches and filters based on microdroplets on a superhydrophobic surface. The sensitivity of the observed spectral drift to the contact angle can also be used

A. Kiraz; Y. Karadag; A. F. Coskun

2008-01-01

112

Fabrication and characterization of a cotton candy like surface with superhydrophobicity  

NASA Astrophysics Data System (ADS)

Superhydrophobic thin films were prepared on glass by air-brushing the in situ polymerization compositions of D 5/SiO 2. The wettability and morphology were investigated by contact angle measurement and scanning electron microscopy. The most superhydrophobic samples prepared had a static water contact angle of 157° for a 5 ?l droplet and a sliding angle of ˜1° for 10 ?l droplet. Thermal stability analysis showed that the surface maintained superhydrophobic at temperature up to 450 °C. Air trapping and capillary force on superhydrophobic behavior were evaluated.

Hu, You; Huang, Chengya; Su, Dong; Jiang, Qiangwei; Zhu, Yunfeng

2011-05-01

113

Learning from superhydrophobic plants: the use of hydrophilic areas on superhydrophobic surfaces for droplet control.  

PubMed

In many countries, the mornings in spring are graced with spectacular displays of dew drops hanging on spiders' webs and on leaves. Some leaves, in particular, sport particularly large droplets that last well into the morning. In this paper, we study a group of plants that show this effect on their superhydrophobic leaves to try to discover how and why they do it. We describe the structures they use to gather droplets and suggest that these droplets are used as a damper to absorb kinetic energy allowing water to be redirected from sideways motion into vertical motion. Model surfaces in the shape of leaves and as more general flat sheets show that this principle can be used to manipulate water passively, such as on the covers of solar panels, and could also be used in parts of microfluidic devices. The mode of transport can be switched between rolling droplets and rivulets to maximize control. PMID:20560556

Shirtcliffe, N J; McHale, G; Newton, M I

2009-12-15

114

Wetting, adhesion and friction of superhydrophobic and hydrophilic leaves and fabricated micro\\/nanopatterned surfaces  

Microsoft Academic Search

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

Bharat Bhushan; Yong Chae Jung

2008-01-01

115

Rebound behaviors of droplets impacting on a superhydrophobic surface  

NASA Astrophysics Data System (ADS)

The rebound behaviors of droplets impacting on a self-fabricated superhydrophobic brass surface (WCA=164.5°) were observed and studied by using high-speed-camera. In accordance with energy conversion, theoretical analysis of different behaviors and rebound mechanism were given. At lower velocities, three behaviors in different velocity ranges were observed: partial rebounding, entire rebounding and ejecting during rebounding. At higher velocities, such two behaviors as rebound after splashing and rebound, ejecting after splashing, occurred alternately and exhibited certain periodicity. A function to predict the critical impact velocity is derived from energy conservation condition, and the prediction values tally with the experimental values, with the maximum relative error about 14%.

Hu, HaiBao; Chen, LiBin; Huang, SuHe; Song, BaoWei

2013-05-01

116

Grazing impact of continuous droplet streams with a superhydrophobic surface  

NASA Astrophysics Data System (ADS)

When high-velocity droplets make grazing impact with a superhydrophobic surface, the droplets undergo significant deformation before recoiling and rebounding from the surface. Two distinct operating regimes describe the response of the reflected droplet stream after impact. In the first regime, the droplets remain discrete and uniform after the impact, but exhibit rotation and significant oscillations. This regime dominates if each droplet can clear the impact region before the next droplet arrives. In the second regime, droplets cannot avoid coalescing into a puddle at the surface. A secondary jet is ejected from the puddle which breaks up into a random droplet stream after traveling a short distance due to the lack of a forced unstable perturbation. The droplet-to-droplet spacing in the incoming stream determines which regime rules, with the critical value correlated by a Weber number. In the first regime, a detailed accounting of the kinetic and potential energies reveals that neither droplet oscillation nor rotation can fully account for the loss of translational kinetic energy, indicating significant internal circulation must occur in the droplets at impact. An application of droplet rebound from a superhydrophobic surface is proposed.

Chiarot, Paul R.; Jones, T. B.

2010-11-01

117

Characterization of Superhydrophobic Surfaces for Anti-icing in a Low-Temperature Wind Tunnel  

SciTech Connect

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 adhesion 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.

Swarctz, Christopher [Stevens Institute of Technology, Hoboken, New Jersey; Alijallis, Elias [Stevens Institute of Technology, Hoboken, New Jersey; Hunter, Scott Robert [ORNL; Simpson, John T [ORNL; Choi, Chang-Hwan [Stevens Institute of Technology, Hoboken, New Jersey

2010-01-01

118

Dewetting Transitions on Superhydrophobic Surfaces: When are Wenzel Drops Reversible?  

SciTech Connect

On superhydrophobic surfaces, drops in theWenzel state can be switched to the suspended Cassie state in some cases, but in other cases are irreversibly impaled in the surface roughness. To date, the question of when dewetting transitions are possible for Wenzel drops has not been resolved. Here, we show that pinned Wenzel drops being stretched out-of-plane cannot reduce their contact angle below a critical value where unstable pinch-off occurs, preventing dewetting for Wenzel drops which exhibit receding contact angles beneath this critical pinchoff angle. Dewetting transitions are therefore only possible for Wenzel drops with moderately large receding contact angles, which requires low surface roughness for one-tier surfaces or a Partial Wenzel wetting state for two-tier surfaces.

Boreyko, Jonathan B [ORNL; Collier, Pat [ORNL

2013-01-01

119

Simulations of Turbulence over Superhydrophobic Surfaces  

Microsoft Academic Search

Significant effort has been placed on the development of surfaces which reduce the amount of drag experienced by a fluid as it passes over the surface. Alterations to the fluid itself, as well as the chemical and physical composition of the surface have been investigated with varying success. Investigations into turbulent drag reduction have been mostly limited to those involving

Michael B Martell

2009-01-01

120

Corrosion resistance properties of superhydrophobic copper surfaces fabricated by one-step electrochemical modification process  

NASA Astrophysics Data System (ADS)

Superhydrophobic copper surfaces have been prepared by a one-step electrochemical modification process in an ethanolic stearic acid solution. In this work, the corrosion properties of hydrophobic copper surface and superhydrophobic copper surfaces were analyzed by means of electrochemical analyses and compared with that of as-received bare copper substrate. The decrease of corrosion current density (icorr) as well as the increase of polarization resistance (Rp) obtained from potentiodynamic polarization curves revealed that the superhydrophobic film on the copper surfaces improved the corrosion resistance performance of the copper substrate.

Huang, Ying; Sarkar, D. K.; Gallant, Danick; Chen, X.-Grant

2013-10-01

121

Formation of superhydrophobic soda-lime glass surface using femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

This paper demonstrates the fabrication of superhydrophobic soda-lime glass surface by engineering periodic microgratings with self-formed periodic micro-ripples inside the microgratings using a single beam femtosecond laser. The wetting property of the microstructured surface is improved from hydrophobic to superhydrophobic, presenting a water droplet contact angle ranges from 152° to 155°. The microstructured glass surface shows excellent transparency, which is higher than 77% in the visible spectrum. We strongly believe that our proposed technology can achieve superhydrophobic glass surfaces over a large area for applications in diverse fields.

Ahsan, Md. Shamim; Dewanda, Fadia; Lee, Man Seop; Sekita, Hitoshi; Sumiyoshi, Tetsumi

2013-01-01

122

A strategy of fast reversible wettability changes of WO 3 surfaces between superhydrophilicity and superhydrophobicity  

Microsoft Academic Search

As-prepared WO3 nanostructure films on alumina or tungsten substrates by a facile hydrothermal method exhibit a superhydrophilic property. An effective strategy is proposed to control the wettability of WO3 films in a reversible manner between superhydrophilicity and superhydrophobicity with a rapid response. By controlling the process of adsorption\\/desorption of n-dodecanethiol associated with the light-induced plating Ag nano-grains on WO3 nanostructures,

Changdong Gu; Jun Zhang; Jiangping Tu

2010-01-01

123

Fabrication of superhydrophobic surface from binary micro-/nano-structure of mullite-whisk-based films  

NASA Astrophysics Data System (ADS)

The wettability of solid surface is a very important property of materials, which depends on both surface chemical composition and the geometry of the solid surface. We herein report a simple and inexpensive method to fabricate superhydrophobic surfaces with the use of mullite whisks (MWs) for the first time. Binary micro-/nano-structural surfaces were created by the incorporation of hydrophilic needlelike MWs with poly(?-methacryloxypropyltrimethoxysilane) to exhibit hydrophobic behavior, which further showed superhydrophobicity with water contact angle of 152.4±2? after modified with stearic acid. The wettability variation from hydrophilicity to hydrophobicity and superhydrophobicity during the assembly process are discussed based on the scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and contact-angle system. The superhydrophobicity of the surface could be attributed to the hierarchical microstructure of the rough surface induced by MWs and low surface energy of stearic acid.

Deng, Zhengyan; Yin, Yongjin; Yang, Shengyang; Wang, Cai-Feng; Chen, Su

2013-04-01

124

Roughness optimization for biomimetic superhydrophobic surfaces  

Microsoft Academic Search

For non-wetting liquids the contact angle with a rough surface is greater than with a flat surface and may approach 180°, as reported for leaves of water-repellent plants, such as lotus. Roughness affects the contact angle due to the increased area of solid–liquid interface and due to the effect of sharp edges of rough surfaces. High roughness may lead to

Michael Nosonovsky; Bharat Bhushan

2005-01-01

125

Superhydrophobic Zr-based metallic glass surface with high adhesive force  

NASA Astrophysics Data System (ADS)

Micro/nano hierarchical structures were constructed on Zr35Ti30Be26.75Cu8.25 metallic glass surface by silicon moulding and subsequently chemical etching. The as-formed surface exhibited both superhydrophobicity and high adhesive force towards water. The superhydrophobicity is rationalized based on the modified Cassie-Baxter model [A. B. D. Cassie and S. Baxter, Trans. Faraday Soc. 40, 546 (1944)]. The origin of the robust adhesion is described in terms of intermolecular capillary forces. The present results not only provide a method to fabricate superhydrophobic metallic glasses surface but also explore an important industrial application as dry adhesives and transport of liquid microdroplets.

Li, Ning; Xia, Ting; Heng, Liping; Liu, Lin

2013-06-01

126

Superhydrophobic surfaces by replication of micro/nano-structures fabricated by ultrafast-laser-microtexturing  

NASA Astrophysics Data System (ADS)

We report a simple and inexpensive method of producing superhydrophobic surfaces by directly replicating micro/nano-structures on to poly(dimethylsiloxane) (PDMS) from a replication master prepared by ultrafast-laser microtexturing process. No additional coatings on PDMS have been required to achieve contact angles greater than 154°. The contact angle can be controlled by changing the height of the microtextures in PDMS. Very low optical reflection properties of micro/nano textured surfaces combined with superhydrophobic characteristics make it an attractive encapsulating material for photovoltaics and other applications. Additionally, this replication method can be applied for large scale production of micro/nano textured superhydrophobic surfaces for commercial applications.

Nayak, Barada K.; Caffrey, Paul O.; Speck, Christian R.; Gupta, Mool C.

2013-02-01

127

Facile fabrication of superhydrophobic ZnO nanoparticle surfaces with erasable and rewritable wettability  

NASA Astrophysics Data System (ADS)

In this article, ZnO nanoparticle surfaces have been fabricated successfully by a simple spray-coating method without limitations the shape and size of substrates. After being chemically modified with stearic acid, the wettability of ZnO surfaces changed from superhydrophilicity to superhydrophobicity. Furthermore, the superhydrophobicity could be erased and rewrote by the alternation of plasma or heat treatment and stearic acid coating. The process has been repeated with full reproducibility more than eight times, demonstrating that the ZnO surfaces exhibit good erasable and rewritable superhydrophobicity.

Li, Jian; Wan, Hongqi; Liu, Xiaohong; Ye, Yinping; Zhou, Huidi; Chen, Jianmin

2012-09-01

128

Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention  

PubMed Central

Summary Superhydrophobic surfaces of plants and animals are of great interest for biomimetic applications. Whereas the self-cleaning properties of superhydrophobic surfaces have been extensively investigated, their ability to retain an air film while submerged under water has not, in the past, received much attention. Nevertheless, air retaining surfaces are of great economic and ecological interest because an air film can reduce friction of solid bodies sliding through the water. This opens perspectives for biomimetic applications such as low friction fluid transport or friction reduction on ship hulls. For such applications the durability of the air film is most important. While the air film on most superhydrophobic surfaces usually lasts no longer than a few days, a few semi-aquatic plants and insects are able to hold an air film over a longer time period. Currently, we found high air film persistence under hydrostatic conditions for the elytra of the backswimmer Notonecta glauca which we therefore have chosen for further investigations. In this study, we compare the micro- and nanostructure of selected body parts (sternites, upper side of elytra, underside of elytra) in reference to their air retaining properties. Our investigations demonstrate outstanding air film persistence of the upper side of the elytra of Notonecta glauca under hydrostatic and hydrodynamic conditions. This hierarchically structured surface was able to hold a complete air film under hydrostatic conditions for longer than 130 days while on other body parts with simple structures the air film showed gaps (underside of elytra) or even vanished completely after a few days (sternites). Moreover, the upper side of the elytra was able to keep an air film up to flow velocities of 5 m/s. Obviously the complex surface structure with tiny dense microtrichia and two types of larger specially shaped setae is relevant for this outstanding ability. Besides high air film persistence, the observation of a considerable fluid velocity directly at the air–water interface indicates the ability to reduce friction significantly. The combination of these two abilities makes these hierarchically structured surfaces extremely interesting as a biomimetic model for low friction fluid transport or drag reduction on ship hulls.

Schneider, Erik S; Melskotte, Jan-Erik; Brede, Martin; Leder, Alfred

2011-01-01

129

Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention.  

PubMed

Superhydrophobic surfaces of plants and animals are of great interest for biomimetic applications. Whereas the self-cleaning properties of superhydrophobic surfaces have been extensively investigated, their ability to retain an air film while submerged under water has not, in the past, received much attention. Nevertheless, air retaining surfaces are of great economic and ecological interest because an air film can reduce friction of solid bodies sliding through the water. This opens perspectives for biomimetic applications such as low friction fluid transport or friction reduction on ship hulls. For such applications the durability of the air film is most important. While the air film on most superhydrophobic surfaces usually lasts no longer than a few days, a few semi-aquatic plants and insects are able to hold an air film over a longer time period. Currently, we found high air film persistence under hydrostatic conditions for the elytra of the backswimmer Notonecta glauca which we therefore have chosen for further investigations. In this study, we compare the micro- and nanostructure of selected body parts (sternites, upper side of elytra, underside of elytra) in reference to their air retaining properties. Our investigations demonstrate outstanding air film persistence of the upper side of the elytra of Notonecta glauca under hydrostatic and hydrodynamic conditions. This hierarchically structured surface was able to hold a complete air film under hydrostatic conditions for longer than 130 days while on other body parts with simple structures the air film showed gaps (underside of elytra) or even vanished completely after a few days (sternites). Moreover, the upper side of the elytra was able to keep an air film up to flow velocities of 5 m/s. Obviously the complex surface structure with tiny dense microtrichia and two types of larger specially shaped setae is relevant for this outstanding ability. Besides high air film persistence, the observation of a considerable fluid velocity directly at the air-water interface indicates the ability to reduce friction significantly. The combination of these two abilities makes these hierarchically structured surfaces extremely interesting as a biomimetic model for low friction fluid transport or drag reduction on ship hulls. PMID:21977425

Ditsche-Kuru, Petra; Schneider, Erik S; Melskotte, Jan-Erik; Brede, Martin; Leder, Alfred; Barthlott, Wilhelm

2011-03-10

130

Wear-resistant rose petal-effect surfaces with superhydrophobicity and high droplet adhesion using hydrophobic and hydrophilic nanoparticles.  

PubMed

Surfaces exhibiting the so-called "petal effect" (superhydrophobicity with high droplet adhesion) have potential for applications such as the transport of small volumes of liquid. It is known that the microstructure pitch value and nanostructure density are important in achieving this effect, both in rose petals themselves and in synthetic petal-effect surfaces. However, the effect of the surface energy of materials on these values has not been systematically studied. In addition, wear resistance, which is critical for industrial applications, has rarely been examined for petal-effect surfaces. In this study, surfaces of varying microstructure pitch and nanostructure density were fabricated by depositing ZnO nanoparticles onto micropatterned substrates. The prepared surfaces were then modified with octadecylphosphonic acid (ODP) in order to hydrophobize the ZnO nanoparticles. The wettability of the surfaces was characterized both before and after ODP modification. The effect of hydrophobizing the nanostructure was examined with regards to the values of microstructure pitch and nanostructure density necessary to achieve the petal effect. In addition, to study wear resistance for industrial applications, a wear experiment was performed using an atomic force microscope (AFM). PMID:22818796

Ebert, Daniel; Bhushan, Bharat

2012-07-04

131

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

NASA Astrophysics Data System (ADS)

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.

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

2013-01-01

132

Novel liquid-solid adhesion superhydrophobic surface fabricated using titanium dioxide and trimethoxypropyl silane  

NASA Astrophysics Data System (ADS)

The present paper reports the preparation of very simple and inexpensive superhydrophobic surfaces fabricated using titanium dioxide and lower alkyl chain silane (trimethoxypropyl silane) in aqueous or non-aqueous solvent. The superhydrophobic surfaces fabricated in aqueous or non-aqueous solvent had same static water contact angle, but showed different contact angle hysteresis and liquid-solid adhesion. Superhydrophobic surface fabricated in aqueous solvent showed high contact angle hysteresis (CAH). In addition, liquid-solid adhesion of superhydrophobic surface fabricated in aqueous solvent is different in which the water droplet roll on the surface but will not roll off out of the surface during tilting and fell down when turned upside down. The reason for such high contact angle hysteresis and novel liquid-solid adhesion behavior is explained on the basis of measurements on the superhydrophobic surface using water contact angle (WCA) data, profilometry, SEM images, XPS and FTIR-ATR analysis. These results are compared with the superhydrophobic surface fabricated in non-aqueous solvent which showed self-cleaning properties. Based on WCA, XPS and FTIR-ATR analysis, it is shown that the difference in the CAH is more chemical in origin than morphology.

Ramanathan, Rajajeyaganthan; Weibel, Daniel E.

2012-08-01

133

Super-hydrophobic surfaces from a simple coating method: a bionic nanoengineering approach  

Microsoft Academic Search

Inspired by the self-cleaning behaviour of lotus leaves in nature, we developed a simple coating method that can facilitate the bionic creation of super-hydrophobic surfaces on various substrates, thus providing a feasible way of fabricating super-hydrophobic surfaces for civil and industrial applications. Micro-nanoscale binary structured composite particles of silica\\/fluoropolymer were prepared using an emulsion-mediated sol-gel process, and then these composite

Yuyang Liu; Xianqiong Chen; J. H. Xin

2006-01-01

134

Recent developments in superhydrophobic surfaces and their relevance to marine fouling: a review  

Microsoft Academic Search

In this review, a brief synopsis of superhydrophobicity (i.e. extreme non-wettability) and its implications on marine fouling are presented. A short overview of wettability and recent experimental developments aimed at fabricating superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e. substratum texture) are reviewed. The formation of responsive\\/“smart” surfaces, which adjust their physico-chemical properties to variations in some

Jan Genzer; Kirill Efimenko

2006-01-01

135

Targets on superhydrophobic surfaces for laser ablation ion sources  

NASA Astrophysics Data System (ADS)

Target preparation techniques for a laser ablation ion source at the Penning-trap mass spectrometer TRIGA-TRAP have been investigated with regard to future experiments with actinides. To be able to perform mass measurements on these nuclides considering their limited availability, an efficient target preparation technique is mandatory. Here, we report on a new approach for target production using backings, which are pretreated in a way that a superhydrophobic surface is formed. This resulted in improved targets with a more homogeneous distribution of the target material compared to standard techniques with unmodified backings. It was demonstrated that the use of these new targets in a laser ablation ion source improved the ion production significantly.

Renisch, D.; Beyer, T.; Blaum, K.; Block, M.; Düllmann, Ch. E.; Eberhardt, K.; Eibach, M.; Nagy, Sz.; Neidherr, D.; Nörtershäuser, W.; Smorra, C.

2012-06-01

136

Bouncing of a Droplet on Superhydrophobic Surface in AC Electrowetting  

NASA Astrophysics Data System (ADS)

Oscillation of a droplet is induced in ac electrowetting by time-dependent electrical wetting tension. A droplet placed on a superhydrophobic surface bounces up like a rubber ball when an ac signal is applied. The bouncing pattern is highly frequency dependent. We investigated how the shape deformation and bouncing of a droplet are affected by applied frequency. The droplet motion is analyzed with the spectral method. The droplet is modeled as a simple linear oscillator, and the mass and spring constants are determined based on analytical results. We found that bouncing occurs periodically at a resonance frequency of the droplet. The motion of a sessile droplet released from a fixed shape is analyzed based on the phase field method. The numerical results show qualitative agreement with the experimental results for a bouncing droplet. Details on the flow field inside a bouncing droplet will be discussed based on numerical results.

Kang, Kwan Hyoung; Lee, Seung Jun; Hong, Jiwoo

2009-11-01

137

Flame soot stably deposited on silicone coatings possess superhydrophobic surface  

NASA Astrophysics Data System (ADS)

A flame soot deposited silicone coating was successfully prepared by butane flame along with a deposition process of flame soot. Field emission scanning electron microscopy equipped with an energy-dispersive X-ray analyzer and X-ray photoelectron spectroscopy were used to analyze the chemical compositions and structure of flame soot, showing that the surface is mainly composed of carbon nanoparticles being closely packed and forming tree branch-like network with micro- and nanoscale roughness. Meanwhile, the flame soot can stably deposit on the silicone coatings during the water-flow impact test. When the deposition time is 20 s, the silicone coating possesses a water contact angle of 168 ± 2° combining with a sliding angle less than 1°, and a transmittance reduced less than 28% for wavelengths above 500 nm compared to glass substrate. The superhydrophobicity has a little increase with the extension of deposition time, but at the expense of transmittance.

Shen, Lie; Wang, Wen; Ding, Hongliang; Guo, Qipeng

2013-11-01

138

Self-cleaning superhydrophobic surface based on titanium dioxide nanowires combined with polydimethylsiloxane  

NASA Astrophysics Data System (ADS)

The present work describes a simple dipping process for the preparation of superhydrophobic coatings based on titanium dioxide nanowires combined with polydimethylsiloxane. The coating surface morphology, composition and wettability were investigated by scanning electron microscope, X-ray photoelectron spectroscope and contact angle measurements, respectively. Interestingly, the superhydrophobic coatings turn into a hydrophilic one after UV irradiation. It is found that the superhydrophobic surface shows almost complete wet self-cleaning of dirt particles with water droplets. Furthermore, the coating surface shows the anti-fouling performance for organic solvents, which can self-remove the organic solvents layer and recovers its superhydrophobic behavior. The advantage of the present approach is that the damaged coating can be easily repaired.

Zhang, Xia; Guo, Yonggang; Zhang, Zhijun; Zhang, Pingyu

2013-11-01

139

Flow past superhydrophobic surfaces with cosine variation in local slip length  

NASA Astrophysics Data System (ADS)

Anisotropic superhydrophobic surfaces have the potential to greatly reduce drag and enhance mixing phenomena in microfluidic devices. Recent work has focused mostly on cases of superhydrophobic stripes. Here, we analyze a relevant situation of cosine variation of the local slip length. We derive approximate formulas for maximal (longitudinal) and minimal (transverse) directional effective slip lengths that are in good agreement with the exact numerical solution and lattice-Boltzmann simulations. Compared to the case of superhydrophobic stripes, the cosine texture can provide a very large effective slip. However, the difference between eigenvalues of the slip-length tensor is smaller, indicating that the flow is less anisotropic.

Asmolov, Evgeny S.; Schmieschek, Sebastian; Harting, Jens; Vinogradova, Olga I.

2013-02-01

140

TOPICAL REVIEW: Magnetic surface nanostructures  

NASA Astrophysics Data System (ADS)

Recent trends in the emerging field of surface-supported magnetic nanostructures are reviewed. Current strategies for nanostructure synthesis are summarized, followed by a predominantly theoretical description of magnetic phenomena in surface magnetic structures and a review of experimental research in this field. Emphasis is on Fe- or Co-based nanostructures in various low-dimensional geometries, which are studied as model systems to explore the effects of dimensionality, atomic coordination, chemical bonds, alloying and, most importantly, interactions with the supporting substrate on the magnetism. This review also includes a discussion of closely related systems, such as 3d element impurities integrated into organic networks, surface-supported Fe-based molecular magnets, Kondo systems or 4d element nanostructures that exhibit emergent magnetism, thereby bridging the traditional areas of surface science, molecular physics and nanomagnetism.

Enders, A.; Skomski, R.; Honolka, J.

2010-11-01

141

Toward understanding whether superhydrophobic surfaces can really decrease fluidic friction drag.  

PubMed

Superhydrophobic surfaces in nature such as legs of water striders can get an extra supporting force from the deformed water surface they contact, leading to an anticipation of using water-repellent surfaces on ship and even submarine hulls to reduce friction drag. Here, we first fabricate superhydrophobic coatings with microstructures on glass balls by introducing hydrophobic silica nanoparticles into a polyethylene terephthalate (PET) film. Then, the movement of a superhydrophobic ball on and below water surface is investigated and compared with that of a highly hydrophilic normal glass ball. The results reveal that a superhydrophobic ball can fall more slowly under water compared with a normal glass ball, because the dense microbubbles trapped at the solid/water interface around the superhydrophobic ball act not as a reducer, but as an enhancer for the friction drag. In contrast, the faster movement of a superhydrophobic ball on the water surface can be mainly attributed to the great reduction of skin friction owing to the increased area of the solid/atmosphere interface. PMID:20000363

Su, Bin; Li, Mei; Lu, Qinghua

2010-04-20

142

In situ surface-modification-induced superhydrophobic patterns with reversible wettability and adhesion.  

PubMed

Herein is described a facile, in situ, ink-regulating approach to rapidly achieve reversible water wettability and adhesion transition, with a large degree of contrast, on superhydrophobic TiO2 nanotube array film. The ink printing and removal process allows the wettability and reversible adhesion transitions to be realized. Experimental results demonstrate the potential application of such site-selective, sticky superhydrophobic patterns for droplet manipulation by in situ surface modification. PMID:23208816

Lai, Yuekun; Pan, Fei; Xu, Cong; Fuchs, Harald; Chi, Lifeng

2012-12-03

143

Preparation of superhydrophobic nanodiamond and cubic boron nitride films  

SciTech Connect

Superhydrophobic surfaces were achieved on the hardest and the second hardest materials, diamond and cubic boron nitride (cBN) films. Various surface nanostructures of nanocrystalline diamond (ND) and cBN films were constructed by carrying out bias-assisted reactive ion etching in hydrogen/argon plasmas; and it is shown that surface nanostructuring may enhance dramatically the hydrophobicity of ND and cBN films. Together with surface fluorination, superhydrophobic ND and cBN surfaces with a contact angle greater than 150 deg. and a sliding angle smaller than 10 deg. were demonstrated. The origin of hydrophobicity enhancement is discussed based on the Cassie model.

Zhou, Y. B.; Liu, W. M.; Wang, P. F. [Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Yang, Y.; Ye, Q.; He, B.; Pan, X. J.; Zhang, W. J.; Bello, I.; Lee, S. T. [Department of Physics and Materials Sciences, Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong (Hong Kong); Zou, Y. S. [Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

2010-09-27

144

Preparation of superhydrophobic nanodiamond and cubic boron nitride films  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces were achieved on the hardest and the second hardest materials, diamond and cubic boron nitride (cBN) films. Various surface nanostructures of nanocrystalline diamond (ND) and cBN films were constructed by carrying out bias-assisted reactive ion etching in hydrogen/argon plasmas; and it is shown that surface nanostructuring may enhance dramatically the hydrophobicity of ND and cBN films. Together with surface fluorination, superhydrophobic ND and cBN surfaces with a contact angle greater than 150° and a sliding angle smaller than 10° were demonstrated. The origin of hydrophobicity enhancement is discussed based on the Cassie model.

Zhou, Y. B.; Yang, Y.; Liu, W. M.; Ye, Q.; He, B.; Zou, Y. S.; Wang, P. F.; Pan, X. J.; Zhang, W. J.; Bello, I.; Lee, S. T.

2010-09-01

145

Study on Super-Hydrophobic and Oleophobic Surfaces Prepared by Chemical Adsorption Technique  

NASA Astrophysics Data System (ADS)

Preparation techniques for super-hydrophobic and oleophobic surfaces were studied by forming a fractally roughened surface and preparing a hydrophobic monolayer. In this study, the fractal structure on the surface of an aluminum substrate was formed by combining sand-blasting with electrolytical etching. Then, a hydrophobic monolayer was prepared on the roughened surface, without decreasing roughness. The surface of the treated substrate can be evaluated by contact angle measurement and field emission scanning electron microscopy (FE-SEM). The surface treated by a technique combining chemical adsorption, sandblasting, and electrolytical etching was super-hydrophobic and highly oleophobic.

Tsuji, Issei; Ohkubo, Yuji; Ogawa, Kazufumi

2009-04-01

146

Study on Super-Hydrophobic and Oleophobic Surfaces Prepared by Chemical Adsorption Technique  

Microsoft Academic Search

Preparation techniques for super-hydrophobic and oleophobic surfaces were studied by forming a fractally roughened surface and preparing a hydrophobic monolayer. In this study, the fractal structure on the surface of an aluminum substrate was formed by combining sand-blasting with electrolytical etching. Then, a hydrophobic monolayer was prepared on the roughened surface, without decreasing roughness. The surface of the treated substrate

Issei Tsuji; Yuji Ohkubo; Kazufumi Ogawa

2009-01-01

147

Nanoparticle-Based Surface Modifications for Microtribology Control and Superhydrophobicity  

NASA Astrophysics Data System (ADS)

The emergence of miniaturization techniques for consumer electronics has brought forth the relatively new and exciting field of microelectromechanical systems (MEMS). However, due to the inherent forces that exist between surfaces at the micro- and nanoscale, scientists and semiconductor manufacturers are still struggling to improve the lifetime and reliability of complex microdevices. Due to the extremely large surface area-to-volume ratio of typical MEMS and microstructured surfaces, dominant interfacial forces exist which can be detrimental to their operational lifetime. In particular, van der Waals, capillary, and electrostatic forces contribute to the permanent adhesion, or stiction , of microfabricated surfaces. This strong adhesion force also contributes to the friction and wear of these silicon-based systems. The scope of this work was to examine the effect of utilizing nanoparticles as the basis for roughening surfaces for the purpose of creating films with anti-adhesive and/or superhydrophobic properties. All of the studies presented in this work are focused around a gas-expanded liquid (GXL) process that promotes the deposition of colloidal gold nanoparticles (AuNPs) into conformal thin films. The GXL particle deposition process is finalized by a critical point drying step which is advantageous to the microelectromechanical systems and semiconductor (IC) industries. In fact, preliminary results illustrated that the GXL particle deposition process can easily be integrated into current MEMS microfabrication processes. Thin films of AuNPs deposited onto the surfaces of silicon-based MEMS and tribology test devices were shown to have a dramatic effect on the adhesion of microstructures. In the various investigations, the apparent work of adhesion between surfaces was reduced by 2-4 orders of magnitude. This effect is greatly attributed to the roughening of the typically smooth silicon oxide surfaces which, in turn, dramatically decreases the "real are of contact" between two contacting surfaces. The studies found that AuNP thin films produced using the lowest initial concentrations of nanoparticles in solution produced estimated real contact areas of around 1%, reducing the adhesion of oxidized Si (100) surfaces from about 37 mJ/m2 down to 0.02 mJ/m 2. In addition, the reducing in real contact area effectively reduced the coefficient of static friction between silicon-based surfaces due to the extremely high dependence of stiction on friction and wear at the microscale. This work also investigated methods of permanently immobilizing AuNP-based films on the silicon surfaces of microstructures in order to create more mechanically robust coatings. The use of organic self-assembled monolayers (SAMs) functionalized with tail-groups known to bond to metallic surfaces were effective in producing much more durable coatings as opposed to non-immobilized AuNP films. Chemical vapor deposition (CVD) techniques were also used to coat rough AuNP films with very thin films of silica (SiO2) to create a robust, rough surface. This method was also very effective in creating a durable coating which is capable of reducing the adhesion energy and friction between two microscale surfaces for extended periods of time. Similar CVD techniques were also used to begin investigating the production of alumina nanoparticle-based superhydrophobic films for use in consumer electronics. Overall, the work presented in this dissertation illustrates that engineered nanoparticle-based surface modifications can be extremely effective in the reduction of the inherent interfacial phenomena that exist on microfabricated systems. This work is can potentially lead us into a new age of the miniaturization of mechanical and electronic devices.

Hurst, Kendall Matthew

148

Superhydrophobic iron material surface with flower-like structures obtained by a facile self-assembled monolayer  

NASA Astrophysics Data System (ADS)

A simple and economical route based on a K2CO3 mediated process was developed to synthesize three-dimensional (3D) flower-like Fe3O4 micro/nanoflakes on the surface of iron plates by a direct in-situ hydrothermal synthesis method. The prepared micro/nanoflakes were characterized by X-ray diffraction and scanning electron microscopy. It was found that the width of the nanoflakes ranges from 50 to 100 nm, and the length of the flakes is about 3 ?m. The morphology of Fe3O4 nanostructures can be tuned from simple isolated nanoflakes to the ordered 3D flower-like shape by increasing the reaction temperature. The wettability of the surface with 3D flower-like micro/nanoflakes was changed from hydrophilicity to superhydrophobicity by chemical modification with vinyl tirethoxy-silane. The static contact angles for water on both of the modified surfaces were larger than 150°, which was closely related to the chemical modification and hierarchical structure. Furthermore, the surfaces retained good superhydrophobic stability in long-term storage as well, which should be critical to the application of iron materials in engineering.

Song, Hao-Jie; Shen, Xiang-Qian; Ji, Hai-Yan; Jing, Xiao-Jing

2010-06-01

149

A superhydrophobic surface with high performance derived from STA-APTES organic-inorganic molecular hybrid.  

PubMed

The chemical originals of natural superhydrophobic surfaces are based on botanic or animal wax or fat, which have poor chemical and thermal resistance. Herein, we report a simple chemical modification of stearic acid (STA) with ?-aminopropyl triethoxysilane (APTES), to obtain an organic-inorganic molecular hybrid STA-APTES compound. A flower-like hierarchically structured surface with superhydrophobicity can be obtained simply by casting the STA-APTES solution under ambient circumstance. The crystallization of the hydrocarbon chain from STA leads to the formation of the binary microstructure and reduces the surface tension, contributing to the superhydrophobicity of the as-formed surface. In addition, the condensation of Si(OCH2CH3)3 from APTES can lead to the cross-linking of the resultant surface, which endows the as-formed superhydrophobic surface with high performances, such as excellent thermal and solvent resistance, etc. This superhydrophobic surface prepared is superior to its many analogs in nature, promising a wide application especially in harsh circumstance. PMID:23895948

Si, Fangfang; Zhao, Ning; Chen, Li; Xu, Jian; Tao, Qingsheng; Li, Jinyong; Ran, Chunbo

2013-07-12

150

Superhydrophobic and self-cleaning bio-fiber surfaces via ATRP and subsequent postfunctionalization.  

PubMed

Superhydrophobic and self-cleaning cellulose surfaces have been obtained via surface-confined grafting of glycidyl methacrylate using atom transfer radical polymerization combined with postmodification reactions. Both linear and branched graft-on-graft architectures were used for the postmodification reactions to obtain highly hydrophobic bio-fiber surfaces by functionalization of the grafts with either poly(dimethylsiloxane), perfluorinated chains, or alkyl chains, respectively. Postfunctionalization using alkyl chains yielded results similar to those of surfaces modified by perfluorination, in terms of superhydrophobicity, self-cleaning properties, and the stability of these properties over time. In addition, highly oleophobic surfaces have been obtained when modification with perfluorinated chains was performed. PMID:20356007

Nyström, Daniel; Lindqvist, Josefina; Ostmark, Emma; Antoni, Per; Carlmark, Anna; Hult, Anders; Malmström, Eva

2009-04-01

151

Effect of ionizing radiation on the properties of superhydrophobic silicone surfaces  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces may be useful for a variety of optical applications as these surfaces exhibit high contact angles with water (>150°) and low-drag. These properties prevent the accumulation of water droplets on the optical surface that would otherwise occur due to condensation or the adhesion of droplets from precipitation. Challenges to producing robust superhydrophobic surfaces for optical applications include the development of cost-effective processes that are compatible with non-planar optical substrates as well as the identification of material systems that exhibit longterm reliability. We have developed a 3D printing technology to create superhydrophobic surfaces by dispensing arrays of high aspect ratio polymeric features onto optical substrates. In this paper, superhydrophobic surfaces were prepared by dispensing silicone elastomers into arrays of features on glass substrates. These samples were exposed to either Cobalt 60 gammarays or 63.8 MeV protons to simulate ionization-induced total dose environments that could be experienced in some space orbits. In addition exposure to other harsh environments, including salt water and 125°C temperatures were evaluated. The effects of these exposure conditions on superhydrophobic properties, as measured by slip angles, are reported. Near-term potential space applications will be discussed.

Lyons, Alan M.; Barahman, Mark; Mondal, Bikash; Taylor, Edward W.

2010-08-01

152

Achieving large slip with superhydrophobic surfaces: Scaling laws for generic geometries  

Microsoft Academic Search

We investigate the hydrodynamic friction properties of superhydrophobic surfaces and quantify their superlubricating potential. On such surfaces, the contact of the liquid with the solid roughness is minimal, while most of the interface is a liquid-gas one, resulting in strongly reduced friction. We obtain scaling laws for the effective slip length at the surface in terms of the generic surface

Christophe Ybert; Catherine Barentin; Cécile Cottin-Bizonne; Pierre Joseph; Lydéric Bocquet

2007-01-01

153

Superhydrophobic surfaces prepared from water glass and non-fluorinated alkylsilane on cotton substrates  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces have been successfully prepared by sol-gel method using water glass as starting material. Such surfaces were obtained first by dip-coating the silica hydrosols prepared via hydrolysis and condensation of water glass onto cotton substrates, then the surface of the silica coating was modified with a non-fluoro compound, hexadecyltrimethoxysilane (HDTMS), to gain a thin film through self-assembly, superhydrophobicity with a water contact angle higher than 151° can be achieved. The morphology and surface roughness were characterized by SEM and AFM.

Li, Zhengxiong; Xing, Yanjun; Dai, Jinjin

2008-01-01

154

Conformal ZnO nanocomposite coatings on micro-patterned surfaces for superhydrophobicity  

Microsoft Academic Search

A conformal coating process is presented to transform surfaces with inherent micro-morphology into superhydrophobic surfaces with hierarchical surface structure using wet chemical spray casting. Nanocomposite coatings composed of zinc oxide nanoparticles and organosilane quaternary nitrogen compound are dispersed in solution for application. The coating is applied to a micro-patterned polydimethylsiloxane substrate with a regular array of cylindrical microposts as well

Adam Steele; Ilker Bayer; Stephen Moran; Andrew Cannon; William P. King; Eric Loth

2010-01-01

155

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

PubMed Central

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.

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

2012-01-01

156

A new model for thermodynamic analysis on wetting behavior of superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces have shown inspiring applications in microfluidics, and self-cleaning coatings owing to water-repellent and low-friction properties. However, thermodynamic mechanism responsible for contact angle hysteresis (CAH) and free energy barrier (FEB) have not been understood completely yet. In this work, we propose an intuitional 3-dimension (3D) droplet model along with a reasonable thermodynamic approach to gain a thorough insight into the physical nature of CAH. Based on this model, the relationships between radius of three-phase contact line, change in surface free energy (CFE), average or local FEB and contact angle (CA) are established. Moreover, a thorough theoretical consideration is given to explain the experimental phenomena related to the superhydrophobic behavior. The present study can therefore provide some guidances for the practical fabrications of the superhydrophobic surfaces.

Zhang, Hongyun; Li, Wen; Fang, Guoping

2012-01-01

157

Synthesis of superhydrophobic SiO2 layers via combination of surface roughness and fluorination  

NASA Astrophysics Data System (ADS)

We describe the preparation of superhydrophobic SiO2 layers through a combination of surface roughness and fluorination. Electrospraying SiO2 precursor solutions that were prepared by a sol-gel route and included trichloro(1H,1H,2H,2H-perfluorooctyl)silane as a fluorination source produced highly rough, fluorinated SiO2 layers. In sharp contrast to the fluorinated flat SiO2 layer, the fluorinated rough SiO2 layer showed much enhanced repellency toward liquid droplets of different surface tensions. The surface fraction and the work of adhesion of the superhydrophobic SiO2 layers were determined, respectively, based on Cassie-Baxter and Young-Dupre equations. The satisfactory long-term stability for 30 days, the ultraviolet resistance and the thermal stability up to 400 oC of the superhydrophobic SiO2 layers prepared in this work confirm a promising practical application.

Kim, Eun-Kyeong; Yeong Kim, Ji; Sub Kim, Sang

2013-01-01

158

Dynamics of Nanostructures at Surfaces  

SciTech Connect

Currently, much effort is being devoted to the goal of achieving useful nanotechnologies, which depend on the ability to control and manipulate things on a very small scale. One promising approach to the construction of nanostructures is 'self-assembly', which means that under suitable conditions desired nanostructures might form automatically due to physical and chemical forces. Remarkably, the forces controlling such self-assembly mechanisms are only poorly understood, even though highly successful examples of self-assembly are known in nature (e.g., complex biochemical machinery regularly self-assembles in the conditions inside living cells). This talk will highlight basic measurements of fundamental forces governing the dynamics of nanostructures at prototypical metal surfaces. We use advanced surface microscopy techniques to track the motions of very small structures in real time and up to atomic resolution. One classic example of self-organized nanostructures are networks of surface dislocations (linear crystal defects). The direct observation of thermally activated atomic motions of dislocations in a reconstructed gold surface allows us to measure the forces stabilizing the remarkable long-range order of this nanostructure. In another example, the rapid migration of nano-scale tin crystals deposited on a pure copper surface was traced to an atomic repulsion between tin atoms absorbed on the crystal surface and bronze alloy formed in the footprint of the tin crystals. It is intriguing to consider the clusters as simple chemo-mechanical energy transducers, essentially tiny linear motors built of 100,000 Sn atoms. We can support this view by providing estimates of the power and energy-efficiency of these nano-motors.

Schmid, Andreas K. (Sandia National Laboratories)

2001-02-28

159

Electrical Switching of Wetting States on Superhydrophobic Surfaces: A Route Towards Reversible Cassie-to-Wenzel Transitions  

Microsoft Academic Search

We demonstrate that the equilibrium shape of the composite interface between superhydrophobic surfaces and drops in the superhydrophobic Cassie state under electrowetting is determined by the balance of the Maxwell stress and the Laplace pressure. Energy barriers due to pinning of contact lines at the edges of the hydrophobic pillars control the transition from the Cassie to the Wenzel state.

G. Manukyan; J. M. Oh; D. van den Ende; R. G. H. Lammertink; F. Mugele

2011-01-01

160

Fabrication of superhydrophobic surfaces on zinc substrates and their application as effective corrosion barriers  

Microsoft Academic Search

Stable superhydrophobic surfaces have been effectively fabricated on the zinc substrates through one-step platinum replacement deposition process without the further modification or any other post processing procedures. The effect of reaction temperatures on the surface morphology and wettability was studied by using SEM and water contact angle (CA) analysis. Under room temperature, the composite structure formed on the zinc substrate

Tao Ning; Wenguo Xu; Shixiang Lu

161

Enzyme biocatalyst route to superhydrophobic surfaces on microstructured poly(ethylene terephthalate) film  

Microsoft Academic Search

A tunable and green enzyme biocatalyst route to develop superhydrophobic surfaces on microstructured poly(ethylene terephthalate) (PET) films by the tailoring of the micro- and nano scale hierarchical structures is described. Upon the aminolysis of PET films with hexamethylenediamine, the primary amine groups are covalently attached onto the PET surfaces and microstructured pattern is formed. The binding of citrate-stabilized Au nanoparticles

Jian-Ping Xu; Fei-Fan Li; Jian Ji; Jia-Cong Shen

2009-01-01

162

Biomimetic superhydrophobic surface of high adhesion fabricated with micronano binary structure on aluminum alloy.  

PubMed

Triggered by the microstructure characteristics of the surfaces of typical plant leaves such as the petals of red roses, a biomimetic superhydrophobic surface with high adhesion is successfully fabricated on aluminum alloy. The essential procedure is that samples were processed by a laser, then immersed and etched in nitric acid and copper nitrate, and finally modified by DTS (CH3(CH2)11Si(OCH3)3). The obtained surfaces exhibit a binary structure consisting of microscale crater-like pits and nanoscale reticula. The superhydrophobicity can be simultaneously affected by the micronano binary structure and chemical composition of the surface. The contact angle of the superhydrophobic surface reaches up to 158.8 ± 2°. Especially, the surface with micronano binary structure is revealed to be an excellent adhesive property with petal-effect. Moreover, the superhydrophobic surfaces show excellent stability in aqueous solution with a large pH range and after being exposed long-term in air. In this way, the multifunctional biomimetic structural surface of the aluminum alloy is fabricated. Furthermore, the preparation technology in this article provides a new route for other metal materials. PMID:24016423

Liu, Yan; Liu, Jindan; Li, Shuyi; Liu, Jiaan; Han, Zhiwu; Ren, Luquan

2013-09-09

163

Fabrication of superhydrophobic aluminium alloy surface with excellent corrosion resistance by a facile and environment-friendly method  

NASA Astrophysics Data System (ADS)

This work develops a facile and environment-friendly method for preparing the superhydrophobic aluminium alloy surface with excellent corrosion resistance. The superhydrophobic aluminium alloy surface is fabricated by the boiling water treatment and stearic acid (STA) modification. Results show that the boiling water treatment endows the aluminium alloy surface with a porous and rough structure, while STA modification chemically grafts the long hydrophobic alkyl chains onto the aluminium alloy surface. Just grounded on the micro- and nano-scale hierarchical structure along with the hydrophobic chemical composition, the superhydrophobic aluminium alloy surface is endued the excellent corrosion resistance.

Feng, Libang; Che, Yanhui; Liu, Yanhua; Qiang, Xiaohu; Wang, Yanping

2013-10-01

164

Role of statistical properties of randomly rough surfaces in controlling superhydrophobicity.  

PubMed

We investigate the effect of statistical properties of the surface roughness on its superhydrophobicity. In particular, we focus on the liquid-solid interfacial structure and its dependence on the coupled effect of surface statistical properties and drop pressure. We find that, for self-affine fractal surfaces with Hurst exponent H > 0.5, the transition to the Wenzel state first involves the short wavelengths of the roughness and, then, gradually moves to larger and larger scales. However, as the drop pressure is increased, at a certain point of the loading history, an abrupt transition to the Wenzel state occurs. This sudden transition identifies the critical drop pressure p(W), which destabilizes the composite interface. We find that p(W) can be strongly enhanced by increasing the mean square slope of the surface, or equivalently the Wenzel roughness parameter r(W). Our investigation shows that, even in the case of randomly rough surface, r(W) is still the most crucial parameter in determining the superhydrophobicity of the surface. An analytical approach is, then, proposed to show that, for any given value of Young's contact angle ?(Y), a threshold value (r(W))(th) = 1/(-cos ?(Y)) exists, above which the composite interface is strongly stabilized and the surface presents robust superhydrophobic properties. Interestingly, this threshold value is identical to the one that would be obtained in pure Wenzel regime to guarantee perfect superhydrophobicity. PMID:23210830

Bottiglione, F; Carbone, G

2012-12-31

165

Wetting on fractal superhydrophobic surfaces from "core-shell" particles: a comparison of theory and experiment.  

PubMed

We report an experimental and theoretical investigation of the wetting behavior of different model polar and nonpolar liquids and their mixtures on superhydrophobic fractal surfaces made of polymer- or silane-coated "core-shell" particles. We compared the experimental results with the theoretical predictions made according to the theories of Onda-Shibuichi (describes wetting on fractal surfaces) and Cassie-Baxter (describes wetting on generic rough composite surfaces). We found that the experimental findings deviate from the behavior predicted by the Onda-Shibuichi model. On the other hand, the wetting properties were found to be close to the predictions made by the Cassie-Baxter model in the hydrophobic region (the intrinsic contact angle on the flat surface is larger than 90 degrees). However, the wetting behavior in the hydrophilic region (the intrinsic contact angle is less than 90 degrees) could not be described by the Onda-Shibuichi or Cassie-Baxter model. The observed inconsistency between the experimental results and theoretical predictions was explained by the formation of metastable states of a liquid droplet on a fabricated fractal surface according to the theory developed by Johnson and Dettre for generic rough surfaces. The entrapments of the liquid droplets in metastable states resulted in superhydrophobic behavior on fractal surfaces as well, made from nonfluorinated material such as polystyrene with a surface free energy of about 30 mJ/m2. This finding is very promising for real industrial applications where fluorinated compounds are willing to be reduced. It can be concluded that employing a texture with fractal geometry is necessary for the design of superhydrophobic coatings. Thereby, extremely lowering the surface free energy of materials by fluorination is not an obligatory factor for the generation of liquid-repellent superhydrophobic materials. We believe that the results we presented in the paper give new insight into the understanding of wetting not only on general superhydrophobic rough surfaces but also on fractal surfaces. PMID:19437778

Synytska, Alla; Ionov, Leonid; Grundke, Karina; Stamm, Manfred

2009-03-01

166

Modeling of biological nanostructured surfaces  

NASA Astrophysics Data System (ADS)

The paper presents a methodology using atom or amino acid hydrophobicities to describe the surface properties of proteins in order to predict their interactions with other proteins and with artificial nanostructured surfaces. A standardized pattern is built around each surface atom of the protein for a radius depending on the molecule type and size. The atom neighborhood is characterized in terms of the hydrophobicity surface density. A clustering algorithm is used to classify the resulting patterns and to identify the possible interactions. The methodology has been implemented in a software package based on Java technology deployed in a Linux environment.

Cristea, P. D.; Tuduce, Rodica; Arsene, O.; Dinca, Alina; Fulga, F.; Nicolau, D. V.

2010-02-01

167

Thermoresponsive PNIPAAm-modified cotton fabric surfaces that switch between superhydrophilicity and superhydrophobicity  

NASA Astrophysics Data System (ADS)

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted onto the cotton fabric by atom transfer radical polymerization (ATRP). Introducing 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTS) onto the surface, the density of PNIPAAm chains can be adjusted because of the competitive reactions of (3-aminopropyl) triethoxysilane (APS) and PFDTS. With the appropriate ratio of APS and PFDTS, the cotton fabric can be switched from superhydrophilic to superhydrophobic by controlling temperature. The prepared cotton fabric may find application in functional textiles, soft and folding superhydrophobic materials.

Jiang, Cheng; Wang, Qihua; Wang, Tingmei

2012-03-01

168

The termiticidal properties of superhydrophobic wood surfaces treated with ZnO nanorods  

Microsoft Academic Search

ZnO is a cost-effective and more environmentally friendly wood preservative than other metallic-based formulations. ZnO-stearate\\u000a treatment imparts superhydrophobicity to wood surfaces, thereby providing triple protection to wood products, i.e., superhydrophobicity,\\u000a inhibition to insects and microorganisms, and UV radiation protection. The objective of this study was to evaluate ZnO-stearate\\u000a hydrophobic treatments of southern pine sapwood for resistance to Formosan subterranean termites.

Todd Shupe; Cheng Piao; Cran Lucas

169

A theoretical prediction of friction drag reduction in turbulent flow by superhydrophobic surfaces  

Microsoft Academic Search

We present a theoretical prediction for the drag reduction rate achieved by superhydrophobic surfaces in a turbulent channel flow. The predicted drag reduction rate is in good agreement with results obtained from direct numerical simulations at Retau~=180 and 400. The present theory suggests that large drag reduction is possible also at Reynolds numbers of practical interest (Retau~105-106) by employing a

Koji Fukagata; Nobuhide Kasagi; Petros Koumoutsakos

2006-01-01

170

The Effects of Superhydrophobic Surfaces on Turbulent Skin Friction and Flow Structure  

Microsoft Academic Search

The application of superhydrophobic surfaces to the reduction of skin friction in turbulent flows is examined through experiments conducted in two facilities: the low-speed turbulent water channel at Brown University and the moderate speed (U = 8m\\/s) boundary layer facility at the Naval Undersea Warfare Center in Newport, RI (NUWC). High resolution PIV measurements are taken in the water channel

Charles Peguero; Charles Henoch; Kenneth Breuer

2007-01-01

171

Superhydrophobic silica aerogel powders with simultaneous surface modification, solvent exchange and sodium ion removal from hydrogels  

Microsoft Academic Search

We report a novel method for the rapid synthesis of superhydrophobic silica aerogel powders based on an inexpensive precursor such as sodium silicate via ambient pressure drying. The sodium silicate was directly polymerized without prior ion exchange by the addition of nitric acid and hexamethyldisilazane (HMDS) to yield silylated hydrogels. The indispensable steps such as surface modification, solvent exchange and

Sharad D. Bhagat; Yong-Ha Kim; Kuen-Hack Suh; Young-Soo Ahn; Jeong-Gu Yeo; Jong-Hun Han

2008-01-01

172

Performance of an Electrostatic Precipitator with Superhydrophobic Surface when Collecting Airborne Bacteria  

Microsoft Academic Search

Modern bioaerosol sampling and analysis techniques that enable rapid detection of low bioagent concentrations in various environments are needed to help us understand the causal relationship between adverse health effects and bioaerosol exposures and also to enable the timely biohazard detection in case of intentional release.We have developed a novel bioaerosol sampler, an electrostatic precipitator with superhydrophobic surface (EPSS), where

Taewon Han; Hey Reoun An; Gediminas Mainelis

2010-01-01

173

Superhydrophobic TiO2-Polymer Nanocomposite Surface with UV-Induced Reversible Wettability and Self-Cleaning Properties.  

PubMed

Multifunctional superhydrophobic nanocomposite surfaces based on photocatalytic materials, such as fluorosilane modified TiO2, have generated significant research interest. However, there are two challenges to forming such multifunctional surfaces with stable superhydrophobic properties: the photocatalytic oxidation of the hydrophobic functional groups, which leads to the permanent loss of superhydrophobicity, as well as the photoinduced reversible hydrolysis of the catalytic particle surface. Herein, we report a simple and inexpensive template lamination method to fabricate multifunctional TiO2-high-density polyethylene (HDPE) nanocomposite surfaces exhibiting superhydrophobicity, UV-induced reversible wettability, and self-cleaning properties. The laminated surface possesses a hierarchical roughness spanning the micro- to nanoscale range. This was achieved by using a wire mesh template to emboss the HDPE surface creating an array of polymeric posts while partially embedding untreated TiO2 nanoparticles selectively into the top surface of these features. The surface exhibits excellent superhydrophobic properties immediately after lamination without any chemical surface modification to the TiO2 nanoparticles. Exposure to UV light causes the surface to become hydrophilic. This change in wettability can be reversed by heating the surface to restore superhydrophobicity. The effect of TiO2 nanoparticle surface coverage and chemical composition on the mechanism and magnitude of wettability changes was studied by EDX and XPS. In addition, the ability of the surface to shed impacting water droplets as well as the ability of such droplets to clean away particulate contaminants was demonstrated. PMID:23889192

Xu, Qian Feng; Liu, Yang; Lin, Fang-Ju; Mondal, Bikash; Lyons, Alan M

2013-09-06

174

Effect of contact angle hysteresis on water droplet evaporation from super-hydrophobic surfaces  

Microsoft Academic Search

Small water drops demonstrate different evaporation modes on super-hydrophobic polymer surfaces with different hysteresis of contact angle. While on the high-hysteresis surface evaporation follows the constant-contact-diameter mode, the constant-contact-angle mode dominates on the low-hysteresis surface. These modes were previously reported for smooth hydrophilic and hydrophobic surfaces, respectively. The experimental data are compared to the previous models describing spherical cap drops

S. A. Kulinich; M. Farzaneh

2009-01-01

175

Nonaligned carbon nanotubes partially embedded in polymer matrixes: a novel route to superhydrophobic conductive surfaces.  

PubMed

A new method for transforming common polymers into superhydrophobic conductive surfaces, with both a high static water contact angle (approximately 160 degrees) and a low sliding angle (2.0 degrees-4.5 degrees), and a low sheet resistance on the order of 10(1)-10(3) ohms/sq is presented. A layer of multiwalled carbon nanotubes (MWNTs) is first distributed on the surface of a polymer substrate, then by a single step of pressing, the MWNTs are partially embedded inside the substrate surface and form a superhydrophobic coating with a "carpet-" or "hair"-like morphology. The infiltration of polymer melts into the porous MWNT layer follows Darcy's law, and the pressing time greatly influence the morphology and superhydrophobicity. Moreover, the coating can be electrically heated by 20-70 degrees C with a voltage as low as 4-8 V at an electric energy density below 1.6 J/cm(2) and therefore can be used for deicing applications. Hydroxylation and fluoroalkylsilane treatment can greatly improve the stability of the superhydrophobicity of MWNTs. This method is convenient and applicable to a variety of thermoplastic polymers and nonpolymer substrates coated by silicone rubber. PMID:20695606

Peng, Mao; Liao, Zhangjie; Qi, Ji; Zhou, Zhi

2010-08-17

176

Synthesis of Temperature-Responsive Dextran-MA\\/PNIPAAm Particles for Controlled Drug Delivery Using Superhydrophobic Surfaces  

Microsoft Academic Search

Purpose  To implement a bioinspired methodology using superhydrophobic surfaces suitable for producing smart hydrogel beads in which\\u000a the bioactive substance is introduced in the particles during their formation.\\u000a \\u000a \\u000a \\u000a \\u000a Methods   Several superhydrophobic surfaces, including polystyrene, aluminum and copper, were prepared. Polymeric solutions composed\\u000a by photo-crosslinked dextran-methacrylated and thermal responsive poly(N-isopropylacrylamide) mixed with a protein (insulin or albumin) were dropped on the superhydrophobic

Ana Catarina Lima; Wenlong Song; Barbara Blanco-Fernandez; Carmen Alvarez-Lorenzo; João F. Mano

2011-01-01

177

Ultralow hysteresis superhydrophobic surfaces by excimer laser modification of SU-8.  

PubMed

We present a new and simple method to produce superhydrophobic surfaces with ultralow hysteresis. The method involves surface modification of SU-8 using an excimer laser treatment. The modified surface is coated with a hydrophobic plasma-polymerized hexafluoropropene layer. The advancing and receding water contact angles were measured to be approximately 165 degrees . The achieved water contact angle hysteresis was below the measurement limit. This low hysteresis can be ascribed to nanoscale debris generated during the excimer laser process. PMID:17154561

Wagterveld, R Martijn; Berendsen, Christian W J; Bouaidat, Salim; Jonsmann, Jacques

2006-12-19

178

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

NASA Astrophysics Data System (ADS)

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.

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

2012-11-01

179

Superhydrophobic poly(L-lactic acid) surface as potential bacterial colonization substrate  

PubMed Central

Hydrophobicity is a very important surface property and there is a growing interest in the production and characterization of superhydrophobic surfaces. Accordingly, it was recently shown how to obtain a superhydrophobic surface using a simple and cost-effective method on a polymer named poly(L-lactic acid) (PLLA). To evaluate the ability of such material as a substrate for bacterial colonization, this work assessed the capability of different bacteria to colonize a biomimetic rough superhydrophobic (SH) PLLA surface and also a smooth hydrophobic (H) one. The interaction between these surfaces and bacteria with different morphologies and cell walls was studied using one strain of Staphylococcus aureus and one of Pseudomonas aeruginosa. Results showed that both bacterial strains colonized the surfaces tested, although significantly higher numbers of S. aureus cells were found on SH surfaces comparing to H ones. Moreover, scanning electron microscopy images showed an extracellular matrix produced by P. aeruginosa on SH PLLA surfaces, indicating that this bacterium is able to form a biofilm on such substratum. Bacterial removal through lotus leaf effect was also tested, being more efficient on H coupons than on SH PLLA ones. Overall, the results showed that SH PLLA surfaces can be used as a substrate for bacterial colonization and, thus, have an exceptional potential for biotechnology applications.

2011-01-01

180

Superhydrophobic poly(L-lactic acid) surface as potential bacterial colonization substrate.  

PubMed

Hydrophobicity is a very important surface property and there is a growing interest in the production and characterization of superhydrophobic surfaces. Accordingly, it was recently shown how to obtain a superhydrophobic surface using a simple and cost-effective method on a polymer named poly(L-lactic acid) (PLLA). To evaluate the ability of such material as a substrate for bacterial colonization, this work assessed the capability of different bacteria to colonize a biomimetic rough superhydrophobic (SH) PLLA surface and also a smooth hydrophobic (H) one. The interaction between these surfaces and bacteria with different morphologies and cell walls was studied using one strain of Staphylococcus aureus and one of Pseudomonas aeruginosa. Results showed that both bacterial strains colonized the surfaces tested, although significantly higher numbers of S. aureus cells were found on SH surfaces comparing to H ones. Moreover, scanning electron microscopy images showed an extracellular matrix produced by P. aeruginosa on SH PLLA surfaces, indicating that this bacterium is able to form a biofilm on such substratum. Bacterial removal through lotus leaf effect was also tested, being more efficient on H coupons than on SH PLLA ones. Overall, the results showed that SH PLLA surfaces can be used as a substrate for bacterial colonization and, thus, have an exceptional potential for biotechnology applications. PMID:22018163

Sousa, Cláudia; Rodrigues, Diana; Oliveira, Rosário; Song, Wenlong; Mano, João F; Azeredo, Joana

2011-10-22

181

Low cost fabrication of a superhydrophobic V-grooved polymer surface.  

PubMed

Engineering of polymer surfaces to control their wetting properties has shown a wide range of potential applications. In this paper we show low cost fabrication of a superhydrophobic polymer surface via a hierarchical combination of hot embossing, O2 reactive ion etching (RIE) and deposition of a hydrophobic silane. The hot embossing and O2 RIE were used to produce respective micro and nanoscale surface roughness which is a requirement for obtaining superhydrophobic surfaces, while the deposition of a hydrophobic silane modified surface chemistry. In order to increase the water/air interface in the Cassie-Baxter composite wetting model, a brass mold with microscale V-grooves was used for hot embossing. Images of droplets in both static water contact angles and dynamic impact tests with the surface clearly show that the wetting state follows the Cassie-Baxter wetting model. The results of this study indicate that our design of the dual level surface roughness and the fabrication process allow for low cost and easy production of a highly superhydrophobic surface. PMID:23755612

Hurst, Steven M; Farshchian, Bahador; Brumfield, Lance; Ok, Jeong Tae; Choi, Junseo; Kim, Jinsoo; Parkl, Sunggook

2013-03-01

182

An effect of silicon micro-nano-patterning arrays on superhydrophobic surface.  

PubMed

Superhydrophobic surface can be fabricated by creating a rough surface at very fine scale and modify it with low-surface energy material. To obtain the optimum superhydrophobicity, the surface roughness must be maximized. To avoid the limitation of scaling down the pattern size by using an expensive lithography tools, the surface roughness factor (r) was increased by means of changing an asperity shape so as to increase its overall surface area. In this paper, the patterns of the asperities under studied were wave stripes, line stripes, cylindrical pillars, square pillars, pentagonal pillars, hexagonal pillars, and octagonal pillars. All pillar shapes were arranged in square arrays, hexagonal arrays, and continuous stripes. The asperities sizes and the pitches were varied from 1 to 5 microm with 10 microm of asperity height. Then the patterned surfaces were coated with polydimethylsiloxane mixed with 10 wt% dicumylperoxide. It was found that the stripe asperities can generate only hydrophobic surface with water contact angle (WCA) of 135 degrees to 145 degrees. The pillars with square and hexagonal arrays had the WCA of 149 degrees to 158 degrees. The pentagonal pillars with square and hexagonal arrays achieved the highest WCA with an average WCA of 156 degrees. It was evident that the pillar shape had significant effect on the superhydrophobicity. PMID:22400288

Atthi, Nithi; Nimittrakoolchai, On-Uma; Supothina, Sitthisuntorn; Supadech, Jakrapong; Jeamsaksiri, Wutthinan; Pankiew, Apirak; Hruanun, Charndet; Poyai, Amporn

2011-10-01

183

A new method for preparing bionic multi scale superhydrophobic functional surface on X70 pipeline steel  

NASA Astrophysics Data System (ADS)

The hydrophobic property of a rough surface with a low free energy coating was theoretically analyzed in this paper. In order to obtain a superhydrophobic surface, a rough surface morphology must be formed in addition to the low free energy coating on the surface. Through the shot blasting, chemical etching with concentrated hydrochloric acid, and low free energy modification with myristic acid ethanol solution, the superhydrophobic surface was obtained on X70 pipeline steel. The better process parameters for preparing superhydrophobic surface on X70 pipeline steel were obtained. The diameter of the stainless steel shot used in the shot blasting was 0.8-1.0 mm. The concentration of hydrochloric acid was 6 mol/L. The chemical etching time was 320 min. The concentration of myristic acid ethanol solution was 0.1 mol/L. The soaking time in myristic acid ethanol solution was 72 h. After X70 pipeline steel surface was treated using the process parameters mentioned above, the biggest contact angle between the specimen surface and distilled water was 153.5°, and the sliding angle was less than 5°.

Yu, Sirong; Wang, Xiaolong; Wang, Wei; Yao, Qiang; Xu, Jun; Xiong, Wei

2013-04-01

184

Analysis of Stokes flow in microchannels with superhydrophobic surfaces containing a periodic array of micro-grooves  

Microsoft Academic Search

Superhydrophobic surfaces have been demonstrated to be capable of reducing fluid resistance in micro- and nanofluidic applications.\\u000a The objective of this paper is to present analytical solutions for the Stokes flow through microchannels employing superhydrophobic\\u000a surfaces with alternating micro-grooves and ribs. Results are presented for both cases where the micro-grooves are aligned\\u000a parallel and perpendicular to the flow direction. The

C. J. Teo; B. C. Khoo

2009-01-01

185

Preparation of super-hydrophobic surface on biodegradable polymer by transcribing microscopic pattern of water-repellent leaf  

Microsoft Academic Search

Super-hydrophobic surface has been prepared onto biodegradable polymer by a combination of transcribing microscopic structure of a water-repellent leaf and a chemical treatment. An aroid leaf has been chosen for the preparation of the super-hydrophobic surface since the leaf has concavity microscopic structure, which is easy to handle for a material use. The microscopic pattern was transcribed onto poly(?-caprolactone) (PCL)

Satoshi Osawa; Masaki Yabe; Makiko Miyamura; Katsumi Mizuno

2006-01-01

186

Chemical control of superhydrophobicity of carbon nanotube surfaces: droplet pinning and electrowetting behavior.  

PubMed

We report the remarkable transformation of a superhydrophobic surface of multiwalled carbon nanotubes after chemical manipulation (functionalization, especially by ozonolysis), which leads to a pinning action and eventually hydrophilic behavior, upon the application of an electric field. The effect of droplet pinning on a hydrophobic surface is an indication of the Wenzel formalism, where it is assumed that the liquid fills up the space between the protrusions on the surface. Also, the ozonized bucky surfaces show fascinating electrowetting behavior in the presence of an electrolyte, which follows a transition from a superhydrophobic, Cassie-Baxter state to a hydrophilic, Wenzel state as a function of the electric field, this has been modelled using a simple approach and the corresponding interfacial capacitance has been determined. PMID:23800839

Kakade, Bhalchandra A

2013-08-01

187

Superhydrophobic surfaces as an on-chip microfluidic toolkit for total droplet control.  

PubMed

We propose and outline a novel technique designed to utilize the unique surface repulsion present between aqueous droplets and customizable superhydrophobic surfaces for the on-chip spatial and temporal manipulation of droplets within microfluidic architectures. Through the integration of carefully designed and prepatterned superhydrophobic surfaces into polymer microfluidic chipsets, it is possible to take advantage of this enhanced surface repulsion to passively manipulate droplets on the microscale for a wide range of droplet operations, including but not limited to acceleration, deceleration, merging, and path control. This work aims to help fulfill and stimulate development based around current requirements for additional passive analytical manipulation and detection techniques in order to enable a reduction in experimental design complexity with the goal of facilitating and improving portability for Lab-on-a-chip devices. PMID:23627493

Draper, Mark C; Crick, Colin R; Orlickaite, Viktorija; Turek, Vladimir A; Parkin, Ivan P; Edel, Joshua B

2013-05-20

188

Bioinspired peony-like beta-Ni(OH)2 nanostructures with enhanced electrochemical activity and superhydrophobicity.  

PubMed

Constructing complex nanostructures has become increasingly important in the development of hydrogen storage, self-cleaning materials, and the formation of chiral branched nanowires. Several approaches have been developed to generate complex nanostructures, which have led to novel applications. Combining biology and nanotechnology through the utilization of biomolecules to chemically template the growth of complex nanostructures during synthesis has aroused great interest. Herein, we use a biomolecule-assisted hydrothermal method to synthesize beta-phase Ni(OH)(2) peony-like complex nanostructures with second-order structure nanoplate structure. The novel beta-Ni(OH)(2) nanostructures exhibit high-power Ni/MH battery performance, close to the theoretical capacity of Ni(OH)(2), as well as controlled wetting behavior. We demonstrate that this bioinspired route to generate a complex nanostructure has applications in environmental protection and green secondary cells. This approach opens up opportunities for the synthesis and potential applications of new kinds of nanostructures. PMID:19998313

Cao, Huaqiang; Zheng, He; Liu, Kaiyu; Warner, Jamie H

2010-02-01

189

Laser induced surface modification of polydimethylsiloxane as a super-hydrophobic material  

Microsoft Academic Search

In order to render the surface of polydimethylsiloxane (PDMS) super-hydrophobic without changing its bulk properties, a PDMS film without photosensitizer was exposed to CO2 pulsed laser, at room temperature, as the excitation source. The modified surfaces have been studied by performing scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDXA) and attenuated total reflectance infrared (ATR-IR) spectroscopy. To

M. T. Khorasani; H. Mirzadeh; P. G. Sammes

1996-01-01

190

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

Microsoft Academic Search

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.

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

2008-01-01

191

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

NASA Astrophysics Data System (ADS)

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.

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

2008-07-01

192

Modeling drag reduction and meniscus stability of superhydrophobic surfaces comprised of random roughness  

NASA Astrophysics Data System (ADS)

Previous studies dedicated to modeling drag reduction and stability of the air-water interface on superhydrophobic surfaces were conducted for microfabricated coatings produced by placing hydrophobic microposts/microridges arranged on a flat surface in aligned or staggered configurations. In this paper, we model the performance of superhydrophobic surfaces comprised of randomly distributed roughness (e.g., particles or microposts) that resembles natural superhydrophobic surfaces, or those produced via random deposition of hydrophobic particles. Such fabrication method is far less expensive than microfabrication, making the technology more practical for large submerged bodies such as submarines and ships. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridges configurations for pipe flows. The present results are compared with theoretical and experimental studies reported in the literature. In particular, our simulation results are compared with work of Sbragaglia and Prosperetti, and good agreement has been observed for gas fractions up to about 0.9. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. This effect peaks at about 30% as the gas fraction increases to 0.98. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. It was found that at a given maximum allowable pressure, surfaces with random post distribution produce less drag reduction than those made up of staggered posts.

Samaha, Mohamed A.; Vahedi Tafreshi, Hooman; Gad-El-Hak, Mohamed

2011-01-01

193

Role of Kinks in the Dynamics of Contact Lines Receding on Superhydrophobic Surfaces  

NASA Astrophysics Data System (ADS)

We have investigated the depinning of the contact line on superhydrophobic surfaces with anisotropic periodic textures. By direct observation of the contact line conformation, we show that the mobility is mediated by kink defects. Full 3D simulations of the shape of the liquid surface near the solid confirm that kinks account for the measured wetting properties. This behavior, which is similar to the Peierls-Nabarro mechanism for dislocations, may open perspectives for the optimization of wetting hysteresis by design.

Gauthier, Anaïs; Rivetti, Marco; Teisseire, Jérémie; Barthel, Etienne

2013-01-01

194

Preparation of superhydrophobic surface for PTFE\\/ePTFE materials by oxygen plasma treatment  

Microsoft Academic Search

The PTFE and expanded PTFE (ePTFE) in sheets has been widely used in varied industrial environments based on its hydrophobic surface, elasticity and porous properties. To enhance their applications, sheet PTFE and ePTFE have been modified by various techniques. Most studies concentrated on the improvement of the hydrophilic properties. This study devoted to produce superhydrophobic surface on PTFE and ePTFE

Hsi-Hsin Chien; Kung-Jeng Ma; Yun-Peng Yeh; Choung-Lii. Chao

2011-01-01

195

Facile transition from hydrophilicity to superhydrophilicity and superhydrophobicity on aluminum alloy surface by simple acid etching and polymer coating  

NASA Astrophysics Data System (ADS)

The transition from the hydrophilic surface to the superhydrophilic and superhydrophobic surface on aluminum alloy via hydrochloric acid etching and polymer coating was investigated by contact angle (CA) measurements and scanning electron microscope (SEM). The effects of etching and polymer coating on the surface were discussed. The results showed that a superhydrophilic surface was facilely obtained after acid etching for 20 min and a superhydrophobic surface was readily fabricated by polypropylene (PP) coating after acid etching. When the etching time was 30 min, the CA was up to 157?. By contrast, two other polymers of polystyrene (PS) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after acid etching. The results showed that the CA was up to 159? by coating PP-g-MAH, while the CA was only 141? by coating PS. By modifying the surface with the silane coupling agent before PP coating, the durability and solvent resistance performance of the superhydrophobic surface was further improved. The micro-nano concave-convex structures of the superhydrophilic surface and the superhydrophobic surface were further confirmed by scanning electron microscope (SEM). Combined with the natural hydrophilicity of aluminum alloy, the rough micro-nano structures of the surface led to the superhydrophilicity of the aluminum alloy surface, while the rough surface structures led to the superhydrophobicity of the aluminum alloy surface by combination with the material of PP with the low surface free energy.

Liu, Wenyong; Sun, Linyu; Luo, Yuting; Wu, Ruomei; Jiang, Haiyun; Chen, Yi; Zeng, Guangsheng; Liu, Yuejun

2013-09-01

196

Superhydrophobic micro/nano dual-scale structures.  

PubMed

In this paper, we present superhydrophobic micro/nano dual structures (MNDS). By KOH-etching of silicon, well-designed microstructures, including inverted pyramids and V-shape grooves, are first fabricated with certain geometry sizes. Nanostructures made of high-compact high-aspect-ratio nanopillars are then formed atop microstructures by an improved controllable deep reactive ion etching (DRIE) process without masks, thus forming MNDS. Resulting from both the minimized liquid-solid contact area and the fluorocarbon layer atop deposited during the DRIE process, the MNDS show a reliable superhydrophobicity. The contact angle and contact angle hysteresis are -165 degrees and less than 1 degrees, respectively. This superhydrophobicity of MNDS is very stable according to squeezing and dropping test, even in high voltage conditions with the electrowetting threshold voltage of -300 V. Therefore, this micro/nano dual-scale structure has strong potential applications to the self-cleaning surface and superhydrophobic micro/nano fluidics. PMID:23646678

Zhang, Xiaosheng; Di, Qianli; Zhu, Fuyun; Sun, Guangyi; Zhang, Haixia

2013-02-01

197

Probing Microscopic Wetting Properties of Superhydrophobic Surfaces by Vibrated Micrometer-Sized Droplets.  

PubMed

We determine contact angles of micrometer-sized NaCl-water droplets on superhydrophobic surfaces by analyzing their lowest-order axisymmetric vibrational resonances driven by vertical oscillations of the surface. Fluorescence spectra of the dye-doped droplets excited by laser light feature whispering-gallery modes (WGMs) whose spectral widths depend on the droplet vibration amplitude, thus enabling precise measurements of the droplet mechanical resonant frequency. Following droplet size determination by WGM mode-matching, we calculate the contact angles from the dependence of the measured mechanical resonant frequency on the droplet size for two surfaces with different superhydrophobicity levels, and find a good correlation with the values measured by direct imaging of millimeter-sized droplets. PMID:21280575

Jona?s?, Alexandr; Karadag, Yasin; Tasaltin, Nevin; Kucukkara, Ibrahim; Kiraz, Alper

2011-01-31

198

Surface plasmon polaritons on nanostructured surfaces and thin films  

Microsoft Academic Search

Abslrnd - Surface plasmon polariton behaviour on periodically nanostructured metal surfaces and thin films is discussed. Such metallic nanostructures act as polaritonic crystals for surface polaritons, in analogy to photonic crystals for light waves. In this paper surface polariton Bloch mode spectrum on the structured surfaces and films is overviewed and manifestations of various surface plasmon modes in the optical

A. V. Zayats; S. A. Darmanyan; D. Gerard; L. Salomon; F. de Fornel

2004-01-01

199

Rapid deposition of transparent super-hydrophobic layers on various surfaces using microwave plasma.  

PubMed

We report herein on a very fast and simple process for the fabrication of transparent superhydrophobic surfaces by using microwave (MW) plasma. It was found that the reaction of various organic liquids in MW argon plasma yields hydrophobic polymeric layers on a large assortment of surfaces, including glass, polymeric surfaces, ceramics, metals, and even paper. In most cases, these polymers are deposited as a rough layer composed of 10-15 nm nanoparticles (NPs). This roughness, together with the chemical hydrophobic nature of the coated materials, is responsible for the superhydrophobic nature of the surface. The typical reaction time of the coating procedure was 1-10 s. The stability of these superhydrophobic surfaces was examined outdoors, and was found to last 2-5 days under direct exposure to the environment and to last 2 months when the sample was protected by a quartz cover. A detailed characterization study of the chemical composition of the layers followed using XPS, solid-state NMR, and IR measurements. Modifications were introduced in the products leading to a substantial improvement in the stability of the products outdoors. PMID:22047036

Irzh, Alexander; Ghindes, Lee; Gedanken, Aharon

2011-11-14

200

Surface initiation from adsorbed polymer clusters: a rapid route to superhydrophobic coatings.  

PubMed

We introduce the use of a hydroborated polyisoprene (PIP) macroinitiator for the rapid surface-initiated growth of superhydrophobic polymethylene (PM) films. Rinsing of a dip-coated PIP film on a methyl-terminated surface atop silicon or gold substrates results in robustly bound, isolated PIP clusters. After hydroboration of the internal olefins, these clusters result in extremely rapid growth of polymethylene coatings upon exposure to a diazomethane solution in diethyl ether at -17 °C. The resulting PM films achieve 6 ?m thicknesses within 20 min of polymerization and become superhydrophobic with advancing and receding water contact angles of 166° and 156°, respectively, within 1 min. The PM films grown from these PIP clusters exhibit 3× greater propagation velocities, 30% lower termination rates, and more highly textured morphologies than PM films grown from hydroborated monolayers. PMID:23465650

Tuberquia, Juan C; Jennings, G Kane

2013-03-25

201

Superomniphobic Surfaces for Military Applications: Nano- and Micro- Fabrication Methods. Chapter 2: Investigation of Wear for Superhydrophobic Surfaces and Development of New Coatings.  

National Technical Information Service (NTIS)

The results of wearing superhydrophobic surfaces and its effect on roughness parameters, surface properties and wetting behaviour are described in this report. An abrasive wear device has been set up to allow consistency, reproducibility and precise contr...

A. Amirfazli

2011-01-01

202

Microchannel flows with superhydrophobic surfaces: Effects of Reynolds number and pattern width to channel height ratio  

NASA Astrophysics Data System (ADS)

Superhydrophobic surfaces are widely adopted for reducing the flow resistance in microfluidic channels. The structures on the superhydrophobic surfaces may consist of longitudinal grooves, transverse grooves, posts, holes, etc. In this paper their effective slip performances are systematically studied and compared in detail through numerical simulations. The numerical results show that channel wall confinement effects have a positive influence on the effective slip length for square posts and longitudinal grooves, and a negative influence for square holes and transverse grooves. Square posts, holes, and transverse grooves all exhibit deteriorating effective slip performances at higher Reynolds numbers, while the effective slip performance of longitudinal grooves remains independent of the Reynolds number. For small pattern width to channel height ratios and at low Reynolds numbers, for low shear-free fractions, the effective slip length of square posts is equivalent of that of transverse grooves, and both geometries yield effective slip lengths which are in turn lower than those of square holes and longitudinal grooves. With increasing shear-free fractions, the effective slip length of square posts surpasses that of square holes and longitudinal grooves, but it becomes lower than that of longitudinal grooves at high Reynolds numbers or large pattern width to channel height ratios. Scaling laws for the effective slip length of superhydrophobic surfaces with square posts, square holes, and transverse grooves have previously been reported for shear-driven flows. This study extends the validity of these scaling laws to pressure-driven channel flows, even at high Reynolds numbers. The findings in this study serve as a useful guide for applications involving the reduction in flow resistance in microchannels containing superhydrophobic surfaces.

Cheng, Y. P.; Teo, C. J.; Khoo, B. C.

2009-12-01

203

Wettable arrays onto superhydrophobic surfaces for bioactivity testing of inorganic nanoparticles  

Microsoft Academic Search

Poly(l-lactic acid) superhydrophobic surfaces prepared by a phase-separation methodology were treated with 30min exposition of UV\\/O3 irradiation using hollowed masks in order to obtain patterned superhydrophilic squared-shaped areas. These wettable areas successfully confined bioactive glass nanoparticles (BG-NPs), by dispensing and drying individual droplets of BG-NPs suspensions. The obtained biomimetic chips were used to test the in vitro bioactivity of binary

Gisela M. Luz; Álvaro J. Leite; Ana I. Neto; Wenlong Song; João F. Mano

2011-01-01

204

Flow past superhydrophobic surfaces containing longitudinal grooves: effects of interface curvature  

Microsoft Academic Search

This article considers Couette and Poiseuille flows past superhydrophobic surfaces containing alternating micro-grooves and\\u000a ribs aligned longitudinally to the flow. The effects of interface curvature on the effective slip length are quantified for\\u000a different shear-free fractions and groove–rib spatial periods normalized using the channel height. The numerical results obtained\\u000a demonstrate the importance of considering interface curvature effects in ascertaining the

C. J. Teo; B. C. Khoo

2010-01-01

205

Superhydrophobic or superhydrophilic surfaces regulated by micro-nano structured ZnO powders  

Microsoft Academic Search

The present study demonstrates a simple technique to decorate a surface for superhydrophobic or superhydrophilic properties by randomly coating an inorganic oxides powder. The superior properties are stable in air for more than half a year. The particulates of the powder are made from aligned single crystalline ZnO nanorods, which aggregate to microspheres with (0?0?0?1¯) ends pointed outside of the

Xingfu Zhou; Xuefeng Guo; Weiping Ding; Yi Chen

2008-01-01

206

Tailored magnetic nanostructures on surfaces  

NASA Astrophysics Data System (ADS)

Nanostructuring has introduced us to a new world of tunable, artificially structured materials. An exciting aspect of this new world is that we control where the atoms, or layers of atoms, are arranged in materials and have learned that this can awaken new properties in them. But, we are only at the beginning stages in developing this control and an understanding of what can be done with it. This dissertation is about an important part of finding our way in this new world; learning to tailor magnetic nanostructures on surfaces. We begin by showing ways in which the magnetic properties of ultrathin films, nanostripes, and isolated nanoclusters can be systematically varied in order to teach us about their behavior. The ultrathin films are from the historically challenging Fe/Cu(100) system. We use small fractions of a single layer of cobalt capping atoms to control their magnetization direction and find a completely new way to cause the magnetization direction to reorient. The nanostripes are made of alloys of iron and cobalt on a tungsten surface. We explore how the magnetic ordering in these stripes is affected by variation of their composition. We then show how changing the size and spacing of isolated Fe dots on a copper surface can teach us about magnetic interactions between them. Finally, we show how our ability to synthesize the dots represented the last piece in an important puzzle. This work enables us to make the first direct observation of how the magnetic properties of a particular amount of a single material change as it is prepared in the form of an ultrathin film, wire array, or dot assembly on a common template.

Pierce, John Philip

207

Morphology-driven nonwettability of nanostructured BN surfaces.  

PubMed

Designing geometrical structures is an effective route to tailoring the wettability of a surface. BN-based hierarchical nano- and microstructures, in particular, vertically aligned and randomly distributed tubes and cones, were synthesized and employed as a platform for studying the influence of surface morphology on their static and dynamic interactions with water droplets. The variation of the contact angle in different hierarchical BN films is attributed to the combined effects of surface roughness and partial liquid-solid contact at the interface. Moreover, the impact response of water droplets impinging on BN arrays with different wetting properties is distinct. In the case of superhydrophobic films, the water droplet bounces off the surface several times whereas in less hydrophobic films it does not rebound and remains pinned to the surface. These results provide a facile route for the selective preparation of hierarchical BN nanostructure array films and a better understanding of their tunable water-repelling behavior, for which a number of promising applications in microelectronics and optics can be envisaged. PMID:23560820

Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

2013-04-17

208

Nanostructured surfaces of dental implants.  

PubMed

The structural and functional fusion of the surface of the dental implant with the surrounding bone (osseointegration) is crucial for the short and long term outcome of the device. In recent years, the enhancement of bone formation at the bone-implant interface has been achieved through the modulation of osteoblasts adhesion and spreading, induced by structural modifications of the implant surface, particularly at the nanoscale level. In this context, traditional chemical and physical processes find new applications to achieve the best dental implant technology. This review provides an overview of the most common manufacture techniques and the related cells-surface interactions and modulation. A Medline and a hand search were conducted to identify studies concerning nanostructuration of implant surface and their related biological interaction. In this paper, we stressed the importance of the modifications on dental implant surfaces at the nanometric level. Nowadays, there is still little evidence of the long-term benefits of nanofeatures, as the promising results achieved in vitro and in animals have still to be confirmed in humans. However, the increasing interest in nanotechnology is undoubted and more research is going to be published in the coming years. PMID:23344062

Bressan, Eriberto; Sbricoli, Luca; Guazzo, Riccardo; Tocco, Ilaria; Roman, Marco; Vindigni, Vincenzo; Stellini, Edoardo; Gardin, Chiara; Ferroni, Letizia; Sivolella, Stefano; Zavan, Barbara

2013-01-17

209

Fabrication of superhydrophobic surface of hierarchical ZnO thin films by using stearic acid  

NASA Astrophysics Data System (ADS)

Flower-like hierarchical ZnO microspheres were successfully synthesized by a simple, template-free, and low-temperature aqueous solution route. The morphology and microstructure of the ZnO microspheres were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The bionic films with hydrophobicity were fabricated by the hierarchical ZnO microspheres modified by stearic acid. It was found that the hydrophobicity of the thin films was very sensitive to the added amount of stearic acid. The thin films modified with 8% stearic acid took on strong superhydrophobicity with a water contact angle (CA) almost to be 178° and weak adhersion. The remarkable superhydrophobicity could be attributed to the synergistic effect of micro/nano hierarchical structure of ZnO and low surface energy of stearic acid.

Wang, Yanfen; Li, Benxia; Xu, Chuyang

2012-01-01

210

Preliminary study on different technological tools and polymeric materials towards superhydrophobic surfaces for automotive applications  

NASA Astrophysics Data System (ADS)

Nature-inspired fabrication of micro-structured superhydrophobic plastic film was aimed in this work in order to achieve smart materials with self-cleaning properties. Replicas of silicon masters were fabricated from different mixtures of base elements and by different processes. Corresponding microstructures were investigated by contact angle measurements, scanning electron microscopy and spectrophotometric analysis. Independently of the technology employed, the obtained films exhibited high contact angle value (larger than 150°), but while the acrylic polymers presented strong demoulding drawbacks, the polydimethylsiloxane (PDMS) films had good properties in terms of both contact angle and optical transparency. The results showed that most of the patterns realized by replica moulding and hot-embossing (on PDMS and polypropylene (PP), respectively) produced superhydrophobic self-cleaning surfaces.

Pruna, A.; Ramiro, J.; Belforte, L.

2013-11-01

211

Superhydrophobic surfaces based on dandelion-like ZnO microspheres  

NASA Astrophysics Data System (ADS)

This study presents a simple method to fabricate superhydrophobic surface based on ZnO nanoneedles. ZnO nanoneedles had been constructed on zinc layers by immersing in an aqueous NH4OH solution at 80 °C. The ZnO films were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The ZnO films exhibited excellent superhydrophilicity (contact angle for water was 0°), while they changed wettability to superhydrophobicity with a water contact angle greater than 150° after further chemical modification with n-dodecanoic acid. The procedure reported here only needs readily available reagents and laboratory equipments, which can be applied to various substrates of any size and shape.

Pan, Qinmin; Cheng, Yuexiang

2009-01-01

212

Superhydrophobic nano-wire entanglement structures  

NASA Astrophysics Data System (ADS)

Superhydrophobic nano-wire entanglement structures (NWES) were fabricated by the dipping method, based on an anodization process in oxalic acid. The pore diameter and the depth were influenced by the applied voltage and the anodizing time. To obtain the NWES, polytetrafluoroethylene (PTFT, Teflon®: DuPont™) replication based on the dipping method was used, with a PTFT solution (0.3 wt%). During replication, the polymer sticking phenomenon due to van der Waals interactions creates microscale bunch structures on the nanoscale wire-entanglement structures. This process provides a hierarchical structure with nanostructures on microstructures and enables commercialization. The diameter of the replicated wires was about 40 nm, and their lengths were 22-75 µm according to the anodizing time. The fabricated surface has superhydrophobicity; the apparent contact angle of the PTFT micro and nanostructures is about 160°-170° and the sliding angle is less than 1°.

Kim, Donghyun; Hwang, Woonbong; Park, Hyun C.; Lee, Kun-H.

2006-12-01

213

Fabrication of microcavity-array superhydrophobic surfaces using an improved template method.  

PubMed

We fabricated the first superhydrophobic (SH) surface with microcavities, using a simple process. The process included an improved template method (ITM) for constructing the SH surface with cavities, using taro leaves as a pattern mask, and a dip-coating method for modifying the SH surface. The results obtained using the ITM are significantly better than those achieved using traditional template methods. In addition, the water-repellence of the microcavities surface was significantly enhanced by decorating with a layer of polymerized n-octadecylsiloxane nanosheets. PMID:23332936

Peng, PanPan; Ke, Qingping; Zhou, Gen; Tang, Tiandi

2012-12-28

214

Effects of the Secondary Length Scale on Hierarchical Superhydrophobic Surfaces Fabricated by Double-Layer Electron Beam Lithography  

NASA Astrophysics Data System (ADS)

Surface topology is a key to superhydrophobicity. Many superhydrophobic surfaces found in nature have more than one characteristic roughness length scales. Very often the primary length scale is on the order of 10?m and the secondary length scale is on the order of 100nm. The secondary length scale is thought to play a key role in the stability and hysteresis of the hydrophobic surface. In our study, a novel method, double-layer electron beam lithography on SU-8 followed by surface silanization on thermally deposited silicon dioxide coating, is used to fabricate superhydrophobic surfaces with well-ordered and controllable secondary length scale patterns. The feature size and spacing of the secondary patterns are varied to study their effects. The size and spacing of the primary scale features will also be varied independently, as well as the surface chemistry. Results of contact angle measurements and hysteresis will be presented.

Feng, Jiansheng; Rothstein, Jonathan

2010-11-01

215

Fabrication of sticky and slippery superhydrophobic surfaces via spin-coating silica nanoparticles onto flat/patterned substrates.  

PubMed

Silica nanoparticles were spin-coated onto a flat/patterned (regular pillar-like) substrate to enhance the surface roughness. The surface was further modified by a self-assembled fluorosilanated monolayer. The advancing/receding contact angle and sliding angle measurements were performed to determine the wetting behavior of a water droplet on the surface. It is interesting to find that a transition from a Wenzel surface to a sticky superhydrophobic surface is observed due to the spin-coating silica nanoparticles. A slippery superhydrophobic surface can be further obtained after secondary spin-coating with silica nanoparticles to generate a multi-scale roughness structure. The prepared superhydrophobic substrates should be robust for practical applications. The adhesion between the substrate and nanoparticles is also examined and discussed. PMID:21979566

Cho, Kuan-Hung; Chen, Li-Jen

2011-10-07

216

Fabrication of sticky and slippery superhydrophobic surfaces via spin-coating silica nanoparticles onto flat/patterned substrates  

NASA Astrophysics Data System (ADS)

Silica nanoparticles were spin-coated onto a flat/patterned (regular pillar-like) substrate to enhance the surface roughness. The surface was further modified by a self-assembled fluorosilanated monolayer. The advancing/receding contact angle and sliding angle measurements were performed to determine the wetting behavior of a water droplet on the surface. It is interesting to find that a transition from a Wenzel surface to a sticky superhydrophobic surface is observed due to the spin-coating silica nanoparticles. A slippery superhydrophobic surface can be further obtained after secondary spin-coating with silica nanoparticles to generate a multi-scale roughness structure. The prepared superhydrophobic substrates should be robust for practical applications. The adhesion between the substrate and nanoparticles is also examined and discussed.

Cho, Kuan-Hung; Chen, Li-Jen

2011-11-01

217

Superhydrophobic surfaces obtained by positive and negative replication of microstructures in PDMS  

NASA Astrophysics Data System (ADS)

Until today, researchers have based themselves on nature to choose the best morphology for obtaining superhydrophobic surfaces. In this context, the morphology of a number of hydrophobic plants have been replicated in a variety of materials in order to reproduce their water repellency. Presently, the literature has presented microstructures in the form of tower and pin patterns or other morphologies in the form of protrusions. Contrarily, in the surfaces presented here, the structures contain microcavities that are negative replicas of the morphology that has been explored so far in the literature. In this essay, determination of the wettability of microstrucutured surfaces with positive and negative replicas of three geometries: parallelepiped, cylindrical and hexagonal. )

Oliveira, Márcio R. S.; Salvadori, Maria C. B. S.

2010-02-01

218

Super-hydrophobic surfaces of layer-by-layer structured film-coated electrospun nanofibrous membranes  

NASA Astrophysics Data System (ADS)

We have recently fabricated super-hydrophobic membrane surfaces based on the inspiration of self-cleaning silver ragwort leaves. This biomimetic super-hydrophobic surface was composed of fluoroalkylsilane (FAS)-modified layer-by-layer (LBL) structured film-coated electrospun nanofibrous membranes. The rough fibre surface caused by the electrostatic LBL coating of TiO2 nanoparticles and poly(acrylic acid) (PAA) was used to imitate the rough surface of nanosized grooves along the silver ragwort leaf fibre axis. The results showed that the FAS modification was the key process for increasing the surface hydrophobicity of the fibrous membranes. Additionally, the dependence of the hydrophobicity of the membrane surfaces upon the number of LBL coating bilayers was affected by the membrane surface roughness. Moreover, x-ray photoelectron spectroscopy (XPS) results further indicated that the surface of LBL film-coated fibres absorbed more fluoro groups than the fibre surface without the LBL coating. A (TiO2/PAA)10 film-coated cellulose acetate nanofibrous membrane with FAS surface modification showed the highest water contact angle of 162° and lowest water-roll angle of 2°.

Ogawa, Tasuku; Ding, Bin; Sone, Yuji; Shiratori, Seimei

2007-04-01

219

Hierarchically structured superhydrophobic coatings fabricated by successive Langmuir Blodgett deposition of micro-/nano-sized particles and surface silanization  

NASA Astrophysics Data System (ADS)

The present study demonstrates the creation of a stable, superhydrophobic surface by coupling of successive Langmuir-Blodgett (LB) depositions of micro- and nano-sized (1.5 µm/50 nm, 1.0 µm/50 nm, and 0.5 µm/50 nm) silica particles on a glass substrate with the formation of a self-assembled monolayer of dodecyltrichlorosilane on the surface of the particulate film. Particulate films, in which one layer of 50 nm particles was deposited over one to five sublayers of larger micro-sized particles, with hierarchical surface roughness and superhydrophobicity, were successfully fabricated. Furthermore, the present 'two-scale' (micro- and nano-sized particles) approach is superior to the previous 'one-scale' (micro-sized particles) approach in that both higher advancing contact angle and lower contact angle hysteresis can be realized. Experimental results revealed that the superhydrophobicity exhibited by as-fabricated particulate films with different sublayer particle diameters increases in the order of 0.5 µm>1.0 µm>1.5 µm. However, no clear trend between sublayer number and surface superhydrophobicity could be discerned. An explanation of superhydrophobicity based on the surface roughness introduced by two-scale particles is also proposed.

Tsai, Ping-Szu; Yang, Yu-Min; Lee, Yuh-Lang

2007-11-01

220

Organic-inorganic hybrid superhydrophobic surfaces using methyltriethoxysilane and tetraethoxysilane sol-gel derived materials in emulsion  

NASA Astrophysics Data System (ADS)

By applying alkaline-catalyzed co-hydrolysis and copolycondensation reactions of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) in organic siloxane modified polyacrylate emulsion (OSPA emulsion), we are able to demonstrate the potential for developing a sol-gel derived organic-inorganic hybrid emulsion for a superhydrophobic surface research. TEOS and MTES derived sol-gel moieties can be designed for a physical roughness and hydrophobic characteristic (Si-CH3) of the hybrid superhydrophobic surface, while OSPA emulsion can be endowed for good film-forming property. The effect of formulation parameters on superhydrophobicity and film-forming property was analyzed. The water contact angle (WCA) on the sol-gel derived hybrid film is determined to be 156°, and the contact angle hysteresis is 5° by keeping the mole ratio of TEOS:MTES:C2H5OH:NH3·H2O:AMP-95 at 1:4:30:10:0.63 and the mass percentage of OSPA emulsion at 25%. The nanoparticle-based silica rough surface is observed as the mole ratio of MTES/TEOS at 4:1. The sol-gel derived organic-inorganic hybrid emulsion shows remarkable film-forming property when the mole ratio of MTES/TEOS reaches or exceeds 4:1. With the primer coating, the performance of superhydrophobic film achieve actual use standard. It reveals that this new procedure is an effective shortcut to obtain a superhydrophobic surface with potential applications.

Wen, Xiu-Fang; Wang, Kun; Pi, Pi-Hui; Yang, Jin-Xin; Cai, Zhi-Qi; Zhang, Li-Juan; Qian, Yu; Yang, Zhuo-Ru; Zheng, Da-Feng; Cheng, Jiang

2011-11-01

221

Thermal Casimir force between nanostructured surfaces  

NASA Astrophysics Data System (ADS)

We present detailed calculations for the Casimir force between a plane and a nanostructured surface at finite temperature in the framework of the scattering theory. We then study numerically the effect of finite temperature as a function of the grating parameters and the separation distance. We also infer nontrivial geometrical effects on the Casimir interaction via a comparison with the proximity force approximation. Finally, we compare our calculations with data from experiments performed with nanostructured surfaces.

Guérout, R.; Lussange, J.; Chan, H. B.; Lambrecht, A.; Reynaud, S.

2013-05-01

222

Electron beam heating effects during environmental scanning electron microscopy imaging of water condensation on superhydrophobic surfaces  

SciTech Connect

Superhydrophobic surfaces (SHSs) show promise as promoters of dropwise condensation. Droplets with diameters below {approx}10 {mu}m account for the majority of the heat transferred during dropwise condensation but their growth dynamics on SHS have not been systematically studied. Due to the complex topography of the surface environmental scanning electron microscopy is the preferred method for observing the growth dynamics of droplets in this size regime. By studying electron beam heating effects on condensed water droplets we establish a magnification limit below which the heating effects are negligible and use this insight to study the mechanism of individual drop growth.

Rykaczewski, K.; Scott, J. H. J. [Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Fedorov, A. G. [G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2011-02-28

223

Analytical modeling and thermodynamic analysis of robust superhydrophobic surfaces with inverse-trapezoidal microstructures.  

PubMed

A polydimethylsiloxane (PDMS) elastomer surface with perfectly ordered microstructures having an inverse-trapezoidal cross-sectional profile (simply PDMS trapezoids) showed superhydrophobic and transparent characteristics under visible light as reported in our previous work. The addition of a fluoropolymer (Teflon) coating enhances both features and provides oleophobicity. This paper focuses on the analytical modeling of the fabricated PDMS trapezoids structure and thermodynamic analysis based on the Gibbs free energy analysis. Additionally, the wetting characteristics of the fabricated PDMS trapezoids surface before and after the application of the Teflon coating are analytically explained. The Gibbs free energy analysis reveals that, due to the Teflon coating, the Cassie-Baxter state becomes energetically more favorable than the Wenzel state and the contact angle difference between the Cassie-Baxter state and the Wenzel state decreases. These two findings support the robustness of the superhydrophobicity of the fabricated Teflon-coated PDMS trapezoids. This is then verified via the impinging test of a water droplet at a high speed. The dependencies of the design parameters in the PDMS trapezoids on the hydrophobicity are also comprehensively studied through a thermodynamic analysis. Geometrical dependency on the hydrophobicity shows that overhang microstructures do not have a significant influence on the hydrophobicity. In contrast, the intrinsic contact angle of the structural material is most important in determining the apparent contact angle. On the other hand, the experimental results showed that the side angles of the overhangs are critical not for the hydrophobic but for the oleophobic property with liquids of a low surface tension. Understanding of design parameters in the PDMS trapezoids surface gives more information for implementation of superhydrophobic surfaces. PMID:20879754

Im, Maesoon; Im, Hwon; Lee, Joo-Hyung; Yoon, Jun-Bo; Choi, Yang-Kyu

2010-09-29

224

Superhydrophobicity â The Lotus Effect  

NSDL National Science Digital Library

Students are introduced to superhydrophobic surfaces and the âlotus effect.â Water spilled on a superhydrophobic surface does not wet the surface, but simply rolls off. Additionally, as water moves across the superhydrophobic surface, it picks up and carries away any foreign material, such as dust or dirt. Students learn how plants create and use superhydrophobic surfaces in nature and how engineers have created human-made products that mimic the properties of these natural surfaces. They also learn about the tendency of all superhydrophobic surfaces to develop water droplets that do not roll off the surface but become âpinnedâ under certain conditions, such as water droplets formed from condensation. They see how the introduction of mechanical energy can âunpinâ these water droplets and restore the desirable properties of the superhydrophobic surface.

NSF CAREER Award and RET Program, Mechanical Engineering and Material Science,

225

Superhydrophobic hierarchical surfaces fabricated by anodizing of oblique angle deposited Al-Nb alloy columnar films  

NASA Astrophysics Data System (ADS)

A combined process of oblique angle magnetron sputtering and anodizing has been developed to tailor superhydrophobic surfaces with hierarchical morphology. Isolated submicron columns of single-phase Al-Nb alloys are deposited by magnetron sputtering at several oblique deposition angles on a scalloped substrate surface, with the gaps between columns increasing with an increase in the deposition angle from 70° to 110°. Then, the columnar films have been anodized in hot phosphate-glycerol electrolyte to form a nanoporous anodic oxide layer on each column. Such surfaces with submicron-/nano-porous structure have been coated with a fluoroalkyl phosphate layer to reduce the surface energy. The porous surface before coating is superhydrophilic with a contact angle for water is less than 10°, while after coating the contact angles are larger than 150°, being superhydrophobic. The beneficial effect of dual-scale porosity to enhance the water repellency is found from the comparison of the contact angles of the submicron columnar films with and without nanoporous oxide layers. The larger submicron gaps between columns are also preferable to increase the water repellency.

Fujii, Takashi; Aoki, Yoshitaka; Habazaki, Hiroki

2011-07-01

226

Acids and alkali resistant sticky superhydrophobic surfaces by one-pot electropolymerization of perfluoroalkyl alkyl pyrrole.  

PubMed

Over the past few years, electropolymerization of semifluorinated monomers like thiophene or pyrrole has been used as a gentle and effective method to generate, in one step, stable superhydrophobic surfaces. The synthetic route mostly involves the coupling reaction between a carboxylic acid and an alcohol, using a carboxy group-activated reagent and a catalyst. As a consequence, the electroformed surfaces present high liquid repellency due to the concomitant effect of roughness and low surface energy. Nevertheless, the ester connector can be cleaved under acidic and basic conditions, preventing its use under a range of environmental conditions. To overcome this drawback, a new perfluoroalkyl alkyl pyrrole has been synthesized, the fluorinated segment being connected to the electropolymerizable part via an alkyl chain, and electropolymerized, leading to surfaces that exhibit a static contact angle with water superior to 150 degrees and no sliding angle, over a wide pH range and with a long lifetime. This represents the first example of a pure conducting polymer surface with sticky superhydrophobicity not only in pure water but also in corrosive solutions such as acids and bases, giving rise to new prospects in practical applications. PMID:20060984

Nicolas, Mael

2009-11-26

227

Bioinspired uniform illumination by vibrated sessile droplet pinned by a hydrophilic/superhydrophobic heterogeneous surface.  

PubMed

We introduce a strategy to generate uniform illumination. The droplet pinned by a hydrophilic/superhydrophobic heterogeneous surface is oscillated, driven by a laterally placed loudspeaker. The vibrated droplet can be considered as a tunable lens, whose focus and focus length can be real-time tuned. The tunable "lens" is presented as a device for uniform illumination by mechanical manipulation. The incident light is scattered by the vibrated droplet during oscillation, and the irradiance distribution on the image plane becomes larger and more homogenous when the droplet is at resonance. PMID:23903122

Zhu, Shuya; Jiang, Weitao; Liu, Hongzhong; Yin, Lei; Shi, Yongsheng; Chen, Bangdao; Ding, Yucheng; An, Ningli

2013-08-01

228

One-step solution immersion process to fabricate superhydrophobic surfaces on light alloys.  

PubMed

A simple and universal one-step process bas been developed to render light alloys (including AZ91D Mg alloy, 5083 Al alloy, and TC4 Ti alloy) superhydrophobic by immersing the substrates in a solution containing low-surface-energy molecules of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS, 20 ?L), ethanol (10 mL), and H2O (10 mL for Al and Mg alloy)/H2O2 (15%, 10 mL for Ti alloy). Field-emission scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle measurements have been performed to characterize the morphological features, chemical composition, and wettability of the surfaces, respectively. The results indicate that the treated light alloys are rough-structured and covered by PFOTS molecules; consequently, the surfaces show static contact angles higher than 150° and sliding angles lower than 10°. This research reveals that it is feasible to fabricate superhydrophobic surfaces (SHS) easily and effectively without involving the traditional two-step processes. Moreover, this one-step process may find potential application in the field of industrial preparation of SHS because of its simplicity and universality. PMID:23895507

Ou, Junfei; Hu, Weihua; Xue, Mingshan; Wang, Fajun; Li, Wen

2013-10-14

229

Achieving large slip with superhydrophobic surfaces: Scaling laws for generic geometries  

NASA Astrophysics Data System (ADS)

We investigate the hydrodynamic friction properties of superhydrophobic surfaces and quantify their superlubricating potential. On such surfaces, the contact of the liquid with the solid roughness is minimal, while most of the interface is a liquid-gas one, resulting in strongly reduced friction. We obtain scaling laws for the effective slip length at the surface in terms of the generic surface characteristics (roughness length scale, depth, solid fraction of the interface, etc.). These predictions are successfully compared to numerical results in various geometries (grooves, posts or holes). This approach provides a versatile framework for the description of slip on these composite surfaces. Slip lengths up to 100 ?m are predicted for an optimized patterned surface.

Ybert, Christophe; Barentin, Catherine; Cottin-Bizonne, Cécile; Joseph, Pierre; Bocquet, Lydéric

2007-12-01

230

Durable, superhydrophobic, superoleophobic and corrosion resistant coating on the stainless steel surface using a scalable method  

NASA Astrophysics Data System (ADS)

In this study, superamphiphobic coating was produced using low surface energy materials and fabrication of hierarchical structures on stainless steel surface. Hierarchical structure was fabricated by silica multilayer coatings and adequate control of particles size in each layer. The surface energy was decreased by fluoropolymer compounds. The maximum static contact angle of DI water, ethylene glycol and fuel oil droplets on the prepared surface increased from 64° to 166°, from 33° to 157° and from 0° to 116°, respectively. Also, the minimum sliding angles of DI water, ethylene glycol and fuel oil droplets on the prepared surface were less than 2°, 5° and 12°, respectively. These results confirmed the superhydrophobicity and superoleophobicity of coated surfaces. These films maintained their superamphiphobicity after 16 days of immersion in water. In electrochemical corrosion evaluation, the highest protection efficiency of fabricated films reached as high as 97.33%. These satisfied results confirmed that this simple method can be used to fabricate large scale samples.

Valipour Motlagh, N.; Birjandi, F. Ch.; Sargolzaei, J.; Shahtahmassebi, N.

2013-10-01

231

Connector ability to design superhydrophobic and oleophobic surfaces from conducting polymers.  

PubMed

In the aim of creating superoleophobic surfaces using monomers with short perfluorinated chains, to avoid drawbacks associated with PFOA, original semifluorinated (C(4)F(9), C(6)F(13)) 3,4-ethylenedioxypyrrole derivatives were synthesized. These monomers were obtained using the faster synthetic method than previously described with some analogues, characterized and electrochemically polymerized on gold plates. The obtained surfaces exhibited superhydrophobic (contact angle with water of 157 degrees and 158 degrees, respectively) and oleophobic properties (contact angle with hexadecane: 88 degrees and 108 degrees, respectively). The comparison between these new monomers and already published analogue EDOP6 confirms the importance of the bipolaronic form of conductive polymer for obtaining surface nanoporosity and as a consequence improving surface oleophobicity. Thus, little change in the molecule design of the connector and the spacer of the monomer can have a significant influence on the surface oleophobicity. PMID:20695602

Zenerino, Arnaud; Darmanin, Thierry; Taffin de Givenchy, Elisabeth; Amigoni, Sonia; Guittard, Frédéric

2010-08-17

232

Bouncing or sticky droplets: Impalement transitions on superhydrophobic micropatterned surfaces  

Microsoft Academic Search

When a liquid drop impinges a hydrophobic rough surface it can either bounce off the surface (fakir droplets) or be impaled and strongly stuck on it (Wenzel droplets). The analysis of drop impact and quasi-static \\

D. Bartolo; F. Bouamrirene; É. Verneuil; A. Buguin; P. Silberzan; S. Moulinet

2006-01-01

233

A novel method to fabricate superhydrophobic surfaces based on well-defined mulberry-like particles and self-assembly of polydimethylsiloxane  

NASA Astrophysics Data System (ADS)

A superhydrophobic surface was obtained by combining application of CaCO 3/SiO 2 mulberry-like composite particles, which originated from violent stirring and surface modification, and self-assembly of polydimethylsiloxane. Water contact angle and sliding angle of the superhydrophobic surface were measured to be about 164 ± 2.5° and 5°, respectively. The excellent hydrophobicity is attributed to the synergistic effect of micro-submicro-nano-meter scale roughness (fabricated by composite particles) and the low surface energy (provided by polydimethylsiloxane). This procedure makes it possible for widespread applications of superhydrophobic film due to its simplicity and practicability.

Yang, Jinxin; Pi, Pihui; Wen, Xiufang; Zheng, Dafeng; Xu, Mengyi; Cheng, Jiang; Yang, Zhuoru

2009-01-01

234

Conversion of an electrospun nanofibrous cellulose acetate mat from a super-hydrophilic to super-hydrophobic surface  

NASA Astrophysics Data System (ADS)

We report a new approach to convert an electrospun nanofibrous cellulose acetate mat surface from super-hydrophilic to super-hydrophobic. Super-hydrophilic cellulose acetate nanofibrous mats can be obtained by electrospinning hydrophilic cellulose acetate. The surface properties of the fibrous mats were modified from super-hydrophilic to super-hydrophobic with a simple sol-gel coating of decyltrimethoxysilane (DTMS) and tetraethyl orthosilicate (TEOS). The resultant samples were characterized by field emission scanning electron microscopy (FE-SEM), x-ray photoelectron spectroscopy (XPS), water contact angle, Brunauer-Emmett-Teller (BET) surface area, atomic force microscopy (AFM), and UV-visible measurements. The results of FE-SEM and XPS showed that the sol-gel (I) films were formed on the rough fibrous mats only after immersion in sol-gel. After the sol-gel (I) coating, the cellulose acetate fibrous mats formed in both 8 and 10 wt% cellulose acetate solutions showed the super-hydrophobic surface property. Additionally, the average sol-gel film thickness coated on 10 wt% cellulose acetate fibrous mats was calculated to be 80 nm. The super-hydrophobicity of fibrous mats was attributed to the combined effects of the high surface roughness of the electrospun nanofibrous mats and the hydrophobic DTMS sol-gel coating. Additionally, hydrophobic sol-gel nanofilms were found to be transparent according to UV-visible measurements.

Ding, Bin; Li, Chunrong; Hotta, Yoshio; Kim, Jinho; Kuwaki, Oriha; Shiratori, Seimei

2006-09-01

235

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

NASA Astrophysics Data System (ADS)

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 159? and a sliding angle of 4?, and the relatively better mechanical robustness.

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

2013-09-01

236

Inertial and channel confinement effects on laminar flow in microchannels with superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

In order to reduce the pressure drop for flow through microchannels, the superhydrophobic surfaces which consist of micro-grooves, posts or holes are widely adopted. In this paper, the effective slip performances of transverse grooves, longitudinal grooves, posts and holes are investigated numerically. The numerical results show that the effective slip lengths of square posts, square holes and transverse grooves decrease with increasing Reynolds number, except those corresponding to longitudinal grooves. For small pattern width to channel height ratios, at low shear-free fractions, the effective slip length corresponding to square posts is equivalent of that of transverse grooves, and their slip lengths are lower than those of square holes and longitudinal grooves. With increasing shear-free fractions, the effective slip length of square posts surpasses those of square holes and longitudinal grooves. Square posts exhibit the highest effective slip length at extremely high shear-free fractions. This study may be useful for applications pertaining to the reduction of flow resistance in microchannels employing superhydrophobic surfaces.

Cheng, Yongpan; Teo, Chiangjuay; Khoo, Boocheong

2009-11-01

237

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

PubMed

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. PMID:23410965

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

2013-02-27

238

Fabrication and analysis of PMMA, ABS, PS, and PC superhydrophobic surfaces using the spray method  

NASA Astrophysics Data System (ADS)

In this study, superhydrophobic surfaces were fabricated using a facile spraying technique with poly(methyl methacrylate) (PMMA), acrylonitrile butadiene styrene (ABS), polystyrene (PS) and polycarbonate (PC). Also, the surface energy was qualitatively analyzed via the water contact angle with respect to the spraying time and the sprayed position. Firstly, PMMA, ABS, PS and PC were dissolved by using solvents such as methyl chloride, methanol, THF (tetrahydrofuran), and methanol, respectively. After that, the dissolved polymer was sprayed onto a thin film of the same polymer for various spraying times. Nozzle size, pressure and spraying distance were fixed as 0.2 mm, 0.1 bar, and 100 mm, respectively, after several feasibility experiments. For the sprayed surfaces, the topology was analyzed with scanning electron microscopy (SEM) and confocal microscopy, and the surface energy was qualitatively analyzed using the water-contactangle measurement. According to a quantitative analysis using the roughness factor and he Wenzel equation, all specimens could be assumed to be in a Wenzel state. To convert the Wenzel state into a Cassie-Baxster state by decreasing the surface energy of polymer-sprayed specimen, we treated the polymer-sprayed surfaces by using trichloro (1H, 1H, 2H, 2H-perfluorooctyl) silane. Consequently, non-sticky superhydrophobic surfaces having water contact angles greater than 155° and water sliding angles lower than 8° were fabricated. The water contact angle and the water sliding angle were measured by using a contact-angle-measuring device. In addition, a brief qualitative analysis of the effect of surface topology on the water sliding angle was conducted for the polymer-sprayed specimens.

Cho, Young-Sam; Ahn, Sang Hyun; Lee, Se-Hwan

2013-07-01

239

Superhydrophobic photocatalytic surfaces through direct incorporation of titania nanoparticles into a polymer matrix by aerosol assisted chemical vapor deposition.  

PubMed

A new class of superhydrophobic photocatalytic surfaces that are self-cleaning through light-induced photodegradation and the Lotus effect are presented. The films are formed in a single-step aerosol-assisted chemical vapor deposition (AACVD) process. The films are durable and show no degradation on continuous exposure to UV-C radiation. PMID:22706974

Crick, Colin R; Bear, Joseph C; Kafizas, Andreas; Parkin, Ivan P

2012-06-18

240

A superhydrophobic to superhydrophilic in situ wettability switch of microstructured polypyrrole surfaces.  

PubMed

We present an electrochemical layered system that allows for the fast, in situ wettability switch of microstructured PPy upon the application of an electric stimulus. We have eliminated the need for PPy to be immersed in an electrolyte to switch between wetting states, laying the groundwork for PPy to be used as a viable material in many applications, including microfluidics or smart textiles. The PPy surface was switched from the superhydrophobic state (contact angle=159) to the superhydrophilic state (contact angle=0) in 3 s. A wettability gradient was also created on a PPy surface using the layered system, causing a 3 µL droplet to travel approximately 2 mm in 0.8 s. PMID:21544891

Chang, Jean H; Hunter, Ian W

2011-03-11

241

Elasticity of the contact line for droplets on anisotropic superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

We present an experimental and numerical investigation on the receding of contact line for water droplets on glass superhydrophobic surfaces. In particular, we focus our attention on surfaces textured with anisotropic lattice posts. We measure that the receding contact angle is not affected by the anisotropy of the lattice. This surprising behavior is closely related to the elastic deformations of the contact line which can be by studied by direct observation. We interpret this phenomenon in term of propagation of kink defects along the lattice. We detail the influence of the morphology of the lattice on the propagation of kinks, as well as the importance of the shape of the posts. Three dimensional numerical simulations confirm that kinks are the key ingredient for the comprehension of the receding contact angle.

Rivetti, Marco; Gauthier, Anais; Teisseire, Jeremie; Barthel, Etienne

2013-03-01

242

Superhydrophobic aluminium-based surfaces: Wetting and wear properties of different CVD-generated coating types  

NASA Astrophysics Data System (ADS)

In view of generating superhydrophobic aluminium-based surfaces, this work presents further results for the combination of anodic oxidation as the primary pretreatment method and chemical vapour deposition (CVD) variants for chemical modification producing coatings of 250–1000 nm thickness. In detail, CVD involved the utilisation of i – hexafluoropropylene oxide as precursor within the hot filament CVD process for the deposition of poly(tetrafluoroethylene) coatings at alternative conditions (PTFE-AC) and ii – 1,3,5-trivinyltrimethylcyclotrisiloxane for the deposition of polysiloxane coatings (PSi) by initiated CVD. The substrate material was Al Mg1 subjected to usual or intensified sulphuric acid anodisation pretreatments (SAAu, SAAi, respectively) affording various degrees of surface micro-roughness (SAAu < SAAi) to the oxidic layers. Performance characteristics were evaluated in the original as-coated states and after standardised artificial weathering and/or mild wear testing.

Thieme, M.; Streller, F.; Simon, F.; Frenzel, R.; White, A. J.

2013-10-01

243

Decorated Electrospun Fibers Exhibiting Superhydrophobicity  

Microsoft Academic Search

Superhydrophobicity, water repellency, and self-cleaning properties of materials have recently attracted tremendous at- tention.(1-3) Superhydrophobic surfaces exhibit extraordinarily high water contact angles, by convention greater than 150°, and extraordinarily low contact-angle hysteresis (i.e., a low difference between advancing and receding contact angles), typically less than 5°-10°. Studies of superhydrophobicity re- alized by insects(4) and many plants,(5,6) particularly the lotus leaf,(6)

Minglin Ma; Malancha Gupta; Zhi Li; Lei Zhai; Karen K. Gleason; Robert E. Cohen; Michael F. Rubner; Gregory C. Rutledge

2007-01-01

244

Flow over Superhydrophobic Hydrofoils  

NASA Astrophysics Data System (ADS)

For several years, superhydrophobic surfaces which are chemically hydrophobic with micron or nanometer scale surface features have been considered for their ability to reduce drag in microfluidic devices. More recently it has been demonstrated that superhydrophobic surfaces reduce friction coefficient in turbulent flows as well. In this talk, we will consider the effect of superhydrophobic surfaces on drag, lift and fluid-structure interactions of hydrofoils and the effect of superhydrophobicity on separation point and vortex structure at high angles of attack. Drag reductions and significant changes to the fluid structure interactions are observed with the presence of superhydrophobic coatings. Hydrofoils are coated with patterned microridge geometries from 5?m to 30?m. Selectively coated symmetrical hydrofoils are also examined to characterize the effect of superhydrophobicity on lift behavior. Particle image velocimetry, streak images and direct force measurements will be presented. Experiments were conducted over the range of Reynolds numbers 100

Daniello, Robert; Sullivan, Jonathan; Rothstein, Jonathan

2010-11-01

245

Switchable static and dynamic self-assembly of magnetic droplets on superhydrophobic surfaces.  

PubMed

Self-assembly is a process in which interacting bodies are autonomously driven into ordered structures. Static structures such as crystals often form through simple energy minimization, whereas dynamic ones require continuous energy input to grow and sustain. Dynamic systems are ubiquitous in nature and biology but have proven challenging to understand and engineer. Here, we bridge the gap from static to dynamic self-assembly by introducing a model system based on ferrofluid droplets on superhydrophobic surfaces. The droplets self-assemble under a static external magnetic field into simple patterns that can be switched to complicated dynamic dissipative structures by applying a time-varying magnetic field. The transition between the static and dynamic patterns involves kinetic trapping and shows complexity that can be directly visualized. PMID:23869012

Timonen, Jaakko V I; Latikka, Mika; Leibler, Ludwik; Ras, Robin H A; Ikkala, Olli

2013-07-19

246

Superhydrophobic Surfaces Prepared by Plasma Fluorination of Lotus-Leaf Amorphous Carbon Films  

NASA Astrophysics Data System (ADS)

Lotus-leaf-like amorphous carbon (a-C) films were fabricated on glass and Si substrates by a magnetron sputtering system and fluorinated in carbon tetrafluoride plasma. The fluorinated films (a-C:F) had a maximum contact angle (CA) of about 162°, which is much larger than that of the nonfluorinated films (105°). Furthermore, the geometric microstructure and chemical composition of the a-C:F films were investigated by scanning electron microscopy and Fourier transform infrared spectrometry, respectively. The characterization results indicated that the CA on the surfaces of the a-C:F films can be improved remarkably by the plasma-fluorinated process. Such a-C:F films that combine superhydrophobicity with other properties may have many potential applications.

Zhou, Ying; Song, Xuemei; Yu, Munan; Wang, Bo; Yan, Hui

247

Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina  

NASA Astrophysics Data System (ADS)

Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting.

Tasaltin, Nevin; Sanli, Deniz; Jonáš, Alexandr; Kiraz, Alper; Erkey, Can

2011-08-01

248

Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina.  

PubMed

Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting. PMID:21827683

Tasaltin, Nevin; Sanli, Deniz; Jonáš, Alexandr; Kiraz, Alper; Erkey, Can

2011-08-09

249

Condensation on superhydrophobic surfaces: the role of local energy barriers and structure length scale.  

PubMed

Water condensation on surfaces is a ubiquitous phase-change process that plays a crucial role in nature and across a range of industrial applications, including energy production, desalination, and environmental control. Nanotechnology has created opportunities to manipulate this process through the precise control of surface structure and chemistry, thus enabling the biomimicry of natural surfaces, such as the leaves of certain plant species, to realize superhydrophobic condensation. However, this "bottom-up" wetting process is inadequately described using typical global thermodynamic analyses and remains poorly understood. In this work, we elucidate, through imaging experiments on surfaces with structure length scales ranging from 100 nm to 10 ?m and wetting physics, how local energy barriers are essential to understand non-equilibrium condensed droplet morphologies and demonstrate that overcoming these barriers via nucleation-mediated droplet-droplet interactions leads to the emergence of wetting states not predicted by scale-invariant global thermodynamic analysis. This mechanistic understanding offers insight into the role of surface-structure length scale, provides a quantitative basis for designing surfaces optimized for condensation in engineered systems, and promises insight into ice formation on surfaces that initiates with the condensation of subcooled water. PMID:22931378

Enright, Ryan; Miljkovic, Nenad; Al-Obeidi, Ahmed; Thompson, Carl V; Wang, Evelyn N

2012-09-27

250

Creation of superhydrophobic stainless steel surfaces by acid treatments and hydrophobic film deposition.  

PubMed

In this work, we present a method to render stainless steel surfaces superhydrophobic while maintaining their corrosion resistance. Creation of surface roughness on 304 and 316 grade stainless steels was performed using a hydrofluoric acid bath. New insight into the etch process is developed through a detailed analysis of the chemical and physical changes that occur on the stainless steel surfaces. As a result of intergranular corrosion, along with metallic oxide and fluoride redeposition, surface roughness was generated on the nano- and microscales. Differences in alloy composition between 304 and 316 grades of stainless steel led to variations in etch rate and different levels of surface roughness for similar etch times. After fluorocarbon film deposition to lower the surface energy, etched samples of 304 and 316 stainless steel displayed maximum static water contact angles of 159.9 and 146.6°, respectively. However, etching in HF also caused both grades of stainless steel to be susceptible to corrosion. By passivating the HF-etched samples in a nitric acid bath, the corrosion resistant properties of stainless steels were recovered. When a three step process was used, consisting of etching, passivation and fluorocarbon deposition, 304 and 316 stainless steel samples exhibited maximum contact angles of 157.3 and 134.9°, respectively, while maintaining corrosion resistance. PMID:22913317

Li, Lester; Breedveld, Victor; Hess, Dennis W

2012-08-31

251

Rapid reversible superhydrophobicity-to-superhydrophilicity transition on alternating current etched brass.  

PubMed

Reversible surface wetting behavior is a hot topic of research because of the potential engineering applications. In the present work, a hierarchical micro/nanostructure is fabricated on brass by alternate current (AC) etching. The superhydrophilic as-prepared etched brass (EB) turns into superhydrophobic after the modification of stearic acid for 1 min. After annealing at 350 °C for 5 min, the superhydrophobic modified EB surface becomes superhydrophilic again. Furthermore, the annealed EB can restore the superhydrophobicity with the remodification of stearic acid. The wetting transition is realized by stearic acid modification and annealing rapidly in 6 min. The wetting transition mechanism is discussed based on the surface chemical analysis. This method is facile and suitable for the construction of large-scale and complex brass surfaces with tunable wetting behaviors. PMID:23627251

Wang, Zhiwei; Zhu, Liqun; Li, Weiping; Liu, Huicong

2013-05-28

252

Two dimensional microfluidic devices for sorting, mixing, and analyzing drops using superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

The effect of sharp transitions in contact angle hysteresis of a superhydrophobic surface on water droplet motion is investigated. The surfaces are created by sanding naturally hydrophobic Teflon, which results in a surface possessing microscale roughness. With careful sanding and masking of the surface, regions with similar advancing contact angles near 150 degrees but varying contact angle hysteresis can be created. This talk presents detailed results on how these sharp transitions can deflect drops when the transition is at an angle to the droplet trajectory. The physics of the droplet-transition interaction is discussed and the sensitivity of the alignment of the angle of transition and Weber number is presented. Deflection using an angled transition in contact angle hysteresis is selective, demonstrating the ability of this fabrication method to sort drops based on size, speed, and wettability. Results of surfaces with stripes of different contact angle hysteresis are presented, showing the ability to more effectively deflect. Finally, a two-dimensional droplet reactor is presented that encompasses droplet sorting, coalescence, mixing, and trapping of two droplets.

Nilsson, Michael; Goumnerov, Hristo; Rothstein, Jonathan

2011-11-01

253

Superhydrophobic Surfaces as Smart Platforms for the Analysis of Diluted Biological Solutions.  

PubMed

The aim of this paper is to expound on the rational design, fabrication and development of superhydrophobic surfaces (SHSs) for the manipulation and analysis of diluted biological solutions. SHSs typically feature a periodic array or pattern of micropillars; here, those pillars were modified to incorporate on the head, at the smallest scales, silver nanoparticles aggregates. These metal nanoclusters guarantee superior optical properties and especially SERS (surface enhanced Raman scattering) effects, whereby a molecule, adsorbed on the surface, would reveal an increased spectroscopy signal. On account of their two scale-hybrid nature, these systems are capable of multiple functions which are (i) to concentrate a solution, (ii) to vehicle the analytes of interest to the active areas of the substrate and, therefore, (iii) to measure the analytes with exceptional sensitivity and very low detection limits. Forasmuch, combining different technologies, these devices would augment the performance of conventional SERS substrates and would offer the possibility of revealing a single molecule. In this work, similar SHSs were used to detect Rhodamine molecules in the fairly low atto molar range. The major application of this novel family of devices would be the early detection of tumors or other important pathologies, with incredible advances in medicine. PMID:22620470

Gentile, Francesco; Coluccio, Maria Laura; Coppedè, Nicola; Mecarini, Federico; Das, Gobind; Liberale, Carlo; Tirinato, Luca; Leoncini, Marco; Perozziello, Gerardo; Candeloro, Patrizio; De Angelis, Francesco; Di Fabrizio, Enzo

2012-06-01

254

Superhydrophobic surfaces on light alloy substrates fabricated by a versatile process and their corrosion protection.  

PubMed

After hydrothermally treated in H2O (for Mg alloy and Al alloy) or H2O2 (for Ti alloy), microstructured oxide or hydroxide layers were formed on light alloy substrates, which further served as the active layers to boost the self-assembling of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) and finally endowed the substrates with unique wettability, that is, superhydrophobicity. For convenience, the so-fabricated superhyrdophobic surfaces (SHS) were abridged as HT-SHS. For comparison, SHS coded as CE-SHS were also prepared based on chemical etching in acid and succedent surface passivation with PFOTES. To reveal the corrosion protection of these SHS, potentiodynamic polarization measurements in NaCl solution (3.5 wt %) were performed. Moreover, to reflect the long-term stability of these SHS, SHS samples were immersed into NaCl solution and the surface wettability was monitored. Experimental results indicated that HT-SHS was much more stable and effective in corrosion protection as compared with CE-SHS. The enhancement was most likely due to the hydrothermally generated oxide layer by the following tow aspects: on one hand, oxide layer itself can lower the corrosion due to its barrier effect; on the other hand, stronger interfacial bonding is expected between oxide layer and PFOTES molecules. PMID:23496751

Ou, Junfei; Hu, Weihua; Xue, Mingshan; Wang, Fajun; Li, Wen

2013-04-03

255

Suppressing surface reconstruction of superhydrophobic PDMS using a superhydrophilic zwitterionic polymer.  

PubMed

Poly(dimethyl siloxane) (PDMS) is extensively used for biomedical applications due to its low cost, ease of fabrication, high durability and flexibility, oxygen permeability, and self-healing properties. PDMS, however, has some significant drawbacks. PDMS endures unacceptably high levels of nonspecific protein fouling when used with biological samples due to its superhydrophobic characteristics. Unfortunately, conventional surface modification methods do not work for PDMS due to its low glass transition temperature. This phenomenon has been well-known for years as "hydrophobic regeneration". For the same reason, it is also very difficult to bring functionalities onto PDMS surfaces. Herein, we demonstrate how a superhydrophilic zwitterionic material, poly(carboxybetaine methacrylate) (pCBMA), can provide a highly stable coating with long-term stabilty due to the sharp contrast in hydrophobicity between pCBMA and PDMS. This material is able to suppress nonspecific protein adsorption in complex media and functionalize desired biomolecules needed in applications, such as diagnostics, without sacrificing its nonfouling characteristics. PMID:22512660

Keefe, Andrew J; Brault, Norman D; Jiang, Shaoyi

2012-04-26

256

Fabrication of a lotus-like micro nanoscale binary structured surface and wettability modulation from superhydrophilic to superhydrophobic  

NASA Astrophysics Data System (ADS)

We report a simple method for fabricating a lotus-like micro-nanoscale binary structured surface of copper phosphate dihydrate. The copper phosphate dihydrate nanosheets were generated by galvanic cell corrosion of a copper foil with aqueous phosphorus acid solution drops and dried in an oxygen gas atmosphere, and they self-organized into a film with a lotus-like micro-nanoscale binary structured surface. The wettability of this surface can be changed from superhydrophilic to highly hydrophobic or superhydrophobic by heating or modifying it with an n-dodecanethiol monolayer.

Wu, Xufeng; Shi, Gaoquan

2005-10-01

257

Pectin-coated chitosan microgels crosslinked on superhydrophobic surfaces for 5-fluorouracil encapsulation.  

PubMed

5-Fluorouracil (5-FU)-loaded chitosan microgels for oral and topical chemotherapy were prepared applying a superhydrophobic surface-based encapsulation technology. Drug-loaded chitosan dispersions were cross-linked and then coated with drug-free chitosan or pectin layers at the solid-air interface in a highly efficient and environment-friendly way. The size of the microgels (with diameters of ca. 280 and 557 ?m for the chitosan seeds and pectin-coated microgels respectively) was the lowest obtained until now using similar biomimetic methodologies. The microgels were characterized regarding 5-FU release profiles in vitro in aqueous media covering the pH range of the gastrointestinal tract, and cytotoxicity against two cancer cell lines sensitive to 5-FU. Owing to their control of 5-FU release in acidic medium, calcium pectinate-coated microgels can be considered as suitable for oral administration. Growth inhibition of cancer cells by 5-FU was greater when incorporated to chitosan microgels; these being potentially useful for treatment of skin and colorectal tumors. PMID:23987352

Puga, Ana M; Lima, Ana Catarina; Mano, Joao F; Concheiro, Angel; Alvarez-Lorenzo, Carmen

2013-06-07

258

Surface Localization of Buried III-V Semiconductor Nanostructures.  

PubMed

In this work, we study the top surface localization of InAs quantum dots once capped by a GaAs layer grown by molecular beam epitaxy. At the used growth conditions, the underneath nanostructures are revealed at the top surface as mounding features that match their density with independence of the cap layer thickness explored (from 25 to 100 nm). The correspondence between these mounds and the buried nanostructures is confirmed by posterior selective strain-driven formation of new nanostructures on top of them, when the distance between the buried and the superficial nanostructures is short enough (d = 25 nm). PMID:20596455

Alonso-González, P; González, L; Fuster, D; Martín-Sánchez, J; González, Yolanda

2009-05-09

259

Superhydrophobic silica coating by dip coating method  

NASA Astrophysics Data System (ADS)

Herein, we report a simple and low cost method for the fabrication of superhydrophobic coating surface on quartz substrates via sol-gel dip coating method at room temperature. Desired surface chemistry and texture growth for superhydrophobicity developed under double step sol–gel process at room temperature. The resultant superhydrophobic surfaces were characterized by Field-emission scanning electron microscopy (FE-SEM), Atomic force microscopy (AFM), water contact angle (WCA) measurement, differential thermal gravimetric analysis-differential thermal analysis (TGA-DTA) calorimetry and optical spectrometer. Coating shows the ultra high water contact angle about 168 ± 2° and water sliding angle 3 ± 1° and superoleophilic with petroleum oils. This approach allows a simple strategy for the fabrication process of superhydrophilic–superhydrophobic on same surfaces with high thermal stability of superhydrophobicity up to 560 °C. Thus, durability, special wettability and thermal stability of superhydrophobicity expand their application fields.

Mahadik, Satish A.; parale, Vinayak; Vhatkara, Rajiv S.; Mahadik, Dinesh B.; Kavale, Mahendra S.; Wagh, Pratap B.; Gupta, Satish; Gurav, Jyoti

2013-07-01

260

Transforming Anaerobic Adhesives into Highly Durable and Abrasion Resistant Superhydrophobic Organoclay Nanocomposite Films: A New Hybrid Spray Adhesive for Tough Superhydrophobicity  

Microsoft Academic Search

The authors report fabrication of tough nanostructured self-cleaning superhydrophobic polymer-organoclay films from anaerobic acrylic adhesives displaying strong adhesion to metal surfaces. Both industrial and bio-grade anaerobic adhesives such as bone cements could be used. Montmorillonite clay filled anaerobic adhesives were modified by blending with a water dispersed fluoro-methacrylic latex in solution to form abrasion resistant interpenetrating polymer network films upon

Ilker S. Bayer; Andrea Brown; Adam Steele; Eric Loth

2009-01-01

261

Calcium carbonate mineralization: X-ray microdiffraction probing of the interface of an evaporating drop on a superhydrophobic surface.  

PubMed

The liquid/air interface of calcium bicarbonate solution drops was probed by synchrotron radiation microbeam scattering. The drops were deposited on a nanopatterned superhydrophobic poly(methyl methacrylate) surface and raster-scanned during evaporation by small-angle and wide-angle X-ray scattering. The appearance of about 200-nm-size calcite crystallites at the interface could be spatially resolved at the onset of crystallization. Diffuse scattering from the interface is attributed to a dense nanoscale amorphous calcium carbonate phase. Calcite was found to be the major phase in the solid residue with vaterite as minor phase. PMID:21663321

Accardo, Angelo; Burghammer, Manfred; Di Cola, Emanuela; Reynolds, Michael; Di Fabrizio, Enzo; Riekel, Christian

2011-06-13

262

Fabrication of superhydrophobic silica-based surfaces with high transmittance by using tetraethoxysilane precursor and different polymeric species  

NASA Astrophysics Data System (ADS)

The preparation of superhydrophobic silica-based surfaces via the sol-gel process through the addition of different polymeric species into the precursor solution was done in this study. The surface roughness of the films was obtained by removing the organic polymer at a high temperature, and then the hydrophobic groups were bonded onto the films with a monolayer by chemical reaction with hexamethyldisilazane (HMDS). The characteristic properties of the as-prepared films were analyzed by contact angle measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), nitrogen adsorption/desorption, and UV-vis scanning spectrophotometer. The experimental results revealed that the superhydrophobic thin films with high transmittance could easily be prepared using polypropylene (PPG), polyethylene (PEG), and poly(vinylpyrrolidone) (PVP). Surface roughness and pore size were enhanced using PPG polymeric species. The distribution of pore size was from the microporous to the mesoporous and marcoporous regions. In addition, the contact angles of the rough surfaces prepared at 500 °C without modification of HMDS were smaller than 5° but larger than 156° after modified by HMDS.

Chen, Yu-Kai; Chang, Kuei-Chien; Wu, Kuan-Yu; Tsai, Yen-Ling; Lu, Juhng-shu; Chen, Hui

2009-07-01

263

Super-hydrophilicity to super-hydrophobicity transition of a surface with Ni micro-nano cones array  

NASA Astrophysics Data System (ADS)

A surface with Ni micro-nano cones array (MCA) was fabricated with electro-deposition method and exhibited super-hydrophilic nature when freshly prepared. Spontaneous transition from super-hydrophilicity to super-hydrophobicity was observed when the surface was exposed in air at room temperature. The special surface structure of MCA played an important role in amplifying the surface wettability. Since the surface structure remained the same as the freshly prepared Ni MCA films during the storage, the transition was proved to be attributed to the change of surface chemical composition. Such wettability transition property of Ni MCA films might shed light on the high-tech areas of self-cleaners, anti-corrosion materials, anti-contamination materials, etc.

Geng, Wenyan; Hu, Anmin; Li, Ming

2012-12-01

264

Fabrication and icing property of superhydrophilic and superhydrophobic aluminum surfaces derived from anodizing aluminum foil in a sodium chloride aqueous solution  

NASA Astrophysics Data System (ADS)

An aluminum foil with a rough surface was first prepared by anodic treatment in a neutral aqueous solution with the help of pitting corrosion of chlorides. First, the hydrophobic Al surface (contact angle around 79°) became superhydrophilic (contact angle smaller than 5°) after the anodizing process. Secondly, the superhydrophilic Al surface became superhydrophobic (contact angle larger than 150°) after being modified by oleic acid. Finally, the icing property of superhydrophilic, untreated, and superhydrophobic Al foils were investigated in a refrigerated cabinet at -12 °C. The mean total times to freeze a water droplet (6 ?L) on the three foils were 17 s, 158 s and 1604 s, respectively. Thus, the superhydrophilic surface accelerates the icing process, while the superhydrophobic surface delays the process. The main reason for this transition might mainly result from the difference of the contact area of the water droplet with Al substrate: the increase in contact area with Al substrate will accelerate the heat conduct process, as well as the icing process; the decrease in contact area with Al substrate will delay the heat conduct process, as well as the icing process. Compared to the untreated Al foil, the contact area of the water droplet with the Al substrate was higher on superhydrophilic surface and smaller on the superhydrophobic surface, which led to the difference of the heat transfer time as well as the icing time.

Song, Meirong; Liu, Yuru; Cui, Shumin; Liu, Long; Yang, Min

2013-10-01

265

Influence of Slip on the Flow Past Superhydrophobic Circular Cylinders  

Microsoft Academic Search

Superhydrophobic surfaces have been shown to produce significant drag reduction for both laminar and turbulent flows of water through large and small-scale channels. In this presentation a series of experiments will be presented which investigate the effect of superhydrophobic-induced slip on the flow past a circular cylinder. In these experiments, circular cylinders are coated with a series of superhydrophobic surfaces

Jonathan Rothstein; Robert Daniello; Nangelie Ferrer; Pranesh Muralidhar

2010-01-01

266

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

PubMed

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. PMID:23978289

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

2013-08-08

267

Wettability behaviour of RTV silicone rubber coated on nanostructured aluminium surface  

NASA Astrophysics Data System (ADS)

A nanostructutered superhydrophobic surface was elaborated by applying an RTV silicone rubber coating on electrochemically processed aluminium substrates. Study of anodisation voltage on surface morphology showed that higher anodising voltage led to larger pore sizes. Scanning electron microscopy image analysis showed bird's nest and beehive structures formed on anodised surfaces at 50 V and 80 V. Water static contact angle on the treated surfaces reached up to 160° at room temperature. Study of superhydrophobic surfaces at super cooled temperature showed important delayed freezing time for RTV hydrophobic surfaces when compared to non-treated aluminium. However, lower wettability was observed when surface temperature went down from 20 °C to -10 °C. Also, it was found that the capacitance of superhydrophobic surfaces decreased with increasing anodising voltage.

Momen, Gelareh; Farzaneh, Masoud; Jafari, Reza

2011-05-01

268

Micro/nanostructural porous surface on titanium and bioactivity.  

PubMed

Porous surfaces can improve both early fixation and long-term stabilization of implants by contrast with smooth surfaces. In this study, a microporous surface on titanium was prepared by acid etching and the size of micropores ranged from 1 to 60 microm. The micro/nanostructural porous layer on this microporous surface was obtained by acid etching and anodization. In this micro/nanostructural porous layer, the diameter of nanotubes was about 100 nm. After heat treatment at 450 degrees C for 6 h, the oxides on micro/nanostructural surface transformed into anatase crystals and the grain size of anatase was about 20 nm. The bioactivity of samples was investigated respectively in simulated body fluid and a bovine serum albumin (BSA) solution. The information of specimen surfaces was detected using scanning electron microscope, X-ray diffractometer, and attenuated total reflection Fourier transform infrared spectroscope. The results showed that the sample with micro/nanostructural porous surface and anatase had excellent bioactivity under nonpretreatment. It had more hydroxyapatite (HA) formation and faster BSA adsorption than other samples under the same conditions. Besides, the HA coating on the micro/nanostructure surface had larger range thickness, no microcrack, and no separated interface from substrate. Therefore, this micro/nanostructural porous surface may be an ideal modification layer for preparing bioactive implants. PMID:18837457

Gao, Ling; Feng, Bo; Wang, Jianxin; Lu, Xiong; Liu, Dali; Qu, Shuxin; Weng, Jie

2009-05-01

269

Facile synthesis of superhydrophobic surface of ZnO nanoflakes: chemical coating and UV-induced wettability conversion  

NASA Astrophysics Data System (ADS)

This work reports an oriented growth process of two-dimensional (2D) ZnO nanoflakes on aluminum substrate through a low temperature hydrothermal technique and proposes the preliminary growth mechanism. A bionic superhydrophobic surface with excellent corrosion protection over a wide pH range in both acidic and alkaline solutions was constructed by a chemical coating treatment with stearic acid (SA) molecules on ZnO nanoflakes. It is found that the superhydrophobic surface of ZnO nanoflake arrays shows a maximum water contact angle (CA) of 157° and a low sliding angle of 8°, and it can be reversibly switched to its initial superhydrophilic state under ultraviolet (UV) irradiation, which is due to the UV-induced decomposition of the coated SA molecules. This study is significant for simple and inexpensive building of large-scale 2D ZnO nanoflake arrays with special wettability which can extend the applications of ZnO films to many other important fields.

Yao, Lujun; Zheng, Maojun; Li, Changli; Ma, Li; Shen, Wenzhong

2012-04-01

270

An experimental investigation into the icing and melting process of a water droplet impinging onto a superhydrophobic surface  

NASA Astrophysics Data System (ADS)

The freezing and melting process of a small water droplet on a superhydrophobic cold surface was investigated using the Laser Induced Fluorescence (LIF) technique. The superhydrophobic surface was prepared using a sol-gel method on a red copper test plate. From the obtained fluorescence images, the phase transition characteristics during the freezing and melting process of a water droplet were clearly observed. It was found that, at the beginning of the droplet freezing process, liquid water turned into ice at a very fast rate. Such phase transition process decreased gradually with time and the volume of frozen ice approached a constant value at the end of the icing process. In addition, the freezing time was found to reduce with the decrease of the test plate temperature. Besides, when the test plate temperature is relatively high, the effect of droplet volume on the freezing time is very significant. Over all, we provide some tentative insights into the microphysical process related to the icing and melting process of water droplets.

Jin, ZheYan; Jin, SongYue; Yang, ZhiGang

2013-09-01

271

Rapid fabrication of nanostructured surfaces using nanocoining.  

PubMed

A new process for creating high quality ordered arrays of nanofeatures called nanocoining is presented. A diamond die with a structured area of nanofeatures (1600 features in a 20 ?m × 20 ?m area) is used to physically transfer features to a mold surface. The die is attached to an actuator capable of producing an elliptical tool-path, the dimensions of which are process dependent and enable the die to match velocity with the moving mold during contact to avoid dragging the nanostructured area along the mold surface (smear). Nanocoining process parameters are discussed which enable indents to be indexed precisely to completely cover target areas. Techniques for die alignment and depth control are also required to create large areas (339 mm(2)) of nanofeatures in short times (?20 min). Nanocoining experiments were performed at 1 kHz (1000 indents or 1.6 million features per second) on a flat electroless nickel sample. UV curable replicates were then created from the nickel mold and both the mold and replicate were examined in an SEM and AFM. PMID:23018619

Zdanowicz, Erik; Dow, Thomas A; Scattergood, Ronald O

2012-09-27

272

Superhydrophobic surfaces allow probing of exosome self organization using X-ray scattering  

NASA Astrophysics Data System (ADS)

Drops of exosome dispersions from healthy epithelial colon cell line and colorectal cancer cells were dried on a superhydrophobic PMMA substrate. The residues were studied by small- and wide-angle X-ray scattering using both a synchrotron radiation micrometric beam and a high-flux table-top X-ray source. Structural differences between healthy and cancerous cells were detected in the lamellar lattices of the exosome macro-aggregates.Drops of exosome dispersions from healthy epithelial colon cell line and colorectal cancer cells were dried on a superhydrophobic PMMA substrate. The residues were studied by small- and wide-angle X-ray scattering using both a synchrotron radiation micrometric beam and a high-flux table-top X-ray source. Structural differences between healthy and cancerous cells were detected in the lamellar lattices of the exosome macro-aggregates. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr34032e

Accardo, Angelo; Tirinato, Luca; Altamura, Davide; Sibillano, Teresa; Giannini, Cinzia; Riekel, Christian; di Fabrizio, Enzo

2013-02-01

273

Wetting mode transition of nanoliter scale water droplets during evaporation on superhydrophobic surfaces with random roughness structure  

NASA Astrophysics Data System (ADS)

During evaporation, shape changes of nanoliter-scale (80-100 nL) water droplets were evaluated on two superhydrophobic surfaces with different random roughness (nm-coating, ?m-coating). The square of the contact radius and the square of the droplet height decreased linearly with evaporation time. However, trend changes were observed at around 170 s (nm-coating) and around 150 s (?m-coating) suggesting a wetting mode transition. The calculated droplet radii for the wetting mode transition from the average roughness distance and the average roughness height of these surface structures were approximately equal to the experimental values at these trend changes. A certain level of correlation between the roughness size and droplet radius at the wetting mode transition was confirmed on surfaces with random roughness.

Furuta, Tsutomu; Isobe, Toshihiro; Sakai, Munetoshi; Matsushita, Sachiko; Nakajima, Akira

2012-01-01

274

Effect of microstructure and surface roughness on the wettability of superhydrophobic sol–gel nanocomposite coatings  

Microsoft Academic Search

Sol–gel nanocomposite coatings were fabricated by spraying precursor mixtures containing hydrophobically modified silica (HMS)\\u000a nanoparticles dispersed in sol–gel matrices prepared with acid-catalyzed tetraethoxysilane (TEOS), and methyltriethoxysilane\\u000a (MTEOS). The hydrophobicity of the coatings increased with increase in the concentration of HMS nanoparticles. Superhydrophobic\\u000a coatings with water contact angle (WCA) of 166° and roll-off angle <2° were obtained by optimizing the sol–gel

Bharathibai J. BasuV; V. Hariprakash; S. T. Aruna; R. V. Lakshmi; J. Manasa; B. S. Shruthi

2010-01-01

275

Fast, active droplet interaction: coalescence and reactive mixing controlled by electrowetting on a superhydrophobic surface.  

PubMed

A novel electrowetting-on-dielectrics (EWOD) device in open planar geometry allows probing of droplet mixing on a superhydrophobic substrate under quasi contact-free conditions. We demonstrate a droplet-based microreactor with integrated convective-flow mixing for the reactive-mixing of CaCl(2)/Na(2)CO(3) solutions. The device provides unique conditions for scattering, spectroscopy and imaging probes requiring an unobstructed droplet-access. PMID:23224020

Accardo, Angelo; Mecarini, Federico; Leoncini, Marco; Brandi, Fernando; Di Cola, Emanuela; Burghammer, Manfred; Riekel, Christian; Di Fabrizio, Enzo

2013-02-01

276

Superhydrophobic conductive carbon nanotube coatings for steel.  

PubMed

We report the synthesis of superhydrophobic coatings for steel using carbon nanotube (CNT)-mesh structures. The CNT coating maintains its structural integrity and superhydrophobicity even after exposure to extreme thermal stresses and has excellent thermal and electrical properties. The coating can also be reinforced by optimally impregnating the CNT-mesh structure with cross-linked polymers without significantly compromising on superhydrophobicity and electrical conductivity. These superhydrophobic conductive coatings on steel, which is an important structural material, open up possibilities for many new applications in the areas of heat transfer, solar panels, transport of fluids, nonwetting and nonfouling surfaces, temperature resilient coatings, composites, water-walking robots, and naval applications. PMID:19281157

Sethi, Sunny; Dhinojwala, Ali

2009-04-21

277

Making micro soccer balls: Spherical macro-clusters of colloidal particles by droplet evaporation on superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

Imagine a clean capillary droplet evaporating in a fakir state on a superhydrophobic micro-structured surface. When the superhydrophobicity is robust enough, the droplet will always remain on top of the micro-structure and the droplet will retain its spherical shape until its ``death.'' Very often one can observe the remains of the impurities within the droplet left on top of the structure at the end of the process. In this work, instead of using clean liquid droplets, we use dilute colloidal dispersion droplets of monodisperse polymer micro-spheres (sizes from 0.2 to 2?m). The colloidal dispersion droplet retains its spherical shape during its whole life, even when the whole solution has been evaporated. The remaining object consist on a spherical-shaped massive cluster of particles with diameters ranging from a few tens of microns up to several hundreds of microns, depending on the amount of micro-particles present in the solution and on the final packing fraction. We will discuss on the different observed packing fractions, particle arrangements and their governing parameters. Additionally some predictions will also be introduced.

Marin, Alvaro; Susarrey-Arce, Arturo; Gardeniers, Han; Lohse, Detlef

2011-11-01

278

Superhydrophobic antibacterial cotton textiles  

Microsoft Academic Search

We present a facile and effective method to prepare superhydrophobic cotton textiles. Silver particles were produced on cotton fibers by treatment with aqueous KOH and AgNO3, followed by reduction treatment with ascorbic acid in the presence of a polymeric steric stabilizer to generate a dual-size surface roughness. Further modification of the particle-containing cotton textiles with octyltriethoxysilane led to hydrophobic surfaces.

Mohammad Shateri Khalil-Abad; Mohammad E. Yazdanshenas

2010-01-01

279

Liquid-infused nanostructured surfaces with extreme anti-ice and anti-frost performance.  

PubMed

Ice-repellent coatings can have significant impact on global energy savings and improving safety in many infrastructures, transportation, and cooling systems. Recent efforts for developing ice-phobic surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces, yet these surfaces fail in high-humidity conditions due to water condensation and frost formation and even lead to increased ice adhesion due to a large surface area. We report a radically different type of ice-repellent material based on slippery, liquid-infused porous surfaces (SLIPS), where a stable, ultrasmooth, low-hysteresis lubricant overlayer is maintained by infusing a water-immiscible liquid into a nanostructured surface chemically functionalized to have a high affinity to the infiltrated liquid and lock it in place. We develop a direct fabrication method of SLIPS on industrially relevant metals, particularly aluminum, one of the most widely used lightweight structural materials. We demonstrate that SLIPS-coated Al surfaces not only suppress ice/frost accretion by effectively removing condensed moisture but also exhibit at least an order of magnitude lower ice adhesion than state-of-the-art materials. On the basis of a theoretical analysis followed by extensive icing/deicing experiments, we discuss special advantages of SLIPS as ice-repellent surfaces: highly reduced sliding droplet sizes resulting from the extremely low contact angle hysteresis. We show that our surfaces remain essentially frost-free in which any conventional materials accumulate ice. These results indicate that SLIPS is a promising candidate for developing robust anti-icing materials for broad applications, such as refrigeration, aviation, roofs, wires, outdoor signs, railings, and wind turbines. PMID:22680067

Kim, Philseok; Wong, Tak-Sing; Alvarenga, Jack; Kreder, Michael J; Adorno-Martinez, Wilmer E; Aizenberg, Joanna

2012-06-15

280

Pyridine-containing block copolymer/silica core-shell nanoparticles for one-step preparation of superhydrophobic surfaces.  

PubMed

Two poly(4-vinylpyridine)-b-polystyrene diblock copolymer/silica core-shell nanoparticles (P4VP-b-PS/SiO2 NPs) are developed in this work. Confirmed by DLS analysis and TEM observation, one comprises a SiO2 core surrounded by a P4VP-b-PS shell and the other comprises a P4VP-b-PS core surrounded by a SiO2 shell, which is facilely prepared by the in situ hydrolysis of tetraethyl orthosilicate (TEOS) using cationic P4VP-b-PS micelles obtained in a THF-H2C2O4 (aq, 0.1 mol L(-1)) mixture and a DMF-H2C2O4 (aq, 0.01 mol L(-1)) mixture as template, respectively. The SCA, CAH, SA and SEM measurements reveal that one-step deposition of P4VP-b-PS/SiO2 NPs with SiO2 cores formed at a high level of TEOS creates a superhydrophobic surface with an SCA of 160°, a CAH of 2° and an SA of around 4° originating from the formation of a typical micro-nanoscale binary structure (MNBS). For the NPs with SiO2 cores formed at a low level of TEOS, the superhydrophobicity with a SCA of 151°, CAH of 3° and SA of around 5° can be induced by the transition of the surface microstructure from an uneven and discontinuous MNBS, created by a one-step deposition process, to the coexistence of MNBS and a nanoscale structure (NS) after annealing with toluene for 30 min. In contrast, one-step deposition of P4VP-b-PS/SiO2 NPs with P4VP-b-PS cores and SiO2 shells usually results in the inhomogeneous precipitation of SiO2 from bulk P4VP-b-PS along with the production of micro-cracks, with which is impossible to achieve surface superhydrophobicity. PMID:23702827

Liang, Junyan; Wang, Li; He, Ling; Sun, Shaodong

2013-05-24

281

How superhydrophobicity breaks down  

PubMed Central

A droplet deposited or impacting on a superhydrophobic surface rolls off easily, leaving the surface dry and clean. This remarkable property is due to a surface structure that favors the entrainment of air cushions beneath the drop, leading to the so-called Cassie state. The Cassie state competes with the Wenzel (impaled) state, in which the liquid fully wets the substrate. To use superhydrophobicity, impalement of the drop into the surface structure needs to be prevented. To understand the underlying processes, we image the impalement dynamics in three dimensions by confocal microscopy. While the drop evaporates from a pillar array, its rim recedes via stepwise depinning from the edge of the pillars. Before depinning, finger-like necks form due to adhesion of the drop at the pillar’s circumference. Once the pressure becomes too high, or the drop too small, the drop slowly impales the texture. The thickness of the air cushion decreases gradually. As soon as the water–air interface touches the substrate, complete wetting proceeds within milliseconds. This visualization of the impalement dynamics will facilitate the development and characterization of superhydrophobic surfaces.

Papadopoulos, Periklis; Mammen, Lena; Deng, Xu; Vollmer, Doris; Butt, Hans-Jurgen

2013-01-01

282

From petal effect to lotus effect: a facile solution immersion process for the fabrication of super-hydrophobic surfaces with controlled adhesion.  

PubMed

In this paper, a convenient approach based on the reaction between an alkyl thiol and hierarchical structured Cu(OH)2 substrates is reported for the fabrication of super-hydrophobic surfaces with controlled adhesion. This reaction can etch the Cu(OH)2 microstructures and simultaneously introduce a coating with low surface energy. By simply controlling the reaction time or the chain length of the thiol, super-hydrophobic surfaces with controlled adhesion can be achieved, and the adhesive force between the surface and the water droplet can be adjusted from extreme low (?14 ?N) to very high (?65 ?N). The tunable effect of the adhesion is ascribed to the different wetting states for the droplet on the surface that results from the change of the morphology and microstructure scale after the thiolate reaction. Noticeably, the as-prepared surfaces are acid/alkali-resisting; the acidic and basic water droplets have similar contact angles and adhesive forces to that of the neutral water droplet. Moreover, we demonstrate a proof of water droplet transportation for application in droplet-based microreactors via our surfaces. We believe that the results reported here would be helpful for the further understanding of the effect of wetting states on the surface adhesion and the fabrication principle for a super-hydrophobic surface with controlled adhesion. PMID:23429404

Cheng, Zhongjun; Du, Ming; Lai, Hua; Zhang, Naiqing; Sun, Kening

2013-04-01

283

Spontaneous Breakdown of Superhydrophobicity  

Microsoft Academic Search

In some cases water droplets can completely wet microstructured superhydrophobic surfaces. The dynamics of this rapid process is analyzed by ultrahigh-speed imaging. Depending on the scales of the microstructure, the wetting fronts propagate smoothly and circularly or---more interestingly---in a stepwise manner, leading to a growing square-shaped wetted area: entering a new row perpendicular to the direction of front propagation takes

Mauro Sbragaglia; Alisia M. Peters; Christophe Pirat; Bram M. Borkent; Rob G. H. Lammertink; Matthias Wessling; Detlef Lohse

2007-01-01

284

Modelling of contact angle hysteresis on rough, non-uniform and superhydrophobic surfaces with lattice Boltzmann method  

NASA Astrophysics Data System (ADS)

Contact Angle Hysteresis (CAH) is usually attributed to surface heterogeneity, contact line pinning, adsorption or interdiffusion. A model of CAH developed recently by Kubiak & Wilson is demonstrated using the lattice Boltzmann method. The model is based on the dynamic surface heterogeneity, reorientation of surface molecules under wetting liquid, physical roughness, chemical heterogeneity and liquid adhesion and evaporation. Once the surface is wetted, the local static contact angle (CA) changes from its advancing value to match the receding static CA over time Ta. When the contact line retracts, the surface recovers its initial properties corresponding to the advancing static CA over time period Te, which corresponds to the physical evaporation. Further development of the model to include surface roughness and chemical heterogeneity is presented. The model shows good agreement with experimental results for several practical configurations i.e. droplet impact and coalescence, drops on tilted surface, and drops on superhydrophobic and non-uniform surfaces etc. The extended model exhibits great potential for predictive modelling using the lattice Boltzmann method, but can be also implemented in other schemes.

Kubiak, K. J.; Wilson, M. C. T.; Castrejón-Pita, J. R.; Hutchings, I. M.

2011-11-01

285

PHOTONICS AND NANOTECHNOLOGY Laser nanostructuring of materials surfaces  

NASA Astrophysics Data System (ADS)

This paper reviews results of experimental and theoretical studies of surface micro- and nanostructuring of metals and other materials irradiated directly by short and ultrashort laser pulses. Special attention is paid to direct laser action involving melting of the material (with or without ablation), followed by ultrarapid surface solidification, which is an effective approach to producing surface nanostructures. Theoretical analysis of recrystallisation kinetics after irradiation by ultrashort laser pulses makes it possible to determine the volume fraction of crystallised phase and the average size of forming crystalline structures as functions of laser treatment regime and thermodynamic properties of the material. The present results can be used to optimise pulsed laser treatment regime in order to ensure control nanostructuring of metal surfaces.

Zavestovskaya, I. N.

2010-12-01

286

Nanostructure-Based Localized Surface Plasmon Resonance Biosensors  

Microsoft Academic Search

\\u000a This chapter reviews the characteristics of localized surface plasmon resonance (LSPR), the excitation of which is mediated\\u000a by nanostructures, and its applications to biosensing. The LSPR is explored in three regimes in terms of creation and coupling\\u000a of localized surface plasmons (LSPs): LSPs created in surface-relief patterns coupled to propagating surface plasmons (SPs),\\u000a LSPs in surface-relief patterns coupled to particle

Donghyun Kim

2010-01-01

287

Nanostructures of organic molecules and proteins on surfaces  

NASA Astrophysics Data System (ADS)

Patterning bioreceptors on surfaces is a key step in the fabrication of biosensors and biochips. State-of-the art technology can produce micrometer-sized biostructures, however, further miniaturization at the nanoscale will require new methods and lithographic tools. In this proceeding, we report three approaches: nanopen reader and writer (NPRW), nanografting and latex particle lithography; for creating nanostructures of small molecules, DNA and proteins. Using nanografting and NPRW, nanostructures of thiol molecules or thiolated ssDNA are fabricated within self-assembled monolayers. Proteins attach selectively to nanopatterns of thiol molecules containing bioadhesive groups such as aldehyde or carboxylates. Using latex particle lithography, arrays of protein nanostructures are produced with high throughput on mica and gold substrates. Near-physiological conditions are used in structural characterization, thus the orientation, reactivity and stability of proteins and DNA molecules within nanostructures may be monitored directly via AFM. While AFM-based approaches provide the highest precision, nanoparticle lithography can produce arrays of protein nanostructures with high throughput. The nanostructures of proteins produced by these approaches provide an excellent opportunity for fundamental investigations of biochemical reactions on surfaces, such as antigen-antibody recognition and DNA-protein interactions. These methods provide a foundation for advancing biotechnology towards the nanoscale.

Amro, Nabil A.; Garno, Jayne C.; Liu, Maozi; Wadu-Mesthrige, Kapila; Liu, Gang-yu

2002-09-01

288

Superhydrophobic graphene foams.  

PubMed

The static and dynamic wetting properties of a 3D graphene foam network are reported. The foam is synthesized using template-directed chemical vapor deposition and contains pores several hundred micrometers in dimension while the walls of the foam comprise few-layer graphene sheets that are coated with Teflon. Water contact angle measurements reveal that the foam is superhydrophobic with an advancing contact angle of ?163 degrees while the receding contact angle is ?143 degrees. The extremely water repellent nature of the foam is also confirmed when impacting water droplets are able to completely rebound from the surface. Such superhydrophobic graphene foams show potential in a variety of applications ranging from anti-sticking and self-cleaning to anti-corrosion and low-friction coatings. PMID:22911509

Singh, Eklavya; Chen, Zongping; Houshmand, Farzad; Ren, Wencai; Peles, Yoav; Cheng, Hui-Ming; Koratkar, Nikhil

2012-08-22

289

Metal-induced nanostructures on surfaces of layered chalcogenides  

NASA Astrophysics Data System (ADS)

The development of layered dichalcogenide crystal surfaces during early stages of metal deposition has been investigated, using ultra-high vacuum electron beam evaporation of copper at ambient temperature onto (0 0 0 1) VSe2 crystal surfaces as model case. Analytical transmission electron microscopy techniques, scanning electron microscopy, and atomic force microscopy have been combined to characterize the microscopic nature of the surface structures and the self-assembled formation of surface nanostructures that form as large nanostructures (lateral dimensions > 100 nm) and as networks of smaller nanostructures (lateral dimensions ˜ several 10 nm). Nearly contiguous ultrathin layers of a copper-rich crystalline surface phase are observed for deposition stages at a nominal Cu coverage of 1 nm and above. The observations indicate that compressive in-plane strains are induced in the VSe2 surface layers by the formation of a copper-rich crystalline phase by intercalation, with possible contributions of an electronic charge transfer from copper atoms to the substrate during the earliest deposition stages. Above a critical value the surface layer strains are relaxed by formation of surface folds, nanostructure networks and interface dislocations.

Hollensteiner, S.; Spiecker, E.; Jäger, W.

2005-02-01

290

In situ X-ray scattering studies of protein solution droplets drying on micro- and nanopatterned superhydrophobic PMMA surfaces.  

PubMed

Superhydrophobic poly(methyl methacrylate) surfaces with contact angles of ?170° and high optical and X-ray transparencies have been fabricated through the use of optical lithography and plasma etching. The surfaces contain either a microscale pattern of micropillars or a random nanofibrillar pattern. Nanoscale asperities on top of the micropillars closely resemble Nelumbo nucifera lotus leaves. The evolution of the contact angle of water and lysozyme solution droplets during evaporation was studied on the micro- and nanopatterned surfaces, showing in particular contact-line pinning for the protein solution droplet on the nanopatterned surface. The microstructural evolution of lysozyme solution droplets was studied on both types of surfaces in situ under nearly contact-free conditions by synchrotron radiation microbeam wide-angle and small-angle X-ray scattering revealing the increasing protein concentration and the onset of precipitation. The solid residuals show hollow sphere morphologies. Rastermicrodiffraction of the detached residuals suggests about a 1/3 volume fraction of ?17 nm lysozyme nanocrystalline domains and about a 2/3 short-range-order volume fraction. About 5-fold larger nanocrystalline domains were observed at the attachment points of the sphere to the substrates, which is attributed to particle growth in a shear flow. Such surfaces represent nearly contact-free sample supports for studies of inorganic and organic solution droplets, which find applications in biochips. PMID:20804171

Accardo, Angelo; Gentile, Francesco; Mecarini, Federico; De Angelis, Francesco; Burghammer, Manfred; Di Fabrizio, Enzo; Riekel, Christian

2010-09-21

291

Superhydrophobic Surfaces for Water-Repellent or Self-Cleaning Behavior:. Chemical Effect  

NASA Astrophysics Data System (ADS)

In this study, a thermodynamic analysis is conducted to investigate the chemical effect, in terms of intrinsic contact angle (CA), on the superhydrophobic behavior. It is theoretically revealed that the essential effect of intrinsic CA is to promote the composite transition. In particular, a large intrinsic CA more than 90° is necessary for such transition. Furthermore, for a pillar system with an intrinsic CA smaller than 90°, composite states are not impossible but is thermodynamically unstable. Once composite states are achieved, the advancing or maximum CA always approaches 180° whether an intrinsic CA is larger or smaller than 90°. In addition, the role of intrinsic CA in the water-repellent or self-cleaning behavior such as contact angle hysteresis (CAH) and equilibrium CA has been discussed in detail.

Zhou, Y. P.; Lin, Z. W.; Brown, J.

292

Preparation of superhydrophobic surface with a novel sol-gel system  

NASA Astrophysics Data System (ADS)

Sol-gel method is a simple and cheap way to prepare superhydrophobic coatings or films, however, most of the researches on sol-gel focus on silica or ZnO sol-gel. The present paper proposes a novel sol-gel which is made from hydrolysis and condensation of the by-product of polymethylhydrosiloxane (PMHS) reacting with ?-aminopropyltriethoxysilane (KH550). The mechanism of formation of the by-product and the sol-gel is discussed and the by-product is characterized by FT-IR. The mass ratio of KH550/PMHS of the sol-gel influences the water contact angle (WCA) and water sliding angle (WSA) of the film made of spraying the sol-gel to microscope glass. When the mass ratio of KH550/PMHS of the sol-gel reaches 0.25, WCA of the corresponding film is 157° and WSA of it is less than 1°. The mechanism of formation of the sol-gel is discussed, and the size of the sol-gel is characterized by polarization microscope as well. The morphology of the film made of the sol-gel is analyzed by means of scanning electron microscope (SEM). It was found that the diameter of the particle of the superhydrophobic film is about 40 ?m, nevertheless, from the larger magnification picture, the particle is found to be composed of micro-balls whose diameter is about 2 ?m, and the micro-ball is composed of nano-sphere whose diameter is less than 200 nm.

Su, Dong; Huang, Chengya; Hu, You; Jiang, Qiangwei; Zhang, Long; Zhu, Yunfeng

2011-11-01

293

One-step fabrication of nanostructured Ni film with lotus effect from deep eutectic solvent.  

PubMed

We report a procedure to fabricate nanostructured Ni films via programmed electrochemical deposition from a choline-chloride-based ionic liquid at a high temperature of 90 °C. Three electrodeposition modes using constant voltage, pulse voltage, and reverse pulse voltage produce a variety of nanostructured Ni films with micro/nanobinary surface architectures, such as nanosheets, aligned nanostrips, and hierarchical flowers. The nanostructured Ni films possess face-centered cubic crystal structure. Amazingly, it is found that the electrodeposited Ni films deliver the superhydrophobic surfaces without any further modifications by low surface-energy materials, which might be attributed to the vigorous micro/nanobinary architectures and the surface chemical composition. The electrochemical measurements reveal that the superhydrophobic Ni film exhibit an obvious passivation phenomenon, which could provide enhanced corrosion resistance for the substrate in the aqueous solutions. PMID:21739965

Gu, Changdong; Tu, Jiangping

2011-07-19

294

Imprinted and injection-molded nano-structured optical surfaces  

NASA Astrophysics Data System (ADS)

Inspired by nature, nano-textured surfaces have attracted much attention as a method to realize optical surface functionality. The moth-eye antireflective structure and the structural colors of Morpho butterflies are well- known examples used for inspiration for such biomimetic research. In this paper, nanostructured polymer surfaces suitable for up-scalable polymer replication methods, such as imprinting/embossing and injection-molding, are discussed. The limiting case of injection-moulding compatible designs is investigated. Anti-reflective polymer surfaces are realized by replication of Black Silicon (BSi) random nanostructure surfaces. The optical transmission at normal incidence is measured for wavelengths from 400 nm to 900 nm. For samples with optimized nanostructures, the reflectance is reduced by 50 % compared to samples with planar surfaces. The specular and diffusive reflection of light from polymer surfaces and their implication for creating structural colors is discussed. In the case of injection-moulding compatible designs, the maximum reflection of nano-scale textured surfaces cannot exceed the Fresnel reflection of a corresponding flat polymer surface, which is approx. 4 % for normal incidence. Diffraction gratings provide strong color reflection defined by the diffraction orders. However, the apperance varies strongly with viewing angles. Three different methods to address the strong angular-dependence of diffraction grating based structural color are discussed.

Christiansen, Alexander B.; Højlund-Nielsen, Emil; Clausen, Jeppe; Caringal, Gideon P.; Mortensen, N. Asger; Kristensen, Anders

2013-09-01

295

Fabrication of superhydrophobicity on cotton fabric by sol-gel  

NASA Astrophysics Data System (ADS)

A superhydrophobic cotton fabric was prepared by dip-coating TiO2 for four times and subsequent surface modification with n-octadecylthiol (ODT). The surface morphology, crystal structure and chemical composition are studied by SEM, XRD, and XPS, respectively. Water contact angle on the superhydrophobic cotton fabric is approximately 151° and the glide angle is less than 20°. The results show that two factors of higher surface roughness and lower surface free energy play a crucial role for the formation of the superhydrophobicity. Finally, the formation mechanism of superhydrophobicity on the cotton fabric was discussed on the basis of Wenzel's and Cassie's theory.

Shi, Yanlong; Wang, Yongsheng; Feng, Xiaojuan; Yue, Guoren; Yang, Wu

2012-08-01

296

Fabrication of super-hydrophobic channels  

NASA Astrophysics Data System (ADS)

A new approach was developed in this work to create channels which had not only super-hydrophobic bottom surfaces but also super-hydrophobic sidewalls. Researchers have demonstrated that a flow experienced less drag forces and thus required smaller driving pressure in a channel of micro/nanostructure-formed top and bottom surfaces. The drag forces should be further reduced in a channel which has not only patterned top and bottom surfaces but also patterned sidewall surfaces. However, due to the limitation of the existing lithographic approaches, sidewalls could not be properly patterned. Therefore, a new approach was developed in this work to overcome this obstacle. Polydimethylsiloxane (PDMS) micropillars of aspect ratios 1.4, 2.0 and 2.7 were first generated on PDMS films using a molding method, and then transferred to the sidewalls and bottom surfaces of three 1 mm wide and 1 mm deep channels, respectively, applying a hot-embossing process. The corresponding deformation mechanism was considered. The widths of the PDMS films had a critical effect on the cross-section profiles of the generated channels. The radii of the channel corners and inclined degrees of the sidewalls increased with the film widths. Contact angles on the PDMS films before and after the deformations were measured and compared. The contact angles in the middle portions of the sidewalls, as well as at the bottoms of the generated channels, were little difference from those on the original PDMS films due to the small changes in the distances between the micropillars. However, the contact angles were increased and decreased, respectively, at the bottom and top corners of the generated channels since the PDMS films were compressed and stretched at these corners during the fabrication. The variation of the contact angle in each channel was further analyzed according to two existing theoretical formulas. These variations increased with the increasing aspect ratios of the PDMS micropillars. The super-hydrophobic channels fabricated could be potentially employed to reduce drag forces in microfluidic applications.

Liu, Xinchuan; Luo, Cheng

2010-02-01

297

Characterization of nanostructured plasmonic surfaces with second harmonic generation.  

PubMed

Because of its high surface and interface sensitivity, the nonlinear optical technique of second harmonic generation (SHG) is a designated method for investigating nanostructured metal surfaces. Indeed, the latter present a high surface-to-volume ratio, but even more importantly, they can exhibit strong near-field enhancements or "hot spots". Hot spots often appear as a result of geometric features on the nanoscale or surface plasmon resonances, which are collective electron oscillations on the surface that, on the nanoscale, can readily be excited by light. In the last 10 years, near-field hot spots have been responsible for dramatic developments in the field of nano-optics. In this Feature Article, the influence of hot spots on the SHG response of nanostructured metal surfaces is discussed on both the microscopic and macroscopic levels. On the microscopic level, the nanostructured metal surfaces were characterized by scanning SHG microscopy, complemented by rigorous numerical simulations of the near-field and of the local electric currents at the fundamental frequency. On the macroscopic level, SHG-circular dichroism and magnetization-induced SHG characterization techniques were employed. PMID:22889193

Valev, V K

2012-08-28

298

Development and characterization of nanostructured-perlite-cementitious surface compounds  

Microsoft Academic Search

The effect of perlite loading on the thermal resistivity, solar reflectance and indirect tensile strength of Nanostructured\\u000a Cementitious Binder is studied. The main objective of this research is to constitute structural lightweight surface compounds\\u000a and to improve their thermal resistivity and reflectivity with suitable mechanical performances as a surface compound. Portland\\u000a White Cement (PWC) was partially substituted by nano clay.

M. S. Morsy; H. A. Aglan

2007-01-01

299

Superhydrophobic membranes with ordered arrays of nanospiked microchannels for water desalination.  

PubMed

Membrane distillation can desalinate seawater using low-grade heat energy or solar heat, but it has limited mass fluxes and membrane fouling issues. Glass membranes with integrated arrays of nanospiked microchannels and a narrow pore size distribution are made through a process that involves glass fiber drawing, dissolving template material from microchannels and differential chemical etching. After surface modification, superhydrophobic glass membranes with water contact angles of over 160 degrees are produced because of the formations of ordered arrays of spiked nanostructures. The superhydrophobic membrane has shown better antifouling ability and higher flux than those of existing polymer membranes, especially at high salt concentration, owing to its large pore diameter, straight pore shape, narrow pore size distribution, high chemical and thermal stabilities, and water-repelling ability. PMID:19341278

Ma, Zeyu; Hong, Yan; Ma, Liyuan; Su, Ming

2009-05-19

300

Development of superhydrophobic coating on paperboard surface using the Liquid Flame Spray  

Microsoft Academic Search

This paper introduces a new method for generating nanoscale coatings in a continuous roll-to-roll process at normal pressure. Nanostructured and transparent coating, based on titanium dioxide nanoparticles, was successfully deposited on-line at atmospheric conditions on pigment coated paperboard using a thermal spray method called the Liquid Flame Spray (LFS). The LFS coating process is described and the influences of process

H. Teisala; M. Tuominen; M. Aromaa; J. M. Mäkelä; M. Stepien; J. J. Saarinen; M. Toivakka; J. Kuusipalo

2010-01-01

301

Effects of long pulse width and high pulsing frequency on surface superhydrophobicity of polytetrafluoroethylene in quasi-direct-current plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Long pulse, high frequency quasi-direct-current (dc) oxygen plasma immersion ion implantation (PIII) is utilized to create a superhydrophobic polytetrafluoroethylene (PTFE) surface with a water contact angle of over 150°. This technique allows the use of a high duty cycle without deleterious effects such as extensive sample heating encountered in conventional PIII. Scanning electron microscopy images review submicrometer-nanometer structures on the PTFE surface after long pulse, high frequency PIII indicative of ion implantation. On the other hand, plasma modification is the dominant effect in short pulse, low frequency PIII. Quasi-dc PIII is demonstrated to offer adjustable synergistic plasma and ion beam effects.

Kwok, Dixon T. K.; Wang, Huaiyu; Zhang, Yumei; Yeung, Kelvin W. K.; Chu, Paul K.

2009-03-01

302

Effect of surface nanostructure on temperature programmed reaction spectroscopy  

NASA Astrophysics Data System (ADS)

Using the catalytic CO oxidation at RuO2(110) as a showcase, we employ first-principles kinetic Monte Carlo simulations to illustrate the intricate effects on temperature programmed reaction (TPR) spectroscopy data brought about by the mere correlations between the locations of the active sites at a nanostructured surface. Even in the absence of lateral interactions, this nanostructure alone can cause inhomogeneities that cannot be grasped by prevalent mean-field data analysis procedures, which thus lead to wrong conclusions on the reactivity of the different surface species. The RuO2(110) surface studied here exhibits only two prominent active sites, arranged in simple alternating rows. Yet, the mere neglection of this still quite trivial nanostructure leads mean-field TPR data analysis [1] to extract kinetic parameters that are in error by several orders of magnitude and that do not even reflect the relative reactivity of the different surface species correctly [2].[1] S. Wendt, M. Knapp, and H. Over, JACS 126, 1537 (2004).[2] M. Rieger, J. Rogal, and K. Reuter, Phys. Rev. Lett (in press).

Rieger, Michael; Rogal, Jutta; Reuter, Karsten

2008-03-01

303

Electrospray on superhydrophobic nozzles treated with argon and oxygen plasma  

NASA Astrophysics Data System (ADS)

We report on a simple process to fabricate electrohydrodynamic spraying devices with superhydrophobic nozzles. These devices are useful, among other things, in mass spectrometry and printing technology. The superhydrophobic nozzle is created by roughening the surface of the polyfluorotetraethylene (PTFE) by argon and oxygen plasma treatment. We have developed a polymer-based electrospray device with a flat, superhydrophobic nozzle capable of maintaining a high contact angle and stable jetting.

Byun, Doyoung; Lee, Youngjong; Tran, Si Bui Quang; Nugyen, Vu Dat; Kim, Sanghoon; Park, Baeho; Lee, Sukhan; Inamdar, Niraj; Bau, Haim H.

2008-03-01

304

[Perspectives of use of polytetrafluoroethylene with nanostructured surface in dentistry].  

PubMed

The perspectives of use of porous polytetrafluorethilen (PTPE) with modified surface combined with mesenchymal stem cells for tissue-engineering constructions were studied. The paper also describes the mode of PTPE surface modification consisting in nanostructured metallic or ceramic layer application resulting in biocompatibility and surface adhesion rates increase. The magnetic atomizing of Ti and Ti-Ca-P-C-O-N nanolayers enhances the material integration potential as well as adhesion rates thus making it perspective when combined with mesenchymal stem cells for bone defects plasty. PMID:23268208

Grigor'ian, A S; Shtanski?, D V; Selezneva, I I; Arkhipov, A V

2012-01-01

305

Slippage of water past superhydrophobic carbon nanotube forests in microchannels  

Microsoft Academic Search

We present an experimental characterization of liquid flow slippage over superhydrophobic surfaces made of carbon nanotube forests, incorporated in microchannels. We make use of a mu-PIV (Particule Image Velocimetry) technique to achieve the submicrometric resolution on the flow profile necessary for accurate measurement of the surface hydrodynamic properties. We demonstrate boundary slippage on the Cassie superhydrophobic state, associated with slip

Pierre Joseph; Cecile Cottin-Bizonne; Jean-Michel Benoit; Christophe Ybert; Catherine Journet; Patrick Tabeling; Lyderic Bocquet

2006-01-01

306

Preparation of functionalized nanostructures on microchannel surface and their use for enzyme microreactors  

Microsoft Academic Search

Microreactors have become a new and promising technology in chemistry, chemical engineering, and biotechnology fields. Nanostructures have attracted interest as a reaction apparatus especially for catalytic reaction. The present study develops a simple method for nanostructure preparation that is suitably functionalized for a pile-up enzyme microreaction system.First, we developed a simple method to prepare a nanostructure on a microchannel surface.

Masaya Miyazaki; Jun Kaneno; Ryo Kohama; Masato Uehara; Kenichi Kanno; Masayuki Fujii; Hazime Shimizu; Hideaki Maeda

2004-01-01

307

Electrodeposition fabrication of Co-based superhydrophobic powder coatings in non-aqueous electrolyte  

NASA Astrophysics Data System (ADS)

A rapid, facile, one-step process was developed to fabricate Co-based superhydrophobic powder coatings on the stainless steel surfaces with a nonaqueous electrolyte by the electrodeposition method. The structure and composition of the superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and contact angle measurement. The results show that the special hierarchical structures along with the low surface energy lead to the high superhydrophobicity of the substrate surface. The shortest process of constructing the superhydrophobic surface is only 30 seconds, the high contact angle is greater than 160°, and the rolling angle is less than 2°. The method can be used to fabricate the superhydrophobic powder coatings at any conductive cathodic surface, and the as-prepared superhydrophobic powder coatings have advantages of transferability, repairability, and durability. It is expected that this facile method will accelerate the large-scale production of superhydrophobic material.

Chen, Zhi; Hao, Limei; Duan, Mengmeng; Chen, Changle

2013-05-01

308

Single ion induced surface nanostructures: a comparison between slow highly charged and swift heavy ions  

Microsoft Academic Search

This topical review focuses on recent advances in the understanding of the formation of surface nanostructures, an intriguing phenomenon in ion-surface interaction due to the impact of individual ions. In many solid targets, swift heavy ions produce narrow cylindrical tracks accompanied by the formation of a surface nanostructure. More recently, a similar nanometric surface effect has been revealed for the

Friedrich Aumayr; Stefan Facsko; Ayman S. El-Said; Christina Trautmann; Marika Schleberger

2011-01-01

309

Restoration of superhydrophobicity in crushed polymer films by treatment with water: self-healing and recovery of damaged topographic features aided by an unlikely source.  

PubMed

The crushing of superhydrophobic polymer multilayers destroys micro/nanoscale topographic features critical for the maintenance of superhydrophobicity. We demonstrate that these surface features can be recovered, and that superhydrophobicity can be fully restored, by treatment of damaged films with liquid water. These polymer-based films can also sustain other forms of severe abuse without loss of superhydrophobicity. This combination of features addresses several important practical issues associated with the durability of artificial superhydrophobic surfaces. PMID:23943399

Manna, Uttam; Lynn, David M

2013-08-13

310

Facets of protein assembly on nanostructured titanium oxide surfaces.  

PubMed

One key for the successful integration of implants into the human body is the control of protein adsorption by adjusting the surface properties at different length scales. This is particularly important for titanium oxide, one of the most common biomedical interfaces. As for titania (TiO(2)) the interface is largely defined by its crystal surface structure, it is crucial to understand how the surface crystallinity affects the structure, properties and function of protein layers mediating subsequent biological reactions. For rutile TiO(2) we demonstrate that the conformation and relative amount of human plasma fibrinogen (HPF) and the structure of adsorbed HPF layers depend on the crystal surface nanostructure by employing thermally etched multi-faceted TiO(2) surfaces. Thermal etching of polycrystalline TiO(2) facilitates a nanoscale crystal faceting and, thus, the creation of different surface nanostructures on a single specimen surface. Atomic force microscopy shows that HPF arranges into networks and thin globular layers on flat and irregular crystal grain surfaces, respectively. On a third, faceted category we observed an alternating conformation of HPF on neighboring facets. The bulk grain orientation obtained from electron backscatter diffraction and thermodynamic mechanisms of surface reconstruction during thermal etching suggest that the grain and facet surface-specific arrangement and relative amount of adsorbed proteins depend on the associated free crystal surface energy. The implications for potentially favorable TiO(2) crystal facets regarding the inflammatory response and hemostasis are discussed with a view to the advanced surface design of future implants. PMID:23142481

Keller, Thomas F; Reichert, Jörg; Thanh, Tam Pham; Adjiski, Ranko; Spiess, Lothar; Berzina-Cimdina, Liga; Jandt, Klaus D; Bossert, Jörg

2012-11-07

311

Correlation effects in insulating surface nanostructures  

NASA Astrophysics Data System (ADS)

We study the role of static and dynamical Coulomb correlation effects on the electronic and magnetic properties of individual Mn, Fe, and Co adatoms deposited on the CuN surface. For these purposes, we construct a realistic Anderson model, solve it by using the finite-temperature exact diagonalization method, and compare the calculated one-particle spectral functions with the LDA+U densities of states. In contrast to Mn/CuN and Fe/CuN, the cobalt system tends to form the electronic excitations at the Fermi level. Based on the calculated magnetic response functions, transverse relaxation times for the magnetic moments of impurity orbitals are estimated. To study the effect of the dynamical correlations on the exchange interaction in nanoclusters, we solve the two-impurity Anderson model for the Mn dimer on the CuN surface. It is found that the experimental exchange interaction can be well reproduced by employing U=3 eV, which is two times smaller than the value used in static mean-field LDA+U calculations. This suggests an important role of dynamical correlations in the interaction between adatoms on a surface. To estimate the correlated exchange interaction in the general case we derive a simple and transparent analytical expression demonstrating that the renormalization of the electronic spectrum due to dynamical correlations leads to a rescaling of the magnetic interactions compared to density functional results.

Mazurenko, V. V.; Iskakov, S. N.; Rudenko, A. N.; Kashin, I. V.; Sotnikov, O. M.; Valentyuk, M. V.; Lichtenstein, A. I.

2013-08-01

312

Creating Long-Lived Superhydrophobic Polymer Surfaces Through Mechanically Assembled Monolayers  

Microsoft Academic Search

We show that elastomeric surfaces can be tailored using ``mechanically assembled monolayers'' (MAMs), structures that are fabricated by combining self-assembly of surface grafting molecules with mechanical manipulation of the grafting points in the underlying elastic surface. The versatility of this surface modification method is demonstrated by fabricating MAMs with semifluorinated (SF) molecules. These SF-MAMs have superior nonwetting and barrier properties

Jan Genzer; Kirill Efimenko

2000-01-01

313

Extreme resistance of super-hydrophobic surfaces to impalement: reversible electrowetting related to the impacting\\/bouncing drop test  

Microsoft Academic Search

The paper reports on the comparison of the wetting properties of super-hydrophobic silicon nanowires (NWs), using drop impact impalement and electrowetting (EW) experiments. A correlation between the resistance to impalement on both EW and drop impact is shown. From the results, it is evident that when increasing the length and density of NWs: (i) the thresholds for drop impact and

P. Brunet; F. Lapierre; V. Thomy; Y. Coffinier; R. Boukherroub

2008-01-01

314

Photocatalytic properties of nanostructured TiO2 surfaces  

NASA Astrophysics Data System (ADS)

Photocatalytic chemical reactions are actively explored for direct production of chemical fuels from sun light through electrolysis or for the clean-up of organic pollutants through photocatalysis. Titanium dioxide is a prototypical photocatalyst which has been studied extensively. However, there are still unanswered questions regarding the relationship between surface morphology and photocatalytic properties. In this study, we used ion beam assisted surface nanopatterning and UV-catalysis to investigate the dependence of photoreactivity on surface nanostructures. Energetic argon gas ions were used to induce self-formation of nanopatterns on TiO2 surfaces and the structure formation was characterized by atomic force microscopy. The influence of the surface structure on the photochemical properties was assessed through photocatalytic degradation of methyl orange in aqueous solution with a flat sample and a nanopatterned sample of TiO2, respectively. The resulting absorbance spectrums were then compared.

Moore, Lauren; Luttrell, Timothy; Batzill, Matthias

2012-02-01

315

Nanomechanical properties of silicon surfaces nanostructured by excimer laser  

NASA Astrophysics Data System (ADS)

Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm-2. A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.

Kumar, Prashant; Kiran, M. S. R. N.

2010-04-01

316

Liquid slip on a nanostructured surface.  

PubMed

We explored a liquid slip, referred to as the Navier slip, at liquid-solid interface. Such a slip is provoked by the physicochemical features of the liquid-solid system. The goal of this study was to investigate the effect of a nanoengineered surface structure on liquid slip by fabricating the self-assembly structure of nano Zinc oxide (n-ZnO). We have also examined how the liquid-solid surface interaction controlled by hydrophobic chemical treatment affects the liquid slip. The findings showed that liquid slip increases with decreasing the characteristic length scales (e.g., channel height and depth), resulting in drag reduction. It was also found that dewetted (Cassie) state due to the generation of air gap developed by n-ZnO was more critical for the liquid slip than the minimization of interface interaction. The linear and nonlinear Navier slip models showed that liquid slip behavior is more obvious when increasing the nonlinearity. This study will contribute to understanding of the underlying physics behind fluid slip phenomena, such as the Navier slip for Newtonian liquids and Maxwell's slip for Newtonian gases. PMID:22717057

Lee, Doo Jin; Cho, Ki Yeon; Jang, Soohwan; Song, Young Seok; Youn, Jae Ryoun

2012-07-05

317

Titanium nanostructural surface processing for improved biocompatibility  

SciTech Connect

X-ray photoelectron spectroscopy, grazing incident x-ray diffraction, transmission electron microscopy, and scanning electron microscopy were conducted to evaluate the effect of titanium hydride on the formation of nanoporous TiO{sub 2} on Ti during anodization. Nano-titanium-hydride was formed cathodically before anodizing and served as a sacrificial nanoprecipitate during anodization. Surface oxidation occurred and a multinanoporous structure formed after cathodic pretreatments followed by anodization treatment. The sacrificial nanoprecipitate is directly dissolved and the Ti transformed to nanoporous TiO{sub 2} by anodization. The formation of sacrificial nanoprecipitates by cathodic pretreatment and of the multinanostructure by anodization is believed to improve biocompatibility, thereby promoting osseointegration.

Cheng, H.-C.; Lee, S.-Y.; Chen, C.-C.; Shyng, Y.-C.; Ou, K.-L. [School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China)and Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China) and Department of Emergency Medicine, Mackay Memorial Hospital, Taipei 110, Taiwan (China); Division of Oral and Maxillofacial Surgery, Kaohsiung Military General Hospital, Kaohsiung 807, Taiwan (China); Graduate Institute of Oral Sciences, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China)

2006-10-23

318

Magnetically induced decrease in droplet contact angle on nanostructured surfaces.  

PubMed

We report a magnetic technique for altering the apparent contact angle of aqueous droplets deposited on a nanostructured surface. Polymeric tubes with embedded superparamagnetic magnetite (Fe(3)O(4)) nanoparticles were prepared via layer-by-layer deposition in the 800 nm diameter pores of polycarbonate track-etched (PCTE) membranes. Etching away the original membrane yields a superparamagnetic film composed of mostly vertical tubes attached to a rigid substrate. We demonstrate that the apparent contact angle of pure water droplets deposited on the nanostructured film is highly sensitive to the ante situm strength of an applied magnetic field, decreasing linearly from 117 ± 1.3° at no applied field to 105 ± 0.4° at an applied field of approximately 500 G. Importantly, this decrease in contact angle did not require an inordinately strong magnetic field: a 15° decrease in contact angle was observed even with a standard alnico bar magnet. We interpret the observed contact angle behavior in terms of magnetically induced conformation changes in the film nanostructure, and we discuss the implications for reversibly switching substrates from hydrophilic to hydrophobic via externally tunable magnetic fields. PMID:21882807

Zhou, Qian; Ristenpart, William D; Stroeve, Pieter

2011-09-07

319

Distinction of heterogeneity on Au nanostructured surface based on phase contrast imaging of atomic force microscopy.  

PubMed

The discrimination of the heterogeneity of different materials on nanostructured surfaces has attracted a great deal of interest in biotechnology as well as nanotechnology. Phase imaging through tapping mode of atomic force microscopy (TMAFM) can be used to distinguish the heterogeneity on a nanostructured surface. Nanostructures were fabricated using anodic aluminum oxide (AAO). An 11-mercaptoundecanoic acid (11-MUA) layer adsorbed onto the Au nanodots through self-assembly to improve the bio-compatibility. The Au nanostructures that were modified with 11-MUA and the concave surfaces were investigated using the TMAFM phase images to compare the heterogeneous and homogeneous nanostructured surfaces. Although the topography and phase images were taken simultaneously, the images were different. Therefore, the contrast in the TMAFM phase images revealed the different compositional materials on the heterogeneous nanostructure surface. PMID:20199848

Jung, Mi; Choi, Jeong-Woo

2010-02-24

320

Thermal stable superhydrophobic polyphenylsilsesquioxane/nanosilica composite coatings  

NASA Astrophysics Data System (ADS)

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.

Yang, Haowei; Cheng, Yuanrong; Xiao, Fei

2011-12-01

321

Simultaneous droplet impingement dynamics and heat transfer on nano-structured surfaces  

Microsoft Academic Search

This study examines the hydrodynamics and temperature characteristics of distilled deionized water droplets impinging on smooth and nano-structured surfaces using high speed (HS) and infrared (IR) imaging at We = 23.6 and Re = 1593, both based on initial drop impingement parameters. Results for a smooth and nano-structured surface for a range of surface temperatures are compared. Droplet impact velocity,

Jian Shen; Christof Graber; James Liburdy; Deborah Pence; Vinod Narayanan

2010-01-01

322

Preparation of superhydrophobic, long-neck vase-like polymer surfaces.  

PubMed

Polymer surfaces comprising nanopillars with various geometries were prepared by nanoimprinting the surface using anodic aluminium oxide templates. In particular, a simple fabrication method for long-neck vase-like stepped nanopillars was established, and the surface showed considerable enhancement in the water contact angle, for example from 95.7° to 150.6° for the polystyrene surface. This enhanced hydrophobicity could be explained by the desirable reduction in the area of the solid-liquid interface and reduced sticking between the nanopillars. PMID:23765131

Hong, Dajung; Ryu, Ilhwan; Kwon, Hyemin; Lee, Jae-Joon; Yim, Sanggyu

2013-06-13

323

Beaming of light from metallic surface plasmon polaritons nanostructure  

NASA Astrophysics Data System (ADS)

We investigate the beaming of light formed by a metallic nanostructure through the coupling of a metallic nanoparticle and a metallic nanoslit flanked with periodic sinusoidal grating on one surface. We employ the boundary element method (BEM) to simulate the transmission resonant spectrum and the optical field distribution. The numerical results show that beaming of light are formed from the metallic nanoslit system. Such device can be used for miniature optical antennas in the optical regime, which can transmit or receive light along a specific direction for a given wavelength. Potential applications include the coupling light in or out of fibers and the achieving the miniature optical source.

Zhang, Guo-ting; Liu, Juan; Hu, Chuan-fei; Sun, Fang; Su, Xiao-xing

2008-03-01

324

Origin of hydrophobicity in FIB-nanostructured Si surfaces.  

PubMed

Surface morphology has been demonstrated to influence the tribological properties at different scales, but the phenomena which occur at the nanoscale have not been completely understood. The present study reports on the effect of focused ion beam nanopatterning on coefficient of friction (CoF) and adhesion of Si(001) surface covered by native oxide. Regular arrays of nanogrooves reduce both CoF and adhesion, related to a hydrophobic character of the patterned surface, but this effect disappears as soon as the separation among the nanostructures approaches the microscopic scale. The dependence of this hydrophobic effect on the pitch is not linked to the corresponding contact area. It has been found that each nanostructure is surrounded by a low-friction region which extends some hundreds of nanometers from it. For pitches of 125 and 250 nm these low-friction regions completely overlap, generating a consistent decrease in CoF and adhesion, while for pitches of 500 and 1000 nm their effect is negligible. The low-friction regions were not observed in humidity-free ambient, indicating that they are the origin of patterns of hydrophobicity. PMID:23556503

Rota, Alberto; Tripathi, Manoj; Gazzadi, GianCarlo; Valeri, Sergio

2013-04-18

325

Nanostructuring of molybdenum and tungsten surfaces by low-energy helium ions  

SciTech Connect

The formation of metallic nanostructures by exposure of molybdenum and tungsten surfaces to high fluxes of low energy helium ions is studied as a function of the ion energy, plasma exposure time, and surface temperature. Helium plasma exposure leads to the formation of nanoscopic filaments on the surface of both metals. The size of the helium-induced nanostructure increases with increasing surface temperature while the thickness of the modified layer increases with time. In addition, the growth rate of the nanostructured layer also depends on the surface temperature. The size of the nanostructure appears linked with the size of the near-surface voids induced by the low energy ions. The results presented here thus demonstrate that surface processing by low-energy helium ions provides an efficient route for the formation of porous metallic nanostructures.

De Temmerman, Gregory; Bystrov, Kirill; Zielinski, Jakub J.; Balden, Martin; Matern, Gabriele; Arnas, Cecile; Marot, Laurent [FOM Institute DIFFER, Ducth Institute For Fundamental Energy Research, Association EURATOM-FOM, Trilateral Euregio Cluster, P.O. Box 1207, 3430 BE Nieuwegein (Netherlands); Max Planck Institute for Plasma Physics, EURATOM Association, 85748 Garching (Germany); Laboratoire PIIM, CNRS/Aix-Marseille Universit, 13397 Marseille (France); Department of Physics, University of Basel, Basel, CH-4056 (Switzerland)

2012-07-15

326

Superhydrophobic Phenomena on Three-Dimensional Surface Structures Coated with Plasma Polymer  

NASA Astrophysics Data System (ADS)

Three-dimensional surface structures composed of micropillars with different diameters (8-110 ?m) and interpillar distances were fabricated using a thick-film photoresist, and the surface was modified with a hydrophobic plasma-polymerized film using hexamethyldisiloxane (HMDS) as a monomer. Surface hydrophobicity was examined by measuring contact angle using a pure water droplet. The effect of adding ethanol was also examined. Water static contact angle increased significantly on the surface coated with the HMDS plasma polymer. Structural parameters, including the diameter and height of the micropillars, were changed, as was the interpillar distance. The dependence of apparent contact angle on these parameters was explained using Cassie’s and Wenzel’s models.

Tsuruta, Shuichi; Morimoto, Katsuya; Hirotsu, Toshihiro; Suzuki, Hiroaki

2006-10-01

327

Strong Casimir force reduction through metallic surface nanostructuring  

PubMed Central

The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100?nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction.

Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A. Alec; Davids, Paul S.; Decca, Ricardo S.; Aksyuk, Vladimir A.; Dalvit, Diego A. R.; Lopez, Daniel

2013-01-01

328

Strong Casimir force reduction through metallic surface nanostructuring.  

PubMed

The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100?nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction. PMID:24071657

Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A Alec; Davids, Paul S; Decca, Ricardo S; Aksyuk, Vladimir A; Dalvit, Diego A R; López, Daniel

2013-09-27

329

Strong Casimir force reduction through metallic surface nanostructuring  

NASA Astrophysics Data System (ADS)

The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100?nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction.

Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A. Alec; Davids, Paul S.; Decca, Ricardo S.; Aksyuk, Vladimir A.; Dalvit, Diego A. R.; López, Daniel

2013-09-01

330

On the measurement of slip length for liquid flow over super-hydrophobic surface  

Microsoft Academic Search

To design a surface with large slip or larger drag reduction is a pop issue in the fields of liquid transporting and body\\u000a swimming. In this context, it is a crucial problem to measure the slip length for these surfaces. Here we propose a novel\\u000a method by using rheometer for this objective. This method is implemented by designing the distribution

Jian Li; Ming Zhou; Lan Cai; Xia Ye; Run Yuan

2009-01-01

331

Fully Reversible Transition from Wenzel to Cassie?Baxter States on Corrugated Superhydrophobic Surfaces  

Microsoft Academic Search

Liquid drops on textured surfaces show different dynamical behaviors\\u000adepending on their wetting states. They are extremely mobile when they are\\u000asupported by composite solid-liquid-air interfaces (Cassie-Baxter state) and\\u000aimmobile when they fully wet the textured surfaces (Wenzel state). By\\u000areversibly switching between these two states, it will be possible to achieve\\u000alarge control over the fluid dynamics. Unfortunately, these

Robert J. Vrancken; Halim Kusumaatmaja; Ko Hermans; An M. Prenen; Olivier Pierre-Louis; Cees W. M. Bastiaansen; Dirk J. Broer

2010-01-01

332

Fully reversible transition from Wenzel to Cassie-Baxter states on corrugated superhydrophobic surfaces  

Microsoft Academic Search

Liquid drops on textured surfaces show different dynamical behaviors depending on their wetting states. They are extremely mobile when they are supported by composite solid-liquid-air interfaces (Cassie-Baxter state) and immobile when they fully wet the textured surfaces (Wenzel state). By reversibly switching between these two states, it will be possible to achieve large control over the fluid dynamics. Unfortunately, these

R. J. Vrancken; H. Kusumaatmaja; K. Hermans; A. M. Prenen; O. Pierre-Louis; C. W. M. Bastiaansen; D. J. Broer

2009-01-01

333

Selective bactericidal activity of nanopatterned superhydrophobic cicada Psaltoda claripennis wing surfaces.  

PubMed

The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on its physical surface structure. As such, they provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. Their effectiveness against a wide spectrum of bacteria, however, is yet to be established. Here, the bactericidal properties of the wings were tested against several bacterial species, possessing a range of combinations of morphology and cell wall type. The tested species were primarily pathogens, and included Bacillus subtilis, Branhamella catarrhalis, Escherichia coli, Planococcus maritimus, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Staphylococcus aureus. The wings were found to consistently kill Gram-negative cells (i.e., B. catarrhalis, E. coli, P. aeruginosa, and P. fluorescens), while Gram-positive cells (B. subtilis, P. maritimus, and S. aureus) remained resistant. The morphology of the cells did not appear to play any role in determining cell susceptibility. The bactericidal activity of the wing was also found to be quite efficient; 6.1?±?1.5?×?10(6) P. aeruginosa cells in suspension were inactivated per square centimeter of wing surface after 30-min incubation. These findings demonstrate the potential for the development of selective bactericidal surfaces incorporating cicada wing nanopatterns into the design. PMID:23250225

Hasan, Jafar; Webb, Hayden K; Truong, Vi Khanh; Pogodin, Sergey; Baulin, Vladimir A; Watson, Gregory S; Watson, Jolanta A; Crawford, Russell J; Ivanova, Elena P

2012-12-19

334

Superhydrophobic silicone fiber mats fabricated by electrospinning from solution  

NASA Astrophysics Data System (ADS)

Fine silicone fibers of 1 -- 20 ?m diameter were fabricated from solution via electrospinning. These are the first examples of fine fibers prepared from silicone homopolymers. Fiber morphology (beaded, ribbon-like, smooth) and diameter were controlled. The nanoscale surface roughness of nonwoven fiber mats created with silicone fibers produced a superhydrophobic surface that had a water contact angle of ˜160^o. The superhydrophobic surface was made reversibly hydrophilic with exposure to oxygen plasma. The combination of high surface area and superhydrophobicity suggests potential applications in the areas of water-repellent textiles, filtration, adsorption and chemical separations, wound dressings, and fuel cells.

Ludwig, Bonnie; Clark, Aneta; Snow, Steven; Hill, Randal; Schmidt, Randall; Fogg, Brad; Lo, Peter

2007-03-01

335

Laser ablative patterning of copoly(imide siloxane)s generating superhydrophobic surfaces.  

PubMed

Low surface energy copoly(imide siloxane)s were generated via condensation polymerization reactions. The generated materials were characterized spectroscopically, thermally, mechanically, and via contact angle goniometry. The decrease in tensile modulus and opaque appearance of copoly(imide siloxane) films indicated phase segregation in the bulk. Preferential surface partitioning of the siloxane moieties was verified by X-ray photoelectron spectroscopy (XPS) and increased advancing water contact angle values (theta(A)). Pristine copoly(imide siloxane) surfaces typically exhibited theta(A) values of 111 degrees and sliding angles from 27 degrees to >60 degrees. The surface properties of these copoly(imide siloxane) films were further altered using laser ablation patterning (frequency-tripled Nd:YAG laser, 355 nm). Laser-etched square pillar arrays (25 microm pillars with 25 microm interspaces) changed theta(A) by up to 64 degrees. Theta(A) values approaching 175 degrees and sliding angles from 1 degree to 15 degrees were observed. ATR-IR spectroscopy and XPS indicated polymer chain scission reactions occurred as a result of laser ablation. Initial particle adhesion studies revealed that the copoly(imide siloxane)s outperformed the corresponding homopolyimides and that laser ablation patterning further enhanced this result. PMID:20446721

Wohl, Christopher J; Belcher, Marcus A; Chen, Lillian; Connell, John W

2010-07-01

336

Optimizing geometrical design of superhydrophobic surfaces for prevention of microelectromechanical system (MEMS) stiction  

Microsoft Academic Search

Due to the surface smoothness of micromachined structures, strong adhesion forces between these fabricated structures and the substrate can be developed. The major adhesion mechanisms include capillary forces, hydrogen bonding, electrostatic forces and van der Waals forces. Once contact is made, the magnitude of these forces is in some cases sufficient to deform and pin these structures to the substrate,

Lingbo Zhu; Yonghao Xiu; Jianwen Xu; Dennis W. Hess; C. P. Wong

2006-01-01

337

Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfaces.  

PubMed

Friction forces have long been associated with the famous Amontons' rule that states that the friction force is linearly dependent on the applied normal load, with the proportionality constant being known as the friction coefficient. Amontons' rule is however purely phenomenological and does not in itself provide any information on why the friction coefficient is different for different material combinations. In this study, friction forces between a colloidal probe and nanostructured particle coated surfaces in an aqueous environment exhibiting different roughness length scales were measured by utilizing the atomic force microscope (AFM). The chemistry of the surfaces and the probe was varied between hydrophilic silica and hydrophobized silica. For hydrophilic silica surfaces, the friction coefficient was significantly higher for the particle coated surfaces than on the flat reference surface. All the particle coated surfaces exhibited similar friction coefficients, from which it may be concluded that the surface geometry, and not the roughness amplitude per se, influenced the measured friction. During measurements with hydrophobic surfaces, strong adhesive forces related to the formation of a bridging air cavity were evident from both normal force and friction force measurements. In contrast to the frictional forces between the hydrophilic surfaces, the friction coefficient for hydrophobic surfaces was found to depend on the surface structure and we believe that this dependence is related to the restricted movement of the three-phase line of the bridging air cavity. For measurements using a hydrophobic surface and a hydrophilic probe, the friction coefficient was significantly smaller compared to the two homogeneous systems. A layer of air or air bubbles on the hydrophobic surface working as a lubricating layer is a possible mechanism behind this observation. PMID:24056733

Hansson, Petra M; Claesson, Per M; Swerin, Agne; Briscoe, Wuge H; Schoelkopf, Joachim; Gane, Patrick A C; Thormann, Esben

2013-10-01

338

Salinity Effects on Superhydrophobic Coatings  

NASA Astrophysics Data System (ADS)

Experiments are carried out to investigate the effect of NaCl concentrations on degree of hydrophobicity and longevity of polystyrene fibrous coating. A rheological study using salt water as a test fluid is performed to observe the generated drag reduction from the coating with increasing salt concentration compared to deionized water. Contact-angle measurements of droplets of solutions on the surface are used to validate the results from the rheometer. In situ noninvasive optical spectroscopy system is used to measure the time-dependent loss of entrapped air within the submerged fibrous coating. water for comparison. The superhydrophobic coating used is made of polystyrene fibers that are deposited using DC-biased AC-electrospinning. Such fabrication methods are far less expensive than ordered-microstructured fabrications, bringing the technology closer to large-scale submerged bodies such as submarines and ships. The present study sheds some light on how properties of a superhydrophobic coating could be influenced by water salinity.

Ochanda, F. O.; Samaha, M. A.; Vahedi Tafreshi, H.; Tepper, G. C.; Gad-El-Hak, M.

2011-11-01

339

Engineering aperiodic nanostructured surfaces for scattering-based optical devices  

NASA Astrophysics Data System (ADS)

Novel optical devices such as biosensors, color displays and authentication devices can be obtained from the distinctive light scattering properties of resonant nanoparticles and nanostructured arrays. These arrays can be optimized through the choice of material, particle morphology and array geometry. In this thesis, by engineering the multi-frequency colorimetric responses of deterministic aperiodic nanostructured surfaces (DANS) with various spectral Fourier properties, I designed, fabricated and characterized scattering-based devices for optical biosensing and structural coloration applications. In particular, using analytical and numerical optimization, colorimetric biosensors are designed and fabricated with conventional electron beam lithography, and characterized using dark-field scattering imaging as well as image autocorrelation analysis of scattered intensity in the visible spectral range. These sensors, which consist of aperiodic surfaces ranging from quasi-periodic to pseudo-random structures with flat Fourier spectra, sustain highly complex structural resonances that enable a novel optical sensing approach beyond the traditional Bragg scattering. To this end, I have experimentally demonstrated that DANS with engineered structural colors are capable of detecting nanoscale protein monolayers with significantly enhanced sensitivity over periodic structures. In addition, different aperiodic arrays of gold (Au) nanoparticles are integrated with polydimethylsiloxane (PDMS) microfluidic structures by soft-lithographic micro-imprint techniques. Distinctive scattering spectral shifts and spatial modifications of structural color patterns in response to refractive index variations were simultaneously measured. The successful integration of DANS with microfluidics technology has introduced a novel opto-fluidic sensing platform for label-free and multiplexed lab-on-a-chip applications. Moreover, by studying the isotropic scattering properties of homogenized Pinwheel aperiodic arrays, angle-insensitive (i.e. isotropic) coloration from nanostructured metal surfaces can be designed and optimized without randomization. Pinwheel nanoparticle arrays on a gold thin film were fabricated for the first time and investigated using dark-field scattering and angle-resolved reflectivity measurements. In sharp contrast to the colorimetric responses of periodically nanopatterned surfaces, which strongly depend on the observation angle, spatially uniform and isotropic green coloration of gold films were demonstrated using these engineered metal surfaces. In addition, the intensity of the scattered light is enhanced by plasmonic resonance originated from gold nanoparticles deposited on the gold substrates. The development of the enhanced isotropic scattering devices could advance plasmonic applications to color display, optical tagging and colorimetric sensing technologies.

Lee, Yuk Kwan Sylvanus

340

Au-coated ZnO nanostructures for surface enhanced Raman spectroscopy applications  

SciTech Connect

Thin ZnO nanostructured films were produced by pulsed laser deposition (PLD) for surface enhanced Raman spectroscopy (SERS) studies. The experimental conditions used for preparation of the samples were chosen to obtain different types of ZnO nanostructures. The Raman spectra of rhodamine 6G (R6G) were measured at an excitation wavelength of 785 nm after coating the ZnO nanostructures with a thin Au layer. The influence of the surface morphology on the Raman signal obtained from the samples was investigated. High SERS signal enhancement was observed from all Au-coated ZnO nanostructures.

Dikovska, A O; Nedyalkov, N N; Imamova, S E; Atanasova, G B; Atanasov, P A

2012-03-31

341

Anomalous Kinetic Roughening of Nanostructured Ag Islands on Liquid Surfaces  

NASA Astrophysics Data System (ADS)

By atomic force microscopy, the surface evolution and kinetic roughening of nanostructured Ag islands on silicone oil surfaces are studied. It is found that the islands are composed of quasi-circular granules with planar size around 50.0 nm, which is approximately independent of nominal thickness d. Our measurement indicates that the geometrical shape of the granules changes from plateau to sphere as d goes up. The dynamic scaling analysis reveal that the roughness exponent ? varies between 0.80 and 0.90 as d increases. The average roughness wrms shows power-law relationship with d and the growth exponent ? = 0.53 ± 0.03 when d ? 4.0 nm. However, wrms deviates obviously from the power-law relationship for the samples with d > 4.0 nm. This anomalous behavior of ? is explained by the competition between the shadowing and reemission processes, and then the kinetic evolution and formation mechanism of the islands are presented.

Zhang, Chuhang; Lv, Neng; Zhu, Yuhong; Zhang, Xiaofei; Ye, Gaoxiang

2012-03-01

342

Bimetallic nanostructures as active Raman markers: gold-nanoparticle assembly on 1D and 2D silver nanostructure surfaces.  

PubMed

It is demonstrated that bimetallic silver-gold anisotropic nanostructures can be easily assembled from various nanoparticle building blocks with well-defined geometries by means of electrostatic interactions. One-dimensional (1D) silver nanowires, two-dimensional (2D) silver nanoplates, and spherical gold nanoparticles are used as representative building blocks for bottom-up assembly. The gold nanoparticles are electrostatically bound onto the 1D silver nanowires and the 2D silver nanoplates to give bimetallic nanostructures. The unique feature of the resulting nanostructures is the particle-to-particle interaction that subjects absorbed analytes to an enhanced electromagnetic field with strong polarization dependence. The Raman activity of the bimetallic nanostructures is compared with that of the individual nanoparticle blocks by using rhodamine 6G solution as the model analyte. The Raman intensity of the best-performing silver-gold nanostructure is comparable with the dense array of silver nanowires and silver nanoplates that were prepared by means of the Langmuir-Blodgett technique. An optimized design of a single-nanostructure substrate for surface-enhanced Raman spectroscopy (SERS), based on a wet-assembly technique proposed here, can serve as a compact and low-cost alternative to fabricated nanoparticle arrays. PMID:19642091

Gunawidjaja, Ray; Kharlampieva, Eugenia; Choi, Ikjun; Tsukruk, Vladimir V

2009-11-01

343

Engineering metallic nanostructures for surface plasmon resonance sensing  

NASA Astrophysics Data System (ADS)

A change in almost any characteristic of a given material can be detected by one or more beams of light. Optical sensors are extremely sensitive, non-destructive, and immune to electromagnetic interference, offering many significant advantages. Being able to harness this enormous potential within the realm of nanotechnology, however, requires manipulation and control of an optical field on scales well below its wavelength. Dielectric structures cannot achieve this due to diffraction. However, metallic nanostructures which support evanescent surface plasmon resonances can provide a solution. Thin gold or silver films, when patterned with nanometer-scale holes, grooves or bumps can efficiently capture incident light and launch an oscillatory motion of the electrons at the film surface, known as a surface plasmon. Using state of the art nanofabrication techniques, we have engineered these plasmonic structures to exhibit unusual optical properties not found in natural materials. Such novel materials are broadly applicable and useful, in particular, for sensing. In this dissertation, patterned metallic nanostructures are used to demonstrate high-resolution sensing of complex biomolecular interactions in a quantitative and high-throughput manner. Additionally, efficient chemical sensing via surface enhanced Raman spectroscopy, and proximity sensing with structures suitable for scanning probe microscopy are also presented. The structures are rigorously analyzed with theoretical computer simulations based on finite-difference time-domain methods. Using a newly developed high-throughput fabrication method based on template stripping of patterned metals, this work may open up avenues for the realization of practical plasmonic devices in a wide variety of disciplines.

Lindquist, Nathan Charles

344

Durability of hydrophobic coatings for superhydrophobic aluminum oxide  

NASA Astrophysics Data System (ADS)

Robust and easily produced superhydrophobic surfaces are of great interest for mechanical applications, including drag reduction and MEMS. We produce novel superhydrophobic surfaces with several different coatings and tested the durability of each of these coatings with respect to long term immersion in water in order to determine the most long-lasting surface preparation. A pair of combinations of spin on polymers, surface features, and adhesion promoters was found that provide long term durability.

Jenner, Elliot; Barbier, Charlotte; D’Urso, Brian

2013-10-01

345

Surface Integral Formulations for the Design of Plasmonic Nanostructures  

NASA Astrophysics Data System (ADS)

Numerical formulations based on surface integral equations (SIEs) provide an accurate and efficient framework for the solution of the electromagnetic scattering problem by three-dimensional plasmonic nanostructures in the frequency domain. In this work, we present a unified description of SIE formulations with both singular and nonsingular kernel and we study their accuracy in solving the scattering problem by metallic nanoparticles with spherical and nonspherical shape. In fact, the accuracy of the numerical solution, especially in the near zone, is of great importance in the analysis and design of plasmonic nanostructures, whose operation critically depends on the manipulation of electromagnetic hot spots. Four formulation types are considered: the N-combined region integral equations, the T-combined region integral equations, the combined field integral equations and the null field integral equations. A detailed comparison between their numerical solutions obtained for several nanoparticle shapes is performed by examining convergence rate and accuracy in both the far and near zone of the scatterer as a function of the number of degrees of freedom. A rigorous analysis of SIE formulations can have a high impact on the engineering of numerous nano-scale optical devices.

Forestiere, Carlo; Iadarola, Giovanni; Rubinacci, Guglielmo; Tamburrino, Antonello; Dal Negro, Luca; Miano, Giovanni

2013-03-01

346

Surface integral formulations for the design of plasmonic nanostructures.  

PubMed

Numerical formulations based on surface integral equations (SIEs) provide an accurate and efficient framework for the solution of the electromagnetic scattering problem by three-dimensional plasmonic nanostructures in the frequency domain. In this paper, we present a unified description of SIE formulations with both singular and nonsingular kernel and we study their accuracy in solving the scattering problem by metallic nanoparticles with spherical and nonspherical shape. In fact, the accuracy of the numerical solution, especially in the near zone, is of great importance in the analysis and design of plasmonic nanostructures, whose operation critically depends on the manipulation of electromagnetic hot spots. Four formulation types are considered: the N-combined region integral equations, the T-combined region integral equations, the combined field integral equations and the null field integral equations. A detailed comparison between their numerical solutions obtained for several nanoparticle shapes is performed by examining convergence rate and accuracy in both the far and near zone of the scatterer as a function of the number of degrees of freedom. A rigorous analysis of SIE formulations and their limitations can have a high impact on the engineering of numerous nano-scale optical devices such as plasmon-enhanced light emitters, biosensors, photodetectors, and nanoantennas. PMID:23201792

Forestiere, Carlo; Iadarola, Giovanni; Rubinacci, Guglielmo; Tamburrino, Antonello; Dal Negro, Luca; Miano, Giovanni

2012-11-01

347

Fabrication of superhydrophobic polyaniline films with rapidly switchable wettability  

NASA Astrophysics Data System (ADS)

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.

Zhou, Xiaoyan; Zhang, Zhaozhu; Men, Xuehu; Yang, Jin; Xu, Xianghui; Zhu, Xiaotao; Xue, Qunji

2011-10-01

348

Cotton fabrics with single-faced superhydrophobicity.  

PubMed

This article reports on the fabrication of cotton fabrics with single-faced superhydrophobicity using a simple foam finishing process. Unlike most commonly reported superhydrophobic fabrics, the fabrics developed in this study exhibit asymmetric wettability on their two faces: one face showing superhydrophobic behavior (highly nonwetting or water-repellent characteristics) and the other face retaining the inherent hydrophilic nature of cotton. The superhydrophobic face exhibits a low contact angle hysteresis of ?(a)/?(r) = 151°/144° (?(a), advancing contact angle; ?(r), receding contact angle), which enables water drops to roll off the surface easily so as to endow the surface with well-known self-cleaning properties. The untreated hydrophilic face preserves its water-absorbing capability, resulting in 44% of the water-absorbing capacity compared to that of the original cotton samples with both sides untreated (hydrophilic). The single-faced superhydrophobic fabrics also retain moisture transmissibility that is as good as that of the original untreated cotton fabrics. They also show robust washing fastness with the chemical cross-linking process of hydrophobic fluoropolymer to fabric fibers. Fabric materials with such asymmetric or gradient wettability will be of great use in many applications such as unidirectional liquid transporting, moisture management, microfluidic systems, desalination of seawater, flow management in fuel cells, and water/oil separation. PMID:23186211

Liu, Yuyang; Xin, J H; Choi, Chang-Hwan

2012-12-05

349

Preparation of Nanostructured Film Arrays for Transmission Localized Surface Plasmon Sensing  

Microsoft Academic Search

This article presents a concise review of preparation methods for transparent nanostructured films, with an emphasis on their\\u000a current applications in transmission-localized surface plasmon resonance (T-LSPR) sensing. One of the first methods used for\\u000a the fabrication of transparent nanostructured metal films is a direct vacuum evaporation of thin gold films. Self-induced\\u000a formations of small gold islands result in transparent nanostructured

Young-Seok Shon; Hyung Y. Choi; Michael S. Guerrero; Chuhee Kwon

2009-01-01

350

First Principles Studies of ABO3 Perovskite Surfaces and Nanostructures  

NASA Astrophysics Data System (ADS)

Perovskite-type complex oxides, with general formula ABO 3, constitute one of the most prominent classes of metal oxides which finds key applications in diverse technological fields. In recent years, properties of perovskites at reduced dimensions have aroused considerable interest. However, a complete atomic-level understanding of various phenomena is yet to emerge. To fully exploit the materials opportunities provided by nano-structured perovskites, it is important to characterize and understand their bulk and near-surface electronic structure along with the electric, magnetic, elastic and chemical properties of these materials in the nano-regime, where surface and interface effects naturally play a dominant role. In this thesis, state-of-the-art first principles computations are employed to systematically study properties of one- and two-dimensional perovskite systems which are of direct technological significance. Specifically, our bifocal study targets (1) polarization behavior and dielectric response of ABO3 ferroelectric nanowires, and (2) oxygen chemistry relevant for catalytic properties of ABO3 surfaces. In the first strand, we identify presence of novel closure or vortex-like polarization domains in PbTIO3 and BaTiO3 ferroelectric nanowires and explore ways to control the polarization configurations by means of strain and surface chemistry in these prototypical model systems. The intrinsic tendency towards vortex polarization at reduced dimensions and the underlying driving forces are discussed and previously unknown strain induced phase transitions are identified. Furthermore, to compute the dielectric permittivity of nanostructures, a new multiscale model is developed and applied to the PbTiO3 nanowires with conventional and vortex-like polarization configurations. The second part of the work undertaken in this thesis is comprised of a number of ab initio surface studies, targeted to investigate the effects of surface terminations, prevailing chemical environment and processing conditions on the surface relaxations, local electronic structure and chemical reactivity. By combining our first principles computations with an in-house developed kMC simulation approach, we describe the thermodynamics, steady-state kinetics and the long-time and large-length scale behavior of the catalytically active (001) MnO2-terminated LaMnO3 surface in contact with an oxygen reservoir, as a function of temperature and partial pressure of oxygen. The results obtained are in excellent agreement with available experimental data in the literature.

Pilania, Ghanshyam

351

Biomimetic superhydrophobic and highly oleophobic cotton textiles.  

PubMed

We report a biomimetic procedure to prepare superhydrophobic cotton textiles. By in situ introducing silica particles to cotton fibers to generate a dual-size surface roughness, followed by hydrophobization with polydimethylsiloxane (PDMS), normally hydrophilic cotton has been easily turned superhydrophobic, which exhibits a static water contact angle of 155 degrees for a 10 microL droplet. The roll-off angle of water droplets depends on the droplet volume, ranging from 7 degrees for a droplet of 50 microL to 20 degrees for a 7 microL droplet. When a perfluoroalkyl chain is introduced to the silica particle surface, the superhydrophobic textile also becomes highly oleophobic, as demonstrated by a static contact angle of 140 degrees and a roll-off angle of 24 degrees for a 15 microL sunflower oil droplet. PMID:17985939

Hoefnagels, H F; Wu, D; de With, G; Ming, W

2007-11-07

352

Superhydrophobic RTV silicone rubber insulator coatings  

NASA Astrophysics Data System (ADS)

On wet days, environmental contamination of outdoor insulation surfaces can reduce the reliability of electrical transmission systems and lead to flashover and arcing over the entire insulator. The use of superhydrophobic coatings would resolve this problem due to their self-cleaning effect. Water droplets can pick up dirt particles and remove contamination from the surfaces of insulators. This paper reports on a study to make a superhydrophobic RTV silicone rubber coating that has contact angles of higher than 145° and good UV durability. The Inclined Plane Test, water durability test and adhesion test are presented to show the effectiveness of this coating and the best formulations. The results of tracking and erosion resistance test (Inclined Plane Test) showed that formulations with at least 35 wt% ATH can be used for superhydrophobic RTV insulator coatings.

Seyedmehdi, Seyed Amirhossein; Zhang, Hui; Zhu, Jesse

2012-01-01

353

Hierarchical roughness makes superhydrophobic states stable  

Microsoft Academic Search

Roughness enhances hydrophobicity of a solid surface leading to high contact angles with water. To achieve low contact angle hysteresis along with a high contact angle, superhydrophobic surfaces should form composite interface (CI) with air pockets in the valleys between asperities. The CI is often unstable and can be irreversibly transformed into the homogeneous interface. We formulate stability criterion, identify

Nosonovsky Michael; Bharat Bhushan

2007-01-01

354

Nanostructures  

NSDL National Science Digital Library

This page from Foothill-De Anza Community College provides a list of nanostructures. For each structure, its properties, structure, process, and application are detailed. Additionally, most pages include a picture, video, and references. The structures include aerogels, biomolecules, carbon, composite materials, ferrofluids, and many others.

2012-11-06

355

Self-assembly of biomolecules: AFM study of F-actin on unstructured and nanostructured surfaces  

NASA Astrophysics Data System (ADS)

Advanced nanofabrication is capable of producing structures in the vicinity of the size of large biomolecules or their aggregates. Some of these protein aggregates emerge as having deleterious medical effects, e.g., degenerative diseases, or essential for biological processes, e.g., actin, cytoskeleton formation. Therefore it became possible, and important, to think of ways of interacting nanostructured surfaces with biomolecular aggregates in a designed manner. Along this line of thinking, we report on a preliminary atomic force microscopy (AFM) investigation of the behavior of F-actin on unstructured surfaces (mica, silicon) and nanostructured surface (13 nm height nanostructured silicon surface).

Naldi, Marina; Vasina, Elena; Dobroiu, Serban; Paraoan, Luminita; Nicolau, Dan V.; Andrisano, Vincenza

2009-02-01

356

Spin dynamics of atoms and magnetic nanostructures on surfaces  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy is a powerful tool for studying the electronic and magnetic properties of magnetic nanostructures on surfaces. Over the last decade, inelastic tunneling spectroscopy has been used to probe discrete energy levels of quantum spin systems. These states can often be described as solutions of simple spin Hamiltonians. In spin excitation spectroscopy, a spin system is kicked from the ground into excited spin states at discrete energy increments. In this talk we will focus on the dynamics of quantum spin systems on surfaces. STM can measure tunnel currents in the range of pico amps with millisecond time resolution. This time resolution is well matched to observing transition between spin states of artificial magnetic nanostructures on surfaces that can be built and measured with STM. We will highlight an example of extended, artificial antiferromagnets on a Cu2N surface (Science 2012). Smaller magnetic clusters relax much faster but their dynamics can be measured with pump probe techniques. A pump voltage pulse drives the spin system into excited states and a subsequent probe pulse measures the resulting population of spin states. An exponential decay back to the ground state is observed when averaging over many pump-probe cycles (Science 2010). We will show results down to nanosecond time resolution with an ultimate limit set by modern electronics at about 100 pico seconds. Individual atoms on Cu2N relax their spin states even faster. Hence, another technique is employed to determine spin relaxation times: small tunnel currents always leave the spin system in the ground state while high currents can create non-equilibrium distributions of spin states. This approach relies on some modeling but allows time domain measurements down to about 1 pico second (Nature Physics 2010). Transition metal atoms on metal surfaces relax even faster, on time scales of about 100 femtoseconds. This fast relaxation manifests itself as a measurable lifetime broadening of spin excitation spectra. Combining these approaches allows measurements of spin relaxation times over about 16 orders of magnitude for spins on surfaces -- while maintaining the atomic scale spatial resolution of STM!

Heinrich, Andreas

2013-03-01

357

Superamphiphobic surface by nanotransfer molding and isotropic etching.  

PubMed

We present a novel method of fabricating superhydrophobic and superoleophobic surfaces with nanoscale reentrant curvature by nanotransfer molding and controlled wet etching of the facile undercut. This method produces completely ordered re-entrant nanostructures and prevents capillary-induced bundling effects. The mushroom-like, re-entrant, overhanging structure demonstrates superhydrophobic and superoleophobic characteristics, as tested by water droplet bouncing and contact angle measurements, and has high transparency on a flexible substrate. Widespread use as self-cleaning surfaces is expected in the near future. PMID:23701230

Lee, Sang Eon; Kim, Han-Jung; Lee, Su-Han; Choi, Dae-Geun

2013-06-04

358

Zinc oxide nanostructures with metal particles based on surface plasmons for optoelectronic device applications  

NASA Astrophysics Data System (ADS)

We fabricate various ZnO (zinc oxide) nanostructures, such as nanorods, nanotips and nanoflowers, as well as ZnO subwavelength grating structures for applications in optoelectronic devices such as solar cells, light emitting diodes, and biosensors. The optical properties are theoretically analyzed using the rigorous coupled-wave analysis method. The fabricated ZnO nanostructures are of wurzite crystal structure. The reflection and absorption characteristics depend strongly on the shape and geometry of Zn nanostructures. The ZnO nanostructures with Au (or Ag) particles, based on surface plasmons, are also investigated.

Yu, Jae Su; Ko, Yeong Hwan; Lee, Hee Kwan; Leem, Jung Woo

2011-02-01

359

Colour centres and nanostructures on the surface of laser crystals  

SciTech Connect

This paper presents a study of structural and radiationinduced colour centres in the bulk and ordered nanostructures on the surface of doped laser crystals: sapphire, yttrium aluminium garnet and strontium titanate. The influence of thermal annealing, ionising radiation and plasma exposure on the spectroscopic properties of high-purity materials and crystals containing Ti, V and Cr impurities is examined. Colour centres resulting from changes in the electronic state of impurities and plasma-induced surface modification of the crystals are studied by optical, EPR and X-ray spectroscopies, scanning electron microscopy and atomic force microscopy. X-ray line valence shift measurements are used to assess changes in the electronic state of some impurity and host ions in the bulk and on the surface of oxide crystals. Conditions are examined for the formation of one- and two-level arrays of ordered crystallites 10{sup -10} to 10{sup -7} m in size on the surface of crystals doped with irongroup and lanthanoid ions. The spectroscopic properties of the crystals are analysed using ab initio self-consistent field calculations for Me{sup n+} : [O{sup 2-}]{sub k} clusters. (interaction of laser radiation with matter. laser plasma)

Kulagin, N A [Firma SIFA Ukraine - Germany Joint Venture, ul. Shekspira 6-48, 61045 Kharkiv (Ukraine)

2012-11-30

360

Colour centres and nanostructures on the surface of laser crystals  

NASA Astrophysics Data System (ADS)

This paper presents a study of structural and radiationinduced colour centres in the bulk and ordered nanostructures on the surface of doped laser crystals: sapphire, yttrium aluminium garnet and strontium titanate. The influence of thermal annealing, ionising radiation and plasma exposure on the spectroscopic properties of high-purity materials and crystals containing Ti, V and Cr impurities is examined. Colour centres resulting from changes in the electronic state of impurities and plasma-induced surface modification of the crystals are studied by optical, EPR and X-ray spectroscopies, scanning electron microscopy and atomic force microscopy. X-ray line valence shift measurements are used to assess changes in the electronic state of some impurity and host ions in the bulk and on the surface of oxide crystals. Conditions are examined for the formation of one- and two-level arrays of ordered crystallites 10-10 to 10-7 m in size on the surface of crystals doped with irongroup and lanthanoid ions. The spectroscopic properties of the crystals are analysed using ab initio self-consistent field calculations for Men+ : [O2-]k clusters.

Kulagin, N. A.

2012-11-01

361

Superhydrophobicity of a material made from multiwalled carbon nanotubes  

SciTech Connect

Superhydrophobic carbon nanotubes (CNTs) were prepared by low-pressure CF{sub 4} glow plasma to provide roughness and fluorination in CNTs. The water droplet falling freely on the superhydrophobic CNT powders bounced dynamically. The superhydrophobicity resulted from the combined effects of the chemical modification and surface roughness. Using the contact angles obtained from the capillary rise method based on the Washburn equation, the total surface free energy of CNT powder treated by CF{sub 4} plasma for 20 min was calculated to be drastically decreased from 27.04 to 4.06x10{sup -7}mJ/m{sup 2}.

Hong, Yong Cheol; Uhm, Han Sup [Department of Molecular Science and Technology, Ajou University, San 5, Wonchon-Dong, Youngtong-Gu, Suwon 443-749 (Korea, Republic of)

2006-06-12

362

Unidirectional superhydrophobic surfaces  

Microsoft Academic Search

It has long been known that the hairy, waxy cuticle of water-walking insects renders them water-repellent; they thus exhibit high static contact angles. We have recently demonstrated that by the virtue of the geometry and flexibility of the hair, the integument is also directionally anisotropic and so plays a key propulsive role. We here report our attempts to design and

Manu Prakash; John Bush

2007-01-01

363

Is superhydrophobicity robust with respect to disorder?  

PubMed

We consider theoretically the Cassie-Baxter and Wenzel states describing the wetting contact angles for rough substrates. More precisely, we consider different types of periodic geometries such as square protrusions and disks in 2D, grooves and nanoparticles in 3D and derive explicitly the contact angle formulas. We also show how to introduce the concept of surface disorder within the problem and, inspired by biomimetism, study its effect on superhydrophobicity. Our results, quite generally, prove that introducing disorder, at fixed given roughness, will lower the contact angle: a disordered substrate will have a lower contact angle than a corresponding periodic substrate. We also show that there are some choices of disorder for which the loss of superhydrophobicity can be made small, making superhydrophobicity robust. PMID:24072468

De Coninck, Joël; Dunlop, François; Huillet, Thierry

2013-09-26

364

Deposition of organic-based superhydrophobic films for anti-adhesion and self-cleaning applications  

Microsoft Academic Search

Surface having superhydrophobic and self-cleaning property is generally found in nature such as lotus leaf and butterfly's wing. Such surfaces consist of protrusions in micrometer scale covered with waxy nanoparticles, giving the surface self-cleaning property as water droplets roll off the rough surface and pick up dirt and fine debris with them. Synthetic superhydrophobic films having similar feature have been

On-Uma Nimittrakoolchai; Sitthisuntorn Supothina

2008-01-01

365

Simultaneous droplet impingement dynamics and heat transfer on nano-structured surfaces  

Microsoft Academic Search

This study examines the hydrodynamics and temperature characteristics of distilled deionized water droplets impinging on smooth and nano-structured surfaces using high speed (HS) and infrared (IR) imaging at We=23.6 and Re=1593, both based on initial drop impingement parameters. Results for a smooth and nano-structured surface for a range of surface temperatures are compared. Droplet impact velocity, transient spreading diameter and

Jian Shen; Christof Graber; James Liburdy; Deborah Pence; Vinod Narayanan

2010-01-01

366

Creation of Principally New Generation of Switching Technique Elements (Reed Switches) with Nanostructured Contact Surfaces  

NASA Astrophysics Data System (ADS)

The cycle of activities of the creation of principally new generation of reed switches with nanostructured contact surfaces was implemented. Experimental justification of the opportunity of reed switches creation with modified contact surface was given (instead of precious metals-based galvanic coating). Principally new technological process of modification of magnetically operated contacts contacting surfaces was developed, based on the usage of the ion-plasma methods of nanolayers and nanostructures forming having specified contact features.

Karabanov, S. M.; Zeltser, I. A.; Maizels, R. M.; Moos, E. N.; Arushanov, K. A.

2011-04-01

367

Surface studies of coarse-grained and nanostructured titanium implants.  

PubMed

The results of XPS measurements of nanostructured Ti (ns-Ti) prepared with a help of severe plastic deformation (SPD) have been presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands before and after treatment of ns-Ti-implants in HF. The obtained data have been compared with XPS measurements of untreated and acid treated coarse-grained Ti (cg-Ti). According to these measurements the surface composition has not practically been changed by reduction of grains size of Ti-implants. It has been found that the surface of both types of implants is covered with thick TiO2 layer. The acid treatment reduces the surface contamination of ns-Ti and cg-Ti by hydrocarbons and induces better passivation and formation of more thick TiO2 layer. It has been shown that severe plastic deformation not only improves mechanical properties but also preserves corrosion stability of Ti-implants. PMID:23421245

Korotin, D M; Bartkowski, S; Kurmaev, E Z; Neumann, M; Yakushina, E B; Valiev, R Z; Cholakh, S O

2012-11-01

368

Transport of liquids using superhydrophobic aerogels  

Microsoft Academic Search

The experimental results of the studies on the transportation of water droplets on a superhydrophobic silica aerogel-powder-coated surface are reported. The superhydrophobic silica aerogels were prepared using sol–gel processing of methyltrimethoxysilane (MTMS) precursor, methanol (MeOH) solvent, and base (NH4OH)-catalyzed water followed by supercritical drying using methanol solvent. The molar ratio of NH4OH\\/MTMS, H2O\\/MTMS, and MeOH\\/MTMS were varied from 1.7×10?1 to

A. Venkateswara Rao; Manish M. Kulkarni; Sharad D. Bhagat

2005-01-01

369

Utilizing Ion Beams for Forming Nanostructures on InP surfaces  

NASA Astrophysics Data System (ADS)

We have investigated the formation of nanostructures on InP surfaces by utilizing 3keV Ar ions. The nanostructures have been studied as a function of ion fluence and show variation in their size and heights. The surface roughness behavior also get modified. The electronic structure investigation suggests that there is excess Indium on the InP surface, after ion irradiation, due to the preferential sputtering of Phosphorus atoms. The In-rich zones lead to the nucleation of nanostructures.

Paramanik, Dipak; Majumder, S.; Sahoo, S. R.; Choudhury, S. K.; Varma, Shikha

2008-10-01

370

Universal mechanism for ion-induced nanostructure formation on III-V compound semiconductor surfaces  

SciTech Connect

We have examined the formation of nanostructures on ion-irradiated compound semiconductor surfaces. We computed the ion doses needed to fully deplete group V elements from the surfaces. These group V depletion doses are in good agreement with the measured threshold ion doses for nucleation of group III-rich nanostructures on a wide variety of III-V compound semiconductor surfaces. Since the group V depletion doses decrease with increasing sputtering yield, these results suggest a universal nanostructure formation mechanism which depends upon the total sputtering yield of each III-V compound.

Kang, M.; Wu, J. H.; Huang, S.; Warren, M. V.; Jiang, Y.; Robb, E. A.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

2012-08-20

371

Direct writing of hafnium diboride metallic nanostructures on silicon (100) surfaces using a UHV-STM  

NASA Astrophysics Data System (ADS)

The patterning of metallic nanostructures on surfaces is of great interest in fabricating nanoelectronics and quantum devices. In this work, we deposited HfB2 nanostructures on silicon surfaces from Hf(BH4)4 by electron beam induced deposition (EBID). At positive sample bias, the electron beam from a STM probe initiates the local CVD by the decomposition of Hf(BH4)4 under STM tip. By repeatedly scanning STM tip along a specific path, well-defined HfB2 nanostructures can be directly written onto the surface. Scanning tunneling spectroscopy was used to characterize the electronic properties of the nanostructures. We have achieved 4 nm linewidths and complete selectivity relative to adjacent H-Si(100) regions. The thickness of the nanostructures is controlled by the exposing time to the electron beam from STM tip, while the width is controlled only by the geometry of the tip apex and the sample-tip separation. STS data confirm that the HfB2 nanostructures deposited are pure metallic, indicating minimum contaminations in the nanostructures, which we attribute to the carbon-free nature of the CVD precursor. To our knowledge this is the first demonstration of sub-5 nm metallic nanostructures in a STM/CVD experiment.

Ye, Wei; Martin, Pamela; Kumar, Navneet; Abelson, John; Girolomi, Greg; Rockett, Angus; Lyding, Joseph

2009-03-01

372

Origin of Au nanostructures on tungsten surface carbides  

NASA Astrophysics Data System (ADS)

The template-assisted self-organization of Au deposited on surface carbides W(110)/C-R(15×12) and W(110)/C-R(15×3) is investigated by means of scanning tunneling microscopy, low energy electron diffraction, and photoelectron spectroscopy. The existence of two principally different ways of self-organization of Au nanostructures is revealed on each of the substrates. The room temperature deposition results in the growth of Au nanoclusters controlled by the potential profile of the carbidic nanomesh. The Au clusters are aligned along the surface carbide and appear uniform but geometrically different on the different carbides. In particular, they are one monolayer high when grown on the R(15×12) structure and two monolayers high on the R(15×3) structure. Subsequent annealing of the sample at 900-1000K produces a rearrangement of Au adatoms toward a one-dimensionally patterned overlayer with nanowirelike reconstruction which is identical on a both W(110)/C-R(15×12) and W(110)/C-R(15×3) and no longer aligned along the surface carbide but along the [001] direction of the W. This delivers strong evidence that self-organization at elevated temperature is driven by chemical Au-W interaction. Additional support for this explanation is found in photoemission spectra from the valence band and the W4f core level. The W4f shows a large core-level shift of +440meV which exists neither for the bare surface carbides R(15×12) and R(15×3) , nor for Au on pure W(110), nor for Au deposited on the surface carbides without annealing.

Varykhalov, A.; Rader, O.; Gudat, W.

2008-01-01

373

Preparation and characterization of self-cleaning stable superhydrophobic linear low-density polyethylene  

NASA Astrophysics Data System (ADS)

Porous superhydrophobic linear low-density polyethylene (LLDPE) surface was prepared by a simple method. Its water contact angle and sliding angle were 153±2° and 10°, respectively. After contamination, 99% of the contaminant particles were removed from the superhydrophobic LLDPE surface using artificial rain. The superhydrophobic LLDPE surface showed high stability in the pH range from 2 to 13. When LLDPE samples were stored in ambient environment for one month, their water contact angle and sliding angle remained constant. Their superhydrophobic property was also maintained after annealing in the temperature range 10-90 °C.

Yuan, Zhiqing; Chen, Hong; Zhang, Jide; Zhao, Dejian; Liu, Yuejun; Zhou, Xiaoyuan; Li, Song; Shi, Pu; Tang, Jianxin; Chen, Xin

2008-12-01

374

Transparent superhydrophobic/superhydrophilic coatings for self-cleaning and anti-fogging  

NASA Astrophysics Data System (ADS)

The high transparent superhydrophobic surface covered with hollow spheres has been fabricated through a carbon template route. The as-prepared coating without treating with low surface energy materials showed superhdrophilic and anti-fogging properties while displayed superhydrophobic characteristics after surface modification. Furthermore, such superhydrophilic/superhydrophobic glasses both exhibited a relatively high transmittance, and it is also demonstrated that the thickness of coating affects the transmittance and wettability from a control experiment. For comparison, we studied the anti-fogging properties of the transparent superhydrophobic, superhydrophilic, and the ordinary glass, showing absolutely different fogging characteristics.

Chen, Yu; Zhang, Yabin; Shi, Lei; Li, Jing; Xin, Yan; Yang, Tingting; Guo, Zhiguang

2012-07-01

375

Surface effects and gold-nanostructure surface coating of whispering-gallery microresonators  

Microsoft Academic Search

Scope and method of study. The purpose of this study is to explore the surface effects of high-quality-factor optical microsphere resonators and thin-film-coated microresonators in various ambient gases. In this work, we present a systematic study of the assembly and characterization of gold nanostructures. We employ a wet-chemical synthesis method for growing gold nanorods and a directed electrochemical method for

Deepak Ganta

2010-01-01

376

Superhydrophobic states  

Microsoft Academic Search

It is well known that the roughness of a hydrophobic solid enhances its hydrophobicity. The contact angle of water on such flat solids is typically of the order of 100 to 120°, but reaches values as high as 160 to 175° if they are rough or microtextured. This result is remarkable because such behaviour cannot be generated by surface chemistry

Aurélie Lafuma; David Quéré

2003-01-01

377

Antimicrobial and osteogenic effect of Ag-implanted titanium with a nanostructured surface.  

PubMed

Ag-implanted titanium with a nanostructured surface was prepared by hydrothermal treatment with H(2)O(2) followed by Ag plasma immersion ion implantation. Streptococcus mutans, Porphyromonas gingivalis and Candida albicans were chosen for antimicrobial tests. Genes related to microbial structure or adhesion, namely glucan-binding proteins B (GbpB), fimbria protein A (FimA), and agglutinin-like sequence4 (Als4), were examined. The osteoblast's attachment, viability, and quantitative analysis of osteogenic gene expression (Alp, Ocn, RunX2) on titanium surfaces were evaluated. Scanning electron microscopy (SEM) revealed that Ag nanoparticles of approximately 10 nm were incorporated on the nanostructured surface of titanium after Ag plasma immersion ion implantation. Trials showed that 93.99% of S. mutans, 93.57% of P. g, and 89.78% of C. albicans were killed on the Ag-implanted titanium with a nanostructured surface. Gene expressions from the three microorganisms confirmed the antimicrobial activities of the Ag-implanted titanium with a nanostructured surface. Furthermore, the adhesive images and viability assays indicated that the Ag-implanted titanium with a nanostructured surface did not impair osteoblasts. The expressions of osteoblast phenotype genes in cells grown on the Ag-implanted titanium surface were significantly increased. The results of this study suggest that the Ag-implanted titanium with a nanostructured surface displays good antimicrobial properties, reducing gene expressions of microorganisms, and excellent cell adhesion and osteogenic effects. PMID:22393287

Zheng, Yanhua; Li, Jinbo; Liu, Xuanyong; Sun, Jiao

2012-02-21

378

Nanosilver on nanostructured silica: Antibacterial activity and Ag surface area  

PubMed Central

Nanosilver is one of the first nanomaterials to be closely monitored by regulatory agencies worldwide motivating research to better understand the relationship between Ag characteristics and antibacterial activity. Nanosilver immobilized on nanostructured silica facilitates such investigations as the SiO2 support hinders the growth of nanosilver during its synthesis and, most importantly, its flocculation in bacterial suspensions. Here, such composite Ag/silica nanoparticles were made by flame spray pyrolysis of appropriate solutions of Ag-acetate or Ag-nitrate and hexamethyldisiloxane or tetraethylorthosilicate in ethanol, propanol, diethylene glucolmonobutyl ether, acetonitrile or ethylhexanoic acid. The effect of solution composition on nanosilver characteristics and antibacterial activity against the Gram negative Escherichia coli was investigated by monitoring their recombinantly synthesized green fluorescent protein. Suspensions with identical Ag mass concentration exhibited drastically different antibacterial activity pointing out that the nanosilver surface area concentration rather than its mass or molar or number concentration determine best its antibacterial activity. Nanosilver made from Ag-acetate showed a unimodal size distribution, while that made from inexpensive Ag-nitrate exhibited a bimodal one. Regardless of precursor composition or nanosilver size distribution, the antibacterial activity of nanosilver was correlated best with its surface area concentration in solution.

Sotiriou, Georgios A.; Teleki, Alexandra; Camenzind, Adrian; Krumeich, Frank; Meyer, Andreas; Panke, Sven; Pratsinis, Sotiris E.

2013-01-01

379

Simple method for preparation of nanostructure on microchannel surface and its usage for enzyme-immobilization.  

PubMed

We developed a novel preparation method of nanostructure on the microchannel surface formed by sol-gel like simple treatment with 3-aminopropyltriethoxysilane, which is suitable for a highly efficient enzyme-immobilized microchannel reactor. PMID:12669868

Miyazaki, Masaya; Kaneno, Jun; Uehara, Masato; Fujii, Masayuki; Shimizu, Hazime; Maeda, Hideaki

2003-03-01

380

Laser generation of nanostructures on the surface and in the bulk of solids  

SciTech Connect

This paper considers nanostructuring of solid surfaces by nano-optical techniques, primarily by laser particle nanolithography. Threshold processes are examined that can be used for laser structuring of solid surfaces, with particular attention to laser swelling of materials. Fundamental spatial resolution issues in three-dimensional (3D) laser nanostructuring are analysed with application to laser nanopolymerisation and 3D optical information recording. The formation of nanostructures in the bulk of solids due to their structural instability under irradiation is exemplified by photoinduced formation of nanocomposites. (photonics and nanotechnology)

Bityurin, N M [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2010-12-29

381

PHOTONICS AND NANOTECHNOLOGY Laser generation of nanostructures on the surface and in the bulk of solids  

NASA Astrophysics Data System (ADS)

This paper considers nanostructuring of solid surfaces by nano-optical techniques, primarily by laser particle nanolithography. Threshold processes are examined that can be used for laser structuring of solid surfaces, with particular attention to laser swelling of materials. Fundamental spatial resolution issues in three-dimensional (3D) laser nanostructuring are analysed with application to laser nanopolymerisation and 3D optical information recording. The formation of nanostructures in the bulk of solids due to their structural instability under irradiation is exemplified by photoinduced formation of nanocomposites.

Bityurin, N. M.

2010-12-01

382

Surface Plasmon Mediated Chemical Solution Deposition of Gold Nanoparticles on a Nanostructured Silver Surface  

SciTech Connect

Utilizing intrinsic surface properties to direct and control nanostructure growth on a large-scale surface is fundamentally interesting and holds great technological promise. Reported here is a novel "bottom-up" approach to fabricating sub-15 nm Au nanoparticles on a nanostructured Ag surface via a liquid-phase chemical deposition by using localized surface plasmon resonance (SPR) excitation. A molecular thermometry strategy was employed to investigate the SPR-mediated photothermal heating of the Ag film on nanosphere (AgFON) substrate and measured the surface temperature to be above 230 °C, which led to an efficient decomposition of CH3AuPPh3 to form Au nanoparticles on the Ag surface. Particle sizes were tunable between 3 to 10 nm by adjusting the deposition time. Moreover, investigation of the deposition kinetics revealed that the Au nanoparticle deposition was surface-limited by the Ag substrate. This SPR-mediated chemical solution deposition (SPMCSD) strategy should be extendable to the deposition of many other materials for various applications.

Qiu, Jingjing; Wu, Yung-Chen; Wang, Yi-Chung; Engelhard, Mark H.; McElwee-White, Lisa; Wei, Wei

2013-01-01

383

A deceleration system at the Heidelberg EBIT providing very slow highly charged ions for surface nanostructuring  

Microsoft Academic Search

Recently, it has been demonstrated that each single-impact of a slow (typically 1–2keV\\/u) highly charged ion (HCI) creates truly topographic and non-erasable nanostructures on CaF2 surfaces. To further explore the possibility of nanostructuring various surfaces, using mainly the potential energy stored in such HCIs, projectiles with kinetic energies as low as possible are required. For this purpose a new apparatus,

R. Ginzel; S. G. Higgins; P. Mrowcynski; P. Northway; M. C. Simon; H. Tawara; J. R. Crespo López-Urrutia; J. Ullrich; G. Kowarik; R. Ritter; W. Meissl; C. Vasko; C. Gösselsberger; A. S. El-Said; F. Aumayr

2010-01-01

384

Synthesis of Complex Plasmonic Nanostructures for Applications in Surface-Enhanced Raman Spectroscopy and Biomedicine  

Microsoft Academic Search

This research centers around techniques to engineer the properties of noble-metal nanostructures for applications in surface-enhanced Raman spectroscopy (SERS) and biomedicine. Many of these potential applications are made possible by the strong localized surface plasmon resonance (LSPR) of noble-metal nanostructures, which is heavily influenced by the particle's morphology. The first part of this work focuses on the solution-phase synthesis of

Claire Cobley

2010-01-01

385

Polymer single crystal-decorated superhydrophobic buckypaper with controlled wetting and conductivity.  

PubMed

Herein we report fabrication of uniform, free-standing nanohybrid buckypaper with high carbon nanotube (CNT) contents (13-70%) using polymer single crystal-decorated CNTs as the precursor. Polyethylene single crystals were periodically grown on CNT surfaces, forming a nanohybrid shish kebab (NHSK) structure. Vacuum filtering a NHSK suspension led to polymer single crystal-decorated buckypaper (named as NHSK paper) with a wide range of CNT contents and uniform CNT dispersion. Porosity, surface roughness, and conductivity of NHSK paper can be controlled by tuning the polymer single crystal size. Because of the hierarchical roughness created by intra- and inter-NHSK nanostructure, NHSK paper with controlled kebab size exhibits both superhydrophobicity and high surface water adhesion, which mimics the rose petal effect. We anticipate that this unique NHSK paper can find applications in sensors, electrochemical devices, and coatings. PMID:22243213

Laird, Eric D; Wang, Wenda; Cheng, Shan; Li, Bing; Presser, Volker; Dyatkin, Boris; Gogotsi, Yury; Li, Christopher Y

2012-01-20

386

Bio-inspired superhydrophobic polyphenylene sulfide/polytetrafluoroethylene coatings with high performance.  

PubMed

Bio-inspired superhydrophobic Polyphenylene sulfide/Polytetrafluoroethylene (PPS/PTFE) coatings were prepared by a simple curing process. The surface morphology characterization by SEM shows that these superhydrophobic coatings have the similar macro-nano-structures to that of lotus leaf. Effect of the content of PTFE as well as the curing condition on the water contact angle of the superhydrophobic coating surface was then systematically studied. A series of tests show that the superhydrophobic coatings exhibit high cohesional strength, excellent impact resistance and high thermal stability. Moreover, we studied the stability of chemical resistance of the as-prepared superhydrophobic PPS/PTFE coatings, and the electrochemical impedance values kept on a high level even after 8 days. The superhydrophobic PPS/PTFE coatings with high performance have potential applications in some specific fields. PMID:23035456

Sun, Na; Qin, Shan; Wu, Juntao; Cong, Chuanbo; Qiao, Yucong; Zhou, Qiong

2012-09-01

387

Surface effects and gold-nanostructure surface coating of whispering-gallery microresonators  

NASA Astrophysics Data System (ADS)

Scope and method of study. The purpose of this study is to explore the surface effects of high-quality-factor optical microsphere resonators and thin-film-coated microresonators in various ambient gases. In this work, we present a systematic study of the assembly and characterization of gold nanostructures. We employ a wet-chemical synthesis method for growing gold nanorods and a directed electrochemical method for assembly of gold nanowires. The adhesion methods of gold nanostructures on high-quality-factor optical microsphere resonators are also investigated. Findings and conclusions. A novel method is employed for measuring thermal accommodation coefficients of various gases like nitrogen, helium and ambient air on several coated and uncoated surfaces of fused-silica microresonators, operating at room temperature. This method is further extended to measure the absorption coefficient of a surface film or water layer on a fused-silica microresonator, and provides a novel method to find the water layer desorption and adsorption rates on the surface of a microresonator in the presence of gases like ambient air and nitrogen. We have adapted methods for growing gold nanorods of different aspect ratios (AR), and developed a novel method of growing high-AR (20-400) gold nanowires from low-AR gold nanorods. Various methods were discovered to coat these gold nanostructures and carbon nanotubes on the fused-silica surface. The most successful method involves surface modification with MPMDMS (i.e., silanization) before coating with gold nanorods. These coating methods have made microresonators useful for plasmonic sensing applications.

Ganta, Deepak

388

Superhydrophobic and superoleophilic nanoparticle film: synthesis and reversible wettability switching behavior.  

PubMed

The present work describes a one-step facile spray deposition process for the fabrication of superhydrophobic and superoleophilic nanoparticle film. The film shows fast response wettability transition between superhydrophobicity and hydrophilicity. The reversible superhydrophobicity to hydrophilicity switching can be easily carried out by adjusting the temperature. The film also demonstrates oil uptake ability and can selectively adsorb oil floating on water surface. Furthermore, the film surface shows the antifouling performance for organic solvents, which can self-remove the organic solvents layer and recover its superhydrophobic behavior. The advantage of the present approach is that the damaged film can be easily repaired by spraying again. PMID:22329929

Zhang, Xia; Guo, Yonggang; Zhang, Pingyu; Wu, Zhishen; Zhang, Zhijun

2012-03-09

389

Selective surface modification of lithographic silicon oxide nanostructures by organofunctional silanes.  

PubMed

This study investigates the controlled chemical functionalization of silicon oxide nanostructures prepared by AFM-anodization lithography of alkyl-terminated silicon. Different conditions for the growth of covalently bound mono-, multi- or submonolayers of distinctively functional silane molecules on nanostructures have been identified by AFM-height investigations. Routes for the preparation of methyl- or amino-terminated structures or silicon surfaces are presented and discussed. The formation of silane monolayers on nanoscopic silicon oxide nanostructures was found to be much more sensitive towards ambient humidity than, e.g., the silanization of larger OH-terminated silica surfaces. Amino-functionalized nanostructures have been successfully modified by the covalent binding of functional fluorescein dye molecules. Upon excitation, the dye-functionalized structures show only weak fluorescence, which may be an indication of a relatively low surface coverage of the dye molecules on length scale that is not accessible by standard AFM measurements. PMID:23616941

Baumgärtel, Thomas; von Borczyskowski, Christian; Graaf, Harald

2013-03-25

390

Selective surface modification of lithographic silicon oxide nanostructures by organofunctional silanes  

PubMed Central

Summary This study investigates the controlled chemical functionalization of silicon oxide nanostructures prepared by AFM-anodization lithography of alkyl-terminated silicon. Different conditions for the growth of covalently bound mono-, multi- or submonolayers of distinctively functional silane molecules on nanostructures have been identified by AFM-height investigations. Routes for the preparation of methyl- or amino-terminated structures or silicon surfaces are presented and discussed. The formation of silane monolayers on nanoscopic silicon oxide nanostructures was found to be much more sensitive towards ambient humidity than, e.g., the silanization of larger OH-terminated silica surfaces. Amino-functionalized nanostructures have been successfully modified by the covalent binding of functional fluorescein dye molecules. Upon excitation, the dye-functionalized structures show only weak fluorescence, which may be an indication of a relatively low surface coverage of the dye molecules on length scale that is not accessible by standard AFM measurements.

von Borczyskowski, Christian; Graaf, Harald

2013-01-01

391

Evidenece for surface states in ZnO nanostructures using non-linear optical spectroscopy  

NASA Astrophysics Data System (ADS)

An unexpected presence of ferromagnetic (FM) ordering in nanostructured ZnO has been reported previously. Recently, from our detailed magnetization studies and ab initio calculations, we attributed this FM ordering in nanostructured ZnO to the presence of surface states, and a direct correlation between the magnetic properties and crystallinity of ZnO was observed. Such defect induced surface states appear as green/yellow emission in the photoluminescence spectrum of ZnO nanostructures. In this study, through a systematic sample preparation of both pristine and Co-doped ZnO nanostructures, and detailed PL and nonlinear optical measurements, we confirm that the observed FM ordering is due to the presence of surface states.

Anand, Benoy; Egblewogbe, Martin; Podila, Ramakrishna; Philip, Reji; Rao, Apparao

2012-02-01

392

Investigations of the Band Structure and Morphology of Nanostructured Surfaces  

NASA Astrophysics Data System (ADS)

In this dissertation, I examine the electronic structure of two very different types of two-dimensional systems: valence band electrons in single layer graphene and electronic states created at the vacuum interface of single crystal copper surfaces. The characteristics of both electronic systems depend intimately on the morphology of the surfaces they inhabit. Thus, in addition to discussing the respective band structures of these systems, a significant portion of this dissertation will be devoted to measurements of the surface morphology of these systems. Free-standing exfoliated monolayer graphene is an ultra-thin flexible membrane and, as such, is known to exhibit large out-of-plane deformation due to substrate and adsorbate interaction as well as thermal vibrations and, possibly, intrinsic buckling. Such crystal deformation is known to limit mobility and increase local chemical reactivity. Additionally, deformations present a measurement challenge to researchers wishing to determine the band structure by angle-resolved photoemission since they limit electron coherence in such measurements. In this dissertation, I present low energy electron microscopy and micro probe diffraction measurements, which are used to image and characterize corrugation in SiO2-supported and suspended exfoliated graphene at nanometer length scales. Diffraction line-shape analysis reveals quantitative differences in surface roughness on length scales below 20 nm which depend on film thickness and interaction with the substrate. Corrugation decreases with increasing film thickness, reflecting the increased stiffness of multilayer films. Specifically, single-layer graphene shows a markedly larger short range roughness than multilayer graphene. Due to the absence of interactions with the substrate, suspended graphene displays a smoother morphology and texture than supported graphene. A specific feature of suspended single-layer films is the dependence of corrugation on both adsorbate load and temperature, which is manifested by variations in the diffraction lineshape. The effects of both intrinsic and extrinsic corrugation factors will be discussed. Through a carefully coordinated study I show how these surface morphology measurements can be combined with angle resolved photoemission measurements to understand the role of surface corrugation in the ARPES measurement process. The measurements described here rely on the development of an analytical formulation for relating the crystal corrugation to the photoemission linewidth. I present ARPES measurements that show that, despite significant deviation from planarity of the crystal, the electronic structure of exfoliated suspended graphene is nearly that of ideal, undoped graphene; the Dirac point is measured to be within 25 meV of EF. Further, I show that suspended graphene behaves as a marginal Fermi-liquid, with a quasiparticle lifetime which scales as (E -- EF)--1 ; comparison with other graphene and graphite data is discussed. In contrast to graphene, which must be treated as a flexible membrane with continuous height variation, roughness in clean single crystal surfaces arises from lattice dislocations, which introduce discrete height variations. Such height variations can be exploited to generate a self assembled nano-structured surface. In particular, by making a vicinal cut on a single crystal surface, a nanoscale step array can be formed. A model system for such nanoscale self assembly is Cu(111). Cu(775) is formed by making an 8.5° viscinal cut of Cu(111) along the [112¯] axis. The electronic states formed on the surface of this system, with a nanoscale step array of 14 A terraces, shows markedly different behavior those formed on Cu(111). In this dissertation, I show that the tunability of a femtosecond optical parametric oscillator, combined with its high-repetition rate and short pulse length, provides a powerful tool for resonant band mapping of the sp surface and image states on flat and vicinal Cu(111)-Cu (775) surfaces, over the photon energy range from 3.9 to 5 eV. Since the tim

Knox, Kevin R.

393

Facile fabrication of colored superhydrophobic coatings by spraying a pigment nanoparticle suspension.  

PubMed

Superhydrophobic coatings were prepared by spraying a pigment nanoparticle suspension. By changing the type of pigment nanoparticles, the colors of the coating could be controlled. The particle size of the pigments, which determines the surface structure of the coatings, played an important role in exhibiting superhydrophobicity. The spray-coating process is applicable to a variety of materials (e.g., copper, glass, paper, coiled wire, and tied thread), and the superhydrophobicity was repairable. PMID:21718077

Ogihara, Hitoshi; Okagaki, Jun; Saji, Tetsuo

2011-07-05

394

Fabrication of super-hydrophobic nano-sized copper films by electroless plating  

Microsoft Academic Search

Super-hydrophobic nano-sized copper films were fabricated on smooth glass substrates by an improved electroless plating technology. The copper film deposited for 1min showed extremely high hydrophobicity with a water contact angle of 138.0o and super-hydrophobicity with a water contact angle of 152.4o when it was modified with 1-octadecanethiol (CH3–(CH2)17–SH). Such super-hydrophobicity is attributed to the combined roles of the surface

Xianli Liu; Zhonghao Jiang; Yuewen Guo; Zhihui Zhang; Luquan Ren

2010-01-01

395

Chemically modified superhydrophobic WO(x) nanowire arrays and UV photopatterning.  

PubMed

A facile route is reported for the fabrication of superhydrophobic tungsten oxide (WO(x)) nanowire surfaces through the chemical adsorption of alkyltrichlorosilane with a static water contact angle (CA) of 163.5 degrees. It is confirmed that CAs on the superhydrophobic surface decreased gradually under UV illumination because of the UV-assisted decomposition of alkyltrichlorosilane chemically adsorbed onto the surface. Superhydrophobic-superhydrophilic switching is also demonstrated by alternating self-assembled monolayer deposition and UV irradiation on the photopatterned nanowire surfaces. Furthermore, the superhydrophobic surface could be transformed selectively into a hydrophilic state by simply exposing the surface to UV through a shadow mask. These studies provide a relatively simple strategy for the design of superhydrophobic surfaces. PMID:20369846

Kwak, Geunjae; Lee, Mikyung; Yong, Kijung

2010-06-15

396

Self-assembled nanostructures on VSe2 surfaces induced by Cu deposition.  

PubMed

Analytical transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been applied for the characterization of evolution, lateral arrangements, orientations, and the microscopic nature of nanostructures formed during the early stages of ultrahigh vacuum electron beam evaporation of Cu onto surfaces of VSe2 layered crystals. Linear nanostructure of relatively large lateral dimension (100-500 nm) and networks of smaller nanostructures (lateral dimension: 15-30 nm; mesh sizes: 500-2000 nm) are subsequently formed on the substrate surfaces. Both types of nanostructures are not Cu nanowires but are composed of two strands of crystalline substrate material elevating above the substrate surface. For the large nanostructures a symmetric roof structure with an inclination angle of approximately 30 degrees with respect to the substrate surface could be deduced from detailed diffraction contrast experiments. In addition to the nanostructure networks a thin layer of a Cu-VSe2 intercalation phase of 3R polytype is observed at the substrate surface. A dense network of interface dislocations indicates that the phase formation is accompanied by in-plane strain. We present a model that explains the formation of large and small nanostructures as consequences of compressive layer strains that are relaxed by the formation of rooflike nanostructures, finally evolving into the observed networks with increasing deposition time. The dominating contributions to the compressive layer strains are considered to be an electronic charge transfer from the Cu adsorbate to the substrate and the formation of a Cu-VSe2 intercalation compound in a thin surface layer. PMID:17481326

Spiecker, Erdmann; Hollensteiner, Stefan; Jäger, Wolfgang; Haselier, Hans; Schroeder, Herbert

2005-10-01

397

Endothelization and adherence of leucocytes to nanostructured surfaces.  

PubMed

We analyse the leucocyte and endothelial cell response to polybromostyrene-polystyrene (PS/PBrS) and the poly-n-butylmethacrylate-polystyrene (PnBMA/PS) systems, both in flat form or nanostructured surfaces consisting of nanohills with increasing hill height (13-95nm). Experiments were carried out first with blood leucocytes alone, endothelial cells (of three different types) alone, and finally, using blood cells and endothelized nanosurfaces. Blocking monoclonal antibodies specific for CD11, CD29, CD31, CD54, CD166 were used to analyse whether and to what extent adhesion molecules could be involved in the adherence of both blood leucocytes and endothelial cells to different nanosurfaces. Expression of CD29 (beta-1 integrin), CD54 (ICAM-1) and CD166 (ALCAM) on blood leucocytes was dependent on the hill height, being most prominent with 13nm (PS/PBrS) and 45nm hill (PnBMA/PS) nanosurfaces. Adherence of a human microvascular endothelial cell line and umbilical primary endothelial cells was also related to hill height, being most prominent with 13nm hill height. An indirect correlation was observed between the extent of endothelization and the degree of leucocyte adherence. In cases of low to medium extent of endothelization, the adherence of monocytes and granulocytes was mediated by the expression of CD166, CD29 and CD11a (alpha-L integrin), CD29, CD31 (PECAM-1), respectively. Scanning electron microscopy studies showed the predominant emission of pseudopodia at the holes of the surfaces and the focal contacts with the nanosurfaces. Our studies emphasize the relevance of testing functional properties in co-culture experiments in the development and optimization of nanosurfaces for biomedical application. PMID:12711519

Buttiglieri, S; Pasqui, D; Migliori, M; Johnstone, H; Affrossman, S; Sereni, L; Wratten, M L; Barbucci, R; Tetta, C; Camussi, G

2003-07-01

398

Optically transparent superhydrophobic silica-based films  

Microsoft Academic Search

Optically transparent superhydrophobic silica-based films were obtained by means of sol–gel processing and self-assembly (SA). Desired surface roughness was obtained by tuning the microstructures of the sol–gels through careful control of hydrolysis and condensation reactions of various silica precursors during sol–gel processing, whereas modification of surface chemistry was done by introducing a monolayer through surface condensation reaction. Such coatings were

H. M. Shang; Y. Wang; S. J. Limmer; T. P. Chou; K. Takahashi; G. Z. Cao

2005-01-01

399

Transforming Anaerobic Adhesives into Highly Durable and Abrasion Resistant Superhydrophobic Organoclay Nanocomposite Films: A New Hybrid Spray Adhesive for Tough Superhydrophobicity  

NASA Astrophysics Data System (ADS)

The authors report fabrication of tough nanostructured self-cleaning superhydrophobic polymer-organoclay films from anaerobic acrylic adhesives displaying strong adhesion to metal surfaces. Both industrial and bio-grade anaerobic adhesives such as bone cements could be used. Montmorillonite clay filled anaerobic adhesives were modified by blending with a water dispersed fluoro-methacrylic latex in solution to form abrasion resistant interpenetrating polymer network films upon spray casting. The adhesive films could cure by thermosetting in oxygen-rich environments. Very high contact angles with low hysteresis were also measured for acidic (pH 2) and basic (pH 11) aqueous buffer solutions indicating resistance to acidic and basic media.

Bayer, Ilker S.; Brown, Andrea; Steele, Adam; Loth, Eric

2009-12-01

400

Anisotropic optical transmission of femtosecond laser induced periodic surface nanostructures on indium-tin-oxide films.  

PubMed

Two types of periodic nanostructures, self-organized nanodots and nanolines, were fabricated on the surfaces of indium-tin-oxide (ITO) films using femtosecond laser pulse irradiation. Multiple periodicities (approximately 800?nm and 400?nm) were clearly observed on the ITO films with nanodot and nanoline structures and were identified using two-dimensional Fourier transformation patterns. Both nanostructures show the anisotropic transmission characteristics in the visible range, which are strongly correlated with the geometry and the metallic content of the laser-induced nanostructures. PMID:23066167

Wang, Chih; Wang, Hsuan-I; Luo, Chih-Wei; Leu, Jihperng

2012-09-07

401

Anisotropic optical transmission of femtosecond laser induced periodic surface nanostructures on indium-tin-oxide films  

PubMed Central

Two types of periodic nanostructures, self-organized nanodots and nanolines, were fabricated on the surfaces of indium-tin-oxide (ITO) films using femtosecond laser pulse irradiation. Multiple periodicities (approximately 800?nm and 400?nm) were clearly observed on the ITO films with nanodot and nanoline structures and were identified using two-dimensional Fourier transformation patterns. Both nanostructures show the anisotropic transmission characteristics in the visible range, which are strongly correlated with the geometry and the metallic content of the laser-induced nanostructures.

Wang, Chih; Wang, Hsuan-I; Luo, Chih-Wei; Leu, Jihperng

2012-01-01

402

Anisotropic optical transmission of femtosecond laser induced periodic surface nanostructures on indium-tin-oxide films  

NASA Astrophysics Data System (ADS)

Two types of periodic nanostructures, self-organized nanodots and nanolines, were fabricated on the surfaces of indium-tin-oxide (ITO) films using femtosecond laser pulse irradiation. Multiple periodicities (approximately 800 nm and 400 nm) were clearly observed on the ITO films with nanodot and nanoline structures and were identified using two-dimensional Fourier transformation patterns. Both nanostructures show the anisotropic transmission characteristics in the visible range, which are strongly correlated with the geometry and the metallic content of the laser-induced nanostructures.

Wang, Chih; Wang, Hsuan-I.; Luo, Chih-Wei; Leu, Jihperng

2012-09-01

403

Effect of electric fields on the surface of nanostructured electrodes on charge formation  

NASA Astrophysics Data System (ADS)

The processing of the atomic force microscopy images of specific nanostructured electrodes made of different metals shows that the shape of a nanostructure's peak can be well approximated using a parabolic dependence. The local electric fields and injection currents are calculated using the data on the nanostructured surface of electrodes with the aid of the Fowler-Nordheim dependence. A qualitative analysis is performed and the applicability of the proposed approach in the construction of the electroconvection mass- and heat-exchange devices is demonstrated.

Kuz'menko, A. P.; Kuz'ko, A. E.; Timakov, D. I.

2013-02-01

404

An Experimental Study of Drag Reduction in a Pipe with Superhydrophobic Coating at Moderate Reynolds Numbers  

Microsoft Academic Search

This paper experimentally investigates drag reduction, durability for operations and effects for preventing microorganism from adhering to the surface when the superhydrophobic coating is applied on a solid surface. The experiments are divided into two parts. In the first part, a pipe flow system was established to measure the drag and to test the durability of the micro-structure of superhydrophobic

J. H. Chen; C. C. Tsai; Y. Z. Kehr; L. Horng; K. Chang; L. Kuo

2010-01-01

405

Surface nanostructuring of Ni/Cu foils by femtosecond laser pulses  

SciTech Connect

This work examines the effect of high-power femtosecond laser pulses on Ni/Cu bilayer foils produced by electrodeposition. We consider nanostructures formed at different laser beam parameters and under different ambient conditions. The surface nanostructures obtained in air and water have mostly the form of quasi-periodic ripples with a characteristic period of 400 - 450 and 370 - 390 nm, respectively, at a laser wavelength of 744 nm, whereas the nanostructures produced in ethanol and benzine have the form of spikes, typically spaced 400 - 700 nm apart. Femtosecond laser nanostructuring of metals is for the first time proposed, and experimentally tested, as a viable approach to producing anti-reflective coatings on the surface of polymer replicas. (laser nanotechnologies)

Korol'kov, V P; Ionin, Andrei A; Kudryashov, Sergei I; Seleznev, L V; Sinitsyn, D V; Samsonov, R V; Maslii, A I; Medvedev, A Zh; Gol'denberg, B G

2011-04-30

406

Multifunctional superhydrophobic coatings for large area applications  

NASA Astrophysics Data System (ADS)

Formulation of flexible superhydrophobic coatings (water droplet contact angles above 150 deg and roll-off angles below 10 deg) with high durability and electrical conductivity, and their fabrication using scalable techniques is a major challenge. The current work lays their foundation using solution processed polymer nanocomposites. Carefully selected polymer(s) are used to disperse filler particles and the dispersions are applied by spraying process. The filler particle size, surface energy and other functionalities are varied to produce the coatings. Sub-micron poly(tetrafluoroethylene) (PTFE) particles and carbon black or other nanoparticles are jointly used to obtain hierarchical morphology (micro-to-nanoscale roughness) and superhydrophobicity. As examples, firstly, acrylonitrile-co-butadiene rubber based nanocomposites are shown to maintain superhydrophobicity up to 200% linear and for 100 cycles of reversible 0 to 100% uniaxial stretching. Secondly, poly(vinylidene fluoride) and poly(methyl methacrylate) blend based nanocomposites containing carbon nanofibers are demonstrated as superhydrophobic coatings with electrical conductivity up to 300 S/m.

Megaridis, Constantine; Schutzius, Thomas; Das, Arindam; Tiwari, Manish; Bayer, Ilker

2009-11-01

407

A facile method to fabricate superhydrophobic cotton fabrics  

NASA Astrophysics Data System (ADS)

A facile and novel method for fabricating superhydrophobic cotton fabrics is described in the present work. The superhydrophobic surface has been prepared by utilizing cationic poly (dimethyldiallylammonium chloride) and silica particles together with subsequent modification of (heptadecafluoro-1,1,2,2-tetradecyl) trimethoxysilane. The size distribution of silica particles was measured by Particle Size Analyzer. The cotton textiles before and after treatment were characterized by using scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The wetting behavior of cotton samples was investigated by water contact angle measurement. Moreover, the superhydrophobic durability of coated cotton textiles has been evaluated by exposure, immersion and washing tests. The results show that the treated cotton fabrics exhibited excellent chemical stability and outstanding non-wettability with the WCA of 155 ± 2°, which offers an opportunity to accelerate the large-scale production of superhydrophobic textiles materials for new industrial applications.

Zhang, Ming; Wang, Shuliang; Wang, Chengyu; Li, Jian

2012-11-01

408

Temperature and humidity effects on superhydrophobicity of nanocomposite coatings  

NASA Astrophysics Data System (ADS)

This work investigates temperature and humidity effects on the superhydrophobicity of polyurethane/organoclay nanocomposites. Previous reports of superhydrophobic degradation at decreasing surface temperatures for both low and high humidity were generally conducted in open environments. However, the present setup allows a thermally homogeneous environment, i.e., the temperature of the nanocomposite, air and water droplet are equal with no spatial temperature gradients. In such conditions, results showed stable retention of superhydrophobicity for both low humidity (RH < 20%) cool-down and warm-up cycles (20 °C to -3 °C to 20 °C). Similar performance was also observed for a high humidity (RH > 80%) cool-down cycle, though superhydrophobicity degraded during the warm-up cycle, which was attributed to dew condensation.

Han Yeong, Yong; Steele, Adam; Loth, Eric; Bayer, Ilker; de Combarieu, Guillaume; Lakeman, Charles

2012-01-01

409

Transparent superhydrophobic and highly oleophobic coatings.  

PubMed

We report a facile process for fabrication of transparent superhydrophobic and highly oleophobic surfaces through assembly of silica nanoparticles and sacrificial polystyrene nanoparticles. The silica and polystyrene nanoparticles are first deposited by a layer-by-layer assembly technique. The polystyrene nanoparticles are then removed by calcination, which leaves a porous network of silica nanoparticles. The cavities created by the sacrificial polystyrene particles form overhang structures on the surfaces. Modified with a fluorocarbon molecule, such surfaces are superhydrophobic and transparent. They also repel liquids with low surface tensions, such as hexadecane, due to the overhang structures that prevent liquids from getting into the air pockets even though the intrinsic contact angles of these liquids are less than 90 degrees. PMID:21043414

Cao, Liangliang; Gao, Di

2010-01-01

410

Investigation of oxygen states and reactivities on a nanostructured cupric oxide surface  

NASA Astrophysics Data System (ADS)

Nanostructured copper (II) oxide was formed on clean copper foil at room temperature using activated oxygen produced by RF discharge. CuO particles of approximately 10-20 nm were observed on the surface by Scanning Tunneling Microscopy (STM). The copper states and oxygen species of the model cupric oxide were studied by means of X-ray Photoelectron Spectroscopy (XPS). These oxide particles demonstrated abnormally high reactivity with carbon monoxide (CO) at temperatures below 100 °C. The XPS data showed that the interaction of CO with the nanostructured cupric oxide resulted in reduction of the CuO particles to Cu 2O species. The reactivity of the nanostructured cupric oxide to CO was studied at 80 °C using XPS in step-by-step mode. The initial reactivity was estimated to be 5 × 10 -5 and was steadily reduced down to 5 × 10 -9 as the exposure was increased. O1s spectral analysis allowed us to propose that the high initial reactivity was caused by the presence of non-lattice oxygen states on the surface of the nanostructured CuO. We established that reoxidation of the partially reduced nanostructured cupric oxide by molecular oxygen O 2 restored the highly reactive oxygen form on the surface. These results allowed us to propose that the nanostructured cupric oxide could be used for low temperature catalytic CO oxidation. Some hypotheses concerning the nature of the non-lattice oxygen species with high reactivity are also discussed.

Svintsitskiy, D. A.; Stadnichenko, A. I.; Demidov, D. V.; Koscheev, S. V.; Boronin, A. I.

2011-08-01

411

Molecular dynamics simulation of atomic-scale frictional behavior of corrugated nano-structured surfaces  

NASA Astrophysics Data System (ADS)

Surface morphology is one of the critical parameters that affect the frictional behavior of two contacting bodies in relative motion. It is important because the real contact area as well as the contact stiffness is dictated by the micro- and nano-scale geometry of the surface. In this regard, the frictional behavior may be controlled by varying the surface morphology through nano-structuring. In this study, molecular dynamics simulations were conducted to investigate the effects of contact area and structural stiffness of corrugated nano-structures on the fundamental frictional behavior at the atomic-scale. The nano-structured surface was modeled as an array of corrugated carbon atoms with a given periodicity. It was found that the friction coefficient of the nano-structured surface was lower than that of a smooth surface under specific contact conditions. The effect of applied load on the friction coefficient was dependent on the size of the corrugation. Furthermore, stiffness of the nano-structure was identified to be an important variable in dictating the frictional behavior.

Kim, Hyun-Joon; Kim, Dae-Eun

2012-06-01

412

Magnetic Behavior of Surface Nanostructured 50-nm Nickel Thin Films  

PubMed Central

Thermally evaporated 50-nm nickel thin films coated on borosilicate glass substrates were nanostructured by excimer laser (0.5 J/cm2, single shot), DC electric field (up to 2 kV/cm) and trench-template assisted technique. Nanoparticle arrays (anisotropic growth features) have been observed to form in the direction of electric field for DC electric field treatment case and ruptured thin film (isotropic growth features) growth for excimer laser treatment case. For trench-template assisted technique; nanowires (70–150 nm diameters) have grown along the length of trench template. Coercive field and saturation magnetization are observed to be strongly dependent on nanostructuring techniques.

2010-01-01

413

A well-ordered flower-like gold nanostructure for integrated sensors via surface-enhanced Raman scattering  

NASA Astrophysics Data System (ADS)

A controllable flower-like Au nanostructure array for surface-enhanced Raman scattering (SERS) was fabricated using the combined technique of the top-down approach of conventional photolithography and the bottom-up approach of electrodeposition. Au nanostructures with a mean roughness ranging from 5.1 to 49.6 nm were obtained by adjusting electrodeposition time from 2 to 60 min. The rougher Au nanostructure provides higher SERS enhancement, while the highest SERS intensity obtained with the Au nanostructure is 29 times stronger than the lowest intensity. The SERS spectra of brilliant cresyl blue (BCB), benzenethiol (BT), adenine and DNA were observed from the Au nanostructure.

Kim, Ju-Hyun; Kang, Taejoon; Yoo, Seung Min; Lee, Sang Yup; Kim, Bongsoo; Choi, Yang-Kyu

2009-06-01

414

A well-ordered flower-like gold nanostructure for integrated sensors via surface-enhanced Raman scattering.  

PubMed

A controllable flower-like Au nanostructure array for surface-enhanced Raman scattering (SERS) was fabricated using the combined technique of the top-down approach of conventional photolithography and the bottom-up approach of electrodeposition. Au nanostructures with a mean roughness ranging from 5.1 to 49.6 nm were obtained by adjusting electrodeposition time from 2 to 60 min. The rougher Au nanostructure provides higher SERS enhancement, while the highest SERS intensity obtained with the Au nanostructure is 29 times stronger than the lowest intensity. The SERS spectra of brilliant cresyl blue (BCB), benzenethiol (BT), adenine and DNA were observed from the Au nanostructure. PMID:19448293

Kim, Ju-Hyun; Kang, Taejoon; Yoo, Seung Min; Lee, Sang Yup; Kim, Bongsoo; Choi, Yang-Kyu

2009-05-18

415

Elaborate- Superhydrophobic Coating  

NSDL National Science Digital Library

This resource from the Midwest Regional Center for Nanotechnology Education (NANO-LINK) features a video on the work done with superhydrophobic technology at Sandia Laboratories. This video demonstration is an excellent introduction to the technology and would be useful in facilitating classroom discussion. Running time for the video is 4:10.

2012-09-25

416

Durable Nanocomposites for Superhydrophobicity and Superoleophobicity  

NASA Astrophysics Data System (ADS)

Anti-wetting surfaces and materials have the potential for dramatic performance improvements such as drag reduction on marine vehicles and fluid power systems as well as anti-fouling on aircraft and wind turbines. Although a wide variety of synthetic superhydrophobic surfaces have been developed and investigated, several critical obstacles remain before industrial application can be realized, including: (1) large surface area application, (2) multi-liquid anti-wetting, (3) environmentally friendly compositions, (4) mechanical durability and adhesion, and (5) long-term performance. In this dissertation, nanocomposite coatings have been investigated to generate high performance anti-wetting surfaces that address these obstacles which may enable application on wind turbine blades. Solution processable materials were used which self-assemble to create anti-wetting nanocomposite surfaces upon spray coating and curing. As a result, the first superoleophobic nanocomposite, the first environmentally friendly superhydrophobic compositions, and the first highly durable superhydrophobic nanocomposite coatings were created. Furthermore, the mechanisms leading to this improved performance were studied.

Steele, Adam

417

Carbon nanotube-based robust steamphobic surfaces.  

PubMed

The wetting behavior of a surface under steam condensation depends on its intrinsic wettability and micrometer or nanoscale surface roughness. A typical superhydrophobic surface may not be suitable as a steamphobic surface because of the nucleation and growth of water inside the valleys and thus the failure to form an air-liquid-solid composite interface. Here, we present the results of steam condensation on chemically modified nanostructured carbon nanotube (CNT) mats. We used a plasma-enhanced chemical vapor deposition (PECVD) process to modify the intrinsic wettability of nanostructured CNT mats. The combination of low surface energy achieved by PECVD and the nanoroughness of the surface provides a mechanism to retain the superhydrophobicity of the CNT mats under steam condensation. The ability to withstand steam temperature and pressure for as long as 10 h implies the remarkably improved stability of the superhydrophobic state of the surface. The thermodynamic calculations carried out using a unit cell model clearly explain the steamphobic wetting behavior of the surface. PMID:22087571

Badge, Ila; Sethi, Sunny; Dhinojwala, Ali

2011-11-22

418

A Review of Recent Results on Superhydrophobic Materials Based on Micro and Nanofibers  

Microsoft Academic Search

Recent developments of superhydrophobic materials in which fibrous structure plays a critical role are reviewed. The role of the fibers with diameters on the length scale of nanometers to micrometers to create a surface of suitable topography is emphasized. Superhydrophobic fibrous materials are first illustrated by analogy to common plant structures in nature. Examples from the synthetic world are drawn

Minglin Ma; Randal M. Hill; Gregory C. Rutledge

2008-01-01

419

Fabrication of Stable Superhydrophobic Coatings with Furfural Acetone Resin\\/PTFE Composites  

Microsoft Academic Search

We describe a simple and inexpensive technique to fabricate superhydrophobic coatings with furfural acetone resin\\/poly (tetrafluoroethylene) (FAR\\/PTFE) composites. An interesting hierarchical structure with dispersed cavities and protuberances in microscale was achieved. The water contact angle (CA) of the superhydrophobic surface is 157° and the sliding angle is about 5°. The coatings can be applied to large substrates by spray coating

Jin Yang; Zhao-Zhu Zhang; Xue-Hu Men; Xiang-Hui Xu

2009-01-01

420

Durability and restoring of superhydrophobic properties in silica-based coatings.  

PubMed

The durability and restorable properties of superhydrophobicity are a most important issue essential for utilization of superhydrophobic materials in industrial and domestic fields. In this work, we have focused on the sol-gel dip coating synthesis, durability, and restoring properties of a superhydrophobic surface composed of spherical silica particles with low energy free surface successfully achieved on the surface of glass substrates. The water contact angle (WCA) of the as-prepared superhydrophobic coatings reached as high as 170±1° (WCA=170±1°) and the sliding angle was 3±1° (WSA=3±1°). The behavior of wettability on superhydrophobic coating surface under various external disturbances including outdoor environments, heat, and mild acidic condition is investigated. It is shown in particular that degradation and repairing of surface methyl groups between two such surfaces leads to a fully restorable coating surface by the surface modification with trimethylchlorosilane (TMCS) at room temperature. T