Superomniphobic Surfaces Research Articles

Preparation of Superhydrophobic Surfaces with Different Degrees of Oleophobicity

Removed due to plagiarism Original work is published Journal of Colloid and Interface Science 409 (2013) 227-236Dual-layered-coated mechanically-durable superomniphobic surfaces with anti-smudge properties Palanikkumaran Muthiah, Bharat Bhushan, Kyungsung Yun, Hirofumi Kondo www.elsevier.com/locate/jcis

Dropwise Condensation of Low Surface Tension Fluids on Omniphobic Surfaces

Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

Micro-and nanostructured silicon-based superomniphobic surfaces

We report on the fabrication of silicon nanostructured superhydrophobic and superoleophobic surfaces also called “superomniphobic” surfaces. For this purpose, silicon interfaces with different surface morphologies, single or double scale structuration, were investigated. These structured surfaces were chemically treated with perfluorodecyltrichlorosilane (PFTS), a low surface energy molecule. The morphology of the resulting surfaces was characterized using scanning electron microscopy (SEM). Their wetting properties: static contact angle (CA) and contact angle hysteresis (CAH) were investigated using liquids of various surface tensions. Despite that we found that all the different morphologies display a superhydrophobic character (CA>150° for water) and superoleophobic behavior (CA≈140° for hexadecane), values of hysteresis are strongly dependent on the liquid surface tension and surface morphology. The best surface described in this study was composed of a dual scale texturation i.e. silicon micropillars covered by silicon nanowires. Indeed, this surface displayed high static contact angles and low hysteresis for all tested liquids.

Transparent, Flexible, Superomniphobic Surfaces with Ultra‐Low Contact Angle Hysteresis

See-through surfaces: High transparency is required to use superomniphobic surfaces, which can be self-cleaning, stain-proof, anti-bio-fouling, drag-reducing, or anti-fogging, for smartphone screens, eye glasses, windshields, or flat panel displays. A spray-based method has now been developed that can fabricate transparent, flexible, and highly superomniphobic surfaces. HD=hexadecane.

Slip flow of diverse liquids on robust superomniphobic surfaces

Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10–20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating.

Dual-layered-coated mechanically-durable superomniphobic surfaces with anti-smudge properties

Bio-inspired surfaces that exhibit high contact angle and low contact angle hysteresis for various liquids and demonstrate mechanical durability and anti-smudge properties are of interest for various applications. The fabrication of such surfaces has often involved complex or expensive processes, required techniques that may not be suitable for various substrates and particles, may require surface post-treatment, or may lack durability. Dual layered coatings of roughness-induced superomniphobic surfaces that demonstrate good mechanical durability were fabricated on glass substrates using hydrophobic SiO2 nanoparticles and low surface energy fluorobinders using dip coating and spray coating techniques. The particle-to-binder ratio was optimized for contact angles of interest. The mechanical durability of these coatings was examined under mechanical rubbing action. The anti-smudge properties were examined by wiping an artificially contaminated coating using oil-impregnated microfiber cloth.

Superomniphobic surfaces: Design and durability

Abstract

Superomniphobic Surfaces for Effective Chemical Shielding

Superomniphobic surfaces display contact angles >150° and low contact angle hysteresis with essentially all contacting liquids. In this work, we report surfaces that display superomniphobicity with a range of different non-Newtonian liquids, in addition to superomniphobicity with a wide range of Newtonian liquids. Our surfaces possess hierarchical scales of re-entrant texture that significantly reduce the solid-liquid contact area. Virtually all liquids including concentrated organic and inorganic acids, bases, and solvents, as well as viscoelastic polymer solutions, can easily roll off and bounce on our surfaces. Consequently, they serve as effective chemical shields against virtually all liquids--organic or inorganic, polar or nonpolar, Newtonian or non-Newtonian.

Robust superomniphobic surfaces with mushroom-like micropillar arrays

We present a simple method for the fabrication of robust superomniphobic surfaces with high transmittance (>90%) and durability (<6 months). The method consists of direct micromolding of mushroom-like micropillars and C4F8 gas surface treatment. Such re-entrant structures were found to be highly resistant against wetting by various liquids and oils with a wide range of surface tensions from 22.3 (ethanol) to 72.1 mN m−1 (water). Optimal structural parameters were derived based on the measurements of static contact angle and contact angle hysteresis.

Sliding Droplets on Superomniphobic Zinc Oxide Nanostructures

This study reports on liquid-repellency of zinc oxide nanostructures (ZnO NS). The ZnO NS are synthesized by an easy and fast chemical bath deposition technique. Three different nanostructured surfaces consisting of nanorods, flowers, and particles are prepared, depending on the deposition time and the presence of ethanolamine in the reaction mixture. Chemical functionalization of the ZnO NS with 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS) in liquid (PFTS L) and vapor phase (PFTS V) or through octafluorobutane (C(4)F(8)) plasma deposition led to the formation of superomniphobic surfaces. A comprehensive characterization of the wetting properties (static contact angle and contact angle hysteresis) has been performed using liquids composed of deionized water and various concentrations of ethanol (surface tension between 35 and 72.6 mN/m). Depending on the nanostructures morphology, coating nature and liquid employed, high static apparent contact angles θ ≈ 150-160°, and low contact angle hysteresis Δθ ≈ 0° are obtained. The different ZnO NS are characterized using scanning electron microscopy (SEM) and contact angle measurements. The results reported in this work permit preparation of sliding omniphobic surfaces using a simple and low cost technique.

Contact angle hysteresis origins: Investigation on super-omniphobic surfaces

Download options Please wait... Article information DOI https://doi.org/10.1039/C1SM05832K Article type Paper Submitted 05 May 2011 Accepted 30 Jun 2011 First published 24 Aug 2011 Download Citation Soft Matter, 2011,7, 9380-9387 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Contact angle hysteresis origins: Investigation on super-omniphobic surfaces R. Dufour, M. Harnois, V. Thomy, R. Boukherroub and V. Senez, Soft Matter, 2011, 7, 9380 DOI: 10.1039/C1SM05832K To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Renaud Dufour Maxime Harnois Vincent Thomy Rabah Boukherroub Vincent Senez

Quantitative Testing of Robustness on Superomniphobic Surfaces by Drop Impact

The quality of a liquid-repellent surface is quantified by both the apparent contact angle θ(0) that a sessile drop adopts on it and the value of the liquid pressure threshold the surface can withstand without being impaled by the liquid, hence maintaining a low-friction condition. We designed surfaces covered with nanowires obtained by the vapor-liquid-solid (VLS) growth technique that are able to repel most of the existing nonpolar liquids including those with very low surface tension as well as many polar liquids with moderate to high surface tension. These superomniphobic surfaces exhibit apparent contact angles ranging from 125 to 160° depending on the liquid. We tested the robustness of the surfaces against impalement by carrying out drop impact experiments. Our results show how this robustness depends on Young's contact angle θ(0) related to the surface tension of the liquid and that the orientational growth of nanowires is a favorable factor for robustness.

Engineering Sticky Superomniphobic Surfaces on Transparent and Flexible PDMS Substrate

Following the achievement of superhydrophobicity which prevents water adhesion on a surface, superomniphobicity extends this high repellency property to a wide range of liquids, including oils, solvents, and other low surface energy liquids. Recent theoretical approaches have yield to specific microstructures design criterion to achieve such surfaces, leading to superomniphobic structured silicon substrate. To transfer this technology on a flexible substrate, we use a polydimethylsiloxane (PDMS) molding process followed by surface chemical modification. It results in so-called sticky superomniphobic surfaces, exhibiting large apparent contact angles (>150°) along with large contact angle hysteresis (>10°). We then focus on the modified Cassie equation, considering the 1D aspect of wetting, to explain the behavior of droplets on these surfaces and compare experimental data to previous works to confirm the validity of this model.

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