Superhydrophobic behavior achieved from hydrophilic surfaces

Wang, Jiadao; Liu, Fengbin; Chen, Haosheng; Chen, Darong

doi:10.1063/1.3212869

Cited by 65 publications

(47 citation statements)

References 20 publications

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“…A large number of papers have focused on superhydrophobic surfaces. [32][33][34][51][52][53][54][55][56]60,61 Those studies have employed microscale patterning with hydrophobic pillars and voids where liquid did not penetrate. They are different from what we report here.…”

Section: ■ Discussionmentioning

confidence: 99%

Drop Detachment and Motion on Fuel Cell Electrode Materials

Gauthier

Hellstern

Kevrekidis

et al. 2012

ACS Appl. Mater. Interfaces

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Liquid water is pushed through flow channels of fuel cells, where one surface is a porous carbon electrode made up of carbon fibers. Water drops grow on the fibrous carbon surface in the gas flow channel. The drops adhere to the superficial fiber surfaces but exhibit little penetration into the voids between the fibers. The fibrous surfaces are hydrophobic, but there is a substantial threshold force necessary to initiate water drop motion. Once the water drops begin to move, however, the adhesive force decreases and drops move with minimal friction, similar to motion on superhydrophobic materials. We report here studies of water wetting and water drop motion on typical porous carbon materials (carbon paper and carbon cloth) employed in fuel cells. The static coefficient of friction on these textured surfaces is comparable to that for smooth Teflon. But the dynamic coefficient of friction is several orders of magnitude smaller on the textured surfaces than on smooth Teflon. Carbon cloth displays a much smaller static contact angle hysteresis than carbon paper due to its two-scale roughness. The dynamic contact angle hysteresis for carbon paper is greatly reduced compared to the static contact angle hysteresis. Enhanced dynamic hydrophobicity is suggested to result from the extent to which a dynamic contact line can track topological heterogeneities of the liquid/solid interface. KEYWORDS: contact angle, hydrophobic, carbon, wetting, carbon fibers, contact angle hysteresis, Teflon ■ INTRODUCTIONWater transport is an essential element of polymer electrolyte membrane (PEM) fuel cell operation. 1−5 Liquid water that is formed at a catalyst/membrane interface is pushed through porous electrodes into gas flow channels. The water drops emerge from the largest pores in the electrode, and grow in the channel. Initially, the drops are held in place by adhesion to the water column in the electrode pore, but as the drops grow surface contact with the porous electrode and surface contact with the walls of the flow channel are the dominate adhesive forces. The drop must be detached and pushed through the gas flow channel in contact with the electrode surface to be removed from the fuel cell. Efficient fuel cell operation requires removal of liquid water drops from the fuel cell with minimal work. The surface properties of the porous electrode play a key role in the energy required to remove water drops from the gas flow channels of the fuel cell. We have been devising experiments to isolate the flow resistances for water transport through the porous electrode and gas flow channel. 6−8 The porous electrode is required to carry the electron current from the electrocatalyst to the external circuit. 9 It must also permit transport of gas reactants and liquid product between the gas flow channels and the catalyst/PEM interface. 4,10,11 The porous electrode, or gas diffusion layer (GDL), of the fuel cell is typically made from carbon fibers, either as a random sheet of fibers in the form of carbon paper or as a woven arr...

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Section: ■ Discussionmentioning

confidence: 99%

Drop Detachment and Motion on Fuel Cell Electrode Materials

Gauthier

Hellstern

Kevrekidis

et al. 2012

ACS Appl. Mater. Interfaces

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“…Plasma-enhanced CVD (PECVD) uses plasma energy that can act to activate the precursors and/or change surface structure. [96] PECVD can be used to deposit films of PTFEtype materials to give water contact angles of > 1008 on flat substrates; if a roughened microstructure is introduced to increase the surface roughness this improves to over 1608. [97] Recent developments have demonstrated that surface roughness can be introduced during the PECVD process.…”

Section: Carbon Nanotubes (Cnts)mentioning

confidence: 99%

Preparation and Characterisation of Super‐Hydrophobic Surfaces

Crick

Parkin

2010

Chemistry A European J

279

171

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The interest in highly water-repellent surfaces has grown in recent years due to the desire for self-cleaning surfaces. A super-hydrophobic surface is one that achieves a water contact angle of 150 degrees or greater. This article explores the different approaches used to construct super-hydrophobic surfaces and identifies the key properties of each surface that contribute to its hydrophobicity. The models used to describe surface interaction with water are considered, with attention directed to the methods of contact angle analysis. A summary describing the different routes to hydrophobicity is also given.

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“…Traditionally, superhydrophobic surfaces have been fabricated either by creating rough structures on an intrinsically hydrophobic surface or by providing an additional low‐surface‐energy coating in a secondary step on top of the rough structured surface. Based on the findings reported by earlier works involving fabrication of superhydrophobic surface using an amphiphilic or hydrophilic surface, it is evident that superhydrophobicity can be achieved when two out of the three design criteria are met: (1) low‐surface‐energy material, (2) micro/nanohierarchical roughness, and (3) reentrant structures …”

Section: Resultsmentioning

confidence: 94%

Continuous manufacturing of reentrant structures via roll‐to‐roll process

Shivaprakash

Zhang

Panwar

et al. 2018

J of Applied Polymer Sci

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Reentrant structures have been deemed necessary for repelling low‐surface‐tension liquids. In this article, a novel manufacturing methodology using the roll‐to‐roll process to enable continuous manufacturing of reentrant structures over large areas on a polymeric film was demonstrated. A two‐stage process, composed of embossing followed by post‐compression, allowed the fabrication of reentrant structures, which cannot be easily fabricated using other processes over large areas in a continuous manner. The treatment of the reentrant surface structures with an additional coating of 1H,1H,2H,2H‐perfluorooctyltrichlorosilane layer provided liquid repellency with contact angles of 155 and 140°, respectively, for water (Ylv = 72 mN m−1) and diiodomethane (Ylv = 50 mN m−1). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 46980.

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Superhydrophobic behavior achieved from hydrophilic surfaces

Cited by 65 publications

References 20 publications

Drop Detachment and Motion on Fuel Cell Electrode Materials

Drop Detachment and Motion on Fuel Cell Electrode Materials

Preparation and Characterisation of Super‐Hydrophobic Surfaces

Continuous manufacturing of reentrant structures via roll‐to‐roll process

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