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

Manukyan, G.; Oh, Jung Min; Ende, Dirk van den; Lammertink, Rob G.H.; Mugele, Friedrich Gunther

doi:10.1103/physrevlett.106.014501

Cited by 152 publications

(143 citation statements)

References 18 publications

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“…A similar intermediate stage of partial penetration also allows reversible electrowetting on some of these surfaces. 97,98 There is some evidence that this is also the case on natural superhydrophobic surfaces, indeed the well known Alchemilla (Alchemilla mollis), which fascinated the alchemists with its tendency to collect dew drops is one such surface that has been shown to collect and transport dew drops across its leaves using this mechanism. 99 Interestingly, the hair-like structures of the Alchimilla are relatively hydrophilic, probably because a contact angle close to 90 aids fixation of flexible features into the liquid interface.…”

Section: Flexible Superhydrophobic Structuresmentioning

confidence: 99%

The superhydrophobicity of polymer surfaces: Recent developments

Shirtcliffe

McHale

Newton

2011

J Polym Sci B Polym Phys

168

108

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Superhydrophobicity is the extreme water repellence of highly textured surfaces. The field of superhydrophobicity research has reached a stage where huge numbers of candidate treatments have been proposed and jumps have been made in theoretically describing them. There now seems to be a move to more practical concerns and to considering the demands of individual applications instead of more general cases. With these developments, polymeric surfaces with their huge variety of properties have come to the fore and are fast becoming the material of choice for designing, developing, and producing superhydrophobic surfaces.

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Section: Flexible Superhydrophobic Structuresmentioning

confidence: 99%

The superhydrophobicity of polymer surfaces: Recent developments

Shirtcliffe

McHale

Newton

2011

J Polym Sci B Polym Phys

168

108

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“…Different impalement scenarios have been discussed. For situations in which inertia is negligible, the two most important ones are depinning and sagging (31,(34)(35)(36)(38)(39)(40)(41)(42)(43). In depinning, the three phase contact line, or briefly contact line, unpins from the edge of the asperity (37).…”

mentioning

confidence: 99%

How superhydrophobicity breaks down

Papadopoulos

Mammen

Deng

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

443

442

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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.micropillars | pinning | wetting transition | contact angle | lithography | self-cleaning | hysteresis

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“…A Cassie-to-Wenzel wetting transition does not happen until the applied voltage exceeds a critical value V c . 20 The confined vapour cannot sustain the above liquid, and therefore suddenly breaks down. 21 Meanwhile, the droplet impales into the pillars.…”

Section: Introductionmentioning

confidence: 99%

Statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale

Zhao

Yuan

2015

Nanoscale

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The statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale are studied using molecular dynamics simulations. Under a gradually increased electric field, a droplet is pushed by the electromechanical force to spread, and goes through the Cassie state, the Cassie-to-Wenzel wetting transition and the Wenzel state, which can be characterized by the electrowetting number at the microscale η m . The expansion of the liquid is direction-dependent and influenced by the surface topology. A positive voltage is induced in the bulk droplet, while a negative one is induced in the liquid confined among the pillars, which makes the liquid hard to spread and further polarize. Based on the molecular kinetic theory and the wetting states, theoretical models have been proposed to comprehend the physical mechanisms in the statics and dynamics of electrowetting, and are validated by our simulations. Our findings may help to understand the electrowetting on microtextured surfaces and assist the future design of engineered surfaces in practical applications.

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

Cited by 152 publications

References 18 publications

The superhydrophobicity of polymer surfaces: Recent developments

The superhydrophobicity of polymer surfaces: Recent developments

How superhydrophobicity breaks down

Statics and dynamics of electrowetting on pillar-arrayed surfaces at the nanoscale

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