Reversible Wetting−Dewetting Transitions on Electrically Tunable Superhydrophobic Nanostructured Surfaces

Krupenkin, Tom N.; Taylor, J. Ashley; Wang, Evelyn N.; Kolodner, Paul; Hodes, Marc; Salamon, Todd

doi:10.1021/la7008557

Cited by 255 publications

(227 citation statements)

References 19 publications

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“…1(d). Note the recovery of the SHPo state shown for sessile droplets surrounded by air [16,17] is not helpful for drag reduction, which pertains to the entire surface being fully immersed underwater.…”

Section: University Of California Los Angeles (Ucla) California 900mentioning

confidence: 99%

Underwater Restoration and Retention of Gases on Superhydrophobic Surfaces for Drag Reduction

2011

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Section: University Of California Los Angeles (Ucla) California 900mentioning

confidence: 99%

Underwater Restoration and Retention of Gases on Superhydrophobic Surfaces for Drag Reduction

2011

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“…In this context, it is worth exhibiting monostable Cassie states where even an accidental transition to the undesired Wenzel state, due to force fluctuations such as encountered in an impact (37) or to pressure applied on the liquid (16,17,33,(46)(47)(48)(49)(50), can be repaired owing to the absence of barrier between both states. Because reported Wenzel-to-Cassie (W2C) transitions generally involve either an external energy input (17,49,(51)(52)(53) or a potential energy release (35,(54)(55)(56), monostable Cassie states might be seen as unreal (57), but we describe here such situations and criteria for achieving them. Our hope is that these findings will shed new light on our fundamental understanding of water repellency.…”

mentioning

confidence: 99%

Monostable superrepellent materials

Quéré

et al. 2017

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

104

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Superrepellency is an extreme situation where liquids stay at the tops of rough surfaces, in the so-called Cassie state. Owing to the dramatic reduction of solid/liquid contact, such states lead to many applications, such as antifouling, droplet manipulation, hydrodynamic slip, and self-cleaning. However, superrepellency is often destroyed by impalement transitions triggered by environmental disturbances whereas inverse transitions are not observed without energy input. Here we show through controlled experiments the existence of a "monostable" region in the phase space of surface chemistry and roughness, where transitions from Cassie to (impaled) Wenzel states become spontaneously reversible. We establish the condition for observing monostability, which might guide further design and engineering of robust superrepellent materials.repellency | Cassie state | monostability | interfaces | dewetting W ater repellency describes the ability of materials to repel water and make it flow with negligible friction and adhesion, compared with usual situations. It is achieved by combining chemical hydrophobicity with micro-and/or nanotextures (1, 2). Water meeting such materials remains at the textures' tops, which generates a composite interface made of hydrophobic solid and air trapped inside the textures (Cassie state) (3). As a consequence, water hardly contacts these solids on which its dynamical behaviors are spectacular (4-7). Repellency also holds if the liquid has a higher surface tension than water (salty water, mercury); using special texture designs, it can even be extended to liquids with smaller surface tension (8), and/or to water at small scale (such as dew) (9, 10), so it was proposed (11) to call such materials "superhygrophobic," from the Greek "hygros" meaning humid.Repellent materials are classically found in nature, in particular at the surface of many plants and insects, two situations where the control of water is crucial for surviving (1, 12). It was reported that these natural surfaces often (yet not always) exhibit dual structures, with microbumps on the scale of 10-100 μm coated by nanostructures of typically 100 nm (1). This results in an amplification of static (13-17) and dynamical (18) repellency, because we can then expect the generation of composite solid/air interfaces at different scales--where we mean by amplification an improved nonwettability (13-15, 17) and a smaller adhesion (16,18,19), two factors that contribute to the liquid mobility.This field of research has been very active for about 20 years, with theoretical, experimental, and computational viewpoints. Researchers discussed the surface energy of materials having different kinds of structures (20-23), various adhesion properties (24-26), diverse geometries of solid-liquid-vapor contact lines (27, 28), or flow interactions between the liquid and its substrate (29-32). In many studies, model hydrophobic textures (such as lines or pillars) were considered, and wetting was found to be usually "bistable": Depending on the history o...

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“…5 All these works involved the use of external energy, such as mechanical energy and electric energy, to overcome the energy barrier between these two states. To reduce the energy barrier and the wetting of liquid, hydrophobic or superhydrophobic surfaces are desired and different methods have been developed to form synthetic superhydrophobic surfaces.…”

mentioning

confidence: 99%

Size effect on the coalescence-induced self-propelled droplet

Wang

Yang

Zhao

2011

Applied Physics Letters

227

233

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Surface charge density model for predicting the permittivity of liquid mixtures and composites materials J. Appl. Phys. 111, 064101 (2012) Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear J. Chem. Phys. 135, 134708 (2011) Extension of the Steele 10-4-3 potential for adsorption calculations in cylindrical, spherical, and other pore geometries J. Chem. Phys. 135, 084703 (2011) Melting of iron at the Earth's core conditions by molecular dynamics simulation AIP Advances 1, 032122 (2011) Equilibrium structure of the multi-component screened charged hard-sphere fluid

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Reversible Wetting−Dewetting Transitions on Electrically Tunable Superhydrophobic Nanostructured Surfaces

Cited by 255 publications

References 19 publications

Underwater Restoration and Retention of Gases on Superhydrophobic Surfaces for Drag Reduction

Underwater Restoration and Retention of Gases on Superhydrophobic Surfaces for Drag Reduction

Monostable superrepellent materials

Size effect on the coalescence-induced self-propelled droplet

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