Impact dynamics of water droplets on chemically modified WOx nanowire arrays

Kwak, Geunjae; Lee, Mi-Kyung; Senthil, Kalaiselvi; Yong, Kijung

doi:10.1063/1.3244597

Cited by 35 publications

(30 citation statements)

References 21 publications

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“…the antiwetting pressure (Pantiwetting). The antiwetting pressure (Pantiwetting) corresponds to the energy difference between the homogeneous and the heterogeneous wetting regimes 16,17,40 . The antiwetting pressure denotes the force per unit area offered to a water droplet as it transitions from a depinned metastable Cassie state to a Wenzel state.…”

Section: Surface Design For Quasi-static Robustness: Pressure Balancementioning

confidence: 99%

“…Penetration depth depends on the manner, in which a surface and drop come in mutual contact 12,13 . Many of the published results on wetting experiments involve deposition of water droplets from the top [13][14][15][16][17][18] . Here, the LA interface comes into contact with the apex of the surface roughness (Cassie state).…”

Section: Introduction: Origin Of Penetration Depthmentioning

confidence: 99%

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Design of a robust superhydrophobic surface: thermodynamic and kinetic analysis

Sarkar

Kietzig

2015

Soft Matter

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The design of a robust superhydrophobic surface is a widely pursued topic. While many investigations are limited to applications with high impact velocities (for raindrops of the order of a few m/s), the essence of robustness is yet to be analyzed for applications involving quasi-static liquid transfer. To achieve robustness with high impact velocities, the surface parameters (geometrical details, chemistry) have to be selected from a narrow range of permissible values, which often entail additional manufacturing costs. From the dual perspectives of thermodynamics and mechanics, we analyze the significance of robustness for quasi-static drop impact, and present the range of permissible surface characteristics. For surfaces with a Young's contact angle greater than 90° and square micropillar geometry, we show that robustness can be enforced when an intermediate wetting state (sagged state) impedes transition to a wetted state (Wenzel state). From the standpoint of mechanics, we use available scientific data to prove that a surface with any topology must withstand a pressure of 117 Pa to be robust. Finally, permissible values of surface characteristics are determined, which ensure robustness with thermodynamics (formation of sagged state) and mechanics (withstanding 117 Pa).

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Section: Surface Design For Quasi-static Robustness: Pressure Balancementioning

confidence: 99%

Section: Introduction: Origin Of Penetration Depthmentioning

confidence: 99%

Design of a robust superhydrophobic surface: thermodynamic and kinetic analysis

Sarkar

Kietzig

2015

Soft Matter

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“…10 However, suppression of bouncing on a heated surface may not be possible because not only is the bouncing height of the solution drop higher than that of a water drop but it also increases with polymer concentration. 11,12 Other schemes include adding particles, 13 modifying the surface, [14][15][16] and utilizing a surface elasticity. 17,18 The control of bouncing in these schemes, however, would be limited when a combination of solid and drop liquid is given.…”

mentioning

confidence: 99%

Control of a bouncing magnitude on a heated substrate via ellipsoidal drop shape

Yun

Lim

2014

Applied Physics Letters

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Non-axisymmetric drops impacting on a solid surface can alter impact dynamics significantly, thereby resulting in rebound suppression. Here, we present a method to control the bounce height of drops impacting on heated surfaces with ellipsoidal shaping. Experimental and numerical studies are used to investigate the effects of the geometrical aspect ratio (AR) of the drop on bouncing dynamics, which shows that maximum bounce heights of ellipsoidal drops can be reduced below spherical cases to nearly 40%. Control of bounce height can be explained in terms of a non-axial kinetic energy distribution during retraction. Interestingly, the non-axisymmetric hydrodynamics allows us to reduce contact time below this theoretical limit, which is explored both experimentally and numerically as a function of AR. This work may provide an understanding of bouncing dynamics on non-wetting surfaces for applications in surface cooling and cleaning.

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“…This is better accomplished by chemical modification of the surface than by altering the geometric parameters of the surface, which usually requires stringent and sophisticated processes. In a previous study, 14 the effects of chemical surface modifications on the wetting transition for impinging water droplets were investigated, but this investigation was performed under limited dynamic conditions of fixed impact velocity. The focus of this paper is to quantitatively determine the requirements for wetting transitions, in terms of the We number, on surfaces that have different surface energies due to different surface modifiers present on the surface.…”

mentioning

confidence: 99%

“…On a hydrophilic surface, a water droplet starts to penetrate into the textured surface as early as the contact stage, as observed in a previous study. 14 If the surface has a relatively high surface energy through the chemical modification of R−SiCl 3 to contain short alkyl chains, the liquid is forced to touch the bottom between nanoposts after the spreading and then soak into the surface (wetting state). If the surface is superhydrophobic enough to endure the kinetic energy of the freely dropped droplet, both ends of the spreading droplet retract, and the droplet bounds off the substrate (rebound state).…”

mentioning

confidence: 99%

A study on the dynamic behaviors of water droplets impacting nanostructured surfaces

et al. 2011

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We have investigated the influence of impact velocity and intrinsic surface wettability of nanostructures on the impact dynamic behaviors of water droplets on nanostructure surfaces. Nanowires array surfaces with tunable wettabilities ranging from superhydrophilic to superhydrophobic were fabricated by the deposition of surface modifiers differing in alkyl chain length. The transition criteria of rebound/wetting state and rebound/splashing state based on the relationship between the Webber (We) number and the surface free energy were determined. We have confirmed that the critical We number that determines the transition of the rebound/wetting increased as surface energy decreased. Additionally, the We number at which fragmentation occurred on our superhydrophobic surface was relatively low compared to previously reported values

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Impact dynamics of water droplets on chemically modified WOx nanowire arrays

Cited by 35 publications

References 21 publications

Design of a robust superhydrophobic surface: thermodynamic and kinetic analysis

Design of a robust superhydrophobic surface: thermodynamic and kinetic analysis

Control of a bouncing magnitude on a heated substrate via ellipsoidal drop shape

A study on the dynamic behaviors of water droplets impacting nanostructured surfaces

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