Wetting and Dewetting Transitions on Hierarchical Superhydrophobic Surfaces

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• 作者：Jonathan B. Boreyko ; Christopher H. Baker ; Celeste R. Poley ; Chuan-Hua Chen
• 刊名：Langmuir
• 出版年：2011
• 出版时间：June 21, 2011
• 年：2011
• 卷：27
• 期：12
• 页码：7502-7509
• 全文大小：959K
• 年卷期：v.27,no.12(June 21, 2011)
• ISSN：1520-5827

文摘

Many natural superhydrophobic structures have hierarchical two-tier roughness which is empirically known to promote robust superhydrophobicity. We report the wetting and dewetting properties of two-tier roughness as a function of the wettability of the working fluid, where the surface tension of water/ethanol drops is tuned by the mixing ratio, and compare the results to one-tier roughness. When the ethanol concentration of deposited drops is gradually increased on one-tier control samples, the impalement of the microtier-only surface occurs at a lower ethanol concentration compared to the nanotier-only surface. The corresponding two-tier surface exhibits a two-stage wetting transition, first for the impalement of the microscale texture and then for the nanoscale one. The impaled drops are subsequently subjected to vibration-induced dewetting. Drops impaling one-tier surfaces could not be dewetted; neither could drops impaling both tiers of the two-tier roughness. However, on the two-tier surface, drops impaling only the microscale roughness exhibited a full dewetting transition upon vibration. Our work suggests that two-tier roughness is essential for preventing catastrophic, irreversible wetting of superhydrophobic surfaces.