Fog Deposition and Accumulation on Smooth and Textured Hydrophobic Surfaces

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• 作者：Tony S. Yu ; Joonsik Park ; Hyuneui Lim ; Kenneth S. Breuer
• 刊名：Langmuir
• 出版年：2012
• 出版时间：September 4, 2012
• 年：2012
• 卷：28
• 期：35
• 页码：12771-12778
• 全文大小：514K
• 年卷期：v.28,no.35(September 4, 2012)
• ISSN：1520-5827

文摘

We investigated the deposition and accumulation of droplets on both smooth substrates and substrates textured with square pillars, which were tens of micrometers in size. After being coated with a hydrophobic monolayer, substrates were placed in an air flow with a sedimenting suspension of micrometer-sized water droplets (i.e., fog). We imaged the accumulation of water and measured the evolution of the mean drop size. On smooth substrates, the deposition process was qualitatively similar to condensation, but differences in length scale revealed a transient regime not reported in condensation experiments. Based on previous simulation results, we defined a time-scale characterizing the transition to steady-state behavior. On textured substrates, square pillars promoted spatial ordering of accumulated drops. Furthermore, texture regulated drop growth: first enhancing coalescence when the mean drop size was smaller than the pillar, and then inhibiting coalescence when drops were comparable to the pillar size. This inhibition led to a monodisperse drop regime, in which drop sizes varied by less than 5%. When these monodisperse drops grew sufficiently large, they coalesced and could either remain suspended on pillars (i.e., Cassie鈥揃axter state) or wet the substrate (i.e., Wenzel state).