Wetting and dewetting transitions on hierarchical superhydrophobic surfaces.

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.

Full Text

Duke Authors

Cited Authors

  • Boreyko, JB; Baker, CH; Poley, CR; Chen, CH

Published Date

  • June 21, 2011

Published In

Volume / Issue

  • 27 / 12

Start / End Page

  • 7502 - 7509

PubMed ID

  • 21604679

Electronic International Standard Serial Number (EISSN)

  • 1520-5827

Digital Object Identifier (DOI)

  • 10.1021/la201587u

Language

  • eng

Citation Source

  • PubMed