A theory for the morphological dependence of wetting on a physically patterned solid surface

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

We present a theoretical model for predicting equilibrium wetting configurations of two-dimensional droplets on periodically grooved hydrophobic surfaces. The main advantage of our model is that it accounts for pinning/depinning of the contact line at step edges, a feature that is not captured by the Cassie and Wenzel models. We also account for the effects of gravity (via the Bond number) on various wetting configurations that can occur. Using free-energy minimization, we construct phase diagrams depicting the dependence of the wetting modes (including the number of surface grooves involved in the wetting configuration) and their corresponding contact angles on the geometrical parameters characterizing the patterned surface. In the limit of vanishing Bond number, the predicted wetting modes and contact angles become independent of drop size if the geometrical parameters are scaled with drop radius. Contact angles predicted by our continuum-level theoretical model are in good agreement with corresponding results from nanometer-scale molecular dynamics simulations. Our theoretical predictions are also in good agreement with experimentally measured contact angles of small drops, for which gravitational effects on interface deformation are negligible. We show that contact-line pinning is important for superhydrophobicity and that the contact angle is maximized when the droplet size is comparable to the length scale of the surface pattern.

Original languageEnglish (US)
Pages (from-to)14227-14237
Number of pages11
JournalLangmuir
Volume28
Issue number40
DOIs
StatePublished - Oct 9 2012

Fingerprint

solid surfaces
wetting
Contact angle
Wetting
Bond number
configurations
Gravitational effects
drop size
gravitational effects
grooves
Free energy
Phase diagrams
Molecular dynamics
Gravitation
free energy
phase diagrams
gravitation
molecular dynamics
continuums
optimization

All Science Journal Classification (ASJC) codes

  • Electrochemistry
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Materials Science(all)
  • Spectroscopy

Cite this

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abstract = "We present a theoretical model for predicting equilibrium wetting configurations of two-dimensional droplets on periodically grooved hydrophobic surfaces. The main advantage of our model is that it accounts for pinning/depinning of the contact line at step edges, a feature that is not captured by the Cassie and Wenzel models. We also account for the effects of gravity (via the Bond number) on various wetting configurations that can occur. Using free-energy minimization, we construct phase diagrams depicting the dependence of the wetting modes (including the number of surface grooves involved in the wetting configuration) and their corresponding contact angles on the geometrical parameters characterizing the patterned surface. In the limit of vanishing Bond number, the predicted wetting modes and contact angles become independent of drop size if the geometrical parameters are scaled with drop radius. Contact angles predicted by our continuum-level theoretical model are in good agreement with corresponding results from nanometer-scale molecular dynamics simulations. Our theoretical predictions are also in good agreement with experimentally measured contact angles of small drops, for which gravitational effects on interface deformation are negligible. We show that contact-line pinning is important for superhydrophobicity and that the contact angle is maximized when the droplet size is comparable to the length scale of the surface pattern.",
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A theory for the morphological dependence of wetting on a physically patterned solid surface. / Shahraz, Azar; Borhan, Ali; Fichthorn, Kristen Ann.

In: Langmuir, Vol. 28, No. 40, 09.10.2012, p. 14227-14237.

Research output: Contribution to journalArticle

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