Hierarchical Superhydrophobic Surfaces Resist Water Droplet Impact
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Varanasi_Hierarchical superhydrophobic.pdf
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Author(s)
Varanasi, Kripa K.
Deng, Tao
Hsu, Ming
Bhate, Nitin
Date Issued
May 2009
Journal
Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, NSTI Nanotech 2009
Publisher
Nano Science and Technology Institute
Citation
Varanasi, Kripa K. et al. "Hierarchical Superhydrophobic Surfaces Resist Water Droplet Impact." in Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, May 3-7, 2009, George R. Brown Convention Center, Houston, Texas, U.S.A.
Version
Author's final manuscript
Abstract
In this paper, we present static and dynamic wetting
interactions of water droplets on a variety of
superhydrophobic surfaces. For sessile droplets, wetting
states were determined by measuring contact angles and
comparing them to that obtained from equilibrium Cassie
and Wenzel states. Surprisingly, we find that roll-off angles
are minimized on surfaces expected to induce Wenzel-like
wetting in equilibrium. We argue that droplets on these
surfaces are metastable Cassie droplets whose internal
Laplace pressure is insufficient to overcome the capillary
pressure resulting from the energy barrier required to
completely wet the posts. In the case of impacting droplets
the water hammer and Bernoulli pressures must be
compared with the capillary pressure. Experiments with
impacting droplets using a high-speed camera and specific
surface textures that can delineate various wetting regimes
show very good agreement with this simple pressurebalance
model. These studies show that hierarchical micronano
surfaces are optimum for droplet impact resistance.
Description
URL to paper listed on conference site
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
http://www.nsti.org/Nanotech2009/abs.html?i=761
