Porous Superhydrophobic Membranes: Hydrodynamic Anomaly in Oscillating Flows

Abstract

We have fabricated and characterized a novel superhydrophobic system, a mesh-like porous superhydrophobic membrane with solid area fraction ${\Phi }_s$, which can maintain intimate contact with outside air and water reservoirs simultaneously. Oscillatory hydrodynamic measurements on porous superhydrophobic membranes as a function of ${\Phi }_s$ reveal surprising effects. The hydrodynamic mass oscillating in-phase with the membranes stays constant for $0.9\le {\Phi }_s\le 1$, but drops precipitously for ${\Phi }_s<0.9$. The viscous friction shows a similar drop after a slow initial decrease proportional to ${\Phi }_s$. We attribute these effects to the percolation of a stable Knudsen layer of air at the interface.

5 pages, 3 figures

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Cited by in corpus (2)

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