Issue 1, 2011

Cassie–Wenzel and Wenzel–Cassie transitions on immersed superhydrophobic surfaces under hydrostatic pressure

Abstract

For incorporating superhydrophobic surfaces in microfluidic systems, it is important to understand the ability of the superhydrophobic state to withstand hydraulic pressure. In this paper we describe experiments to probe the collapse transition on superhydrophobic surfaces completely covered by water, where the air film formed on the surface is closed. Polyethylene foils nanoimprinted with micrometre sized pillars in different geometries and densities are used as the model superhydrophobic surfaces. The pressure required for the transition from Cassie to Wenzel state is measured for all surfaces and also compared to analytical and numerical models. We find that the closed film of trapped air helps stabilise the Cassie state at low pillar densities and that the effect of a small change in pillar sidewall angle can drastically change the collapse behaviour. Finally, the reverse transition, from Wenzel to Cassie state, is observed on densely pillared surfaces at low water pressure.

Graphical abstract: Cassie–Wenzel and Wenzel–Cassie transitions on immersed superhydrophobic surfaces under hydrostatic pressure

Supplementary files

Article information

Article type
Paper
Submitted
29 Jun 2010
Accepted
26 Aug 2010
First published
20 Sep 2010

Soft Matter, 2011,7, 104-109

Cassie–Wenzel and Wenzel–Cassie transitions on immersed superhydrophobic surfaces under hydrostatic pressure

P. Forsberg, F. Nikolajeff and M. Karlsson, Soft Matter, 2011, 7, 104 DOI: 10.1039/C0SM00595A

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