Bouncing or sticky droplets: Impalement transitions on superhydrophobic micropatterned surfaces

Abstract

When a liquid drops impinges a hydrophobic rough surface it can either bounce\noff the surface (fakir droplets) or be impaled and strongly stuck on it (Wenzel\ndroplets). The analysis of drop impact and quasi static ''loading'' experiments\non model microfabricated surfaces allows to clearly identify the forces\nhindering the impalement transitions. A simple semi-quantitative model is\nproposed to account for the observed relation between the surface topography\nand the robustness of fakir non-wetting states. Motivated by potential\napplications in microfluidics and in the fabrication of self cleaning surfaces,\nwe finally propose some guidelines to design robust superhydrophobic surfaces.\n