Bouncing or sticky droplets: Impalement transitions on superhydrophobic micropatterned surfaces

¹ Laboratoire de Physique Statistique de l'ENS, CNRS, UMR 8550 associée aux Universités Paris 6 et Paris 7 - 24 rue Lhomond, 75231 Paris Cédex 05, France
² Laboratoire de Physico-Chimie Curie, Institut Curie, CNRS, UMR 168 26 rue d'Ulm, 75248 Paris Cédex, France

Corresponding authors: denis.bartolo@espci.fr sebastien.moulinet@lps.ens.fr

Received: 18 November 2005
Accepted: 14 February 2006

Abstract

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