Dynamics of sliding drops on superhydrophobic surfaces

¹ The Rudolf Peierls Centre for Theoretical Physics, University of Oxford 1 Keble Road, Oxford OX1 3NP, UK
² Institute of Computational Science, ETH Zurich - 8092 Zurich, Switzerland

Received: 22 December 2005
Accepted: 8 May 2006

Abstract

We use a free energy lattice Boltzmann approach to investigate numerically the dynamics of drops moving across superhydrophobic surfaces. The surfaces comprise a regular array of posts small compared to the drop size. For drops suspended on the posts the velocity increases as the number of posts decreases. We show that this is because the velocity is primarily determined by the contact angle which, in turn, depends on the area covered by posts. Collapsed drops, which fill the interstices between the posts, behave in a very different way. The posts now impede the drop behaviour and the velocity falls as their density increases.