Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Wetting, Superamphiophobicity, Micro- and Nanofluidics I
CPP 18.7: Talk
Tuesday, April 1, 2014, 11:15–11:30, ZEU 222
Gibbs condition for a volatile completely wetting liquid — •Mariano Galvagno1, Ioannis Tsoumpas2, Pierre Colinet2, and Uwe Thiele1,3 — 1Department of Mathematical Sciences, Loughborough University, UK — 2TIPs–Fluid Physics, Université Libre de Bruxelles, Belgium — 3Institut für Theoretische Physik, Universität Münster, Germany
We study the profile of evaporating liquid drops on substrates with a corner. A continuous influx allows us to study steady drops of different volume even in this non-equilibrium situation. Experimental results are qualitatively reproduced employing a 2d long-wave mesoscopic hydrodynamic description that incorporates wettability via a Derjaguin (disjoining) pressure. In particular, we study (i) the dependence of the evaporation-induced apparent contact angle on the position of the contact line and (ii) the pinning and depinning of a droplet at a corner - that is for non-volatile liquids well described by Gibbs’ criterion. Our results suggest that for volatile liquids, a simple modification of Gibbs’ criterion is valid: replacing the equilibrium contact angle by the evaporation-caused apparent contact angle. Most importantly, the calculations confirm the experimental observation, that there exists a dynamically produced critical angle for depinning that increases with the evaporation rate.