8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.26Thu 811:10-14:00Gibbs’ criterion for a sessile nanodroplet on atrapezoidal substrateFilip Dutka, 1 Marek Napiórkowski, 2 and Siegfried Dietrich 11 Max Planck Institute for Metals Research, Heisenbergstrasse 3, 70569, Stuttgart,Germany2 Institute of Theoretical Physics, Warsaw, PolandBy taking into account the mesoscopic precursor films of nanodroplets on trapezoidal substratesit turns out that there is no three-phase contact line pinning as it appears for liquids within amacroscopic description and gives rise to an undetermined contact angle at the edge of the substrate(Gibbs’ criterion). Upon increasing the volume of the nanodroplet the apparent contact anglechanges continuously between two limiting values fulfilling Gibbs’ criterion while the contactline interface moves smoothly across the edge of the trapezoidal substrate. However the spatialextension of the region within which the three-phase contact line passes across the edge is of theorder of ten fluid particle diameters and thus mesoscopic. We analyze this transition for variousYoung contact angles and parameters characterizing the substrate potential.26