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

Thu 811:10-14:00P7.21The role of mesoscopic surface disorder on wetting atlow capillary numberKristina Davitt 1 and Etienne Rolley 11 Laboratoire de Physique Statistique, Ecole Normale Superieure, 24, rue Lhomond 75005,Paris, FranceIt is generally accepted that the way in which a liquid wets a solid is influenced by the defectspresent on the surface. Although disorder is commonly used to explain static contact anglehysteresis, it is most often neglected when considering wetting dynamics. We think that undercertain conditions, existing models can be reinterpreted and that the microscopic parameters thatfigure in the theory can be related to the disorder. This hypothesis is supported by an experimenton the wetting of cesium by liquid hydrogen in which it was shown that the activation energy ofthermally activated motion of the contact line is on the order of the hysteresis [1]. However, nodirect link between the activation area and the length scale of the disorder could be made. Westudy the dynamics of wetting on evaporated gold films coated with a monolayer of alkylthiol torender them partially wetting. By changing the evaporation conditions, we are able to adjust thedisorder and obtain films with lateral grain sizes ranging from 10 to 200 nm. We find that theactivation area deduced from wetting experiments with tetradecane is coherent with these sizes;however, the precise relation to the scale of disorder is not clear.[1] E. Rolley and C. Guthmann, PRL 98 16, 166105 (2007)21