title: Thermally activated wetting dynamics in the presence of surface roughness.
abstract: From simple models of thermally activated contact line dynamics far below the depinning transition, one expects the velocity to depend exponentially on the applied force and the activation area to be the size of the defects on the surface. We study contact line motion on evaporated gold films and find that the dynamics are activated, but the activation area is not straightforwardly linked to the surface roughness. Surprisingly, the activation area can be significantly smaller than any features on the surface. Furthermore, it depends strongly on the liquid. We show that this indicates that the line is close to the depinning threshold at experimentally accessible velocities. A model based on independent defects is developed and used to show deviations from the purely exponential law. The dynamics are written entirely in terms of properties of the surface and partially wetting liquid. In addition, we are able to show that the region of validity of models of thermal activation on mesoscopically rough surfaces typically corresponds to velocities of less than 1 mm/s.
authors.affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, UPMC Univ Paris 06, Université Paris Diderot, CNRS, Paris, France. kristina.davitt@lps.ens.fr
authors.forename: Kristina
authors.initials: K
authors.lastname: Davitt
authors.forename: Michael S
authors.initials: MS
authors.lastname: Pettersen
authors.forename: Etienne
authors.initials: E
authors.lastname: Rolley
mesh_terms: D006046:Gold / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature; D017155:Wettability
chemical_list: D006046:Gold