Drops on microstructured surfaces coated with hydrophilic polymers: Wenzel's model and beyond.
In the experiments described in this paper, micromachined silicon post surfaces were coated with thin films of a polymer for which the contact angle on the smooth material was around 70 degrees . Drops wetted these surfaces in the Wenzel or "penetration" mode. We have determined the advancing and receding angles as a function of the roughness geometry and quantitatively compared our results to the contact angles predicted by Wenzel's model. We discuss reasons for discrepancies and propose a model for the motion of the meniscus where we take into account the precise shape of the liquid front during its movement through the post structure.
Dorrer
Christian
C
Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103, D-79110 Freiburg, Germany.
Rühe
Jürgen
J