Regensburg 2010 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Micro and Nanofluidics I

CPP 26.11: Talk

Wednesday, March 24, 2010, 16:45–17:00, H39

Advancing and receding contact ancles on structured topographic surfaces — Ciro Semprebon, •Stephan Herminghaus, and Martin Brinkmann — Max Planck Institute for Dynamics and Self-Organization, Goettingen, Germany

The static advancing and receding contact angles of a liquid in contact to topographically structured substrate is studied numerically using a minimization of the interfacial energy. As surface topographies we consider a square array of posts with circular or square cross section which is fully characterized by the diameter, spacing, and height of the posts. The materical contact angle of the wetting liquid on the homogeneous surface, θ_o, is varied between 45^∘ and 135^∘. Depending on the combination of these three parameters, we find transitions between several possible configurations of the liquid-vapor interface as the apparent contact angle θ_a is increased. During this increase the liquid font passes through a sequence of configurations. The instability of the last configuration triggers the detachment from the row of posts and leads to a jump of the contact line to the next row of posts. The resulting advancing contact angle shows a number of unexpected behaviours depending on the materical contact angle and the particular shape of the pillars. For the same systems we determine the corresponding receding angles and the corresponding contact angle hysteresis.