Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Interfaces and Thin Films I

CPP 3.1: Talk

Monday, March 14, 2011, 10:30–10:45, ZEU 160

Depinning of 2D Droplets in a Free Energy Model — •Daniel Herde, Stephan Herminghaus, and Martin Brinkmann — MPI for Dynamics and Self-Organization, Göttingen, Germany

While the problem of a moving contact line on an ideal substrate has been studied for some time, the dynamic behaviour on a heterogeneous substrate is not yet fully understood. Even the pinning behaviour of droplets, where they stay in place even though an external force is applied, is not characterised properly. We use a free energy approach to numerically describe the depinning of 2D droplets at single defects, on periodic and on randomly patterned substrates in the static limit.

The simulations for a single defect agree with a simple prediction for the force required for depinning, relating it to the maximum wettability contrast. Periodic substrate wettabilities lead to a set of new phenomena, as the system can display more than one stable pinned state. The determined depinning forces deviate strongly from the single pinning site case. These findings agree with our small Reynolds number fluid dynamics simulations.