Regensburg 2004 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 16: POSTER: Computational Physics, Complex Systems
CPP 16.14: Poster
Tuesday, March 9, 2004, 17:00–19:00, B
Switching of wetting morphologies by electrowetting: open microfluidics — •Ralf Seemann1,2, Jean-Christophe Baret1,3, and Stephan Herminghaus1,2 — 1Abteilung Angewandte Physik, Universitaet Ulm — 2MPI fuer Stroemungsforschung, Goettingen — 3Philips Research, Eindhoven
We have studied, both experimentally and theoretically, the wetting behavior of a liquid in rectangular grooves with chemically homogeneous walls. The length scale has been chosen to be small compared to the capillary length in order to avoid gravitational effects, but large enough that for long range wetting forces (such as the van der Waals force) to be irrelevant. We derived (theoretically) the morphological phase diagram of liquid channels confined in the grooves as a function of aspect ratio and contact angle. Droplets form elongated morphologies for large aspect ratios and high wettability of the substrate. For sufficient large contact angles or small aspect ratios no confinement occurs. For manipulating small amounts of liquids on that substrate we used electrowetting. This way we could change the contact angle of the liquid on the substrate and switch in between various equilibrium wetting morphologies of the free liquid surface. Using this effect, liquids could be transported on a substrate bearing appropriate steps and grooves. Particular emphasis will be on the switching behavior of the various liquid morphologies.