Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 24: POSTER Microfluidics
CPP 24.6: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
Wetting Morphologies in Triangular Grooves — •Krishnacharya Kareh1, Martin Brinkmann1, Evgeny Gurevich1, Bruce Law2, Stephan Herminghaus1, and Ralf Seemann1 — 1MPI for Dynamics and Self-Organisation, Bunsenstr. 10, D-37073 Göttingen, Germany — 2Kansas State University, Department of Physics, 327 Cardwell Hall, Manhattan, KS 66506, USA
We studied the wetting behavior of liquids in triangular 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 for long range wetting forces (such as the van der Waals force) to be irrelevant. Droplets form elongated morphologies with negative mean curvature for contact angles smaller than 90deg minus half the opening angle of the groove. For larger contact angles, the liquid either forms elongated filaments of finite length and positive mean curvature or drop-like morphologies. For in situ manipulation of small amounts of liquid on this substrate topography (open microfluidics), we used electrowetting. We could vary the contact angle of the liquid on the substrate as a function of the applied Voltage. The filling and drainage behavior of these grooves were studied as a function of time and contact angle. In contrast to grooves with rectangular cross section, the liquid filaments in triangular grooves undergo a dynamic instability when being quenched from a filling to a non-filling situation. The liquid filament breaks up into isolated droplets with a preferred distance which compares favorably with a straightforward theoretical