Berlin 2005 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 30: POSTER: Chemical physics

CPP 30.45: Poster

Dienstag, 8. März 2005, 16:30–18:30, Poster TU D

Wetting Morphologies in Triangular Grooves — •Krishnacharya Khare, Evgeny Gurevich, Bruce Law, Stephan Herminghaus, and Ralf Seemann — MPI for Dynamics and Self-Organization, D-37073 Göttingen

We have studied the wetting behavior of a various 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 for contact angles smaller than 90 degree minus half the opening angle of the groove. For manipulating small amounts of liquids on that substrate (open microfluidics), we used electrowetting. We could vary the contact angle of the liquid on the substrate as a function of the applied Voltage. 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 an instability when being quenched from a filling to a non-filling situation. The liquid filament breaks up into isolated droplets with a preferred distance. The separation of the droplets depends upon the quench depth in a characteristic manner.