Berlin 2005 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 12: Selforganized and supramolecular assemblies I

CPP 12.1: Talk

Monday, March 7, 2005, 09:45–10:00, TU C243

Liquid manipulation via morphological transitions — •Jean-Christophe Baret¹, Michel Decré¹, Stephan Herminghaus², and Ralf Seemann² — ¹Philips Research Laboratories, NL-5656AA Eindhoven — ²MPI for Dynamics and Self-Organization, D-37073 Göttingen

In microfluidic applications, on-demand manipulation of small volumes of fluids is a basic need. Among the possible actuation systems for liquid structures, electrowetting is one of the most promising solutions. It has been shown recently that liquid deposited on rectangular grooves with rectangular cross section, has a variety of possible liquid morphologies determined by the contact angle of the drop on the planar substrate and the aspect ratio of the liquid channel (i.e. ratio of depth to width of the channel) [1]. In our experiments, electrowetting is used to tune the contact angle of the liquid reversibly from 100 to 50 degrees, leading to a reversible transition between a droplet morphology at large contact angles and extended liquid filaments for small contact angles. The transition is capillarity-driven but the behavior of the liquid above the transition is influenced by the electrical properties of the liquid. The length of the liquid filament is a function of the applied Voltage and could be explained by a simple electrical model. This gives us a precise handle to manipulate liquid on-demand in open microfluidic microchannels.

[1] Matching surface topography and wettability: a new route to open microfluidic systems, R. Seemann, M. Brinkmann, E. J. Kramer, F. F. Lange and R. Lipowsky, submitted.