Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 22: SYMPOSIUM Microfluidics II: Soft objects in flow, open geometries
CPP 22.6: Invited Talk
Thursday, March 30, 2006, 15:45–16:15, ZEU 160
Unconventional Microfluidics — •Ralf Seemann1, Jean-Christophe Baret2, K. Khare1, Craig Priest1, and Stephan Herminghaus1 — 1MPI for Dynamics and Self-Organisation, Bunsenstr. 10, D-37073 Göttingen, Germany — 2Philips Research Laboratories, NL-5656AA Eindhoven, The Netherlands
Microfluidics usually involves single phase liquids transported through closed microchannel networks. Instead, we explore open systems with freely accessible liquid interfaces as well as compartmented liquids in closed microchannels. In our project we study the wetting morphologies on topographic substrates and explore the possibility to transport liquid by switching in the various liquid morphologies. The morphologies are determined by the contact angle of the liquid and the geometry of the grooves [1]. Electrowetting is used to tune the contact angle, leading to reversible transitions between a drop-like morphology and extended liquid filaments. The transition is capillarity-driven but the behavior of the liquid above the transition is influenced by the electrical properties of the liquid [2]. Furthermore, we employ monodisperse emulsions to compartment liquids for microfluidic processing. If the volume fraction of the continuous phase is small, the dispersed compartments (droplets) assemble into well-defined arrangements, analogous to foam. Hence, the position of a single droplet within an ensemble of droplets is fully determined while being transported through microfluidic channels. We demonstrate an in situ method for the production of such monodisperse emulsions, suitable for microfluidic processing [3] and a variety of channel geometries for positioning, sorting, dividing, and selectively induced coalescing of droplets in ’lab-on-chip’ style processing.
[1] R. Seemann, et al. PNAS 102, 1848 (2005)
[2] J.-C. Baret, M. Decré, S. Herminghaus, and R. Seemann, Langmuir (in press)
[3] C. Priest, S. Herminghaus, and R. Seemann, Appl. Phys. Lett. (in press)