Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Microfluidics I: Applications and Devices

CPP 34.8: Talk

Thursday, March 26, 2009, 11:30–11:45, ZEU 160

Stability and transitions of droplet arrangements confined in microchannels — •Enkhtuul Surenjav¹, Julia Burkhardt¹, Martin Brinkmann¹, Stephan Herminghaus¹, and Ralf Seemann^1,2 — ¹MPIDS, Göttingen, Germany — ²Experimental Physics, Saarland University, Saarbrücken, Germany

We focus on organization and manipulation of monodisperse gel emulsions in microchannels both in dynamic and static droplet arrangements. Transitions between certain foam-like topologies in an emulsion flowing through a channel can be induced e.g. by varying the geometry of the channel. Due to the finite energy required to change a certain droplet arrangement ("T1"-Transition) topology transitions are inherently hysteretic and depend not only on the droplet size but also on the volume fraction of the dispersed phase. By incorporating corners into the microfluidic channel network we performed precise manipulation of the individual droplet positions with respect to the neighboring droplets. The number of phase shifts as a function of drop size, volume fraction and corner angles were studied and show reasonable agreement with the theoretical consideration based on the path length differences. In stopped flow conditions, quasi two-dimensional structural transitions of static emulsion topologies have been studied as a function of lateral force. By applying a lateral force to the static droplet arrangement, we could vary the equilibrium conditions of different arrangements due to the variation of dispersed phase volume fraction during the droplet compression. We compared the experimental results with the numerical calculation and found qualitative agreement.