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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 34: Microfluidics I: Applications and Devices
CPP 34.5: Vortrag
Donnerstag, 26. März 2009, 10:30–10:45, ZEU 160
Internal flow and surfactants' dynamics in confined emulsions — •Audrey Steinberger1, Ralf Seemann1,2, and Stephan Herminghaus1 — 1MPI for Dynamics and Selforganization, D-37073 Goettingen — 2Experimental Physics, Saarland University, D-66041 Saarbruecken
We study the flow of emulsions confined in microchannels whose lateral dimensions are on the same scale as the size of the drops. This system is not only a promising tool for handling liquids in microfluidic processes but also a convenient model system to study the dissipation mechanisms associated to the flow of confined emulsions. Interfacial friction induces a recirculation flow -controlling the mixing- within the droplets. Our aim is to investigate the interaction between those internal flows and the dynamics of the surfactants used to stabilize the emulsion: what is the effect of the viscous stress on the surfactants' layer that surrounds the drops and stabilizes the emulsion? Reciprocally, what is the impact of the surfactants' frictional properties significantly on the internal flow? And what happens in very concentrated emulsions, where the thickness of the continuous phase lamellas separating the drops becomes very small, and possibly reduces to a surfactant bilayer?
To answer those questions, we have developed a micro-PIV setup that allows us to measure simultaneously the velocity field within the drops and the local concentration of fluorescent surfactants on two separate color channels. Here we describe this setup and report on the first results we obtained with it.