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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 46: Poster: Wetting, Nano- and Microfluidics

CPP 46.8: Poster

Wednesday, March 9, 2016, 18:15–21:00, Poster B2

Particle Confinement by Marangoni Convection in Microchannels — •Michael Orlishausen, Lorenz Butzhammer, and Werner Köhler — Physikalisches Institut, Universität Bayreuth, Universitätsstr. 30 95447 Bayreuth

We have investigated the flow of unary and binary liquids near a liquid-gas interface in a mirochannel device due to Marangoni Convection caused by a gradient in temperature and concentration (in the case of the binary liquids). By using latex microparticles of 1*m diameter we were able to visualize the resulting currents through optical microscopy. Depending on the position of the meniscus in the microchannel and other factors, one or two convection rolls appear. Surprisingly, however, the particles are confined to certain streamlines and regions in the microchannel and characteristic depletion zones form around them. In order to explain the origin of this observation we have performed finite elements simulations to the flow in the microchannel and identified the outermost streamline containing particles as being connected to the minimum distance to the meniscus one of those particles can take up. Additionally, we have investigated the influence of diffusion on particles in such a flow by means of Langevin simulations. The counter-intuitive result is an enhanced particle confinement caused by particle diffusion between different streamlines.