Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Poster 1

CPP 12.18: Poster

Montag, 5. September 2022, 18:00–20:00, P1

Particle sorting by Marangoni convection in microfluidic channels — •Roman Reh, Lorenz Kiel, Daniel Zapf, and Werner Köhler — Physikalisches Institut, Universität Bayreuth, Germany

Thermosolutal and thermocapillary Marangoni convection at a liquid-gas interface in a T-shaped microchannel structure of approximately 100 × 20 µm² cross section creates localized vortices that can be used for particle trapping, steering, and sorting. Experiments have been performed with water-ethanol mixtures as carrier liquid and dispersed micrometer-sized polystyrene beads. Due to collisions with the meniscus, particles are displaced from streamlines that approach the interface closer than one particle radius. These streamlines feed liquid volumes that are entirely cleared of particles. Particle accumulations structures form inside the vortex, from where only small particles can escape by diffusion. Since the critical streamline, which separates the depletion from the accumulation region, depends on the particle radius, the mechanism can be used for particle sorting by superposition of a Poiseuille flow and splitting of the flow downstream from the meniscus. In the simplest case, the initially homogeneous flow is split into two arms, one where the particles are enriched and one where all particles are removed from the liquid. The microchannel structures consist of crosslinked PDMS and the dispersed particles are observed by video microscopy. Numerical simulations are performed that almost perfectly match the experimental observations.