Regensburg 2016 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 39: Active Matter (Joint Session with DY)
BP 39.7: Vortrag
Mittwoch, 9. März 2016, 11:30–11:45, H46
Dynamics of self-propelled Janus particles in viscoelastic fluids — •Juan Ruben Gomez-Solano1 and Clemens Bechinger1,2 — 12. Physikalisches Institut, Universitaet Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany — 2Max-Planck-Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
The motion of many natural micro-swimmers, such as bacteria and spermatozoa, commonly takes place in viscoelastic media. The understanding of their swimming mechanisms has triggered a lot of experimental and theoretical work in recent years as well as the development of artificial self-propelled particles. Although the motion of micro-swimmers in Newtonian fluids has been extensively studied, so far only few investigations have focused on the swimming of microorganisms in viscoelastic fluids. In this work, we experimentally investigate the dynamics of spherical Janus colloidal particles in a viscoelastic fluid. The particles are self-propelled by local demixing of a critical binary polymer mixture induced by laser illumination. We observe a dramatic enhancement of both translational and rotational diffusion with increasing particle velocity, even at low Weissenberg number, where the drag force on the particle exerted by the fluid obeys the Stokes law. We observe a similar enhancement for passive particles driven by an external constant force, e.g. gravity. Our results suggest that these effects originate from the coupling between the thermal fluctuations of the particle and the surrounding flow field, which displays large relaxation times of several seconds.