Dresden 2014 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Active Colloids
CPP 39.2: Talk
Thursday, April 3, 2014, 10:00–10:15, ZEU 260
Gravitaxis of asymmetric microswimmers — •Felix Kümmel1, Borge ten Hagen2, Raphael Wittkowski3, Hartmut Löwen2 und Clemens Bechinger1,4 — 12. Physikalisches Institut, Universität Stuttgart, Germany — 2Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Germany — 3SUPA, School of Physics and Astronomy, University of Edinburgh, United Kingdom — 4Max-Planck-Institut für Intelligente Systeme, Stuttgart, Germany
Micron-sized self-propelled colloidal particles can serve as models for real biological swimmers [1]. For giving better insight into the swimming properties of biological microorganisms with an asymmetric shape, we recently studied the motional features of L-shaped microswimmers under bulk conditions [2]. However, most motile objects additionally respond to an external gravitational field, a phenomenon called gravitaxis. For many flagellates and ciliates, such as Chlamydomonas or Paramecium, negative gravitaxis has been observed, i.e. a swimming motion opposed to the gravitational field. Such a behavior often originates from an inhomogeneous mass distribution, which aligns the cell similar to a buoy. In contrary, we study the motion of asymmetric L-shaped microswimmers with homogeneous mass distribution, in the presence of a gravitational force. In experiments and by theoretical modeling we demonstrate that a shape anisotropy alone is sufficient to induce gravitactic motion. [1] G. Volpe, et al., Soft Matter 7, 8810 (2011). [2] F. Kümmel, et al., Phys. Rev. Lett. 110, 198302 (2013).