Berlin 2012 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 18: Posters: Statistical Physics in Biological Systems

BP 18.29: Poster

Mittwoch, 28. März 2012, 17:30–19:30, Poster A

Dynamics of a spherical microswimmer in Poiseuille flow — •Andreas Zöttl and Holger Stark — Institut für Theoretische Physik, TU Berlin

Microorganisms in the human body have to respond to confining boundaries and fluid flow, like sperm cells in the Fallopian tube or pathogens in blood vessels. Also, artificial microswimmers would have to swim in narrow channels like arteries if one day they may be used as drug deliverers in the human body. Due to vorticities in the flow field and hydrodynamic interactions with bounding surfaces, microswimmers change their swimming speeds and orientations.

To capture both effects of fluid flow and confinement, we analyze the dynamics of a spherical microswimmer in Poiseuille flow, moving in a cylindrical microchannel. Neglecting the finite extent of the swimmer and its hydrodynamic interaction with the bounding wall, the dynamic equation for a swimmer in 2D is given by a simple pendulum equation. Swimmers swing around the centerline of the channel while oriented upstream, or tumble when the flow is strong enough. In 3D the swimmer can perform helical and helical-like trajectories while its angular momentum is conserved. Accounting also for hydrodynamic interactions between the swimmer and the wall, we show that pushers such as sperm cells or bacteria and pullers like the algae Chlamydomonas show different behavior. We find that upstream motion in the center of the channel is stabilized for pullers but becomes unstable for pushers which move on a stable limit cycle.