8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P4.47Non-equilibrium dynamics of a semiflexible polymerunder Poiseuille flow in a microchannelSebastian Reddig 1 and Holger Stark 11 Technische Universitaet Berlin, Sekr. EW7-1, Hardenbergstr. 36 10623, Berlin,GermanyWe address recent experiments on single actin filaments that were driven out of equilibrium underthe influence of a Poiseuille flow in a microchannel [1]. These experiments measured a center-ofmassdistribution with a bimodal shape, where the polymer is depleted at the centerline and close tothe walls of the microchannel. This is in stark contrast to thermal equilibrium without flow wherethe distribution around the centerline is constant. We model the polymer by a bead-spring chainwith bending rigidity and couple it to the fluid by introducing the two-wall Green tensor of theStokes equation as the cross-mobility tensor of point-like beads. We indeed observe the bimodaldistribution which becomes more pronounced with increasing strength of the Poiseuille flow. Analternative approach to observe this distribution is used in Ref. [2]. Based on our numerical results,we perform a careful analysis of the Smoluchowski equation for the center-of-mass distributionacross the channel and reveal that its bimodal shape is strongly determined by deterministic driftcurrents across the channel. They occur when the polymer, driven by the Poiseuille flow, interactshydrodynamically with the bounding walls and with itself. The influence of a diffusive currentdue to variations in the diffusion constant of the polymer lateral to the channel decreases when thestiffness of the polymer increases. [1] D. Steinhauser, Actin filaments and bundles in flow, Ph.D.thesis, University of Göttingen (2008). [2] R. Chelakkot, R. G. Winkler, G. Gompper, EPL 91,14001 (2010).47