Berlin 2012 – wissenschaftliches Programm
DY 12.7: Vortrag
Dienstag, 27. März 2012, 12:15–12:30, H 1028
Self-propelled rod-like microswimmers near surfaces — •Kristian Marx and Gerhard Gompper — Theoretical Soft Matter and Biophysics, Institute of Complex Systems, Forschungszentrum Jülich
Self-propelled microswimmers (e.g. sperm, E. coli and the alga Chlamydomonas) are biological organisms that propel themselves through fluid. In future applications, microswimmers may also be used as biosensors on lab-on-a-chip devices. They can be classified as having pusher or puller polarity, which are driven from the rear or the front, respectively. We study the behavior of a general polar rod model at high swimmer densities in three dimensions, in particular close to walls, including hydrodynamics and volume-exclusion interactions. We employ hydrodynamics simulations using a mesoscale particle based technique (multi-particle collision dynamics) implemented on GPU hardware. The swimmer behavior is found to strongly depend on the swimmer polarity: Pushers experience parallel alignment with the walls and strongly aggregate near them. Due to mutual hydrodynamic attraction the rods form motile clusters at the walls. Interacting clusters can form swirls, destroying long-range nematic order. Pullers aggregate into giant immotile clusters that span the entire system at high densities. While they are overall isotropic, the puller clusters show a typical hedgehog structure at the walls, with most of the swimmers pointing towards the walls. Finally, unpolar driven rods interact only weakly via hydrodynamics and show an isotropic-nematic phase transition at critical densities much lower than passive rod systems.