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DY: Fachverband Dynamik und Statistische Physik

DY 46: Active Matter 5 - organized by Carsten Beta (Potsdam), Andreas Menzel (Magdeburg) and Holger Stark (Berlin) (joint session DY/BP)

DY 46.3: Talk

Wednesday, March 24, 2021, 15:10–15:30, DYb

Shape-anisotropic Microswimmers: Influence of Hydrodynamics — •Arne W. Zantop and Holger Stark — Institute of Theoretical Physics, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany

Constituents of active matter, e.g. bacteria or active filaments, are often elongated in shape. The shape and the stiffness of the active components clearly influence their individual dynamics and collective pattern formation. On length scales much larger than the size of the constituents, active materials exhibit many fascinating phenomena such as the formation of vortices or turbulent structures [1,2]. To identify how steric and hydrodynamic interactions as well as thermal fluctuations influence collective behavior is subject of current research.
In this context, we model shape-anisotropic microswimmers with rod shape by composing them of overlapping spherical squirmers. We simulate their hydrodynamic flow fields using the method of multi-particle collision dynamics. With increasing aspect ratio of the rods, we find that a force quadrupole moment dominates the hydrodynamic flow field, whereas in quasi-2D confinement between two parallel plates (Hele-Shaw geometry) the far field is determined by a two-dimensional source dipole moment [3]. Investigating the collective dynamics of the squirmer rods, we identify with increasing density and aspect ratio of the rods a disordered, a swarming, and a jamming state.

[1] Dunkel et al., Phys. Rev. Lett. 110, 228102 (2013)

[2] Wensink et al., Proc. Natl. Acad. Sci. 109, 14308-14313 (2012)

[3] A. W. Zantop and H. Stark, Soft Matter 16, 6400-6412 (2020)