Regensburg 2022 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 14: Active Matter 3 (joint session BP/CPP/DY)

BP 14.4: Vortrag

Mittwoch, 7. September 2022, 10:15–10:30, H16

Microswimmers in viscosity gradients — •Sebastian Ziegler¹, Maxime Hubert¹, and Ana-Sunčana Smith^1,2 — ¹PULS Group, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany — ²Division of Physical Chemistry, Ruder Bošković Institute Zagreb, Croatia

Regions of variant viscosity are ubiquitous in both inanimate systems as well as in living systems. It is therefore of great interest to understand the effect of viscosity gradients on the mobility of both passive particles as well as on active systems. We firstly study a system of passive spheres and provide a general expression for the asymptotic mobility matrix in small viscosity gradients. We apply this result to linear viscosity gradients, where we unveil the existence of radially constant flows and elaborate on the effect of asymmetry of the particle position within the finite-size gradient, which hitherto has not been considered.

These results are subsequently applied to bead-spring microswimmers as model systems for self-propelling active matter. In contrast to the common approach of prescribing the stroke of the swimmer, we here employ a force-based swimmer model, allowing for an adaption of the swimming stroke to the environment, and reveal the rich viscotactic properties of such a microswimmer. We also construct a simple swimmer inspired by the Chlamydomonas algae and compare the viscotactic behavior of the biological swimmer to ours.