SKM 2023 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Microswimmers and Fluid Physics of Life (joint session DY/CPP)

CPP 38.12: Vortrag

Mittwoch, 29. März 2023, 18:00–18:15, MOL 213

Orientational dynamics and rheology of active suspensions in viscoelastic media — •Akash Choudhary1, Sankalp Nambiar2, and Holger Stark11Institute of Theoretical Physics, Technische Universität Berlin, 10623 Berlin, Germany — 2KTH Royal Institute of Technology and Stockholm University, Stockholm 10691, Sweden

Active suspensions are systems of motile organisms or active filaments that are driven out of equilibrium through self-propulsion. This localized energy-work conversion imparts rich phenomenology and anomalous macroscale properties that are in stark contrast to passive suspensions and polymeric fluids. Motivated by the ubiquitous microbial systems in biological fluids, we analyse the impact of non-Newtonian fluids on the rheological response of active suspensions to steady shear flows.

We first study the suspension at an individual level and show that elongated pushers (representative of E. coli) and pullers (C. reinhardtii) exhibit diverse orbital dynamics in a weakly viscoelastic shear flow. We find that the active stresses not only modify the Jeffery orbits well-known from Newtonian fluids, but microswimmers can exhibit alignment and shear-plane rotation states. To analyze the impact of such behavior on the bulk rheological response, we study an ensemble of a dilute suspension of such swimmers in the presence of stochastic noise from bacterial tumbling and rotary diffusion. In comparison to Newtonian media, the polymeric elastic stresses substantially amplify the swimmer-induced viscosity, in particular, the superfluid transition observed in pusher solutions.

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