Séminaire de Roland G. Winkler (Forschungszentrum Jülich) :
Mesoscale hydrodynamic simulation of microswimmers and active matter
le lundi 17 juin 2019 à 13h30, salle 101, couloir 32-42, 1er étage (salle des conseils de l’UFR de chimie).
Résumé
Locomotion is a major achievement of biological evolution. Microorganisms, such as bacteria, algae, and sperm cells are equipped with flagella and are able to exploit drag for their propulsion. In assemblies of motile microorganisms, cooperativity plays a major role as they exhibit highly organized movements with remarkable large-scale patterns in form of networks, complex vortices, or swarms [1]. Hydrodynamic interactions play a major role in the locomotion and collective motion of microswimmers. Multiparticle collision dynamics (MPC), a particle-based mesoscale simulation technique, is a suitable approach for simulating complex fluids. MPC captures thermal fluctuations and is easily coupled with, e.g., molecular dynamics simulations for embedded objects [2]. In this contribution, simulation results for the swimming motion of a detailed E.coli model in bulk and at interfaces will be presented [3,4]. We find that E.coli senses the nanoscale slip length of the surface and responds with a circular trajectory of a particular radius. The collective behavior of microswimmers is addressed by a more coarse-grained model, namely spheroidal squirmers in a slit geometry [5]. We find a drastic influence of hydrodynamic interactions on the phase behavior of squirmers compared to non-hydrodynamic active Brownian particles (ABPs). Specifically, hydrodynamic interactions suppress motility-induced phase separation (MIPS) for spherical squirmers, an effect characteristic for ABPs. In contrast, hydrodynamics enhances MIPS for spheroidal squirmers [7]. Our studies reveal the decisive influence of hydrodynamics and microswimmer shape on their phase behavior.
[1] J. Elgeti, R. G. Winkler, G. Gompper, Rep. Prog. Phys. 78, 056601 (2015)
[2] G. Gompper, T. Ihle, D. M. Kroll, R. G. Winkler, Adv. Polym. Sci. 221, 1 (2009)
[3] J. Hu, M. Yang, G. Gompper, and R. G. Winkler, Soft Matter 11, 7843 (2015)
[4] J. Hu, A. Wysocki, R. G. Winkler, G. Gompper, Sci. Rep. 5, 9586 (2015)
[5] M. Theers, E. Westphal, G. Gompper, R. G. Winkler, Soft Matter 12, 7372 (2016)
[6] M. Theers, E. Westphal, K. Qi, R. G. Winkler, and G. Gompper, Soft Matter 14, 8590 (2018)
