LMP Seminar: Microswimmers: From collective motion under gravity to smart navigation
14:00 - 15:30
Prof. Dr. Holger Stark
- Institut für Theoretische Physik, Technische Universität Berlin
Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
SR 0.79, Am Faßberg 17, Göttingen
MPIDS / LMP
Active motion of biological and artificial microswimmers is relevant in the real world, in microfluidics, and biological applications but also poses fundamental questions in non-equi- librium statistical physics. Microswimmers interact by their self-generated flow fields and thereby show appealing dynamic patterns as a consequence of the non-equilibrium. A new development in the field is how microswimmers learn to navigate in a complex environment.
Using multi-particle collision dynamics, we simulate squirmer model swimmers and study how they behave under gravity. We find a variety of different phenomena depending on the ratio of swimming to bulk sedimentation velocity. Single squirmers can float or slide above the bottom wall. A collection of squirmers exhibits a very dynamic sedimentation profile with dense layering at the bottom and exponential decay towards the top, where large-scale convective flow arises. When they become bottom-heavy, they exhibit inverted sedimentation, convective rolls and plumes reminiscent of patterns seen in bioconvection, and also spawning clusters. Finally, a single layer of squirmers under strong gravity shows different collective dynamics including “hydrodynamic Wigner fluids” and swarming.
At the end I discuss optimal steering of microswimmers in order to optimize their travel time in a potential landscape and how smart microswimmers with some some internal information processing machinery can use reinforcement learning to perform this task autonomously.