CCB Seminar: Wet active matter: Controlling the dynamics of microswimmers (Holger Stark, Ph.D., Technical University of Berlin)

Speaker: Holger Stark, Ph.D.

Institute for Theoretical Physics 

Technical University of Berlin 

Title: Wet active matter: Controlling the dynamics of microswimmers

Wet active matter refers to microswimmers in a fluid environment, where they initiate flow fields around themselves. In the talk I will review some of our work using particle-based and continuum descriptions, which we use to illustrate how their dynamics is controllable under external fields. First, we will look at a microswimmer under inertial microfluidic flow and show the complex state diagram of its swinging and tumbling motion [1]. Second, we performed numerical simulations with the method of multi-particle collision dynamics, where we investigate the collective dynamics of spherical and elongated model microswimmers using squirmers [2,3]. Depending on the neutral and pusher/puller swimmer type, they exhibit a variety of fascinating emergent collective dynamics: this includes plumes and convective rolls that form under gravity, as well as active turbulence observed for pusher squirmer rods. Finally, we rely on a continuum description of the active paranematic state, where local nematic order is induced just by activity. We show how the resulting active turbulence can be controlled by a periodic activity pattern resulting in a multi-lane flow state.