2017-04-12
10:15 at HCP F 43.4

Numerical study of artificial microswimmers propelled by Marangoni flow

Laura Stricker

Max Planck Institute for Dynamics and Self-Organization, Gottingen, Germany

In order to understand the behaviour of biological microswimmers, such as bacteria and spermatozoa, it is important to know which aspects are governed merely by the physics of the system and which aspects are biology-related. In the present study we address the mechanisms of locomotion of non-biological swimmers. In particular, we consider the behaviour of a single artificial microswimmer, namely an active droplet moving by Marangoni flow. We provide a numerical treatment for the main factors playing a role in real systems, such as advection, mass diffusion and the presence of several mutually interacting chemical species. The flow field inside and outside the droplet is modelled, to account for the two-way coupling between the motion of the swimmer and the surrounding fluid. We also consider the evolution of two concentration fields: the surfactant concentration in the liquid surrounding the droplet, and the surfactant concentration on the surface, related to the surface tension. We examine different interaction mechanisms between the concentration fields, such as the case of insoluble surfactants and the case of soluble surfactants with adsorption/desorption at the surface. The numerical results have been validated through comparison with analytical calculations. We show that our model can reproduce the typical pusher/puller behaviour presented by squirmers. It is also able to capture the self-propulsion mechanism of droplets driven by Belousov-Zhabotinsky (BZ) reactions, as well as a typical chemotactic behaviour.