Cross-stream migration of spherical active particles
- Event time: 1:00pm until 2:00pm
- Event date: 13th February 2017
- Speaker: Dr William Uspal (Max Planck Institute for Intelligent Systems, Stuttgart)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
For natural microswimmers, the interplay of swimming activity and external flow can promote robust directional motion, e.g. propulsion against (upstream rheotaxis) or perpendicular to the direction of flow. These effects are generally attributed to their complex body shapes and flagellar beat patterns. We report on a strong directional response that occurs for spherical active particles exposed to flow near a surface. Using catalytic Janus particles as a model experimental system, we find that the particles align their propulsion axes to be nearly perpendicular to both the direction of the flow and the normal vector of the bounding surface. The aligned particles swim across the streamlines of the external flow. Within a deterministic theoretical model of an axisymmetric, surface-actuated microswimmer, we show how the alignment emerges from the interplay of shear flow and near-surface swimming activity. Adding the effect of thermal noise, we obtain probability distributions for the swimmer orientation that show decent agreement with the experimental distributions. Our findings demonstrate that microswimmers can exhibit unexpected and robust behavior in confined flows, which occur in many envisioned microswimmer applications.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..