Regensburg 2016 – scientific programme

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BP: Fachverband Biologische Physik

BP 30: Microswimmers I (Joint Session with DY)

BP 30.5: Talk

Tuesday, March 8, 2016, 10:45–11:00, H47

Droplet swimmers in complex geometries: Autochemotaxis and trapping at pillars. — •Chenyu Jin, Corinna Maaß, Carsten Krüger, and Stephan Herminghaus — MPI for Dynamics and Self-Organization, 37077 Göttingen, Germany

Many organisms communicate by trail mediated signalling or autochemotaxis: their motion is influenced by their own emission of a chemical attractant or repellent, diffusing slowly compared to typical agent velocities. This causes gradient forces acting both on themselves as well as on other individuals. Meanwhile, geometrical confinement also influences the behaviour of microswimmers, e.g., pusher-type swimmers attach to curved interfaces depending on the interplay of hydrodynamic interaction and trajectorial persistence. It is of high biological relevance to have a well-controlled, tunable artificial model system exhibiting these traits.

A promising candidate are self-propelling liquid crystal droplets in an aqueous surfactant solution. They gain propulsion energy by micellar solubilisation, with filled micelles acting as a chemical repellent. We can tune the key parameters swimmer size, velocity and persistence length. We use microfluidic pillar arrays of variable radii to provide a convex wall to attract the swimmer, bend its trajectory and to force it to revert to its own trail. Hence, we investigate the interplay of wall attraction, persistence of motion, and negative auto-chemotaxis. We observe repulsion for highly curved surfaces, stable trapping at large pillars, and a narrow transition region, where negative autochemotaxis makes the swimmers detach after a single orbit.