Regensburg 2019 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 44: Active Matter C (joint session DY/CPP)
DY 44.9: Talk
Thursday, April 4, 2019, 12:15–12:30, H19
Pairing, waltzing and scattering of chemotactic active colloids — •Suropriya Saha1, Sriram Ramaswamy2, Ramin Golestanian1, and Ramin Golestanian1 — 1Max Planck Institute for Dynamics and Self-Organization, Am Faßberg 17 37077 Göttingen — 2Indian Institute of Science, Bangalore, India
Two chemotactic active colloids, which can rotate their polar axis to align with an imposed chemical gradient, form bound states by cancellation of velocities. Their interactions are dynamical in origin, with contributions from self-propulsion and phoretic response to chemical field generated by each other, are thus non-central and non-reciprocal. Two swimmers remain bound at long times when the chemotactic response of at least one of the swimmers is positive, i.e. it rotates its polar axis to point up a linear gradient. These bound states fall in two broad categories *(i) active dimers, separation fixed and polar axes orient along a line (ii) periodic orbits, relative inclination of the polar axes fixed, while the centre of mass executes cyclic motion. Chemotactic swimmers unbind and scatter away depending on initial conditions or with an increase of self-propulsion; while mutually anti-chemotactic swimmers always scatter away. These findings are summarized in state diagrams and representative trajectories are calculated to illustrate the rich dynamics. For the special case of a swimmer moving in a localised source of fuel, the fixed points underlying the bound states and the bifurcations that lead to transition between from one type of f inal state to another are classified.