Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Aktive Matter I (joint session DY/BP/CPP, organized by DY)

CPP 44.5: Talk

Wednesday, March 22, 2017, 16:00–16:15, HÜL 186

Dynamics of microswimmer molecules — Sonja Babel, Niklas Küchler, Hartmut Löwen, and •Andreas M. Menzel — Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany

In recent years, the dynamical properties of individual microswimmers have been investigated intensively. The same applies for their collective dynamical behavior in dilute and dense suspensions. Here we address an intermediate level. We study the dynamics of compound objects of coupled swimmers that we term “microswimmer molecules” [1,2].

First, we address three spherical magnetic microswimmers connected by elastic springs to a straight object [1]. The magnetic interactions support the straight arrangement. However, with increasing active drive, hydrodynamic interactions destabilize the straight shape. Technically, this occurs via a subcritical Hopf bifurcation. The oscillatory feature of this bifurcation is connected to a cork-screw-like motion of the molecule.

Second, we consider an active microswimmer coupled by elastic springs to one or more passive swimmers [2]. The dynamics of this type of molecule in an external planar swirl flow is investigated, while hydrodynamic interactions are neglected to lowest order. Because of the finite extension and deformability of these molecules, interesting dynamical features arise. They comprise an expulsion from or undertow into the swirl, rotations of the deformed trajectories, and changes in the sense of the trajectory rotations.

[1] Babel et al., EPL (Europhys. Lett.) 113, 58003 (2016).

[2] Küchler et al., Phys. Rev. E 93, 022610 (2016).