Dresden 2017 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 31: Particulate Matter I: From microscopic interactions to collective motion (Focus session)

DY 31.3: Talk

Wednesday, March 22, 2017, 10:30–10:45, ZEU 118

How does a magnetic snake swim in a pool billiard? — Florian Johannes Maier, Markus Sesselmann, Ingo Rehberg, and •Reinhard Richter — Experimentalphysik 5, Universität Bayreuth, 95440 Bayreuth, Germany

We experimentally investigate magnetic surface swimmers on water. Those are moving objects, which self-assemble from ferromagnetic micro-particles, floating on the liquid surface due to interface tension, under the influence of an harmonically oscillating homogeneous magnetic field oriented vertically and a non-magnetic disc. The magnetic field is distinguished by its amplitude and frequency. The speed of the surface swimmers strongly depends on these parameters. We observe the swimmers by means of a camera from above. Via object-tracking, the position of the disc can be protocolled as a function of time, allowing us to reproduce trajectories and to calculate the speed.

The functional dependencies between speed and amplitude and between speed and frequency are investigated by independently varying both control parameters. In the first case, the data obtained are in good agreement with the predicted scaling whilst there are some deviations in the latter case.

Moreover, due to the interplay between the surface bound swimmers and the liquid meniscus at the edge of the experimental vessel different dynamics can be realized. We observe periodic and quasiperiodic trajectories in a circular vessel and aperiodic trajectories in a vessel shaped like a Bunimovich-stadium.