Dance to the Vibrations – Motion of Active Granular Rotors

Speaker: Dr Christian Scholz –  Friedrich-Alexander University Erlangen-Nuremberg

Venue   : Thu 8 Sept 2016 – 4pm (Murdoch University, venue tba)

The majority of animal life performs active motion, i.e. organisms store energy within internal degrees of freedom and later release it in terms of directed motion. While in biological organisms this topic itself has been studied extensively, from swimming bacteria to flocks of animals, interest grew also in physical systems of inanimate objects that perform active motion. Most noticeable artificial microswimmers, but also active granular walkers.

Many studies consider translational active motion, but it has been shown that also rotational active motion leads to interesting novel effects in many-particle systems. In simulations of actively rotating spinners, a counter-intuitive separation of particles into patches of equal sense of rotation has been observed.

We use a particle design established in to experimentally create a system of 3D-printed active rotors, driven by vertical vibrations. Our experiments confirm the numerical observation of a phase separated stationary state. The evolution of the patterns from the mixed initial state can be quantified from the size of the clusters from the Voronoi triangulation or the length of the interface between patches, by counting Delaunay bonds between particles of opposite sense of rotation. The particle motion can be mapped onto a Langevin equation, which allows a direct comparison between experiment and simulation.