Berlin 2024 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 15: Active Matter II (joint session BP/CPP/DY)
DY 15.4: Talk
Tuesday, March 19, 2024, 10:15–10:30, H 1028
Magnetic colloidal crystals activated by light-driven bacteria — •Helena Massana-Cid1, Claudio Maggi1,2, Giacomo Frangipane1, and Roberto Di Leonardo1,2 — 1Department of Physics, Sapienza University of Rome, Rome, Italy — 2NANOTEC-CNR, Institute of Nanotechnology, Rome, Italy
Active solids, or self-propelling units elastically coupled on a lattice, are recently of growing interest and are predicted to show emerging out-of-equilibrium behaviour, while they can inspire the design of numerous applications. We show for the first time an experimental realisation of a large ordered active solid with activity and confinement tuneable in-situ and on-command. This two-dimensional active solid is composed of repulsive magnetic particles activated by a photokinetic bacterial bath. The bacteria induce active motion into the crystal by pushing its particles and, in a simplified picture, this can be described by an equilibrium state with a higher effective temperature. Nevertheless, this framework breaks down qualitatively because of the active fluctuations time correlations due to the persistent motion of bacteria. We explore the emerging dynamics of this active solid for different values of activity, controlled by the applied light, and repulsion strength, determined by the external magnetic field. Furthermore, we show how we can melt the crystal by increasing activity. Our findings pave the way to unveil the properties of a novel out-of-equilibrium system, an active colloidal solid, which presents questions vastly interesting from a statistical mechanics point of view.
Keywords: Active particles; Soft matter physics; Statistical physics; Biophysics