The dynamics of intermediate scale active matter

In the context of soft matter, active matter systems are often studied at the microscopic scale (e.g. colloidal particles) where thermal noise has a strong effect, but inertia is negligible. Contrarily, in the context of nonlinear dynamics, active matter systems are often studied at the meter scale, such as flocks of birds, where thermal noise is neglected but inertia dominates. We seek to study an intermediate scale where the dynamics of a centimeter-scale particle is governed by both noise and inertia. We use a vibrating motor to create self-propelled particles that crawl along a solid/dry surface. Our active particles can be described using statistical mechanics and exhibit common features of both larger and smaller active matter, namely scale-free Brownian-like motion and a directional persistence due to inertia and activity. Here we present our centimeter-scale active matter system, some interesting single-particle dynamics, and our observations on the density dependence of the collective dynamics. In our combined experimental and theoretical approach, we investigate single and multiparticle dynamics of intermediate-scale active matter.