Corralling Active Brownian Particles With "Active Billiard" Particles*

We examine the role of boundary conditions in a heterogenous active matter system in a bounded domain. The system consists of two types of particles: active Brownian particles, such as Janus particles, and "active billiard" particles, inspired by microorganisms that move in straight paths until they bounce off boundaries at a specific angle determined by their body morphology. This model has been of recent interest in robotics but also applies to microscale active matter systems. Here, we develop a parameterized model of particle type mixtures and characterize how "corralling" behavior emerges. We define corralling as system configurations where the billiard particles converge to a stable periodic orbit with a greater density of active Brownian particles within the convex hull of the orbit than its complement. We confirm that corralling behavior occurs in our model active matter system, in simulation. In previous work, we analytically determined the conditions guaranteeing such stable orbits, as a function of environment geometry and billiard departure angle. We will present extensions of this theoretical approach to statistical models of our example active matter system, with a focus on developing strategies for control.