Dynamics of self-propelled particles at the air-water interface*

We study the behavior of active (self-propelled) particles at the millimeter scale using camphor-infused discs that glide at the air-water interface. The particles are driven by variations in surface tension generated by the diffusion and evaporation of camphor and move within a circular boundary providing strong confinement. Long-ranged interactions provide a system to study the dynamics of strongly interacting particles under confinement. These interactions with the boundary and other particles give rise to complex dynamics that are affected by active non-thermal noise and inertial effects. We report interesting single-particle behavior and observations on the density dependence of multi-particle dynamics. Using our combined experimental and theoretical approach, we are able to explore the strongly interacting active particles in confinement and how their behavior depends on density.