Clustering and Pair Dynamics of Induced-Charge Electrophoresis Driven Janus Particles

Active colloids far from equilibrium can interact to generate remarkable collective behaviors. Among different propulsion methods, induced-charge electrophoresis (ICEP) holds a unique advantage of fine control over direction and energy flux. Herein, we report the pair dynamics and clustering of ICEP-driven Janus particles. At moderate densities, clusters are smaller than those in known diffusiophoresis experiments, suggesting there to be interactions suppressing cluster growth. In the dilute regime, the mean pair lifetime is an order smaller than the mean time between collisions, which corroborates an absence of clustering. The pair correlation function yields a prominent peak outside of hard-sphere range, suggesting interparticle repulsion. In simulations of active Brownian particles with long-range repulsive forces, we find particles parameterized with the pair dynamics produce consistently smaller clusters when compared with a hard-disk model. We rationalize that repulsive hydrodynamic forces which slows down particles over a distance are the primary role players. Our results indicate long-range interactions as a key control parameter for the cluster phase of active colloids.