Active Sculpting of Colloidal Crystals

The development of colloidal particles that can become self-propelled when exposed to a source of light of a given frequency represents one of the most exciting new developments in the field of active matter. In this paper, we perform numerical simulations to explore several properties of crystalline colloidal aggregates in the presence of such external light fields. We show how permanent gaps of tunable size can be carved into these crystals as a result of a solid-gas transition that occurs above a threshold light intensity. We compare this phenomenon to that occurring in a parent system obtained by replacing self-propulsion with an effective temperature and discuss the main differences between the two setups. Finally, we show how moving the light field across a solid-fluid boundary allows us to transfer or transport the fluid component into or across the solid one. We discuss the dynamics of this process and set limits associated with its performance.