Agilely Reconfigurable Swarms Stimulated by Light in an Electric Field*

Collective behaviors represent a wide range of phenomena that exist both in nature and artificial systems. Simple interactions among many constituting members in a system can result in complex structures and motions. Here, we report an innovative colloidal system made of dense Si nanorods that exhibit agilely reconfigurable swarming behaviors that can be readily switched by visible light in an AC rotating field. We observed two distinct self-organizing phenomena, i.e., nanowires form into interconnected 2D networks and self-assembled multi-droplets. Theoretical modeling considering light-controlled electrostatic interactions well explains the observation. This research presents an emerging swarm system that opens new opportunities for fundamental research and applications.