Controlling the self-assembly of colloids via temporal modulation of activity

Self-organization phenomena in ensembles of self-propelled particles open pathways to the synthesis of new dynamic states not accessible by traditional equilibrium processes. The challenge is to develop a set of principles that facilitate the control and manipulation of emergent active states. Here, we report that dielectric rolling colloids energized by a pulsating electric field self-organize into alternating square lattices with a lattice constant controlled by the parameters of the field. We combine experiments and simulations to examine spatiotemporal properties of the emergent collective patterns and investigate the underlying dynamics of self-organization. We reveal the resistance of the dynamic lattices to compression/expansion stresses leading to a hysteretic behavior of the lattice constant. The general mechanism of patterns synthesis and control in active ensembles via temporal modulation of activity could be applied to other active colloidal systems.