Spatio-temporal control of the phase separation of chemically active immotile colloids

Understanding and controlling phase separation in nonequilibrium colloidal systems are of both fundamental and applied importance. In this article, we investigate the spatiotemporal control of phase separation in chemically active immotile colloids. We show that a population of silver colloids can spontaneously phase separate into dense clusters in hydrogen peroxide (H2O2) due to phoretic attraction. The characteristic length of the formed pattern was quantified and monitored over time, revealing a growth and coarsening phase with different growth kinetics. By tuning the trigger frequency of light, the lengths and growth kinetics of the clusters formed by silver colloids in H2O2 can be controlled. In addition, structured light was used to precisely control the shape, size, and contour of the phase-separated patterns. This study provides insight into the microscopic details of the phase separation of chemically active colloids induced by phoretic attraction, and presents a generic strategy for controlling the spatiotemporal evolution of the resulting mesoscopic patterns.