(63g) Non-Reciprocal Interactions in the Co-Assembly of Active and Passive Particles

Non-reciprocal in nature appear to break the action-reaction symmetry of Newton’s third law. This apparent breaking is due to dissipation of energy and generation of entropy in the medium. The non-reciprocal interactions are known to play a significant role in self-organization of living matter. However, their impact in synthetic active colloids remains poorly understood, primarily due to the hindrance they pose to the assembly on account of hydrodynamic interactions which emerge from surrounding fluid flows. We hypothesize the existence of concurrent dipolar and hydrodynamic forces between passive and active particles in alternating current (ac) electric fields to drive these assemblies. In this study, we use high-speed microscopy as to measure forces between pairs of passive and active microspheres subjected to ac electric field. These force measurements allow us to determine the degree of reciprocity in interactions in pair-clusters, which is tunable by designing the active particle and its trajectory. Large clusters showcase collective dynamics and display programmable stability and reconfigurability by controlling the fraction of active particles. Through this study, we use non-reciprocal interactions as a tool to design reconfigurable metastable assemblies of synthetic colloids with interesting collective dynamics as analogues that mimic self-assembled living matter.