Emergent structures and re-entrant transitions in active-passive colloidal mixtures

Dipolar interactions have long been used to control the self-assembly of colloids, but experimental studies on mixtures of active and passive colloids remain limited, with only a few simulations suggesting their potential. We investigate binary mixtures of electric field-driven active colloids and passive dielectric particles and demonstrate that they can produce interesting self-assembled structures including space spanning percolated networks. In this talk, I will discuss the state diagram of steady states in active-passive mixtures, where the dipolar interactions are non-reciprocal and multimodal with intraspecies repulsion and interspecies attraction. The complex directed interactions lead to mesoscale organization and orientational ordering of the active colloids, resulting in new re-entrant transitions in the phase space of active and total area fractions. We identify the critical role played by the orientational ordering of active colloids in dictating the overall stability and dynamics of the observed percolated networks. Our study provides an experimental demonstration of how active-passive colloidal mixtures can be used to tune the structural and dynamical properties of colloidal gels.