Coexistence of nonequilibrium phases in assemblies of driven nematic colloids

We combine experiments, theory, and simulations to investigate the coexistence of nonequilibrium phases emerging from interacting colloidal particles that are electrokinetically propelled in a nematic liquid crystal solvent. We directly determine the mechanical pressure within the radial assemblies and measure a non-equilibrium equation of state for this athermal driven system. A generic model combines phoretic propulsion with the interplay between electrostatic effects and liquid-crystal-mediated hydrodynamics, which are effectively cast into a long-range interparticle repulsion, while elasticity plays a subdominant role. Simulations based on this model explain the observed collective organization process and phase coexistence quantitatively. Our colloidal assemblies provide an experimental test-bed to investigate the fundamental role of phoretic pressure in the organization of driven out-of-equilibrium matter.