Activation of colloidal patchy particle networks

Abstract

Active physical gels, exemplified by the cytoskeleton in muscle and plant tissues, are characterized by continuous energy injection, leading to rich but poorly understood non-equilibrium physics. Activated self assembled colloidal architectures consisting of patchy particles and self-propelled particles can provide a well-controlled (experimental) model system that allows exploring the non-equilibrium behavior of such active physical gels. We conduct a numerical investigation of the effect of introducing self-propelled colloids modeled as active Brownian particles into a network-forming colloidal dispersion of dipatch and tripatch particles. We find a rich response of the self-assembled networks upon increasing activity. At low active forces, the networks form inhomogeneous void-rich structures. At medium active force, the network fragments in clusters of chains, and develops broad local density distributions. Finally, at high active force, the system exhibits motility-induced phase separation. These structural and dynamical responses are intimately related to the system's bond probability that can increase or decrease as function of active force magnitude and direction, as well as attraction strength, affecting both the rate of bond formation and breakage. We discuss how our predictions compare to experiments.