Controlling the microstructure and phase behavior of confined soft colloids by active interaction switching

Abstract: We explore the microstructure and phase behavior of confined soft colloids which can actively switch their interactions at a predefined kinetic rate. For this, we employ a reaction-diffusion approach based on a reactive dynamical density-functional theory (R-DDFT) and study the effect of a binary (two-state) switching of the size of colloids interacting with a Gaussian pair potential. The rate of switching interpolates between a near-equilibrium binary Gaussian mixture at low rates and an effective monodisperse liquid for large rates, hence strongly affecting the one-body density profiles, adsorption, and pressure at confining walls. Importantly, we demonstrate that sufficiently fast switching impedes the phase separation of an (in equilibrium) unstable liquid, allowing the dynamic control of the degree of mixing/condensation and local micro-structuring in a cellular confinement by tuning the switching rate.