Propagating interfaces in mixtures of active and passive Brownian particles

Abstract

The emergent collective dynamics in phase-separated mixtures of isometric active and passive Brownian particles is studied numerically in two-dimensions. A novel steady-state of well-defined propagating interfaces is observed, where the interface between the dense and the dilute phase propagates and the bulk of both phases is (nearly) at rest. Two kind of interfaces, advancing and receding, are formed by spontaneous symmetry breaking, induced by an instability of a planar interface due to the formation of localized vortices. The propagation arises due to flux imbalance at the interface, resembling the growth behavior of rough surfaces far from equilibrium. Above a threshold, the interface velocity decreases linearly with increasing fraction of active particles.

Emergent behavior in active colloids

“…Very recently, travelling fronts in polydisperse phaseseparating mixtures of active and passive disks were observed [378]. Finally, by performing event-driven Brownian dynamics simulations, Ni et al [379] realized that a small number of active particles helps to crystallize passive polydisperse glassy hard spheres in 3D.…”

Effective equilibrium states in mixtures of active particles driven by colored noise

“…Another special case, which recently has attracted much interest, is a mixture of an active and a passive Brownian species [24][25][26]. Given the prior results, the only way to set up a meaningful theoretical description of such a system is to fix D (1) a = D (2) a = 1, since the persistence times τ (2) = 0 of the passive and τ (1) of the active species are different by necessity in the OUPs model.…”

“…This step is always exact in one dimension, compare the conversion from Eq. (25) to Eq. (36) of the main text, and we expect that it results only in minor deviations in higher dimensions, based on the similar conclusion drawn for a single component [44].…”

“…The most intriguing feature of such multicomponent active systems is their capability to demix, which cannot be attributed to the physical mechanisms also present in equilibrium mixtures. Some recent investigations have focused on such a binary mixture of an active and a passive species [24][25][26] or particles with different finite activities [26][27][28][29]. Quite intuitively, active phase separation phenomena can be described using the concept of an effective temperature, enhanced by activity [30], which has also been applied to mixtures [27,31,32].…”

Conformational and dynamical properties of semiflexible polymers in the presence of active noise

“…Active matter systems, e.g., assemblies of active Brownian particles (ABPs) [1][2][3][4][5][6][7][8][9][10], exhibit a wide spectrum of fascinating phenomena, such as motility-induced phase separation or large-scale collective motion, emerging from the intrinsic nonequilibrium character of their constituents [3,[11][12][13][14][15][16][17][18]. The properties of connected active particles as in linear chains are particularly interesting, because of the intimate coupling of conformational properties and propulsion .…”