Clustering and phase separation of circle swimmers dispersed in a monolayer

Abstract

We perform Brownian dynamics simulations in two dimensions to study the collective behavior of circle swimmers, which are driven by both, an (effective) translational and rotational self-propulsion, and interact via steric repulsion. We find that active rotation generally opposes motility-induced clustering and phase separation, as demonstrated by a narrowing of the coexistence region upon increase of the propulsion angular velocity. Moreover, although the particles are intrinsically assigned to rotate counterclockwise, a novel state of clockwise vortices emerges at an optimal value of the effective propulsion torque. We propose a simple gear-like model to capture the underlying mechanism of the clockwise vortices.

Dynamical self-assembly of dipolar active Brownian particles in two dimensions

“…To gain further information, we calculate position-resolved local area fractions, φ , based on a Voronoi tessellation. 36,42 (We note that, contrary to ref. 36, we did not perform a short time average of φ , since the polar clusters characterizing the dense state migrate over time and, therefore, are not stationary within the short-time interval.…”

“…As described in ref. 36, we find that the relationship between these two diffusion constants of a hard sphere in the low Reynolds number regime is given via D r = 3D t /σ 2 h . We also define the diameter of an effective (eff) hard sphere via σ e f f = ∞ 0 (1 − exp [−β u sr (r)]) dr. With the repulsive strength ε * = 10 considered in the present system, σ e f f ≈ 1.07851σ .…”

“…Specifically, two a Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36 particles with point dipoles at their center tend to align headto-tail, where the arrowhead of one dipole moment is directed toward the arrowtail of the other dipole. In contrast, particles configured side by side favor antiparallel alignment.…”

Configuration dynamics of a flexible polymer chain in a bath of chiral active particles

“…Here we would like to point out that the rotation directions of the cluster (for v 0 = 15) and the ring (for v 0 = 22.5) observed here are consistent with those observations in Ref. [61] and Ref. [62].…”

“…In Ref. [61], the authors studied the phase separation of chiral active crowders, finding that the passive cluster rotates in the opposite direction to that of the chiral active particles. There the authors argued that the passive cluster with non-smooth boundary formed a 'gear', which was the reason for opposite rotating behavior.…”