Defect dynamics for self-propelled rods in a doublet of circular confinement

Abstract

Rod-shaped active micro/nano-particles, such as bacterial and bipolar metallic micro/ nano-motors, exhibit emergent collective phenomena far from equilibrium state compared to passive particles. We apply a simulation approach —dissipative particle dynamics (DPD)— to explore the collectively ordered states of self-propelled rods (SPRs) which rely on the defect dynamics in the rod cluster. The SPRs are confined in a doublet of circular confinement and repel each other when two rods touch each other. When the rod flow in the connecting passage of the circles is suppressed, namely the small passage width, the steady vortex pattern is obtained in the two circles for weak activity. In binary-passage system, long single-passage system, and short single-passage system, ferromagnetic vortices (FMV), uncorrelated vortices (UV), and anti-ferromagnetic vortices (AFMV) can be obtained, respectively. For intermediate activity, a regular periodic oscillation of the rod number n r in one circle can be seen clearly. For strong activity, mixing of high- and low-frequency oscillation is observed. The amplitude of the rod current in the passage I p follows the relation , where F a denotes the self-propelled force.

Spontaneous population oscillation of confined active granular particles

“…Nevertheless, a recent numerical work shows that “dry” run-and-tumble particles confined in two circular chambers connected by a narrow channel can bring a novel collective oscillation, in which active particles alternately (nearly) fill two chambers, 31 further supported by the follow-up simulations with similar dry active particles. 32,33 This finding extends our knowledge of spontaneous collective oscillation in active matter, implying the hydrodynamic interactions are not a necessary condition for self-sustained collective oscillation of active matter. However, so far, the predicted population oscillation still lacks an experimental verification, presumably since it is nontrivial to choose an appropriate active system to perform the corresponding experiment.…”