Effect of polydispersity on the dynamics of active Brownian particles

We numerically study the dynamics and the phases of self-propelled disk-shaped particles of different sizes with soft repulsive potential in two dimensions. Size diversity is introduced by the polydispersity index (PDI) e, which is the width of the uniform distribution of the particle's radius. The self-propulsion speed of the particles controls the activity v. We observe enhanced dynamics for large size diversity among the particles. We calculate the effective diffusion coefficient Deff in the steady state. The system exhibits four distinct phases, jammed phase with small Deff for small activity and liquid phase with enhanced Deff for large activity. The number fluctuation is larger and smaller than the equilibrium limit in the liquid and jammed phases, respectively. Further, the jammed phase is of two types: solid jammed and liquid jammed for small and large PDI. Whereas the liquid phase is called motility induced phase separation (MIPS) liquid for small PDI and for large PDI, we find enhanced diffusivity and call it the pure liquid phase. The system is studied for three packing densities phi, and the response of the system for polydispersity is the same for all phi's. Our study can help understand the behavior of cells of various sizes in a tissue, artificial self-driven granular particles, or living organisms of different sizes in a dense environment.

Automated summary

In this study, we numerically investigated the dynamics and phases of self-propelled disk-shaped particles of different sizes with soft repulsive potential in two dimensions. The introduction of size diversity resulted in enhanced dynamics among the particles, with the system exhibiting four distinct phases including jammed and liquid phases. This research can contribute to understanding the behavior of cells, artificial self-driven granular particles, and living organisms of different sizes in dense environments.