Rapid-Prototyping a Brownian Particle in an Active Bath

TL;DR

This paper introduces a minimal, experimentally relevant model for particles in an active bath, capturing key behaviors like Gaussian displacements, diffusion perturbations, and heat dissipation, validated against experimental tracer mobility data.

Contribution

The work presents a simple, generic model for active matter systems that can simulate Brownian particles in active baths without detailed mechanistic knowledge.

Findings

Model reproduces experimental tracer mobility in active baths.

Conditions for Gaussian and non-Gaussian displacements identified.

Quantifies heat dissipation necessary for non-equilibrium steady states.

Abstract

Particles kicked by external forces to produce mobility distinct from thermal diffusion are an iconic feature of the active matter problem. Here, we map this onto a minimal model for experiment and theory covering the wide time and length scales of usual active matter systems. A particle diffusing in a harmonic potential generated by an optical trap is kicked by programmed forces with time correlation at random intervals following the Poisson process. The model's generic simplicity allows us to find conditions for which displacements are Gaussian (or not), how diffusion is perturbed (or not) by kicks, and quantifying heat dissipation to maintain the non-equilibrium steady state in an active bath. The model reproduces experimental results of tracer mobility in an active bath of swimming algal cells. It can be used as a stochastic dynamic simulator for Brownian objects in various active baths without mechanistic understanding, owing to the generic framework of the protocol.