Approximating microswimmer dynamics by active Brownian motion: Energetics and efficiency

TL;DR

This paper demonstrates that active Brownian motion can approximate microswimmer dynamics but often underestimates energy dissipation, highlighting the importance of full system observation for accurate energetics and efficiency assessment.

Contribution

It introduces a method to approximate microswimmer dynamics with active Brownian motion and analyzes the limitations in estimating energy dissipation from partial observations.

Findings

Active Brownian motion approximates microswimmer dynamics.

The model underestimates total energy dissipation.

Full system observation is necessary for accurate energetics.

Abstract

We consider the dynamics of a microswimmer and show that they can be approximated by active Brownian motion. The swimmer is modeled by coupled overdamped Langevin equations with periodic driving. We compare the energy dissipation of the real swimmer to that of the active Brownian motion model, finding that the latter can massively underestimate the complete dissipation. This discrepancy is related to the inability to infer the full dissipation from partial observation of the complete system. We introduce an efficiency that measures how much of the dissipated energy is spent on forward propulsion.