Efficiency of isothermal active matter engines: Strong driving beats weak driving

TL;DR

This paper investigates the efficiency of microscopic active matter engines powered by single active particles, revealing that strong driving can enhance efficiency beyond the linear response regime, contrary to traditional expectations.

Contribution

It provides analytical insights into the thermodynamic efficiency of active matter engines, highlighting the impact of driving strength on energy recovery.

Findings

Efficiency increases with propulsion speed beyond linear response

Maximum efficiency occurs at large propulsion speeds

Strong driving regimes improve energy recovery in active engines

Abstract

We study microscopic engines that use a single active particle as their "working medium". Part of the energy required to drive the directed motion of the particle can be recovered as work, even at constant temperature. A wide class of synthetic active particles can be captured by schematically accounting for the chemical degrees of freedom that power the directed motion without having to resolve the exact microscopic mechanism. We derive analytical results for the quasi-static thermodynamic efficiency, i.e., the fraction of available chemical energy that can be recovered as mechanical work. While this efficiency is vanishingly small for colloidal particles, it increases as the dissipation is increased beyond the linear response regime and goes through a maximum at large propulsion speeds. Our results demonstrate that driving beyond the linear response regime has non-trivial consequences for the efficiency of active engines.