Active engines: Thermodynamics moves forward

¹ Department of Physics and Materials Science, University of Luxembourg - L-1511 Luxembourg
² DAMTP, Centre for Mathematical Sciences, University of Cambridge - Wilberforce Road, Cambridge CB3 0WA UK

^(a) etienne.fodor@uni.lu (corresponding author)

Received: 28 January 2021
Accepted: 16 April 2021

Abstract

The study of thermal heat engines was pivotal to establishing the principles of equilibrium thermodynamics, with implications far wider than only engine optimization. For nonequilibrium systems, which by definition dissipate energy even at rest, how to best convert such dissipation into useful work is still largely an outstanding question, with similar potential to illuminate general physical principles. We review recent theoretical progress in studying the performances of engines operating with active matter, where particles are driven by individual self-propulsion. We distinguish two main classes, either autonomous engines exploiting a particle current, or cyclic engines applying periodic transformation to the system, and present the strategies put forward so far for optimization. We delineate the limitations of previous studies, and propose some future perspectives, with a view to building a consistent thermodynamic framework far from equilibrium.