Active engines: Thermodynamics moves forward

TL;DR

This paper reviews recent theoretical advances in understanding active matter engines, focusing on their performance, optimization strategies, and future directions for developing a thermodynamic framework for nonequilibrium systems.

Contribution

It distinguishes between autonomous and cyclic active engines, summarizes current optimization strategies, and discusses future perspectives for nonequilibrium thermodynamics.

Findings

Identified two main classes of active engines: autonomous and cyclic.

Summarized current strategies for engine performance optimization.

Outlined limitations of existing studies and proposed future research directions.

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 futures perspectives, with a view to building a consistent thermodynamic framework far from equilibrium.