Active engines: Thermodynamics moves forward

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. Copyright (C) 2021 EPLA

Automated summary

The study of thermal heat engines is crucial for establishing equilibrium thermodynamics principles, while the conversion of energy in non-equilibrium systems remains a significant question with potential to illuminate general physical principles. Recent theoretical progress on engines operating with active matter has identified two main classes and strategies for optimization, with limitations in previous studies suggesting the need for a coherent thermodynamic framework far from equilibrium.