title: Colloidal heat engines: a review.
abstract: Stochastic heat engines can be built using colloidal particles trapped using optical tweezers. Here we review recent experimental realizations of microscopic heat engines. We first revisit the theoretical framework of stochastic thermodynamics that allows to describe the fluctuating behavior of the energy fluxes that occur at mesoscopic scales, and then discuss recent implementations of the colloidal equivalents to the macroscopic Stirling, Carnot and steam engines. These small-scale motors exhibit unique features in terms of power and efficiency fluctuations that have no equivalent in the macroscopic world. We also consider a second pathway for work extraction from colloidal engines operating between active bacterial reservoirs at different temperatures, which could significantly boost the performance of passive heat engines at the mesoscale. Finally, we provide some guidance on how the work extracted from colloidal heat engines can be used to generate net particle or energy currents, proposing a new generation of experiments with colloidal systems.
authors.affiliation: Laboratoire de Physique, École Normale Supérieure, CNRS UMR5672, 46 Allée d'Italie, 69364 Lyon, France.
authors.forename: Ignacio A
authors.identifier: http://orcid.org/0000-0002-0208-7790
authors.initials: IA
authors.lastname: Martínez
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, Nöthnitzer strasse 38, 01187 Dresden, Germany and GISC - Grupo Interdisciplinar de Sistemas Complejos, Madrid, Spain.
authors.forename: Édgar
authors.identifier: http://orcid.org/0000-0001-7196-8404
authors.initials: É
authors.lastname: Roldán
authors.affiliation: GISC - Grupo Interdisciplinar de Sistemas Complejos, Madrid, Spain and Departamento de Fisica Atómica, Molecular y Nuclear, Universidad Complutense Madrid, 28040 Madrid, Spain.
authors.forename: Luis
authors.identifier: http://orcid.org/0000-0003-2064-2396
authors.initials: L
authors.lastname: Dinis
authors.affiliation: ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain. rul@ugr.es.
authors.forename: Raúl A
authors.identifier: http://orcid.org/0000-0001-5308-9422
authors.initials: RA
authors.lastname: Rica