Play. Pause. Rewind. Measuring Local Entropy Production and Extractable Work in Active Matter.

Time-reversal symmetry breaking and entropy production are universal features of nonequilibrium phenomena. Despite their importance in the physics of active and living systems, the entropy production of systems with many degrees of freedom has remained of little practical significance because the high-dimensionality of their state space makes it difficult to measure. We introduce a local measure of entropy production and a numerical protocol to estimate it. We establish a connection between the entropy production and extractability of work in a given region of the system and show how this quantity depends crucially on the degrees of freedom being tracked. We validate our approach in theory, simulation and experiments by considering systems of active Brownian particles undergoing motility induced phase separation, as well as active Brownian particles and E. Coli in a rectifying device in which a wall of funnel-shaped openings drives the accumulation of active particles in one chamber.