Brownian Carnot Engine

At the microscale, the energy transfer between a system and its surroundings becomes random and a new theoretical framework -stochastic thermodynamics [1]- is necessary to account for those fluctuations. In particular, stochastic thermodynamics can be used to analyze the performance of small motors, like Brownian engines or molecular machines. Here we will report on a recent experiment that reproduces the Carnot cycle with a single Brownian particle as working substance [2]. The experiment uses optical tweezers to confine the particle and a noisy electrostatic force to mimic a high temperature reservoir. To analyze this Brownian Carnot engine, we will review some basic aspects of stochastic thermodynamics and discuss fundamental differences between driven and autonomous machines that arise from their behavior under time reversal [3].

[1] U. Seifert, Stochastic thermodynamics, fluctuation theorems and molecular machines. Reports on Progress in Physics 75, (2012).
[2] I.A. Martinez, E. Roldan, L. Dinis, D. Petrov, J.M.R. Parrondo y R.A. Rica, Brownian Carnot engine. Nat Phys 12, 67-70 (2016).
[3] M. Esposito y J.M.R. Parrondo, Stochastic thermodynamics of hidden pumps. Physical Review E 91, (2015).