A Brownian Ratchet is a small engine which is conceived to extract work from molecular fluctuations. Examples of Brownian Ratchets occur in the cell, see for instance this nice movie about kinesin.
As well explained by Richard Feynmann, a Brownian Ratchet cannot perform its own task in an equilibrium environment, i.e. the fluctuations feeding energy to the ratchet cannot originate from a single thermal bath, in accordance with the second principle of thermodynamics. In this paper we have shown that a Brownian Ratchet can be fed with equilibrium fluctuations, provided that some energy dissipation is guaranteed by inelastic collisions or by sliding friction. Such result has been achieved with analytical computations on a kinetic model, numerical simulations and granular experiments.