We construct a molecular model of an internal combustion engine, by coupling a Brownian ratchet with an exothermic chemical cycle. We derive explicitly the thermodynamically allowed couplings, and show that almost every such coupling will result in motion. We compute from this formalism the maximal transmission efficiency of Brownian gears.

• Received 14 December 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.2656