The Little Engine That Could

A car engine is an everyday example of a heat engine—a device that turns thermal energy into mechanical work. Scaled down to microscopic sizes, however, these devices can harness work from otherwise unwanted random thermal motion. But such stochastic heat engines are typically nonautonomous because they rely on an external control system to operate. As a result, they consume more energy than the work they produce. Chiara Daraio and Marc Serra-Garcia from the Swiss Federal Institute of Technology (ETH), Zurich, and colleagues have now come up with a design for an autonomous, classical stochastic heat engine. The system could be an ideal toy model with which to study thermodynamics on the microscale.