Team claims to have made world's smallest steam engine

The team, made up of physicists from Stuttgart University and the Max Planck Institute for Intelligent Systems, claims that its micro-sized engine could be used towards making highly efficient, small heat engines.

In a regular Stirling engine, a gas-filled cylinder is periodically heated and cooled so that the gas expands and contracts. This makes a piston execute a motion with which it can, for example, drive a wheel.

’We successfully decreased the size of the essential parts of a heat engine, such as the working gas and piston, to only a few micrometres and then assembled them to a machine,’ said Stuttgart University’s Valentin Blickle.

The working gas in the Stuttgart-based experiment is represented by an observable plastic bead, measuring three micrometres, which floats in water.

The physicists replaced the piston, which moves periodically up and down in a cylinder, with a focused laser beam whose intensity is periodically varied. The optical forces of the laser limit the motion of the plastic particle to a greater and a lesser degree, like the compression and expansion of the gas in the cylinder of a large heat engine.