At the University of Stuttgart and the nearby Max Planck Institute for Intelligent Systems, researchers are taking the notion of smaller, more compact engines to a micro-machinery extreme. Their new power generator is a single particle--just 3 mircrometers wide--that functions like a Stirling engine to generate actual work.

A Stirling engine essentially works by heating and cooling a fixed volume of gas inside a cylinder, using the expansion and contraction of that gas to push a piston. The 200-year-old design is extremely efficient, though it never caught on quite like the more powerful internal combustion and steam engines did (though Segway inventor and all-around smart guy Dean Kamen is a big fan).

In their micro-scale analog, the researchers in Stuttgart have replaced the machinery of a Stirling engine with a microscopic bead of malamine (that’s like a plastic-ey, resin-ey compound used in all kinds of things like dry-erase boards and kitchen countertops) floating in water and a couple of lasers. The first laser confines the motion of the particle. A second laser quickly heats and, when switched off, quickly cools the water around the bead.