The gears are tiny, only 380 microns wide, which is about 8 times thicker than a human hair. They are turned by a swarm of bacteria randomly colliding into them.
It only takes a few hundred bacteria to start the gears turning, and the gears can be stopped and started by decreasing or increasing oxygen to the bacteria. Researchers at Argonne Labs, who pioneered the process, hope this is the beginning of hybrid biological machines than can work on microscopic levels.
