Japanese scientists have developed a micromotor powered by the movement of bacteria:
The 20-micron (1 micron = 1 millionth of a meter) diameter revolving motor has 6 blades, each with a foot that sits in a 0.5-micron deep, 13-micron diameter groove etched into a silicon substrate. The surfaces of the feet and the groove are treated with proteins that cause the bacteria (introduced via a connecting groove) to move in one direction, pushing the feet (and spinning the motor) as they pass through the groove.
The researchers believe microbial motion can be harnessed as a power source for microdevices in the future, with potential applications that include motors for micromachines and miniature pumps for tiny medical devices.