Italian scientists from the University of Rome managed to harness free floating E. coli bacteria to turn a tiny crankshaft. Although potential uses for such a tiny and unusual motor drive are not yet clear, no doubt interesting applications in medicine and life sciences should present themselves over time.
The Physics arXiv Blog explains:
Angelani and co say there is in important difference between Brownian and bacterial motion: the former is in equilibrium but the latter is an open system with a net income of energy provided by nutrients. This breaks the time symmetry allowing energy to be extracted in the form of directed motion.
Now Angelani and co have built one these asymmetric and persuaded a bath full of E. Coli to push it round at a of 1rpm. Interestingly, Angelani and co report that most of the work is done by just a few bacteria, saying that only 2 out of 10 bacteria attached to a single tooth seem to be contributing to the torque.
In theory, they could speed up the rotation rate by persuading the others to put their backs into it. The linear motion of the gears is currently about 2 micrometres per second while the maximum speed of the bacteria is about 20 micrometers per second.