Past single-molecule motors tended to be triggered with light, like this pump-like molecule. But light tends to also affect lots of other molecules nearby, and sometimes has an unpredictable effect. This new one (the molecule in question is an 18-atom molecule which, according to MSNBC, "gives brandy its distinctive smell." More importantly, it can be controlled by a stream of electrons shot from a Scanning Tunneling Microscope, which not only triggers the molecule to start spinning, it also enables viewing of the event.

That microscope is so precise that it can direct a beam of electrons at individual butyl methyl sulfide molecules (which are about one nanometer in size--for comparison, a human hair is 60,000 nanometers thick), causing one to turn without affecting any others.

There are caveats, of course; the experiments are being performed at excessively cold temperatures, about 5 degrees Kelvin, to try to slow down the movement. At that temperature, the molecule spins about 120 times per second. At 100 degrees Kelvin -- about -173 degrees Celsius -- that jumps to over a million, which, is as you can imagine, pretty difficult to monitor.

Still, there are lots of possible uses for such a tiny motor, from nanorobots that can perform surgery on a single cell to providing power for tiny nanoscale sensors. Those might be "several decades away," but at least the Guinness Book is convinced that this is the world's smallest motor.

[via MSNBC]