From MSNBC:
Scientists recently unveiled the tiniest electric motor ever built. You could stuff hundreds of them into the period at the end of this sentence. One day a similar engine might power a tiny mechanical doctor that would travel through your body in the ultimate house call. The motor works by shuffling atoms between two molten metal droplets in a carbon nanotube.
The technique exploits the fact that surface tension — the tendency of atoms or molecules to resist separating — becomes more important at small scales. The motor, a surface-tension-driven nanoelectromechanical relaxation oscillator, was built by a team of researchers led by Alex Zettl at the University of California, Berkeley.
Although the amount of energy produced is small — 20 microwatts — it is quite impressive in relation to the tiny scale of the motor. The whole setup is less than 200 nanometers on a side, or hundreds of times smaller than the width of a human hair. If it could be scaled up to the size of an automobile engine, it would be 100 million times more powerful than a Toyota Camry’s 225 horsepower V6 engine, the researchers say.
More here.