Creating nanomachines can be unprofitable because of the time necessary to create and then assemble the components. But researchers at Columbia University have found a way to make machines assemble themselves:
To make the gears, a thin copper sheet is laid over a heat-expanded polymer. When the polymer cools, it shrinks faster than the metal, which causes the metal to bend. When the metal bends, it creates regularly spaced teeth in the polymer, effectively making a microscopic gear. Stiffer metal that's harder to bend creates a gear with fewer, larger teeth, while a more supple metal creates gears with smaller, more numerous teeth.
The team has already made a number of different types of gears, all at the six-to-25 millimeter range, and are now ready to shrink the process down further, to create gears smaller than a micrometer.