The Tiniest Electric Motor in the World
1. Scientists recently made public 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 to remove your disease.
2. The motor works by shuffling(来回运动) atoms(原子) between two molten metal droplets(小滴) in a carbon nanotube(纳米管). One droplet is even smaller than the other. When a small electric current is applied to the droplets, atoms slowly get out of the larger droplet and join the smaller one. The small droplet grows but never gets as big as the other droplet and eventually bumps into the large droplet. As they touch, the large droplet rapidly sops up (吸入)the atoms it had previously lost. This quick shift in energy produces a power stroke(动力行程).
3. The technique exploits the fact that surface tension -- the tendency of atoms or molecules to resist separating -- becomes more important at small scales. Surface tension is the same thing that allows some insects to walk on water.