The Tiniest Electric Motor in the World
　　1　Scientists recently made public the tiniest electric motor ever1 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 atoms between two molten metal droplets in a carbon nanotube. 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 the atoms it had previously lost. This quick shift in energy produces a power stroke.2
　　3　The technique exploits the fact that surface tension — the tendency of atoms or molecules to resist separating — becomes more important at small scales3. Surface tension is the same thing that allows some insects to walk on water.
　　4　Although the amount of energy produced is small — 20 microwatts — it is quite impressive in relation to the tiny scale of the motor4. The whole setup5 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 engine6, it would be 100 million times more powerful than a Toyota Camry's 225 horsepower V6 engine.
　　5　In 1988, Professor Richard Muller and colleagues made the first operating micromotor, which was 100 microns across7, or about the thickness of a human hair. In 2003, Zettl's group created the first nanoscale motor. In 2006, they built a nanoconveyor, which moves tiny particles along like cars in a factory.
　　6　Nanotechnology engineers try to mimic nature, building things atom-by-atom. Among other things, nanomotors could be used in optical circuits to redirect light, a process called optical switching. Futurists envision a day when nanomachines, powered by nanomotors, travel inside your body to find disease and repair damaged cells.
　　詞匯：
　　shuffle來回運(yùn)動 molten 溶化的 droplet 小滴
　　nanoconveyor 納米傳送帶 bump 碰撞 sop 吸入
　　microwatt 微瓦 nanomachine 納米機(jī)器 nanometer 納米，微毫米
　　micromotor 微電機(jī) nanotube 納米管
　　nanotechnology 納米技術(shù)
　　mimic 模仿 stroke 行程，沖程 nanomotor 納米發(fā)動機(jī)