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2014年职称英语理工类教材学习部分内容及解析 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 stroke2. 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 Camrys 225 horsepower V6 engine. | 
