理工A概括大意讲解.doc

第十一篇 The Tiniest Electric Motor in the World 世界上昀小的电动机 第十二篇 A Strong Greenhouse Gas 一种强烈的温室气体 第十三篇 Face Masks May Not Protect from Super-Flu 口罩也许无法预防感冒 第十四篇 The Magic Io Personal Digital Pen io私人数字笔 第十五篇 Maglev Trains 磁悬浮列车 第十一篇 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 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 microwatt s — 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 too 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