劍橋科學家研製出世上最小的引擎

Scientists have developed a microscopic engine, the smallest in the world, that they say is the first one capable of driving nanobots, including medical robots that could travel through the body.

科學家研製出一種微型引擎，它是世界上最小的引擎。科學家們表示，這是第一種能驅動納米機器人——包括能在人體中行走的醫用機器人——的引擎。

The prototype device, known as an actuating nano-transducer or Ant, combines microscopic gold balls with a special polymer gel. It generates a propulsive force on a microscopic scale that is a hundred times greater per unit weight than any known motor or muscle.

這一原型設備稱爲作動納米換能器(actuating nano-transducer)或“螞蟻”（actuating nano-transducer的首字母縮寫Ant），由微型金球和一種特殊的聚合物凝膠組合而成。它可產生一種微觀尺度上的推動力，其單位重量推力是任何已知馬達或肌肉的100倍。

“People have been talking about making nanobots for many years but they do not exist yet,” said Professor Jeremy Baumberg, leader of the project at Cambridge university. “Why not? Because so far there has been no way of making them move through liquids — which is like swimming through treacle on the nanoscale because the molecular forces are so strong.”

“多年來，大家一直在談論製造納米機器人，但它們仍未問世。”劍橋大學(Cambridge)教授、該項目帶頭人傑裏米•邦伯格(Jeremy Baumberg)說，“爲什麼呢？這是因爲直至今天，我們仍無法讓納米機器人在液體中移動——這就像是在納米尺度的糖漿中游泳，分子力太強了。”

He says Ant engines, described for the first time in Proceedings of the National Academy of Sciences, would provide sufficient power. “Like real ants they provide large forces for their weight,” he said. “The challenge we now face is how to control the force for nano-machinery applications.”

他說，“螞蟻”引擎——最初發佈於《美國國家科學院院刊》(Proceedings of the National Academy of Sciences)——將提供充足的動力。“就像真正的螞蟻一樣，它們能夠提供比自身重量大得多的力量。”他說，“我們目前面臨的挑戰是，如何控制這一力量爲納米機械所用。”

The Ant is powered by physical rather than chemical reactions. It contains gold nanoparticles, each about 0.06 microns, or a thousandth of the width of a human hair, in diameter in water with a gel-like polymer called pNIPAM.

“螞蟻”的動力源自物理反應而不是化學反應。它包含金納米顆粒，每個顆粒的直徑約爲0.06微米（相當於人類頭髮寬度的千分之一），這些顆粒與一種名爲聚N-異丙基丙烯酰胺(pNIPAM)的凝膠狀聚合物一起泡在水裏。

When the temperature is above the critical temperature of 32C, the gold particles are bound tightly together with the polymer through intermolecular attraction. When it falls below 32C, the polymer suddenly absorbs water and expands — and the gold particles are pushed rapidly apart like a spring.

當溫度升到臨界溫度32攝氏度以上時，金顆粒通過分子間吸引力與聚合物一道被緊緊束縛在一起。當溫度降到32攝氏度以下時，聚合物突然吸收水分並膨脹——聚集的金顆粒被快速推散開來，就像彈簧一樣。

“It’s like an explosion,” said Tao Ding, another member of the team. “We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them.”

“這就像是爆炸，”該團隊的另一成員Tao Ding說，“當水分子讓金顆粒周圍的聚合物膨脹時，數百個金球在百萬分之一秒內飛散開來。”

The reaction is completely and rapidly reversible, experiments show. When the temperature rises again, the Ant stores a large amount of elastic energy in a fraction of a second as the polymer coating expels water from the gel and contracts around the gold particles. “The whole process is like a nano-spring,” said Prof Baumberg.

實驗表明，這一反應是完全、快速可逆的。當溫度再度升高時，隨着聚合物包裹物把水分排出凝膠並圍繞金顆粒收縮起來，“螞蟻”可在瞬間儲存大量彈性能。“整個過程就像是納米彈簧，”邦伯格教授說。

The prototype Ant uses laser light to control the system’s temperature but other mechanisms could be used instead. The transition point could also be adjusted, for example to set the energy release point close to 37C — the human body’s normal temperature.

“螞蟻”原型引擎用激光來控制系統的溫度，但也可採用其他機制。臨界點也可調整，比如把能量釋放點設定爲接近37攝氏度——人體的正常溫度。

The Ant might drive a nanobot through a series of piston strokes, rather like a car engine but on a scale many billions of times smaller.

“螞蟻”或可通過一系列活塞衝程來驅動納米機器人，這很像汽車的引擎，只是其尺寸是後者的數十億分之一。

“The concept can underpin a plethora of future designs,” Prof Baumberg said. The team is working with Cambridge Enterprise, the university’s commercialisation arm, to develop practical applications for the technology.

“這一概念可爲大量的未來設計提供支撐，”邦伯格教授說。該團隊正與劍橋大學的商業化機構“劍橋實業”(Cambridge Enterprise)合作，開發這項技術的實際應用。