Actuating nano-transducers (ANT's), the smallest engine ever developed, have been successfully designed and built by researchers at University of Cambridge. This tiny device, small enough to enter cells, could herald a new age of ultra-small robots, which could be utilized for a wide range of purposes. This tiny device is just one-millionth the size of a typical ant.

Miniature robots constructed using these engines could travel through water, sensing changes to the environment happening around them. Constructed of electrically-charged spheres of gold, the minuscule engines are powered by sunlight. The tiny gold globes are held within a polymer gel, which responds to heat. When struck with a laser, the gel forcibly ejects water, collapsing in on itself, drawing the gold particles close together. This stores potential energy in the form of a compressed polymer. As the material cools, it absorbs water, pushing the gold spheres apart, similar to the action of a spring.

"It's like an explosion. We have hundreds of gold balls flying apart in a millionth of a second when water molecules inflate the polymers around them," Tao Ding of the Cavendish Laboratory at University of Cambridge, said.

For decades, physicists and electronic engineers have attempted to design nano-engines. However, powering such minuscule devices has proven to be a challenge. This new system, developed at Cambridge, is capable of delivering a good deal of force for its size, and can operate at rapid speed. The engine is 100 times more powerful, for its size, than any muscle or motor.

As electrons orbiting around atomic nuclei change the electrical attraction between atoms and molecules, this results in the movement of these building blocks of matter. This process is known as Van der Waals forces. Researchers in this study found a way to use this energy to "wind up" the motors, which later expel water, completing the cycle.

Investigators are currently working with commercial development firms to create ways of using this technology to build ultra-small robots capable of traveling within human cells, like a scene from the science fiction classic Fantastic Voyage - without the miniaturized human crew.

Development of the world's smallest engine was detailed in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) on May 2.

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