Using this UV-light booster, the scientists said, rotors a tenth the size of viruses could be harnessed to operate pulleys in synthetic muscles.

"You could even wind up chains and store energy like that," researcher David Leigh, an organic chemist at the University of Edinburgh in Scotland, told United Press International.

Although the objects in everyday life tend to move only when pushed, at the molecular level things are always in motion. They slow down only if cooled to temperatures near absolute zero, nearly minus 460 degrees Fahrenheit (minus 273 degrees Celsius), the coldest temperature theoretically possible.

Because it would be impractical to speed up or slow down microscopic devices by dosing them constantly with extreme heat or cold, Leigh and his team sought other ways to control molecular activity.

They experimented with rotors called rotaxanes -- rings with rods threaded through them. Previously, Leigh and his team had braked the continuously spinning rings by applying pulsating electric fields. Weak molecular forces known as hydrogen bonds bind the rings to their threads, and the fields can strengthen these bonds by lining them up, which in turn slows down ring spinning "by up to a thousand times," Leigh said.

Leigh and colleagues in Italy and Amsterdam discovered when they beamed ultraviolet light from a 150-watt mercury lamp on the rotaxanes they had floating in chloroform, the light broke the hydrogen bonds and allowed "the rings to spin freely about the threads," Leigh said, adding a million-fold boost in speed is possible by heating the rotors with a roughly 200-degree Fahrenheit (90-degree Celsius) increase in heat.

There are many kinds of rotaxanes, each of which requires different wavelengths of light to trigger its speed boost. Although the lamp takes about 10 minutes to weaken the hydrogen bonds, lasers can break them within millionths of a second.

"The big issue is how to couple all the components of molecular machinery together to make molecular machines that do something useful," Leigh said. His team is now working on controlling the rings to rotate clockwise or counterclockwise for use in molecular pulleys. If implanted in membranes, the rotating rings also could change surface properties with a flip of a switch -- creating, for example, instant non-stick, self-cleaning surfaces, he suggested.

Organic chemist Ben Feringa, of the University of Groningen in the Netherlands, found the technique "extremely elegant" and added the rotors could be used as switches that can be flicked on and off by light for data storage.

The scientists published their findings in this week's online version of the Proceedings of the National Academy of Sciences.

(Reported by Charles Q. Choi, UPI Science News, in New York)