| http://www.guardian.co.uk/uk_news/story/0,3604,485634,00.html
Objects moved by the power of light James Meek, science correspondent Friday May 4, 2001 The Guardian Researchers in Scotland have come up with a laser device able to grip and twist objects at a distance. The device, invented by a team from the physics department at St Andrews University, is able to rotate microscopic objects, such as a tiny glass rod, twice the thickness of a human hair, with nothing more than the power of light. "We've only just begun to realise the possibilities for what we might do with this technology," said Kishan Dholakia, one of the researchers who wrote a paper on the "tractor beam" in today's edition of the journal Science. Particles of light have a tiny amount of mass and high velocity, meaning laser beams exert a slight force on objects they touch. This property has already been used to create "laser tweezers", tightly focused beams which can trap microscopic objects and move them from place to place. But those lasers could not, like traditional tweezers in a human hand, turn most objects around. By using two lasers together, the St Andrews team created an interference pattern in the form of a spiral of light which traps an object in the arms. Adjusting the beams causes the spiral to rotate, taking the object with it. As well as the glass rod, which could be used to stir tiny amounts of liquid, the scientists have rotated a hamster chromosome, showing how their technique could be used to study the innermost workings of cells for medical research. Another use for the "tractor beam" is in nanotechnology, the science of building microscopic machines from components not much larger than a few molecules. "Our technique could be used to drive motors, mixers, centrifuges, and other rotating parts in cheap, tiny, automated technologies of the future," Dr Dholakia said. Another member of the team, Michael McDonald, said it would not be practical to scale up the beam to move bigger objects. The power of the lasers used was very low, but that did not mean that a laser 100 times as powerful would be able to move an object 100 times as big. |
