Tractor Beam Developed at Australian National University

"Scientists Invent a Tractor Beam"
FOXNews (September 8, 2010)

"Tractor beams, energy rays that can move objects, are a science fiction mainstay. But now they are becoming a reality -- at least for moving very tiny objects.

"Researchers from the Australian National University have announced that they have built a device that can move small particles a meter and a half using only the power of light.

"Physicists have been able to manipulate tiny particles over miniscule distances by using lasers for years. Optical tweezers that can move particles a few millimeters are common....

"...The device works by shining a hollow laser beam around tiny glass particles. The air surrounding the particle heats up, while the dark center of the beam stays cool. When the particle starts to drift out of the middle and into the bright laser beam, the force of heated air molecules bouncing around and hitting the particle's surface is enough to nudge it back to the center.

"A small amount of light also seeps into the darker middle part of the beam, heating the air on one side of the particle and pushing it along the length of the laser beam. If another such laser is lined up on the opposite side of the beam, the speed and direction the particle moves can be easily manipulated by changing the brightness of the beams...."

The particle has to be about the size of a bacterium for this "tractor beam" to work. It's a pretty small-scale effect, but could have practical applications: like when researchers are testing really dangerous substances or disease organisms, need to move the things - and don't want to touch them with anything.

One problem that hasn't been studied is just how much heat reaches the object being moved.

All in all, a fascinating new gadget.

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