'Tractor beam' moves objects a (relatively) long way

Posted by Emma Woollacott

Star Trek tractor beams have existed for some time, but have only been able to move tiny objects for very short distances.

Indeed, they're generally known as 'optical tweezers' - which doesn't exactly have the same ring to it.

But now researchers from the Australian National University have been able to increase the effective distance of such devices to a meter and a half using a laser beam.

Professor Andrei Rode says his team used the hollow laser beam to trap light-absorbing particles in a 'dark core'. The particles are then moved up and down the beam of light, which acts like an optical pipeline.

"When the small particles are trapped in this dark core, very interesting things start to happen. As gravity, air currents and random motions of air molecules around the particle push it out of centre, one side becomes illuminated by the laser whilst the other lies in darkness," says Rode.

"This creates a tiny thrust, known as a photophoretic force that effectively pushes the particle back into the darkened core. In addition to the trapping effect, a portion of the energy from the beam and the resulting force pushes the particle along the hollowlaser pipeline."

Unfortunately, the laser beam won’t work in the vacuum of space. But
there are plenty of applications here on Earth, says Rode.

"These include directing and clustering nano-particles in air, the micro-manipulation of objects, sampling of atmospheric aerosols, and low contamination, non-touch handling of sampling materials," he says.

"On top of this, the laser beam could be used for the transport of dangerous substances and microbes, in small amounts."