Laser beams used to contain and move tiny objects
Although it’s been years since optical tweezers have been used to move particles, the previous methods weren’t able to move them on distances larger than few millimeters. Researchers at the Australian National University (ANU) made a breakthrough by developing a method which can move objects much further by using laser beams. The researches have managed to move objects at a much larger distance of a meter and a half (almost 5 feet).
According to team leader Professor Andrei Rode, his team from the Laser Physics Centre at ANU used a hollow laser beam to trap light-absorbing particles in a “dark core”. The device works by shining its beam around tiny glass particles. The hollow laser beam heats up the air surrounding the particles, but the dark center of the beam is directed toward them which allows the particles to remain cool. As they gravitate and are drawn toward the laser beam, the particles are pushed back toward the center by heated molecules. Particle speed and direction can be manipulated by changing the brightness of the beams.
“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 center, one side becomes illuminated by the laser while the other lies in darkness. 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 hollow laser pipeline”, said Rode.
The researchers claim that this technology could be used to move particles at even greater distances of up to 10 meters (30 feet) away, but their initial demonstration was limited by the size of the optical table in the lab.
Since the laser beam requires the use of heated gas, this technology can’t be applied in environments such as vacuum, but the researchers pointed that there are other practical applications that can be considered for use here on Earth. 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. The laser beam could also be used for the transport of dangerous substances and microbes, in small amounts.
According to the ANU website, a full article about the team’s laser beam research will be available online starting September 23 through the university’s science magazine named Science Wise. Although the researchers themselves dubbed their achievement as a tractor beam, we didn’t use that term which repeats itself throughout various sci-fi since it is rather a “net” from multiple sources and it doesn’t work in large scale or in outer space.