World's most powerful tractor beam 'like a pair of robot hands'
The levitation technique uses a bank of speakers to create a "tornado" of soundwaves, which can lift and contain small objects.
Tuesday 20 February 2018 20:30, UK
Researchers have for the first time used a tractor beam to move a levitating object around an obstacle course.
Sky News filmed the breakthrough at the University of Bristol, where engineers were able to manoeuvre a polystyrene ball that had been suspended in mid-air by the power of sound.
The levitation technique used 256 tiny loudspeakers arranged around a laboratory test rig.
The speakers generate ultrasound that’s too high pitched for the human ear to hear.
But at 170 decibels (dB), far louder than a jet engine, the sound is powerful enough to lift and manipulate an object.
Asier Marzo, an engineer at the University of Bristol, used a standard game controller to move the 1.6mm ball in three dimensions through a series of tubes.
He said: “You have seen the particle moving in mid-air. We want to do the same but in your body.
“You may have a kidney stone, which is very painful.
“The advantage of this technique is that you don’t need to cut the body.
“You would apply the ultrasound device from the outside and it would be like an invisible hand that goes inside and moves the stone out.”
The levitation technique uses a bank of speakers to create a "tornado" of soundwaves, which lift and contain an object within a spinning wall of energy.
By switching speakers on and off in sequence the engineers were able to steer the ball with a high degree of accuracy.
Star Trek popularised the tractor beam in the 1960s, but it’s taken until now for science to catch up.
However, the University of Bristol engineers have their sights on tiny objects rather than alien battleships.
Bruce Drinkwater, professor of ultrasonics, said he envisaged contactless production lines, with electronics or medicines being made without any risk of contamination.
“You can think of the acoustic manipulator as, an invisible robot,” he said.
“It’s like a pair of robot hands, but it’s only a force-field applying the required position, rotation and then moving things into place.”
At the power levels used in the lab the technique is safe. An ant made to "fly" in the levitation chamber was later able to crawl away apparently unharmed.
But to levitate a human the rig would need to be scaled up, with 40,000 speakers producing ten times more sound energy - almost certainly enough to burn skin.
For now, some things are best left to science fiction.