Star Trek-style tractor beams that can levitate humans have moved a step closer to reality.
At least, that’s according to engineers in Bristol who have created the world’s most powerful tractor beam that can move objects using sound.
The system works by transforming sound waves into ‘mini tornadoes’ that have enough power to transport large objects and keep them afloat mid-air.
The tractor beam has so far only been tested on a 2cm piece of polystyrene.
But researchers insist that the same system could one day transport larger objects such as people, or even vehicles.
Researchers have been attempting to use the power of rotating sound fields to do this for decades. Up until now, this has proved impossible.
This is because a rotating sound field transfers some of its spinning motion to the objects causing them to orbit faster and faster and become unstable.
Now, instead of using a spinning field of sound to keep an object steady, researchers have created a device that creates ‘mini tornadoes’ out of sound waves.
‘Acoustic researchers had been frustrated by the size limit for years, so its satisfying to find a way to overcome it. I think it opens the door to many new applications’, lead author Dr Asier Marzo said.
The new approach, published in Physical Review Letters, uses rapidly fluctuating sound vortexes.
These are similar to tornadoes of sound, made of a twister-like structure with a loud sound surrounding silent core.
This silent core is where the object can hover.
By quickly changing the rotational direction of the mini-tornadoes, researchers found the core increased in size, allowing larger objects to levitate.
‘In the future, with more acoustic power it will be possible to hold even larger objects’, said Dr Mihai Caleap, Senior Research Associate.
‘This was only thought to be possible using lower pitches making the experiment audible and dangerous for humans’, he said.
Working with ultrasonic waves at a pitch of 40kHz, a similar pitch to that which only bats can hear, the researchers held a two-centimetre polystyrene sphere in the tractor beam.
This sphere measures over two acoustic wavelengths in size and is the largest yet trapped in a tractor beam.
The research suggests that, in the future much larger objects could be levitated in this way.
‘Acoustic tractor beams have huge potential in many applications’, said Dr Bruce Drinkwater, Professor of Ultrasonics from the Department of Mechanical Engineering and supervisor of the project.
I’m particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them’, said Dr Drinkwater.