Ultra-powerful acoustic tractor beam could one day levitate humans

22 Jan 2018

Image: g-stockstudio/Shutterstock

A major trope of science fiction just took a massive step towards becoming science fact with the building of a powerful levitation device.

The beginning of every great scientific breakthrough starts off by dismantling the assumption that something is impossible to science.

Now, one such instance could lead us to a whole new field of medicine as well as the ability to actually levitate a human being.

In a paper published to the journal Physical Review Letters, a team of engineers from the University of Bristol revealed that it built a device that could stably trap objects larger than the wavelength of sound in an acoustic tractor beam.

Until now, the scientific consensus has been that acoustic tractor beams could only levitate small objects because any previous attempts to trap particles larger than the wavelength had been unstable, with objects spinning uncontrollably.

This is down to the fact that the rotating sound field transfers some of its spinning motion to the objects, causing them to orbit faster and faster until they are ejected.

But now, this breakthrough has smashed that theory by using rapidly fluctuating acoustic vortices – or ‘tornados of sound’ – that can be accurately controlled by rapidly changing the twisting direction of the vortices, thus stabilising the tractor beam.

With this knowledge, the team worked with ultrasonic waves at a pitch of 40kHz, allowing the tractor beam to hold a 2cm polystyrene sphere in mid-air, making it the largest object ever levitated.

‘Huge potential in many applications’

Going by the researchers’ findings, the tractor beam could hold much larger objects in the future.

While its current potential could allow for the manipulation of drug capsules or microsurgical implements within the body, it could also, in theory, support human levitation and a whole new realm of science-fiction-like applications.

“In the future, with more acoustic power, it will be possible to hold even larger objects,” said Dr Mihai Caleap, a senior research associate involved in the project. “This was only thought to be possible using lower pitches, making the experiment audible and dangerous for humans.”

Meanwhile, the supervisor of the project, Prof Bruce Drinkwater, added: “Acoustic tractor beams have huge potential in many applications. I’m particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them.”

Colm Gorey was a senior journalist with Silicon Republic