The ability to perform ‘magic’ could be a lot closer than we previously thought, after a team of researchers found a way to levitate large objects, even humans.
You won’t be needing a spell to send people floating, but it does help if you have access to the world’s most powerful acoustic tractor beam located at the University of Bristol.
The machine, which uses the power of sound to hold particles in mid-air, has shown for the first time that it is possible to trap objects larger than itself.
Dr Asier Marzo, lead author, said: “Acoustic researchers had been frustrated by the size limit for years, so its satisfying to find a way to overcome it.”
In this field, acoustic waves are generally considered the best way to levitate objects, because unlike magnetic methods they can grab most solids or liquids.
However, previous research had always found that the size of the object was limited to the size of the wavelength of sound used. Meaning you could not levitate big objects.
This was due to the way the sound works in a tornado-like structure, with loud sound surrounding a silent core. Before, when the object was larger than the silent core, they had been really unstable and spun uncontrollably quickly, until they were ejected.
Dr Mihai Caleap, senior research associate, who developed the simulations, said: “This was only thought to be possible using lower pitches making the experiment audible and dangerous for humans.”
But now the team have found that they can finely control the rate of rotation by changing the twisting direction of the vortices, keeping it stable. They were then able to increase the size of the silent core to allow it to hold larger objects.
Working with ultrasonic waves at a pitch of about 40kHz, a similar to pitch that only bats can hear, held a two-centimetre polystyrene sphere.
This was the largest object trapped in a tractor beam yet.
Although the idea of levitating humans is exciting, the real world applications for such technology could be producing contactless production lines, where delicate objects are assembled without touching them.
Or opening the door for delivering drug capsules or micro-surgical implements within the body.
In 2016, a research team at University of São Paulo in Brazil and Heriot-Watt University in Edinburgh successfully levitated a polystyrene ball 3.6 times bigger than the wavelength lifting it, using ultrasound.