The idea of humans levitating in mid-air may soon be taken out of the realms of science fiction and into reality, as scientists have found a way to trap larger objects in acoustic tractor beams.
Acoustic tractor beams use sound waves to suspend small particles in mid-air. But previously, these particles could only be the same size as the wavelengths of sound.
It had been thought that using larger objects was impossible as it caused the objects trapped in the beam to spin uncontrollably.
However, a team of engineers from the University of Bristol was able to trap a two-centimeter polystyrene ball and successfully keep it stable. The ball measured two centimeters and is the largest object ever held in an acoustic tractor beam.
“Acoustic researchers had been frustrated by the size limit for years, so it’s satisfying to find a way to overcome it. I think it opens the door to many new applications,” said Dr. Asier Marzo, the lead author of the paper.
The results were published in the journal Physical Review Letters.
This revolutionary discovery could lead to advances in surgery, as delicate operations could be done hands-free, and possibly could create the means to someday levitate humans.
The engineers were able to manipulate the rate of rotation of acoustic vortices, or essentially sound tornadoes. The beam creates an acoustic cyclone, and in the “eye,” or core, it’s silent.
When the research team quickly changed the twisting direction of the vortices, they were able to stabilize the beam and hold larger objects in the silent core.
The engineers used ultrasonic waves, at a pitch of 40 kHz, to trap the small polystyrene sphere in the core.
The results show for the first time it is possible to trap larger objects in an acoustic beam in a stable way, and the researchers are excited about the implications their study could have on future technology.
“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,” said Bruce Drinkwater, a supervisor of the research.