Jan. 22 (UPI) -- For the first time, scientists have developed a tractor beam capable for levitating objects larger than an acoustic wavelength. Scientists believe the breakthrough could pave the way for tractor beams powerful enough to levitate humans.

Until now, larger objects trapped in acoustic tractor beams proved unstable. Acoustic waves tend to transfer some of their rotational energy to objects, causing them to spin out of control.


The latest technology features a kind of tornado of sound, fluctuating acoustic vortices. The tractor beam produces an inner core of silence surrounded by a twisting shell of strong acoustic waves.

The size and spin rate of the twister can be controlled by rapidly changing the direction of the acoustic vortices. Using 40 kHz frequency waves, scientists trapped a small polystyrene sphere in the tractor beam. The ball measured twice the length of an acoustic wave -- the largest object trapped in a tractor beam.

Researchers described the feat this week in the journal Physical Review Letters.

"Acoustic researchers had been frustrated by the size limit for years, so its satisfying to find a way to overcome it," lead researcher Asier Marzo, a mechanical engineer at the University of Bristol in England, said in a news release. "I think it opens the door to many new applications."

Scientists believe the new technology can be eventually deployed to levitate even larger objects.

"This was only thought to be possible using lower pitches making the experiment audible and dangerous for humans," said researcher Mihai Caleap.

The technology could have a variety of commercial applications.

"I'm particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them," said Bristol professor Bruce Drinkwater.