Bristol researchers demonstrate world’s most powerful tractor beam

A series of vortices create a stable area for levitation
25th January 2018

Bristol is continuing to show its expertise in using ultrasound to manipulate the real world with the world’s most powerful tractor beam.

Acoustic tractor beams have already used the power of sound to hold particles, either solid or liquid, in mid-air. Now researchers at the University of Bristol have been able to trap objects larger than the wavelength of sound in a beam. This opens the door to the manipulation of drug capsules or even controlling tiny surgical implements within the body in sterile environments.

Check out this advanced levitation in action in the video below:

 

“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,” says Bruce Drinkwater, Professor of Ultrasonics at the University’s Department of Mechanical Engineering.

Acoustic vortices

Current theory says these tractor beams were fundamentally limited to levitating small objects as all the previous attempts to trap particles larger than the wavelength had been unstable, with objects spinning uncontrollably.

Instead the team used rapidly fluctuating acoustic vortices, which are similar to tornadoes of sound, to create a stable core. They were then able to increase the size of the silent core allowing it to hold larger objects. Working with ultrasonic waves at a pitch of 40kHz, the researchers held a 2cm polystyrene sphere in the tractor beam (pictured left).

This sphere is over twice the acoustic wavelength 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 by boosting the power of the ultrasound.

“Acoustic researchers have 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,” says Dr. Asier Marzo at Bristol’s Department of Mechanical Engineering.

Ultrasound is a key area for Bristol. The University team has previously shown smaller objects being moved around by the beams, while Ultrahaptics in the city is using focused ultrasound beams to provide the feeling of touch in mid-air.

For more details see Ultrasonic particle manipulation at the University.