Any fan of Star Trek knows that if you want to stop an alien spaceship dead in its tracks you just immobilise them with your tractor beam. Well, it’s science fiction no longer, and the tractor beam created by the Universities of Bristol and Sussex, in collaboration with Bristol-based Ultrahaptics, is right here on Earth.

The tractor beam uses high-amplitude sound waves to generate an acoustic hologram which can pick up and move small objects seemingly in mid air. The device uses 64 miniature loudspeakers to create high-intensity sound waves which surround the object you want to move creating a force field that keeps the object in place. By carefully controlling the output of the loudspeakers the object can be either held in place, moved or rotated with apparently no means of support.

“In our device we manipulate objects in mid-air and seemingly defy gravity”


Asier Marzo, PhD student and the lead author of a paper in Nature Communications which describes the technique, says: “It was an incredible experience the first time we saw the object held in place by the tractor beam. All my hard work has paid off, it’s brilliant.” You can see it in action in the video below below:


Sriram Subramanian, Professor of Informatics at the University of Sussex and co-founder of Ultrahaptics, explains: “In our device we manipulate objects in mid-air and seemingly defy gravity. Here we individually control dozens of loudspeakers to tell us an optimal solution to generate an acoustic hologram that can manipulate multiple objects in real-time without contact.”

What can it be used for?

The team believe the technique could be developed for a wide range of applications, for example a sonic production line could transport delicate objects and assemble them, all without physical contact.  On the other hand, a miniature version could grip and transport drug capsules or microsurgical instruments through living tissue.


Bruce Drinkwater, Professor of Ultrasonics in the University of Bristol’s Department of Mechanical Engineering, adds: “We all know that sound waves can have a physical effect. But here we have managed to control the sound to a degree never previously achieved.”

The team have shown that three different shapes of acoustic force fields work as tractor beams.  The first is an acoustic force field that resembles a pair of fingers or tweezers.  The second is an acoustic vortex, the objects becoming stuck-in and then trapped at the core and the third is best described as a high-intensity cage that surrounds the objects and holds them in place from all directions.

You can see more about the technique in ‘Holographic acoustic elements for manipulation of levitated objects’ published in  Nature Communications. And you can keep up-to-date with more from Ultrahaptics at, or on Twitter@ultrahaptics.

 Image and video credits: Courtesy of Asier Marzo, Bruce Drinkwater and Sriram Subramanian © 2015