Tractor beam built from sound

Researchers have built the world's first sonic tractor beam that can lift and move objects using sound waves

Researchers have built the world's first sonic tractor beam that can lift and move objects using sound waves.

Tractor beams are rays that can grab and lift objects. Researchers from Bristol and Sussex University have built a working tractor beam by using high-amplitude sound waves to generate an 'acoustic hologram' to pick up and move small objects.

Researchers say the technique, which has published in the journal 'Nature Communications', could be used in a production line to transport delicate objects and assemble them without physical contact. A miniature version could grip and transport drug capsules or microsurgical instruments through living tissue.

The researchers used an array of 64 miniature loudspeakers to create high-pitch and high-intensity sound waves. The tractor beam works by surrounding the object with this high-intensity sound to create a  force field that keeps the objects in place. By carefully controlling the output of the loudspeakers the object can be either held in place, moved or rotated.

The team have shown that three different shapes of acoustic force fields work as tractor beams: a pair of fingers or tweezers, a vortex; and a high-intensity cage that surrounds the objects and holds them in place from all directions.

Previous work on acoustic studies has surrounded the object with loudspeakers, which limits the extent of movement and restricts many applications. Last year, the University of Dundee presented the concept of a tractor beam but no objects were held in the ray.

Asier Marzo, lead researcher said: "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."

Bruce Drinkwater, professor of Ultrasonics at the University of Bristol's department of mechanical engineering, sad: "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."

Sriram Subramanian, professor of Informatics at the University of Sussex said: "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."