Now We Have a (Tiny) Tractor Beam

Researchers in England have created, essentially, a tractor beam that uses highly targeted sound waves to move objects in the air as though pulled and pushed by invisible fingers.

The ability to manipulate objects with sound was demonstrated back in 2001, when E. H. Brandt used sound waves to lift heavy balls of tungsten. But he used multiple arrays of sophisticated speakers that essentially enclosed the object in a box. Today’s researchers were able “to rotate and manipulate particles using even a single-sided emitter,” according to the their paper published Monday in the journal Nature.

Their breakthrough utilizes a formula built around the Gor’Kov potential, named for Russian-American physicist Lev Petrovich Gor’kov,  a means of measuring the force of sound on an object in an arbitrary sound field.

Researchers from the University of Bristol and Sussex in the United Kingdom, working with a company called Ultrahaptics, were able to levitate, rotate, and move expanded-polystyrene particles up to 3.1mm in diameter. They used special speakers called acoustic transducers that were 10mm in diameter to produce sounds at 40 kHz frequency.

The breakthrough holds potential for non-lethal weapons of the sort that the military is looking to use to stop attackers at checkpoints. Beyond that, you could potentially move objects to build bases in places where you don’t want put boots on the ground. Someday, the principle might help to capture aircraft in flight or even objects in other hard-to-reach areas. Of course, any tractor beam is less fun on the receiving end.