Quirks & Quarks

A Tractor Beam Made of Sound

A clever "acoustic hologram" can act as a tractor beam, lifting and manipulating small objects in three dimensions.

A device uses sound pressure to make virtual tools

A visualization of the invisible acoustic "tool" superimposed on an image of the tractor beam. (Asier Marzo/Bruce Drinkwater/Sriram Subramanian)
A group of researchers in the UK has figured out how to make an acoustic tractor beam out of sound, which can manipulate small objects in three dimensions. Sound waves can produce a small force, and scientists have used this in the past for acoustic levitation, allowing them to lift things.

Now Bruce Drinkwater, a Professor of Ultrasonics in the Department of Mechanical Engineering at the University of Bristol, and his colleagues, have taken this one step further. Using an array of small speakers, they've produced complex patterns of sound they're calling "acoustic holograms." They then use these to make tools from sound that can hold, and manipulate small objects, allowing them to move them in three dimensions, and rotate them as well.

They think this technology could be useful in "touch-less" manufacturing, and also possibly as a medical device allowing invisible fingers of sound to manipulate things inside the human body.

Related Links

Paper in Nature Communications
- University of Bristol release
- Science Magazine news story
- Live Science story
- BBC News story