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Star Wars style sonic tractor beam invented by scientists

High-amplitude sound waves generate an 'acoustic hologram' that can suspend a 4mm-wide polystyrene ball in space

Chris Green
Tuesday 27 October 2015 17:01 GMT
It is the first time an object has been successfully held and controlled in mid-air
It is the first time an object has been successfully held and controlled in mid-air (Asier Marzo, Bruce Drinkwater and Sriram Subramanian)

Darth Vader’s Death Star and Captain Kirk’s Starship Enterprise both had one. Now the tractor beam, that science fiction favourite deployed to memorable effect in numerous films and television series over the years, has finally arrived on Earth.

A team of researchers at two British universities has created the world’s first fully functioning sonic tractor beam, capable of suspending, moving and manipulating small objects using only the power of sound waves.

From science fiction to reality – sonic tractor beam invented

Previous studies have shown that tractor beam technology is possible, but the new study is significant as it is the first time an object has been successfully held and controlled in mid-air. High-amplitude sound waves were used to generate an “acoustic hologram” capable of suspending a 4mm-wide polystyrene ball in space.

The technique, refined by scientists at the Universities of Bristol and Sussex, has a wide range of applications and could in the future be used to manipulate objects inside the human body without the need for an invasive medical procedure.

The study, published in the journal Nature Communications, details how the researchers used an array of 64 miniature loudspeakers to surround the polystyrene ball with high-pitched, high-intensity sound waves, creating an acoustic “force field” capable of lifting it into mid-air. By carefully controlling the output of the speakers, the ball can then be held in place, moved or rotated.

“Unprecedented acoustic structures shaped as tweezers, twisters or bottles emerge as the optimum mechanisms for tractor beams or containerless transportation,” the researchers wrote, adding that the technique could also be used for the “levitation of living things”.

“Single-beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically-controlled micro-machines that do not interfere with magnetic resonance imaging (MRI),” they continued.

Last year researchers at the University of Dundee successfully created their own sonic tractor beam, but the device was not capable of exerting control over objects for long periods. Optical tractor beams which use high-powered lasers have also been built, but have only succeeded in moving miniscule objects.

Asier Marzo, the PhD student who made the breakthrough in a laboratory at the University of Bristol six months ago, told The Independent that when he levitated an object for the first time he immediately took a photograph and sent it to the other scientists working on the project.

“It was an incredible experience the first time we saw the object held in place by the tractor beam,” he added. “Finally, after months of beads being spitted uncontrollably from the tractor beam we had success. All my hard work has paid off, it’s brilliant.”

Mr Marzo is “excited” about the potential of the technology, which he said could eventually be used to create “more powerful tractor beams capable of levitating bigger objects from farther distances”. Such a device might allow astronauts to control objects floating in space without leaving the safety of their capsules, he added.

In hospitals, tractor beams could be used to manipulate things inside the human body without the need for an incision, including blood clots, kidney stones, microsurgical instruments, he said. Drug capsules could also be moved to the part of the body where they would have the most benefit.

Tractor beams: A brief history

  • The term “tractor beam” was reportedly coined by the early American science fiction author E.E. Smith in his novel Spacehounds of IPC, which was serialised in the magazine Amazing Stories in 1931.
  • Tractor beams are used frequently in Star Trek, including in the original 1960s television series. As well as for towing spaceships – sometimes at warp speed – the technology also proves useful for deflecting incoming asteroids and repelling enemy fire.
  • The Death Star, the planet-sized killing machine created by the Galactic Empire in Star Wars, uses a giant tractor beam to pull in Han Solo’s Millennium Falcon spacecraft in the original 1977 film. Obi-Wan Kenobi later deactivates the beam, allowing Luke Skywalker and others to escape.

Bruce Drinkwater, Professor of Ultrasonics at Bristol’s Department of Mechanical Engineering and one of the study’s lead authors, said the tractor beam demonstrated how sound waves could not only be used as a physical force, but could also be controlled and manipulated.

“What we’ve got is a fully working tractor beam,” he said. “We can grab objects, we can twist them, we can rotate them, we can move them. Previously people knew that these forces were present, but it’s another thing to harness them in a stable way.”

The frequency of the sound waves used in the tractor beam was set at 40KHz – audible to bats, but too high for the human ear to detect. Although levitating larger and heavier objects should be possible using lower frequencies, the downside is that the sound of the beam’s operation would become much louder.

“It’s hard to get across just how weird it is to see things levitating in space, when you can’t see or hear anything,” Professor Drinkwater added. “One minute it didn’t work, and the experiments were the most disappointing you could ever imagine, with little things firing off in the wrong direction – and then suddenly there they were, levitating before your eyes.”

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