World first as scientists use tractor beams to make objects dance

In addition to creating tractor beams like the ones straight out of Star Trek researchers have also been making more "traditional" tractor beams using sound waves, as well as light, for a couple of years now that they've been using to levitate and manipulate objects in fluids and in mid air. First researchers used these tractor beams to manipulate just molecules, then small polystyrene balls, quickly followed by larger ones using refined version of the technology that could one day be scaled up to levitate much bigger objects, and then these tractor beams were combined with 3D printing to create the world’s first 3D printer capable of printing and assembling electronics all in one device. A manufacturing revolution in the making if you excuse the pun. And as if all that wasn’t amazing enough now two of the teams behind some of these breakthroughs, from the University of Bristol in the UK and the Universidad Publica De Navarra in Spain, have done it again and taken tractor beams to the next level.

They have created what they refer to as “Acoustic tweezers,” which involve levitating multiple objects at the same time, but controlling them all individually. This could be used for everything from creating a simple 3D “pixel” display in mid-air to stitching up internal injuries without a surgeon, or robot surgeons like the US military are currently trialling in the battlefield, ever having to physically touch the patient in question. It sounds like the stuff of science fiction but a demonstration by the researchers is pretty darn convincing.

“We have trapped several particles in mid-air using the forces exerted by sound,” said Dr. Asier Marzo from Bristol’s department of mechanical engineering. “What is more important, for the first time the generated acoustic field can manipulate various particles simultaneously and independently from each other. This was possible thanks to a custom-made sound modulator - an array with loads of tiny speakers, 256 in our case. Another key element to achieve this was the use of an optimised algorithm capable of calculating in real time what each speaker should emit in order to generate a field that traps the particles at the target position.”

Threading a needle using a tractor beam - impressive

As can be seen in the video, there are a range of intriguing use cases for the technology, such as assembling particles in a set formation in the air or connecting multiple particles together with threads to carry out actions like stitching. The idea of using levitation to, for instance, control particles inside a patient’s body seems far-fetched, but Marzo points out that it could actually be more straightforward than levitating particles in air. That’s because sound travels better through our bodies, which contain a high proportion of water, than it does through air.

At the moment the team can only move up to 25 particles at the same time. However, Marzo noted that with better hardware, namely, a superior sound modulator, it should be possible to manipulate hundreds of floating particles at once, and this would give them a swarm of levitated particles to play with.

A paper describing the work, titled “Holographic Acoustic Tweezers,” was recently published in the journal PNAS.