Researchers use sound waves to levitate up to 25 tiny objects at the same time

Researchers have been using sound waves to levitate tiny objects for a while now. But a new project from scientists at the U.K.’s University of Bristol and Spain’s Universidad Publica De Navarra takes things 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 individually. This could be used for everything from creating a simple three-dimensional “pixel” display in mid-air to conceivably stitching up internal injuries without a surgeon 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,” Dr. Asier Marzo, from Bristol’s department of mechanical engineering, told Digital Trends. “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 optimized 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.”

As can be seen in the video at the top of this article, 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 present, 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. 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.