Madrid, Oct 28 (EFE).– An object can levitate or move without anything touching it using acoustic holograms created by experts from Britain’s Bristol and Sussex universities led by Spaniard Asier Marzo, an article in the journal Nature Communications said.

Marzo told EFE that the study proved that the hologram principle also applies to sound because “ultimately both light and sound are waves.”

Researchers used an array of 64 miniature loudspeakers (driven at 40 Khz with 15Vpp) to create high-pitched and high-intensity sound waves to levitate a spherical bead (of up to 4mm in diameter) made of expanded polystyrene.

“Sound is a mechanical wave, it can exert force on an object,” Marzo said. “You can notice that when you go to a concert and the music is loud, and you feel the vibration in your chest.”

For a particle to levitate, it is necessary to exert force converging from all directions, “trapping it,” and the only way to do so is by creating a tri-dimensional acoustic field wrapping it.

The team produced an acoustic hologram that cannot be seen or heard and whose only visible effect is the force it exerts on particles.

“It is as if the invisible man could grab a particle,” Marzo, who holds a degree in computer engineering, said. “You couldn’t hear or see him, but you know he’s there because you see the particle levitating.”

Marzo, who began working on this project a year ago, noted that a traditional acoustic levitation had already been done at Bristol with two sound devices facing each other to surround the particle, but his challenge was to attain levitation with just one flat device.

“We all know that soundwaves can have a physical effect. But here we have managed to control the sound to a degree never previously achieved,” Bruce Drinkwater, professor of ultrasonics in Bristol’s Department of Mechanical Engineering, said.

“In our device, we manipulate objects in mid-air and seemingly defy gravity. We can individually control dozens of loudspeakers to tell us an optimal solution to generate an acoustic hologram that can manipulate multiple objects in real-time without contact,” Sriram Subramanian, professor of computer science at the University of Sussex and co-founder of Ultrahaptics, said.

The technique can be developed for a wide range of applications, including a sonic production line able to move and assemble delicate objects without physical contact.

Marzo’s goal, however, is to make the current prototype even smaller to cause levitation inside the human body.

“This is possible because sound can travel through water and tissue in the human body,” the researcher said.

The goal would be “to cause levitation in particles inside the body, which may be blood clots, tumors, or kidney stones, to grab them and move them,” Marzo said.

The method could also be used to grab and move capsules containing medications or micro-surgery instruments through live tissues. EFE