Researchers have invented a new sort of material with a built-in superpower: it can bend, shape and focus sound waves that pass through it, opening up new possibilities for medical imaging, personal audio and other acoustic devices. The precisely engineered surface is a metamaterial, a new class of materials that can sometimes seem to do the impossible, like power a real invisibility cloak straight out of science fiction.

The video below demonstrates how a team of researchers from the University of Sussex and University of Bristol put together a layer of the finely engineered material in the form of small bricks that can introduce a phase change to sound waves passing through them – this is similar to the effect that allows for the control of sound waves as they pass through woodwind instruments.

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By arranging 16 different types of the bricks into a single layer on a grid, the team was able to use sound waves to actually levitate a tiny polystyrene bead. The team was also able to successfully levitate the bead using a different configuration made up of only eight different types of bricks.

The bricks work by slowing down incoming sound to allow for it to be transformed.

"We want to create acoustic devices that manipulate sound with the same ease and flexibility with which LCDs and projectors do to light," explained Prof. Sriram Subramanian, Head of the Interact Lab at the University of Sussex.

Precisely shaped sounds are used in medical imaging and therapy as well as in consumer audio products. The researchers envision new applications like creating audio hotspots or focusing high-intensity ultrasound waves to attack tumors in the body.

"In the future I think there will be many exciting applications of this technology," said Bruce Drinkwater, Professor of Ultrasonics at the University of Bristol. "We are now working on making the metamaterial layers dynamically reconfigurable. This will mean we can make cheap imaging systems which could be used either for medical diagnostics or crack detection."

The team's research was published Monday in the journal Nature Communications, and lays out a cheap and simple way to take advantage of the new metamaterials.

"Our metamaterial bricks can be 3D printed and then assembled together to form any sound field you can imagine," said Dr. Gianluca Memoli at the University of Sussex, who led the study. "You can think of a box of our metamaterial bricks as a do-it-yourself acoustics kit."

Source: University of Bristol

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