Scientists invent sound-shaping super-material

These quantal metamaterial bricks form together to create a new super-material that can manipulate sound. (Interact Lab, University of Sussex, copyright © 2017)

Researchers are forever pushing the boundaries of materials, attempting to develop new ones with properties that defy natural characteristics. A team from the Universities of Sussex and Bristol have done just that by developing a unique super-material that bends, shapes and focuses sound waves that pass through it.

The scientists are touting that this new creation pushes the boundaries of metamaterials in a way unlike any other. Metamaterials are a class of finely-engineered surfaces that perform nature-defying tasks.

Researchers have already developed materials that show remarkable results with light manipulation — even allowing scientists to create a real-life version of Harry Potter’s invisibility cloak, for example.

However, the team has taken this steps further by enable the material to be manipulated using sound waves.

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

This could have significant implications for medical imaging and personal audio. Finely shaped sound fields are used in medical imaging and therapy as well as in a wide range of consumer products such as audio spotlights and ultrasonic haptics.

The research team was able to assemble a metamaterial layer out of small bricks that each coil up space. The space coiling bricks act to slow down the sound meaning that incoming sound waves can be transformed into any required sound field.

The new metamaterial layers could be used in many applications. For example, large versions could be used to direct or focus sound to a particular location and form an audio hotspot. Much smaller versions could be used to focus high intensity ultrasound to destroy tumours deep within the body.

“Our metamaterial bricks can be 3D printed and then assembled together to form any sound field you can imagine,” explains Dr Gianluca Memoli, from the Interact Lab at the University of Sussex who led the study. “We also showed how this can be achieved with only a small number of different bricks. You can think of a box of our metamaterial bricks as a do-it-yourself acoustics kit.

The research is published in Nature Communications and shows a simple and cheap way of creating these shaped sound waves using acoustic metamaterials.
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