These quantal metamaterial bricks are combined together to form a new super-material that can manipulate sound. Photo: Interact Lab, University of Sussex, copyright © 2017.A super-material that bends, shapes and focuses sound waves as they pass through it has been invented by British scientists. This creation pushes the boundaries of metamaterials – a new class of finely-engineered surfaces that perform nature-defying tasks.
Metamaterials have already shown remarkable results with light manipulation, allowing scientists to create a real-life version of Harry Potter's invisibility cloak, for example. But a research team from the universities of Sussex and Bristol in the UK has now shown that metamaterials can also work with sound waves, potentially transforming 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. Reported in a paper in Nature Communications, this new research offers a simple and cheap way of creating these shaped sound waves using acoustic metamaterials.
The collaborative research team assembled its metamaterial layer out of lots of small bricks that each coil up space. These 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 find use in many applications. 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 tumors deep within the body. For this application, a metamaterial layer could be tailor-made to fit the body of a patient and tuned to focus the ultrasound waves where they are needed most. In both cases, the layers could be fitted to existing loudspeaker technology, and be made rapidly and cheaply.
"Our metamaterial bricks can be 3D printed and then assembled together to form any sound field you can imagine," said 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."
Sriram Subramanian, head of the Interact Lab at the University of Sussex, added: "We want to create acoustic devices that manipulate sound with the same ease and flexibility with which LCDs and projectors do to light. Our research opens the door to new acoustic devices combining diffraction, scattering and refraction, and enables the future development of fully digital spatial sound modulators, which can be controlled in real time with minimal resources."
"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."
This story is adapted from material from the University of Sussex, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.