Acoustic Breakthrough: A New Way to Direct Sound

Just over 10 years ago, researchers produced the first 3D topological insulator — a material that does not conduct electrical current through its bulk, but can channel current along its edges. Now, a team of CUNY physicists has developed a new material with a similar idea, but this time for sound rather than electricity.

Their results, which appear in Nature Materials, could help improve technologies that use sound waves, such as sonar.

The labs of Andrea Alù, director of the Photonics Initiative at The Graduate Center’s Advanced Science Research Center, and Professor Alexander Khanikaev, a professor in the electrical engineering and physics departments at The City College of New York who is also affiliated with the ASRC, came together to create a material that guides sound along its edges, and localizes sound at its corners. The material does not let sound travel through its middle, and it maintains these unique properties even in the face of fabrication defects.

 “We’re showing, fundamentally, that it is possible to enable new forms of sound transport that are much more robust than what we are used to,” Alù said.

3D-printed trimers
3D-printed trimers

The triangular, 3D-printed material’s acoustic features are derived from a field of study called topology. In mathematics, topology explores properties that do not change when you deform an object, as long as you don’t cause a break or tear. Scientists have recently brought these mathematical ideas into the physical realm, making it possible for real materials to have similarly unyielding properties.

This hardiness could make acoustic technologies, including ultrasound and underwater imaging, more resistant to imperfection and signal noise.

“We have been recently working on even more complex 3D metamaterial designs based on these techniques, which will further expand the properties of acoustic materials and expand capabilities of acoustic devices,” Khanikaev said.

Ph.D. students Xiang Ni and Matthew Weiner were also authors on the study.

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Andrea Alù (Einstein Professor, Physics) | Profile 1 | Profile 2
Alexander B. Khanikaev (Associate Professor, Electrical Engineering) | Profile 1 | Profile 2