Acoustic metamaterials are specially designed materials with carefully engineered structures that control how sound or elastic waves move through them. While researchers have explored these materials through computer models and theoretical studies, creating physical versions has so far been limited to large-scale structures and low-frequency applications.
“The multifunctionality of metamaterials — being simultaneously lightweight and strong while having tunable acoustic properties — make them great candidates for use in extreme-condition engineering applications,” explains Carlos Portela, the Robert N. Noyce Career Development Chair and assistant professor of mechanical engineering at MIT. “But challenges in miniaturizing and characterizing acoustic metamaterials at high frequencies have hindered progress towards realizing advanced materials that have ultrasonic-wave control capabilities.”
Portela, along with Rachel Sun, Jet Lem, and Yun Kai from MIT’s Department of Mechanical Engineering, and Washington DeLima from the U.S. Department of Energy’s Kansas City National Security Campus, recently developed a new design framework for controlling ultrasound waves in microscopic acoustic metamaterials. Their findings, detailed in the paper “Tailored Ultrasound Propagation in Microscale Metamaterials via Inertia Design,” were published in the journal Science Advances.
“Our work proposes a design framework based on precisely positioning microscale spheres to tune how ultrasound waves travel through 3D microscale metamaterials,” says Portela. “Specifically, we investigate how placing microscopic spherical masses within a metamaterial lattice affects how fast ultrasound waves travel throughout, ultimately leading to wave guiding or focusing responses.”
To read more, click here.