CAREER: Non-Local Metamaterials and Metasurfaces for Next Generation Non-Reciprocal Acoustic Devices

This Faculty Early Career Development (CAREER) award will fund research that enables acoustic metamaterials and metasurfaces leveraging non-local unit cell interactions. The non-reciprocal acoustic devices will enable independent modification of transmitted and reflected waves, with transformative impact in applications such as biomedical ultrasound, ultrasonic imaging, underwater communication, and the design of aerospace structures, thereby promoting the progress of science. This research will establish a novel class of metamaterials and metasurfaces whose constituent unit cells can interact non-locally and implement arbitrary non-reciprocal (i.e., asymmetric) wave behaviors, fundamentally expanding the possibilities for acoustic wave manipulation. These non-local systems achieve non-reciprocal acoustic behaviors in a simpler way than existing methods, shifting the paradigm for how acoustic waves can be used to solve engineering problems. The educational component of the project will focus on the creative manipulation of sound, introducing concepts of noise and vibration control from the research component of the project, to increase student participation in STEM and acoustics. In collaboration with the Stevens Teaching and Learning Center, the project will initiate an “Acoustics Day” outreach program hosted in the Stevens anechoic chamber. The program will host middle school students from the local area, emphasizing the connections between sound, urban environments, and different engineering careers. This research aims to enable complete control over acoustic waves by investigating non-local acoustic metamaterials and metasurfaces that break acoustic reciprocity. Unlike local, phase-delayed interactions, non-local interactions can have a directional bias, resulting in broken symmetry and non-reciprocal behavior. Conventional materials do not interact non-locally; instead, this project will build upon research in acoustic metamaterials and metasurfaces, which use a small-scale repeated unit cell to manipulate wave propagation, reflection, and transmission. This project will shift the paradigm of conventional acoustic metamaterials and metasurfaces through a comprehensive theoretical and experimental investigation of non-local acoustic metamaterials and metasurfaces, leveraging piezoelectric transducers that interact non-locally via electrical circuitry. The results of this research will unlock new types of acoustic phenomena, provide fundamental insight into non-Hermitian physics, and initiate new research directions in acoustic circuits that freely manipulate acoustic waves. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.