Towards Mechanical Resonators With Zero Leakage Using Elastic Metastructures

This grant will support research to generate new knowledge related to mechanical resonators, promoting the frontiers of technology and advancing national prosperity. Examples of mechanical vibrators include communication devices, vibration isolators and energy harvesting devices. Existing resonators suffer from intrinsic limitations due to leakage of energy into the surrounding structure and offer limited or no means to release energy on demand. This research will introduce and investigate a class of artificially engineered structures, known as metastructures, that can achieve zero energy leakage. It will also investigate the possibility of confining and releasing energy by applying a force. These novel mechanical resonantors will open new avenues for elastic wave-based computation and signal processing, with potential applications in robotics and Internet of Things devices. Therefore, results from this research will benefit the U.S. economy and society. Furthermore, the accompanying educational and outreach activities will help broaden participation of underrepresented groups in research and positively impact engineering education. This research will investigate the possibility of achieving mechanical resonators that have zero leakage, are defect-insensitive and can confine and release energy on demand using metastructures. Current designs suffer from the fact that they leak energy into the surrounding structure and are unable to release energy on demand. The research will overcome these limitations by drawing inspiration from two recent advances in wave physics: the demonstration of electromagnetic bound modes in the continuum (BICs) and topologically protected elastic waves that enable defect-insensitive energy transport. It will test the hypothesis that exploiting the symmetry and topology of the dispersion surfaces can lead to topologically protected BICs in elastic media. The research will use a combination of analytical calculations based on the plane wave expansion method, numerical simulations using finite element analyses and experimental measurements on fabricated samples by using laser Doppler vibrometry to measure the displacement field. Metastructures of increasing complexity, i.e., beams, plates, shells and three-dimensional architected solids, will be introduced and investigated. The results of this research are applicable across a wide spectrum of length scales and will translate across disciplines to acoustic, electromagnetic and plasmonic metastructures. 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.