CAREER: Metamaterials as Elastic Rectifiers: Exploiting the Non-reciprocal Mechanics of Time-Periodic Structures

Suny At Buffalo, Amherst NY

Investigators

Abstract

This Faculty Early Career Development Program (CAREER) award will support fundamental research to understand and exploit elastic metamaterials with time-varying material and non-reciprocal structural properties. Metamaterials are artificially assembled materials-structures designed to have mechanical properties that are not naturally available. The research aims at developing a novel class of metamaterials which break the transmission symmetry of incident dynamic loads, thereby forcing mechanical excitations to travel differently in opposing directions along the same channel. The study of non-reciprocal structures enables a realization of mechanical systems which are analogous to electronic components, such as rectifiers, switches, and logic elements that have eluded the mechanical domain for decades. New functionalities provided by such metamaterials will propel new applications in vibration isolation and suppression in engine mounts, turbine blades, and other aerospace and civil infrastructures. Reflection-immune metamaterials are also envisioned to have a lasting impact on medical imaging and photoacoustic tomography where detrimental artifacts from reflections can be remedied. An integrated research-education program will leverage metamaterials as an overarching theme for several educational and broadening participation efforts. The developed educational tools will cater to students at all levels from elementary, through a partnership with the Boys and Girls Club of Buffalo, to aspiring undergraduates via partnerships with the Louis Stokes Alliance for Minority Participation (LSAMP) and NY State's Collegiate Science & Technology Program (CSTEP). Research outcomes will culminate in a series of educational demonstrations of resonance and vibrations concepts to young engineers. The notion of exploiting time-periodic materials as means to break elastic reciprocity has faced several challenges pertaining to practicality and physical realization. This CAREER award aims to investigate a feasible path to the practical implementation of non-reciprocal metamaterials by exploiting the inherent geometric-dependence of elastic properties in non-axisymmetric cross-sections, while departing from hard-wired and shunted configurations. The project will derive the mechanics of a tunable elastic rectifier, which transmits energy in one-direction only via unidirectional band gaps relying on a prescribed phase shift between the geometric orientations of an array of rotating resonators, to induce a spatiotemporal stiffness profile. By developing a framework for the non-reciprocal wave dispersion mechanics in 2D/3D structures, the directivity of wave transmission will be characterized and translated into unprecedented material functions, including directional excitation filtering, diode-like effects, and the ability to confine the response to prescribed regions of a given structure. 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.