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

该学院早期职业发展计划（Career）奖将支持基础研究，以理解和利用具有时变材料和非互反结构特性的弹性超材料。超材料是人工组装的材料——被设计成具有自然不具备的机械性能的结构。这项研究旨在开发一种新型的超材料，这种材料可以打破入射动载荷的传输对称性，从而迫使机械激励沿着同一通道以不同的相反方向传播。非互易结构的研究使机械系统的实现类似于电子元件，如整流器、开关和逻辑元件，几十年来一直逃避机械领域。这种超材料提供的新功能将推动发动机支架、涡轮叶片以及其他航空航天和民用基础设施在隔振和抑制方面的新应用。预计反射免疫超材料还将对医学成像和光声断层扫描产生持久影响，在这些领域，反射产生的有害伪影可以得到补救。一个综合的研究教育计划将利用超材料作为几个教育和扩大参与努力的总体主题。通过与布法罗男孩女孩俱乐部的合作，开发的教育工具将满足各个层次的学生，从小学到有抱负的本科生，通过与路易斯斯托克斯少数民族参与联盟（LSAMP）和纽约州立大学科学与技术计划（CSTEP）的合作。研究成果将在一系列共振和振动概念的教育演示中达到高潮，以年轻工程师为对象。利用时间周期材料来打破弹性互易的概念在实用性和物理实现方面面临着一些挑战。该奖项旨在通过利用非轴对称截面中弹性特性的固有几何依赖性，同时脱离硬连线和分流配置，研究非互易超材料的实际实现可行途径。该项目将推导出可调弹性整流器的力学，该整流器仅通过依赖于旋转谐振器阵列几何方向之间的规定相移的单向带隙在一个方向上传输能量，以诱导时空刚度剖面。通过开发2D/3D结构中非互易波色散力学的框架，波传输的指向性将被表征并转化为前所未有的材料功能，包括定向激励滤波，二极管效应，以及将响应限制在给定结构的规定区域的能力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.