Reconfigurable Metasurfaces for Controlling Elastic Wavefront

弹性超材料和声子晶体是一种人工构造的复合材料，可以操纵和控制弹性波。虽然它们在许多超声应用中都被证明是有用的，但它们的波功能仅限于低频区域。由于大量能量是由在机械或民用系统中传播的低频波携带的，因此开发紧凑的结构以实现对低频弹性波的宽带控制而不需要进一步的结构修改是至关重要的。这笔赠款将支持研究如何在较小的占地面积内有效地定制低频弹性波，并通过可重新配置的超表面概念推进最先进的技术。可重构的亚表面将使宽带波聚焦和高功率能量收集器将低频振动转换为可用电能，克服无线传感器网络与能源相关的限制。该奖项支持基础研究和在机械、民用和航空航天系统中的应用，以实现紧凑且易于集成到现有结构中的下一代波器件。因此，这项研究的结果将使美国经济和更广泛的社会受益。综合教育计划还将有助于扩大未被充分代表的群体在研究中的参与，并为密歇根大学科学与工程夏令营的女孩们提供K-12外展模块。该项目的研究目标是通过紧凑的可重新配置的亚表面来操纵和控制低频弹性波(~数百赫兹)，这种亚表面可以适应环境条件，以实现更大的动态波功能，如在宽带频率范围内操纵和聚焦。这项研究将引入主动弹性亚曲面和非线性弹性亚曲面，它们将分别在外部电载荷和机械载荷作用下进行调谐。其关键思想是利用弹性/电弹性单胞的线性/非线性动力学，并利用现有结构在广泛的频率范围内定制弹性波前。将建立一个理论框架，以实现所需的相位梯度，以实现所需的动态波前形状。在通过调整变形表面的折射特性来控制弹性波传播的同时，波的反射将被最小化，以确保通过有源/非线性变形表面层的最大波传输。这项研究将创建下一代亚表面，以调制机械、民用和航空航天系统中高冲击应用中的低频波前。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Elastic metamaterials and phononic crystals are artificially structured composite materials that can manipulate and control elastic waves. While they are proven to be useful in many ultrasonic applications, their wave functionality is limited to the low frequency regime. Since a significant amount of energy is carried by low frequency waves propagating in mechanical or civil systems, it is crucial to develop compact structures enabling broadband control of low frequency elastic waves without the need for further structural modifications. This grant will support research that will answer how to effectively tailor low frequency elastic waves within a small footprint and advance the state-of-art via reconfigurable metasurface concepts. The reconfigurable metasurfaces will enable broadband wave focusing and high-power energy harvesters converting low frequency vibrations into usable electricity, overcoming the energy related limitations of the wireless sensor networks. This award supports fundamental research and advances applications in mechanical, civil, and aerospace systems to achieve next-generation wave devices that are compact and easy to integrate within existing structures. Therefore, results from this research will benefit the U.S. economy and broader society. The integrated education program will also help broaden participation of underrepresented groups in research and features a K-12 outreach module for the Girls in Science and Engineering Camp at the U-M.The research goal of this is to manipulate and control low frequency elastic waves (~hundreds of Hz) via compact reconfigurable metasurfaces which can adapt to environmental conditions to achieve greater dynamic wave functionalities such as steering and focusing in a broadband frequency range. This research will introduce active elastic metasurfaces and nonlinear elastic metasurfaces which will be tuned by external electrical and mechanical loads, respectively. The key idea is to leverage the linear/nonlinear dynamics of the elastic/electro-elastic unit cells and tailor elastic wavefronts over a broad range of frequencies using the existing structure. A theoretical framework will be established to implement the required phase gradient for achieving desired dynamic wavefront shapes. While manipulating the elastic wave propagation by tailoring the refraction properties of the metasurface, wave reflections will be minimized to ensure maximum wave transmission through the active/nonlinear metasurface layer. The research will create next-generation metasurfaces to modulate low frequency wavefronts in high impact applications in mechanical, civil, and aerospace systems.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.