Elastic Metasurfaces for Full Wavefront Control and Low-Frequency Energy Harvesting
Elastic Metasurfaces for Full Wavefront Control and Low-Frequency Energy Harvesting
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DOI：
10.1115/1.4050275
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发表时间：
2021-12
期刊：
影响因子：
--
通讯作者：
Zhen Lin;S. Tol
中科院分区：
文献类型：
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作者：
Zhen Lin;S. Tol
在过去的几十年里，通过人工构造的超材料、声子晶体和超表面来控制和操纵弹性波/声波得到了越来越多的研究兴趣。与其他表面不同的是，亚表面是主介质中的单层，具有亚波长尺度的图案阵列，在波传播路径中引入突然的相移。在这项研究中，提出了一种由细长梁谐振器阵列组成的弹性亚表面来控制低频弯曲波的弹性波前。基于斯内尔定律的位相梯度是通过调整连接两个弹性介质的细梁谐振器的厚度来实现的。通过解析和数值模型，设计并验证了位相调制亚表面可以实现偏转、非傍轴传播和聚焦三种动态波功能。文中还给出了一个斜入射波的例子，说明了所提出的多方向入射波能聚焦设计的通用性。实验测得的聚焦变形表面在设计焦点处有近三倍的波放大，验证了设计和理论模型的正确性。此外，利用聚焦准表面进行低频能量采集，与没有准表面的纯板上的基准采集器相比，压电采集器的采集功率输出提高了近9倍。
Controlling and manipulating elastic/acoustic waves via artificially structured metamaterials, phononic crystals, and metasurfaces have gained an increasing research interest in the last decades. Unlike others, a metasurface is a single layer in the host medium with an array of subwavelength-scaled patterns introducing an abrupt phase shift in the wave propagation path. In this study, an elastic metasurface composed of an array of slender beam resonators is proposed to control the elastic wavefront of low-frequency flexural waves. The phase gradient based on Snell’s law is achieved by tailoring the thickness of thin beam resonators connecting two elastic host media. Through analytical and numerical models, the phase-modulated metasurfaces are designed and verified to accomplish three dynamic wave functions, namely, deflection, non-paraxial propagation, and focusing. An oblique incident wave is also demonstrated to show the versatility of the proposed design for focusing of wave energy incident from multiple directions. Experimentally measured focusing metasurface has nearly three times wave amplification at the designed focal point which validates the design and theoretical models. Furthermore, the focusing metasurface is exploited for low-frequency energy harvesting and the piezoelectric harvester is improved by almost nine times in terms of the harvested power output as compared to the baseline harvester on the pure plate without metasurface.