Frequency‐Coded Passive Multifunctional Elastic Metasurfaces

Abstract

As an emerging material, metasurfaces open the door to a wide range of applications based on ultrasonic and elastic waves. However, most of the existing elastic metasurfaces have a fixed functionality and operate at a fixed frequency, which make them difficult to adapt to changing working requirements and/or environments. Although several recently proposed reconfigurable designs can relax this limitation, they either need laborious tuning or complex active control systems. In this work, by encoding multiple functionalities onto a single metasurface through operation frequencies, passive metasurfaces with switchable multifunctionalities are proposed and realized. Different wave manipulation functions of a single metasurface can be switched from one to another simply by changing the operation frequency. The design of these metasurfaces is realized using a systematic design approach based on topology optimization. Frequency-coded multiple elastic wave manipulation functions, including wave beam steering and focusing, are numerically and experimentally demonstrated. Good agreement between the numerical simulations and experimental measurements is achieved. The proposed design strategy significantly enhances the functionalities and adaptivity of metasurfaces, moving them closer towards real-world applications.

Metamaterials and Metasurfaces: A Review from the Perspectives of Materials, Mechanisms and Advanced Metadevices

“…Active metamaterial that is tuning its electromagnetic properties can be achieved by processing the size, shape and the composition, and by modifying the near-field interaction between individual meta-atoms or metamolecule resonators [ 101 ]. Reconfigurable and tunable metadevices can be classified as (i) electrically tunable metasurfaces (ETMs) [ 4 ], (ii) mechanically switchable metasurfaces (MSMs) [ 102 ], (iii) optically tunable metasurfaces (OTMs) [ 103 ], (iv) thermally tunable surfaces (TTMs) [ 97 , 103 ] and finally, (v) chemically tunable/reconfigurable metasurfaces [ 104 , 105 ], as presented in Figure 9 .…”

Reconfigurable flexural waves manipulation by broadband elastic metasurface

“…The phase shift of elastic waves can be tuned mainly by changing their velocities through a resonant or non-resonant way. Usually, the former can be achieved by introducing resonant units such as pillars or columns [13][14][15][16][17][18][19][20], zigzag units [21][22][23][24][25], and blocks [26][27][28][29][30] into the structure. The latter, however, can be realized by grooves [31], notched units [32], strips [33,34] or composite strips [35,36], etc.…”

“…[28], a double-unit elastic metasurface composed of a phase modulator and an impedance matcher was proposed to realize full-wave tailoring of longitudinal wave [29]. Topology optimization was utilized to obtain resonant units for the deflection and focus of a plate longitudinal wave [30].…”

Transmission Reflection Integrated Programmable Metasurface for Real‐Time Beam Control and High Efficiency Transmission Polarization Conversion

“…For instance, different functions within multibands are achieved by changing the intrinsic properties of the incident EM wave such as polarization, [19] helicity, [20] or frequency, [21] Because of high reliability, low cost, and simplicity of structural configuration, passive multifunctional metasurfaces have attracted extensive investigation interest. [22][23][24][25][26][27] However, they still have deficiencies such as passive work patterns and static function, which cannot meet the growing demand of reconfigurable devices.…”