一、导读

近年来，超材料在太赫兹吸波与屏蔽等应用方面展现出巨大的潜力，而随着太赫兹通信、安检成像、智能传感等应用场景的不断拓展，电磁环境愈发复杂多变，这对太赫兹吸波器件的动态可调谐性能提出了更高、更迫切的实际需求。但通过依赖结构重构或材料性质改性的方式实现性能调控的方法，往往会对超材料结构造成不可逆的损伤且对材料的相关性质要求较高，导致大幅降低了器件的使用寿命与可重复性。

近日，福建省太赫兹功能器件与智能传感重点实验室在国际知名光学期刊《Advanced Optical Materials》（中科院2区，IF:7.2）发表了题为“Fatigue-Free Mechanically Tunable Terahertz Metamaterial Absorber with High Modulation Capability Based on PVDF-MoS₂ Piezoelectric Films”的论文。本文创新性地提出了利用压电调谐策略构建吸波器来解决上述问题。通过模拟及实验验证发现，在非接触式的机械刺激下，实现了对高Q值完美吸收峰的精准多级调控。这项研究展示了压电调控策略在搭载不同谐振器和介电层时太赫兹超材料吸波器的电磁响应特征，为可调谐太赫兹超材料吸波器的设计提供了一种新的方法。得益于基于压电的调谐策略，该太赫兹超材料吸波器能实现非接触式的机械调谐，有效地避免了疲劳损伤并提高了器件的耐久性。重点实验室孙福伟副教授与2023级硕士研究生郭聪同学为论文的共同第一作者，重点实验室主任钟舜聪教授为论文的通讯作者。

二、内容简介

本研究基于PVDF-MoS₂纳米复合薄膜的压电效应，结合Drude模型提出了一种夹层结构的机械可调太赫兹超材料吸波器（PM-TMA），通过由压电效应所产生的载流子来调谐PM-TMA的谐振频率。

Figure 1. Mechanically tunable terahertz metamaterial absorber (PM-TMA) based on piezoelectric effect of PVDF-MoS₂ composite films. (a) Schematic diagram of the modulation of piezoelectric effect and charge transfer mechanism under mechanical stimulation and MoS₂ doping. (b) Schematic diagram of the operation mechanism of PM-TMA. (c) Carrier concentration variation principle for the top gold resonator of PM-TMA.

利用CST电磁仿真平台，本文结合该结构的类电感物理模型建立了超材料结构的机械刺激仿真模型，通过参数化调节复阻抗边界进而等效实际机械刺激频率。仿真结果表明，随着机械刺激频率的增加，其吸收峰发生规律性极强的红移。

Figure 2. Unit cell structure and simulated terahertz absorption spectrum of PM-TMA. (a) Schematic of the unit cell structure of PM-TMA with micro-square resonator (dielectric layer without MoS₂ doping). (b) Schematic of the cell structure of PM-TMA with micro-cross resonator dielectric layer with (MoS₂ doping concentration of 2 wt%). (c) Terahertz absorption spectra of PM-TMA (micro-square resonator) with undoped and 2 wt% MoS₂-doped dielectric layers under different mechanical stimulation frequencies. (d) Terahertz absorption spectra of PM-TMA (micro-cross resonator) with undoped and 2 wt% MoS₂-doped dielectric layers under different mechanical stimulation frequencies.

利用固溶铸造技术、电子束蒸镀、化学刻蚀及光刻等多种手段，本文可以实现对所设计超材料结构的加工和制备。

Figure 3. Fabrication and morphological characterization of the PM-TMA. (a) Schematic diagram of the fabrication process for the PM-TMA. (b,c) Schematic of the array and unit cell of PM-TMA with a pure PVDF film dielectric layer. (d,e) Schematic of array and unit cell of PM-TMA with PVDF-MoS₂ composite film (2 wt%) as dielectric layer. (f) Optical photograph of the fabricated PM-TMA with a pure PVDF film as the dielectric layer. (g,h) SEM images of the gold micro-square resonators. (i) Optical photograph of the fabricated PM-TMA with a PVDF-MoS₂ composite film (2 wt%) as the dielectric layer. (j,k) SEM images of the gold micro-cross resonators.

通过实验测量证实，在不同机械刺激频率下。PM-TMA的吸收峰同样发生了规律性的红移，并且吸收峰始终保持超过95%的高吸收率，验证了该策略的可行性。

Figure 4. Terahertz absorption performance of PM-TMA with different resonator geometries and doping concentrations under mechanical stimulation frequencies from 0 to 4 Hz. a) Absorption spectra of the Cross-0%. b) Magnified view of the dominant absorption peak from (a). c) FWHM and Q-factor of the absorption peak for the Cross-0% as a function of mechanical stimulation frequency. d) Absorption spectra of the Cross-2%. e) Magnified view of the dominant absorption peak from (d). f) FWHM and Q-factor of the absorption peak for the Cross-2% device as a function of mechanical stimulation frequency. g) Absorption spectra of the Square-0%. h) Magnified view of the dominant absorption peak from (g). i) FWHM and Q-factor of the absorption peak for the Square-0%. j) Absorption spectra of the Square-0%. k) Magnified view of the dominant absorption peak from (j). l) FWHM and Q-factor of the absorption peak for the Square-0%.

三、总结

本研究基于压电响应对谐振器载流子浓度的影响设计了一种近乎无疲劳损伤的调控策略，通过机械刺激和MoS₂掺杂的双重协同调控实现了对吸收性能的多级调控。结合物理模型提出了机械刺激仿真模型，引入复阻抗边界条件，精准计算出不同机械刺激频率下的吸收特性。机理分析表明，MoS₂掺杂可诱导PVDF的α相转β相，增强压电响应与介电性能，结合机械刺激对偶极子取向的调控，实现表面电荷密度的多级精准调节，为吸收峰的调谐提供核心驱动力。实验测量表征了在不同机械刺激频率下的PM-TMA的吸收性能，其吸收红移规律和仿真保持高度一致，并且吸收峰始终保持大于95%的高吸收率和高品质因子。该研究提出的压电基调控策略为动态太赫兹器件提供了高效、普适且可持续的解决方案，在太赫兹屏蔽与吸收等领域展现出重要的应用前景。

原文链接

https://doi.org/10.1002/adom.202501996