基于液态金属的柔性可重构频率选择表面

Flexible and Reconfigurable Frequency Selective Surface Based on Liquid Metal

传统的频率选择表面(FSS)不仅电磁特性固定、功能单一,而且大都采用硬质材料,难以适应复杂多变的电磁环境和实现曲面物体的共形贴附。提出一种基于柔性复合材料的多层级联可重构频率选择表面,分别利用柔性聚合物的可弯曲性实现器件的共形、液态金属的流动性,以实现频率重构。首先,从多层级联互补型结构可实现多频通带的特性出发,设计了一种三层方环形互补结构,包括上层填充液态金属的方环层、中间介质层和与上层结构互补的孔径型金属层。利用微流控技术,通过是否加载液态金属实现单频滤波和双频滤波的切换。其次,利用全波电磁仿真软件及等效电路模型对器件的功能进行仿真,验证了该结构具有良好的极化稳定性和角度稳定性。然后,采用软光刻工艺制作了SU-8模具,并浇注聚二甲基硅氧烷(PDMS)作为填充液态金属上层结构,用柔性印制电路板(FPCB)工艺在聚酰亚胺(PI)基底上制作了下层互补金属结构,器件整体结构厚度仅为1.537 mm,具有良好的柔性。最后,对研制的可重构频率选择表面进行了组装测试,结果显示,液态金属非填充情况下,在9.6 GHz处产生一个通频带;液态金属填充情况下,在5.8和9.9 GHz处共产生两个通频带。实验测试结果与仿真结果基本一致,利用该柔性频率选择表面实现了单频和双频带通的切换。

Traditional frequency selective surface(FSS)have fixed electromagnetic properties and single functionality,and they are mostly made of rigid materials,making them difficult to adapt to complex and changing electromagnetic environments and achieve conformal attachment on curved surfaces.A flexible composite material-based-reconfigurable FSS with a multi-layer cascade structure was proposed,utilizing the bendability of flexible polymer to achieve conformability of the device and the fluidity of liquid metal to achieve frequency reconfigurability.Firstly,based on the characteristic that the multi-layer cascade complementary structure could realize multi-frequency passbands,a three-layer square annular complementary structure was designed,which consisted of an upper square annular layer filled with liquid metal,an intermediate dielectric layer,and a lower aperture-type metal layer complementary to the upper structure.By using microfluidic technology,the switching between single-frequency filtering and dual-frequency filtering can be achieved by loading or unloading liquid metal.Secondly,full-wave electromagnetic simulation software and equivalent circuit models were used to simulate the functions of the device,demonstrating good polarization stability and angular stability of the structure.Thirdly,SU-8 molds were fabricated by the soft lithography,and polydimethylsiloxane(PDMS)was poured into the molds as the upper layer structure with filling liquid metal.The lower complementary metal structure was fabricated on a polyimide(PI)substrate by flexible printed circuit board(FPCB)technology.The overall structure of the device has a thickness of only 1.537 mm and exhibits good flexibility.Finally,the developed reconfigurable FSS was assembled and tested,revealing a single passband at 9.6 GHz without liquid metal filling and two passbands at 5.8 and 9.9 GHz with liquid metal filling.The experimental test results are in good agreement with the simulation results,realizing the switching between single-frequency and dual-frequency passbands by the flexible FSS.