Electromagnetically Induced Reflectance-Like Honeycomb-Structured Metasurface Sensors With Metal Displacement Detection

We proposed an electromagnetically induced reflectance-like (EIR-like) metasurface that can detect the displacement of metal strips. Two different compound modes of honeycomb structures (HSs) were etched on a dielectric slab (F4B). High reflectance values were achieved, with peaks located at 6.83 and 7.61 GHz, and respective reflection coefficients of 93% and 92%. The measured data and calculated curve of the equivalent circuit model were similar to the simulation results. The two reflectance windows were attributed to the coupling between dark and dark modes, as explained by observations of the electric field and surface current distributions. Furthermore, it manifested that the antiparallel electric dipoles in different metal layers generated interaction to obtain the EIR-like phenomenon. Because of high reflectance, the designed EIR-like metasurface exhibited high sensitivity for metal strip displacement. Furthermore, the geometry parameters of the unit cell had a significant influence on the reflection spectra and sensitivity. The parameter variation does not affect the sensing function in the proposed metasurface sensor, and when the metal strip was moved from the center to the left, the resonance frequency of the first reflection peak exhibited a blueshift. When it was moved to the right, the second reflection peak appeared, which exhibited a variation in reflection amplitude. Therefore, the proposed EIR-like metasurface has potential applications in displacement sensors for structural health monitoring (SHM).