Design, fabrication and characterization of metamaterial absorber for sensing applications

A perfect metamaterial absorber (MMA) is suggested, analyzed, and fabricated for sensing applications. The reported design enhances the absorption at the resonance frequency by suppressing the reflectance and transmittance concurrently. A back metallic reflector is used to eliminate the transmission through the proposed design, while the reflection is minimized by the impedance matching between the proposed MMA and that of free space. Moreover, simultaneous electric and magnetic resonances are supported with nearly perfect absorption at the resonance frequency. The reported design has simulated absorptivity of 99.33% at 28.146 GHz which falls within the mm-Wave spectrum, a band of critical importance for next-generation 5G communication and high-frequency biosensing. Further, the fabricated absorber achieves a measured absorption of 96.5% at 28.12 GHz with a narrow absorption bandwidth. In addition, the resonance frequency strongly depends on the surrounding refractive index, which makes the absorber an effective platform for RI sensing. The simulated sensitivity of the proposed RI sensor is 9520 GHz/RIU when the analyte refractive index changes from 1.3 to 1.35 with simulated Q-factor and FoM of 817 and 427 RIU^-1, respectively. A prototype is fabricated and characterized with excellent agreement with the simulation results. High measured sensitivity of 14.44 GHz/RIU is obtained (the analyte layer changed from air to water) from the prototype characterization with a Q-factor of 513 and FoM of 427 RIU^-1. The potential of using the proposed metamaterial absorber as a biosensor for cancer cell detection is also demonstrated for Breast cell, Cervical cell, Jurkat cell, MCF-7 cell, and PC12 cell with an average simulated sensitivity of 9.023 GHz/RIU. Therefore, the reported perfect metamaterial absorber has good potential in sensing applications.