Structured Split-Ring Resonator for Sensing Applications: Dielectric-Material Characterization and Label-Free Detection of Biomolecules

The classic split-ring resonator (SRR) is structured in this paper to optimize the frequency-shifting sensitivity of SRR-based RF/microwave sensors. The SRR is designed on the top layer of a substrate and another mirrored SRR is duplicated in the ground plane of the substrate. The two SRRs are electrically connected to each other to realize closed-loop structures inside the substrate, which results in the engineered structured split-ring resonator (SSRR). It is shown that the frequency-variation sensitivity in this approach of RF/microwave sensor is significantly increased by using the proposed SSRR by more than 200% in relation to conventional counterparts. The experimental results confirm a sensitivity enhancement by a ratio of 2.2:1 with regard to a sensor with among the highest sensitivities ever reported for high-permittivity lossy-material characterization. Furthermore, the sensor is experimentally examined in a biomedical scenario to monitor antibody, demonstrating a sensitivity enhancement by a ratio of 5:1 compared to a recent SRR-based sensor counterpart.