Comparative study of Complementary Split Ring Resonator (CSRR) designs for non-invasive blood glucose monitoring using microwave sensors

This paper presents a comparative analysis of a transmission-based microwave sensors for non-invasive glucose monitoring for diabetes management. Three distinct Complementary Split Ring Resonator (CSRR) geometries – square, hexagonal, and circular – are investigated to evaluate how unit cell shape influences key sensing metrics, including sensitivity, quality factor, and resonance. All configurations are implemented on a Rogers RT/Duroid 3003 substrate and incorporate three concentric CSRRs to enhance electric field confinement. Glucose detection is initially validated using aqueous glucose solutions with concentrations ranging from 0 to 400 mg/dL, to model the electromagnetic response of human blood. The results show that the proposed sensor achieves maximum sensitivities of 9.529 MHz/(mg/dL), 0.4077°/(mg/dL), and 0.0098 dB/(mg/dL) in the frequency, phase, and magnitude domains, respectively. This work not only demonstrates the effectiveness of the transmission-based meta-surface approach but also provides new insights into the geometry-driven optimization of resonant sensors for future integration into painless, non-invasive glucose-monitoring systems.