High-Sensitivity Microwave Resonator Sensor for Aqueous Glucose Detection Using Field-Concentrating Elements

In this study, we present a highly sensitive microwave sensor for determining the concentration of aqueous glucose solutions in the microwave regime. The proposed sensor is based on a single split-ring resonator (SRR) printed on a Rogers RO3003 substrate and operates at 2.9 GHz. The sensitivity of this sensor is enhanced by using a narrow gap of approximately 100 μm, which increases the capacitance of the SRR and, more importantly, produces a localized field enhancement within the gap region. Moreover, the proposed design operates with only 2 μL of sample, a notable improvement over sensors that typically require larger liquid volumes. Both the simulation and measurement results showed a clear linear shift in the resonance frequency over a concentration range of 0-400 mg/dL, with the ability to detect minimal concentration variations as small as 50 mg/dL. These results confirm the effectiveness of the sensor for noninvasive glucose detection and represent a significant advancement in the field of microwave sensing.