Concentration Detection of Sodium Chloride and Glucose Solutions Using an IDC-Based Microwave Sensor With Eliminating Environmental Effects

In this paper, a microwave sensor based on Interdigital Capacitor (IDC) structure using a switching circuit is proposed for the non-invasive detection of sodium chloride (NaCI) and glucose concentrations. Sodium chloride and glucose concentrations were set at 500–900 mg/dL and 0–400 mg/dL, respectively, considering the substances in human blood. The sensor could detect the concentration via a fluidic channel, which in the strongest electric field region of the resonator. A switching circuit was used to eliminate environmental effects, and according to the experimental results, the proposed sensor exhibited an increase in reflection coefficient of 0.41 dB and 1.43 dB for sodium chloride and glucose solutions, respectively. Furthermore, reproducibility was confirmed by conducting measurements ten times for each concentration.