Detection of Sodium Chloride and Glucose Concentration in Aqueous Solutions Using Resonator Based on Interdigital Capacitor

This study used a resonator based on an interdigital capacitor (IDC) to detect variations in the S-parameter with the concentrations of sodium chloride and glucose solutions in the microwave frequency range. The resonance frequency was selected by considering factors such as the resonator size and variations in the dielectric constant of water with temperature. A fluidic channel was positioned at the location with the strongest electric field distribution in the resonator, and simulations and measurements were conducted. The concentration of the glucose solution was set from 0~400 mg/dL to reflect the blood glucose levels in the human body. In the case of the sodium chloride solution, the concentrations of sodium and chloride ions in the human body were considered and were set from 500~900 mg/dL. The measurement results showed that the reflection coefficients of sodium chloride and glucose solutions varied by ~4.44 and 0.9 dB, respectively, confirming that the proposed resonator sensitively detects variations in solution concentrations.