High-Q non-invasive Glucose Sensor using MicrostripLine Main Field and Split Ring Resonator

A high-Q sensor integrating microstrip line (MLIN) main field and split ring resonators is presented for non-invasive glucose sensing. The proposed sensor combines the field-focusing effects of split ring resonators with the enhanced field substrate interaction properties of the MLIN main field, using the reflection coefficient (S11) of an open-ended MLIN with the finger as the substrate and operating at 750 MHz and 1.5 GHz. The permittivity of blood inside the finger depends on the glucose concentration, which in turn affects the S11 of the system. Sensor geometry was optimized using Method-of-Moments simulation before the sensor was fabricated and validated on standard solutions of glucose concentrations between 0 to 126 mg/dL within the physiological range, and a human test subject. In both experiments, a near inverse-linear relationship between the S11 peak magnitude and the glucose concentration was observed, demonstrating the sensitivity of the proposed sensor for detecting changes in blood glucose concentration at physiological conditions.