Joint NIR-BIS Based Non-Invasive Glucose Monitoring System

A low cost, high accuracy, joint non-invasive glucose monitoring system is proposed. Multi-wavelengths near- infrared spectroscopy (NIRS) and bio-impedance spectroscopy (BIS) are used, where the final result is obtained by integrating the results of both techniques. The BIS circuit measures the lowest impedance of the skin which is at the resonant frequency and relates it to the glucose level. In order to improve the accuracy for the Bio-impedance sensor, two frequency sweeps are performed: 1) Frequency sweep from 10 kHz to 100 kHz with a step of 10 kHz, and 2) A continuous frequency sweep between the two lowest impedance points with 1 kHz step. For the NIRS technique, three wavelengths are used: 850 nm, 880 nm and 940 nm. Each wavelength is used 3 times on 3 different positions on the forearm to ensure high accuracy. The results are averaged together by the control unit and sent via Bluetooth to the user through a designed mobile application. The system provides a Correlation Coefficient of 0.91805 and a mean error of 3.794 mg/dL. All points were proven to be in the clinically accurate region (Zone A) in the Clarke Grid Analysis. The final design is a wearable custom-made PCB that measures glucose level real- time.