A novel compact highly sensitive non-invasive microwave antenna sensor for blood glucose monitoring

In the present work, a novel compact and highly sensitive microwave antenna sensor at 2.45 GHz is proposed for evaluating glucose concentration in blood. The antenna is printed on an FR-4 substrate of compact dimensions 35 mm x 13.5 mm x 1.6 mm. A human finger phantom model is constructed in the EM simulation high frequency structure simulator environment consisting of skin, blood, fat, and bone layers. In the study, finger models with various shapes like rectangular, cylindrical, and ellipsoid are considered, and the results are compared. The glucose concentration is changed from 0 to 500 mg/dL, and the corresponding shift is evaluated by keeping the finger phantom at different locations near the antenna. The frequency shifts obtained in the designed experiment are used to evaluate glucose concentration in blood samples. In this work, a minimum and a maximum frequency shift of around 1.25 and 5 MHz, respectively, are observed when the finger phantom is placed at the top of the radiating element. Simulated antenna results are found to be in good agreement with the measured results. The developed method is validated with a two-antenna model by calculating time delay and isolation for different glucose concentrations. An experiment of placing a real human finger around a fabricated antenna presents good correspondence with the simulation results.