Design of a microwave sensor for non-invasive monitoring of blood glucose level with high sensitivity using electromagnetic properties

This paper introduces a novel, portable microwave sensor for rapid, non-invasive blood glucose monitoring. The design features an octagonal array of complementary split ring resonators (CSRRs) on a dielectric substrate, operating safely in the industrial, scientific, and medical (ISM) frequency band. Its key innovation, an engineered 180^∘ phase difference between adjacent unit cells, generates a highly concentrated electromagnetic (EM) field at the sample interface. This focused interaction significantly enhances measurement sensitivity and overall detection capability. The sensor accurately detects glucose concentrations across the 50-500 mg/dL clinical range, demonstrating a remarkable sensitivity of 2.3 MHz/(mg/dL) in laboratory settings and 1.78 MHz/(mg/dL) in realistic scenarios, surpassing existing microwave sensors. This superior performance is attributed to the CSRR architecture, which maximizes the sample's EM field interaction, enabling the precise quantification of subtle dielectric changes corresponding to varying glucose levels. Laboratory verification using a vector network analyzer (VNA) confirmed significant frequency shifts with glucose samples from 80 to 340 mg/dL. Beyond its high sensitivity, the sensor's compact size, simple fabrication, affordability, and non-ionizing operation establish it as a promising candidate for developing practical, real-time, non-invasive glucose monitoring systems to advance diabetes management.