A Microwave Sensor Based on Double Complementary Split-Ring Resonator Using Hexagonal Configuration for Sensing Diabetics Glucose Levels

In this article, we propose a compact microwave sensor for monitoring the blood glucose level of diabetes patients. The presented sensor utilizes eight cells of hexagonal-shaped complementary split-ring resonators (CSRRS), lined up in honey-cell configuration, fabricated on Rogers RO3210 substrate, and fed by a 50 Ohm microstrip line. For sensing glucose, the index and middle figures are placed on the sensing area. The biosensor can detect the small changes in the dielectric properties (relative permittivity and dielectric dissipation (Tan Delta)) of the blood's glucose across the signal path. This design's main concept is the strong interaction with electromagnetic fields concentrated in the sensing area. The resonator exhibits higher sensitivity performance than the single counterpart demonstrated by simulations in a 3D fullwave EM simulator CST. Along with theoretical estimations, the sensor is validated experimentally using a convenient setup of a vector network analyzer (VNA) that operated in measuring the transmission coefficient S21 and the phase. The sensor showed a shift in the resonant frequency by around 3 MHz/(mg/dL) of blood glucose concentration, which is significantly better sensitivity compared to previous studies. This sensor concept is a promising candidate for wearable non-invasive blood glucose monitoring devices.