Comparative Study of Uniform and Nonuniform Waveguide Bragg Grating Sensors for Measuring Blood Glucose Concentration

Accurate monitoring of blood glucose concentration is highly importantcc for the diagnosis, treatment, and long-term management of diabetes. Although conventional electrochemical blood glucose sensors are widely applied in clinical practice, they generally suffer from inherent limitations such as susceptibility to electromagnetic interference, rapid decay of enzyme activity, and short service life. In this work, three optical waveguide Bragg grating (WBG) blood glucose sensors structures are designed and fabricated on a silicon-on-insulator (SOI) platform: a narrow-in/narrow-out bilateral uniform WBG, a narrow-in/narrow-out bilateral apodized WBG, and a narrow-in/wide-out bilateral uniform WBG. A stable glucose oxidase (GOD) biosensing layer is constructed on the grating surface via silane-coupling covalent immobilization to enable specific recognition and sensing of blood glucose molecules. The experimental results show that the narrow-in/wide-out bilateral uniform WBG sensor achieves the best overall performance, with a measured sensitivity of 169.598 nm/RIU in the concentration range of 0–2.4 mg/mL; the narrow-in/narrow-out bilateral uniform WBG sensor exhibits a measured sensitivity of 110 nm/RIU in the linear range of 0–3 mg/mL; and the narrow-in/narrow-out bilateral apodized WBG sensor reaches a measured sensitivity of 135.860 nm/RIU in the linear range of 0–2.3 mg/mL. All three devices demonstrate good anti-interference capability and stable operation over 8 h, and the fingertip blood test results agree well with those obtained using a commercial blood glucose meter. This work provides a feasible technical scheme and experimental evidence for the design of high-precision wearable photonic devices for continuous blood glucose monitoring.