Micro-3D printed Concanavalin A hydrogel based photonic devices for high-sensitivity glucose sensing

Concanavalin A (Con A)-based hydrogels have been widely studied in the field of glucose detection as Con A can selectively bond to glucose molecules. Many sensors have been proposed for detecting glucose using fluorescence or optical methods. However, these sensors suffer from limited sensitivity and fabrication issues. In this study, a label-free optical-fiber long-period grating-based glucose sensor is proposed. Con A-based UV-curable hydrogel was used as the sensing material, which can be rapidly prototyped using the micro-3D printing technique to realize microscale structures. Polymerized hydrogel grating structures patterned onto the fiber surface can periodically modulate the refractive index of the fiber modes affecting the resonant spectrum of the device. The structures swelled upon the addition of a glucose solution, which caused a wavelength shift in the transmission spectrum. The experiments showed that glucose-induced swelling/deswelling was reversible, and the wavelength versus glucose concentration was linear with a response sensitivity of 0.206 nm/mM over a wide range of 0–25 mM with high linearity (R2 = 0.998). The device works well at room temperature and has a short response time. It has significant potential for use in real time continuous glucose monitoring.