Bridging Optical Sensing and Wearable Health Monitoring: A Functionalized Plasmonic Nanopillar for Non-Invasive Sweat Glucose Detection

Abstract: Continuous glucose monitoring (CGM) is vital for diabetes care, but current systems rely on invasive implants or electrochemical sensors that often cause discomfort and skin irritation. Non-invasive alternatives remain limited by low sensitivity and poor compatibility with complex sweat environments, highlighting the urgent need for a comfortable and reliable solution. Here, we report the development of a wearable optical sensor watch that integrates surface plasmon resonance (SPR) technology with a functionalized silver-coated silicon nanowire (Ag/SiNW) substrate for real-time, non-invasive glucose monitoring in sweat. The nanostructured sensor is functionalized with 4-mercaptophenylboronic acid (4-MPBA), enabling selective glucose capture and optical signal transduction through both Raman scattering and SPR shift. The dual-mode detection strategy was systematically optimized, and a miniaturized SPR system operating at 638 nm was successfully integrated into a wearable watch format with wireless data transmission to a mobile application. This wearable device demonstrated excellent sensitivity (LOD down to 0.12 mM) and high selectivity in detecting glucose within physiological sweat concentration ranges. Human subject trials confirmed its applicability in real-life scenarios. This study offers a promising non-invasive alternative to traditional CGM and highlights the potential of integrating nanophotonic sensors with wearable platforms for continuous health monitoring and personalized medicine.