Wearable Biosensing of Caffeine via Microfluidic-Integrated Agarose Hydrogels for Personalized Metabolic Monitoring

Wearable sweat sensors have gained tremendous attention on account of performing noninvasive and real-time monitoring of sweat analytes, providing a view of the human physiological state at the molecular level. Caffeine is a methylxanthine alkaloid, and its levels in the human body are directly related to health. Developing a wearable device for dynamically assessing caffeine levels in sweat could facilitate real-time personalized health monitoring. In this study, we introduced a wearable agarose hydrogel based sensor integrated with a microfluidic module for the real-time tracking of caffeine in sweat. The hydrogel based caffeine sensor demonstrated highly sensitive detection of caffeine over a broad range from 4 nM to 18.2 μM and showed a low detection limit of 1 nM. On-body tests confirmed the ability of the hydrogel based sensor to detect sweat caffeine levels continuously and dynamically, which offers a novel strategy for the instantaneous monitoring of sweat biomarkers, making it promising for subsequent daily personalized health management.