A simple yet multifunctional sensing platform inspired by healing-assembly hydrogels serving motion and sweat monitoring

Health monitoring devices have emerged with the growing concern for personalized health monitoring. One of the non-negligible trends of health monitoring devices is to integrate physical sensing and biochemical sensing into one device to achieve multiplexed analysis. This work reported a multifunctional platform consisting of a strain sensing unit and a sweat detection unit, which was built based on hydrogels functionalized with reduced graphene oxide (rGO) and luminol (Lum). Hydrogel functionalized with rGO (rGO@hydrogel) served as the strain sensing unit for perceiving motion behaviors during exercise, followed by spontaneous healing with Lum modified hydrogel (Lum@hydrogel) to form a closed bipolar electrode (c-BPE). Sweat detection was fulfilled by c-BPE, wherein luminol at the anode generated electrochemiluminescence (ECL) signals in response to the analytes at the cathode. On-body assays showed that the fabricated platform rapidly responded to motion behaviors and also performed well in the analysis of several physiological indicators (urea, lactic acid, and chloride ion) in sweat. The fabricated device enabled in-situ sweat collection by means of 3D porous structure of hydrogel, and also circumvented the issues arising from the compositional complexity of sweat in virtue of the inherently separated anodic and cathodic compartments of c-BPEs. It was proved to be low-cost, convenient and bodyfriendly, thanks to intrinsically flexible and self-healing hydrogels, bridging the gap between the ideal of versatile systems and the reality of cumbersome design. This work is expected to provide useful guidance and insights in expanding daily health care.