Wearable sensors based on polypyrrole@graphene fibers fabric for real-time monitoring of lactate in sweat.

Wearable electrochemical devices for non-invasive lactate monitoring play a pivotal role in the in situ evaluation of training level and functional status of trainees. However, most conventional devices rely on enzymes and are typically fabricated on a polymer substrate, which can hardly be integrated into breathable fabrics with efficient sweat transport capabilities. In this study, a flexible Janus fabric sensor capable of directional sweat transport was established. The sensing region is composed of polypyrrole@graphene-polyurethane fiber (PPy@GPUF), where the graphene-polyurethane fiber (GPUF) substrate was fabricated via green wet spinning at room temperature. Notably, this design eliminates the need for enzymes as sensing elements. The proposed sensor demonstrates excellent specificity and high electrochemical sensitivity for lactate detection. Specifically, it achieves a linear range of 1-30 mM, with respective sensitivities of 11.873 μA mM-1 cm-2 (0-18 mM) and 5.592 μA mM-1 cm-2 (18-30 mM). This superior performance is attributed to the efficient transfer paths of electrons and electrolytes in the synthetic electrode, and improved utilization rate of the active materials by spontaneous absorption and directional transport of sweat by the fiber fabrics. Furthermore, the as-prepared fabric sensor was integrated into a wearable patch for real-time, non-invasive monitoring of lactate in sweat. Performance tests confirmed that this sensor exhibits comparable accuracy with commercial lactate meters. This study provides valuable insights for advancing the development of non-invasive, real-time sweat monitoring based on wearable devices.