A Wearable Graphene-Based Sweat Sensor for Real-Time Health Monitoring

This paper presents a novel, flexible, and self-powered graphene-based sweat sensor designed for real-time health monitoring applications. The sensor is fabricated using a straightforward and scalable solution casting and coating method, resulting in a composite membrane composed of three distinct sectors: polyvinylidene fluoride (PVDF)/graphene nanoplatelets (GNPs), pure PVDF, and PVDF/GNP coated on aluminum foil. By leveraging the galvanic coupling between the PVDF/GNP and the PVDF/GNP-coated aluminum, the sensor generates a voltage signal upon contact with sweat, eliminating the need for external power sources or complex reference electrodes. Morphological analysis via field emission scanning electron microscopy confirmed a uniform GNP distribution in the PVDF and robust electrode stability following repeated testing. Electrochemical characterization demonstrated a linear response to NaCl concentrations ranging from 10 mM to 100 mM, with a rapid response time of approximately 4.38 seconds. In a wearable application test conducted on a human subject during physical exercise, the sensor exhibited clear signal variations corresponding to different levels of sweat secretion, reflecting varying running intensities. These results highlight the sensor's potential for continuous, non-invasive hydration monitoring, athletic performance tracking, and seamless integration into low-power wearable systems.