A Sustainable-by-Design Wearable Sweat Sensor 7 via Compostable Microfluidics and Laser-Induced Graphene Electrodes for Real-Time Monitoring of Physical Exercise

Abstract The growing demand for non-invasive, real-time health monitoring has accelerated the development of wearable sweat sensors. However, most existing platforms rely on resource-intensive, non-recyclable materials and fabrication processes that impose a significant environmental burden. Here, we present a fully biodegradable, sustainable-by-design wearable sweat sensor that integrates environmentally conscious material selection, scalable fabrication processes, and robust on-body performance, while quantitatively evaluating sustainability through a dual-level life cycle assessment (LCA). The sensor features laser-induced graphene (LIG) electrodes directly engraved onto biodegradable chitosan/paper substrates and a compostable microfluidic platform that passively transports sweat across impedimetric total ionic strength and sweat-rate sensors. In vitro characterization demonstrated ionic strength monitoring across 1–200 mM with a sensitivity of 70 μS/log(mM), and sweat-rate sensing over 0.5–5 μL min–1. On-body exercise measurements demonstrated continuous sweat-rate monitoring, while ionic strength was tracked off-body using collected sweat samples. A dual-level LCA at the whole-device and electrode levels showed consistently reduced environmental impacts compared with conventional PDMS- and metal-based sensor designs across EF 3.1 impact categories. By embedding sustainability at the design stage, this work establishes a pathway toward wearable biosensors with substantially reduced environmental footprints while maintaining functionality.