Wearable sensors using ionic conductive gels for sweat analysis and sports monitoring system development

To enhance the life safety of firefighters in high-temperature and high-humidity environments, flexible multimodal wearable sensors that can withstand harsh conditions and capture rich physiological information are urgently needed. Here, we report a non-invasive, firefighter-oriented sweat-sensing patch based on a hydrophobic deep eutectic solvent (DES) eutectogel (Deep eutectic solvent–Ethylene glycol phenyl ether acrylate– N , N -dimethylacrylamide) that integrates strain sensing, multiplexed sweat analysis and plantar-pressure recognition. The eutectogel is formed by in situ photopolymerization of soft and hard monomers in a methyltrioctylammonium chloride/ethyl nipagin (TOMAC/EP) DES, yielding a transparent, self-adhesive and rapidly self-healing network with excellent mechanical robustness (fracture strain ≈ 740% and fracture stress ≈ 0.6 MPa). Owing to its continuous ionic pathways and dynamically cross-linked network, the strain sensor exhibits a high gauge factor of 3.55 at 70–100% strain and maintains highly stable responses over 200 cycles at 60 °C and 80% relative humidity, outperforming representative hydrogel and ionogel strain sensors in the literature. The hydrophobic DES matrix endows the eutectogel with minimal swelling and long-term stability, enabling reliable electrochemical detection of four key sweat biomarkers—pH, uric acid, tyrosine and ascorbic acid—with wide linear ranges and low limits of detection. Furthermore, by combining a 10-region plantar pressure array with an artificial neural network classifier, the wearable system recognizes ten typical firefighting motions and discriminates different individuals with an overall accuracy of 95.7%. These results demonstrate that DES-based eutectogels provide a powerful platform for robust wearable electronics and offer substantial potential for firefighter health monitoring and emergency-rescue applications.