Modulus-Graded Liquid Metal Electrochemical Fibers for Continuous and Insusceptible Monitoring of Multiple Sweat Biomarkers during Exercise

Wearable electrochemical biosensors enable non-invasive monitoring of sweat biomarkers for exercise physiology and personalized health management. However, maintaining signal stability under intense body motion remains challenging, as conventional rigid or fiber-based sensors suffer from mechanical deformation-induced interfacial instability. Here, we report modulus-graded liquid metal fibers (MGLMFs) for the simultaneous, real-time monitoring of sweat pH, uric acid (UA), and lactate (LA) during various exercise modalities. By selectively coating high-modulus carbon-based sensing layers onto low-modulus, strain-insensitive liquid metal fibers, our design achieves localized mechanical reinforcement while preserving global stretchability. The resulting sensors exhibit high sensitivity (pH: 68.82 mV pH-1, UA: 39.78 nA μM-1, LA: 4.69 μA mM-1), excellent selectivity, and remarkable electrochemical stability under both static (0-100%) and dynamic (0-50%) strain with minimal signal fluctuation (<5%). After being integrated into a textile-based wireless system, the MGLMFs successfully captured dynamic biomarker changes during jogging, weightlifting, and cycling in human trials, revealing distinct metabolic patterns across aerobic, resistance, and anaerobic exercises. This modulus-graded strategy offers a robust platform for motion-artifact-free wearable electrochemical sensing.