Imperceptible Hydrogel Electronic Skin for Early Intervention in Neck Pain: Multimodal Wireless Monitoring of...

Precise, synchronous monitoring of cervical kinematics and muscle electrophysiology is critical for early intervention in neck pain, yet remains constrained by the unimodal functionality, limited biocompatibility, and restricted accuracy of existing wearable technologies. To overcome these limitations, we developed an imperceptible multimodal, hydrogel-based electronic skin based on tannic acid (TA)-modified polyacrylamide-carrageenan (PCT) hydrogel, which simultaneously enables high-fidelity strain sensing and surface electromyography (sEMG) acquisition with optimized conductivity (1.03 S/m), stretchability (>300%), and tissue adhesion (12.1 kPa). TA doping (100 mg/mL) achieves balanced adhesion-conductivity-mechanical robustness trade-offs. Strain sensing exhibits gold-standard correlation with 3D motion capture (r = 0.9904) and high linearity at cervical-relevant strains (0-30%: GF = 1.15, R² > 0.999). The first multimodal biosafety validation was conducted via fNIRS-based cortical pain mapping, confirming zero neural activation during wear. A cervical spine strain sensor and a trapezius sEMG array interface were integrated with flexible electronics for real-time wireless fatigue/posture alerts. This platform enables proactive neck pain management through precision biomechanical telemonitoring, advancing human-machine interfaces for tele-rehabilitation.