A Nepenthes-Inspired Hydrogel Hybrid System for Sweat-Wicking Electrophysiological Signal Recording during Exercises

Abstract

Collecting electrophysiological (EP) signals (e.g., electrocardiogram (ECG), electromyogram (EMG)) during exercises is crucial for feedback of cardiac health and muscle injuries. However, since several interferences exist in the skin interface (e.g., deformation, perspiration, and motion artifacts), commercial rigid electrodes/systems have difficulty in recording high-fidelity EP signals. Here, a wireless Nepenthes-inspired hydrogel (NIH) hybrid system is developed for high-quality EP signal detection by establishing seamless-integrated and rapidly directional sweat-wicking device/skin interfaces during exercises. The adhesive strength of poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAAC)-based double-network hydrogels is significantly increased by more than sixfolds. Nepenthes-inspired microstructures are further fabricated on hydrogels to enhance the directional transport speed of droplets by 4.5 times. Notably, the NIH electrodes can maintain an intimate coupling with the skin during continuous artificial sweat injection while showing the lowest impedance and highest signal-to-noise ratio (>19 dB) of EMG signals under complex conditions (i.e., vibration and perspiration). Finally, the NIH hybrid system is fabricated by decorating silicone joints and hollow structures to avoid stress concentration. This system can record high-quality ECG waveforms and heart rate curves with relative deviations of <2.6% during exercises and rest. This NIH hybrid system represents a promising platform for precise EP signal monitoring in exercising scenarios.