A Skin-Compatible Carboxymethyl Cellulose-Reinforced Gelatin Hydrogel with High Adhesion and Low Impedance for High-Fidelity Electrocardiogram Monitoring

Electrocardiogram (ECG) skin electrode is a critical bioelectronic interface for cardiac electrical signal monitoring. However, existing skin electrodes often suffer from dehydration-induced instability with elevated interfacial impedance and adhesion degradation during prolonged wear, impairing the quality of monitoring signal and wearing comfort. Herein, we present a skin-compatible, highly adhesive, and low-impedance glycerol-containing carboxymethyl cellulose-reinforced gelatin hydrogel (CCG hydrogel) electrode, which enables long-term, stable acquisition of high-fidelity ECG signals through a dynamic crosslinking network mediated by multiple hydrogen bonds and electrostatic interactions, coupled with ionic conductive pathways. This hydrogel exhibits a skin-like Young's modulus (0.1-0.3 MPa), a high water vapor transmission rate (975 g·m-2·day-1), and biocompatibility. Its abundant hydrogen bonds provide robust and conformal adhesion to skin (adhesion energy of 11.8 J·m-2). The network effectively retains water, maintaining a superior water retention even at 40 °C, thereby sustaining a low and stable interfacial contact impedance (15.2 kΩ at 100 Hz). This electrode possesses a signal-to-noise ratio (>20) and signal stability superior to commercial electrodes in 15-day long-term monitoring and 8-h simulated office scenarios. This work provides a skin-level design strategy that overcomes the traditional trade-offs in electrode degradation, showing promise for wearable and comfortable long-term health monitoring.