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

Abstract

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.