Roll-to-roll graphene films for non-disposable electrocardiogram electrodes

Graphene has good electrical properties, flexibility, and biocompatibility, making it an ideal material to monitor electrocardiogram (ECG) signals. However, the production cost and the feasibility of large-scale production limit the application of graphene electrodes. Here, we demonstrate a roll-to-roll (R2R) method to transfer graphene grown by open-R2R chemical vapor deposition onto an ethylene vinyl acetate/polyethylene terephthalate (EVA/PET) substrate to make non-disposable ECG electrodes. This method can produce a continuous graphene/EVA/PET film with 15 cm width, and the length can reach several meters. The graphene/EVA/PET film has excellent flexibility and transparency (75.08% transmittance at 780 nm). Compared with commercial silver/silver chloride (Ag/AgCl) electrodes, R2R graphene electrodes have lower electrode-skin impedance below 1 kHz and can obtain ECG signals with similar performance to Ag/AgCl electrodes. Besides, R2R graphene electrodes have good washability. After ten times cleaning, the resistance of the R2R graphene electrode only increased by 23.2%, which was lower than that of the previous graphene electrodes. This work has great potential in the long-term and real-time healthcare monitoring system.