Wearable ECG signal sensing system based on easily peelable highly conductive hydrogel

Electrocardiogram (ECG) signals are important data reflecting the health of the human heart. However, the Ag/AgCl electrodes commonly used in current wearable devices suffer from the problem of being difficult to peel off, which may lead to discomfort. Therefore, in this study, we report a fully flexible wearable ECG sensor based on an easy-to-peel highly conductive hydrogel (adhesion of 12.54 ± 0.43 kPa and contact impedance of 190.79 Ω). The ECG acquisition system adopts a dual-lead configuration with conductive hydrogel as the conductive medium, which is capable of monitoring the cardiac status for a long period of time. The addition of silver nanowires (AgNWs) into the hydrogel improves its conductivity compared to the hydrogel only containing poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The toughness and stretchability of the hydrogel were enhanced by the use of polyacrylic acid (PAA) and polyvinyl alcohol (PVA) to form a dual network hydrogel. In addition, the integrated flexible circuit board (FPCB) enables to achieve seamless integration of ECG acquisition, processing, and wireless transmission. Further, a convolutional neural network (CNN) algorithm was used for the processing and analysis of ECG data. In this study, ECG signals from three body states (lying, sitting and standing) were analyzed using a CNN. The CNN was able to differentiate between the three body poses with an accuracy of over 97.9 %. This innovative integrated ECG monitoring system provides a new way for portable and smart ECG monitoring applications.