Graphene/Carbon Nanotube Conductive Ink-Based Biomimetic Structure for Self-Powered Flexible Medical Monitoring Devices

Abstract

Soft wearable sensing devices have attracted extensive research attention in the fields of e-skin and human health monitoring due to the advantages of integrated functions and good biocompatibility. However, existing sensors are unable to achieve a highly sensitive response over a wide sensing range. In addition, the sensors require an external power supply during utilization. To overcome this key challenge, in this paper, we propose a conductive ink of GN-CNTs prepared with graphene and carbon nanotubes as conductive fillers and N,N-dimethylformamide as the solvent. A self-powered flexible wearable sensing microsystem with a bionic round-leaf motherwort structure is constructed using a thermoplastic polyamide film as a flexible substrate. The bionic round-leaf motherwort structure (BRMS), which can reduce the stress concentration distribution, can obtain a larger tensile strain range. The prepared BRMS flexible electrodes can be used for electrocardiography (ECG) signal acquisition and recording at three different sites such as the chest, fingertip, and wrist. The flexible electrodes have a higher ECG signal amplitude and signal-to-noise ratio. The friction layer electrodes are printed with conductive ink prepared by printing GN-CNT conductive inks. Following this, a friction nanogenerator is assembled to collect low-frequency mechanical energy. Supercapacitors were prepared by an assembly process using conductive silver paste and GN-CNT conductive ink coating. There is no obvious capacitance decay phenomenon under different angles and other deformation states, and it has an excellent energy storage performance. In this sensing microsystem, strain sensors and flexible electrodes can be directly driven from a power source consisting of a friction nanogenerator and a supercapacitor. It can be used for a long time for low-power detection of human motion detection and medical ECG monitoring.