Stable Bioelectric Signal Acquisition Using an Enlarged Surface-Area Flexible Skin Electrode

Numerous wearable devices were developed to measure bioelectric signals for continuous healthcare monitoring. The electrode, which interconnects electronics and the human body, significantly affects the signal quality. Although Ag/AgCl electrodes have been commonly used, noble-metal electrodes are more promising in terms of long-term reusability and flexibility. However, the signal-to-noise ratio (SNR) of noble metals is still insufficient for highly accurate biosignal acquisition. In this study, we propose an approach to enhance the electrical characteristics of a noble-metal skin electrode by surface modification using gold nanoparticles. The process parameters for nanoparticle deposition were optimized to maximize the surface area, thereby significantly improving the SNR of the electrode. The SNR value was increased by 51% in electrocardiogram and by 63% in electromyogram (EMG). We also propose an approach to quantify the motion artifact by spectral analysis, and the high flexibility of our electrode reduced the motion noise by 95% compared to the conventional Ag/AgCl electrode. The enhanced electrode interface paves the way for analyzing complex biosignals such as EMG and electroencephalogram in wearable applications.