Optimization of Reduced GO-Based Cotton Electrodes for Wearable Electrocardiography

The quality of Electrocardiography (ECG) signal is dependent on the electrode's performance. Comfort and long-term monitoring are the main benefits of a dry and flexible electrode compared to conventional silver/silver chloride (Ag/AgCl) electrode. The main objective of this study is to develop high performance textile-based electrode by optimising fabrication method and electrode design. Cotton fabric was dipped into graphene oxide (GO), followed by reduction process to form reduced graphene oxide-cotton (rGOC), where L-ascorbic acid (C6H8O6) was used as the reducing agent. Conductivity and skin-electrode interface impedance of the fabricated cotton were characterized using Four-point probe (Van der Pauw) and Potentiostat, respectively. This study focuses on the investigation of electrode design that includes fabrication methods, electrode sizes and shapes. The performance of the reduced GO-based cotton (rGOC) electrode in terms of ECG signal quality was compared to conventional Ag/AgCl electrode and metal clamp under static and dynamic wearable conditions. Results from the conducted experiments show that the fabricated electrode's performance is influenced by dipping time and electrode design, with circle-shape electrode shows the highest conductivity (up to 9k S/m at 1 cm(2) area) compared to square- and rectangular-shape electrodes (<8k S/m and 14.55 S/m, respectively, at 1 cm(2) area). The circle-shape rGOC electrode's performed better (SNR 14.85 +/- 0.22 dB) than Ag/AgCl electrode (SNR 11.26 +/- 0.18 dB) and metal clamp (SNR 12.28 +/- 0.72 dB) in capturing static ECG signal. A wearable circle rGOC electrode with 1.7 cm radius performed also similarly under static (SNR 32.60 +/- 0.72 dB) and dynamic (SNR 30.27 +/- 1.37 dB) ECG monitoring, respectively.