Cotton fabric-based flexible electrode for electrocardiography

Abstract

Early detection of heart abnormalities is one of the proposed methods to reduce number of death due to cardiovascular disease. Electrocardiography (ECG) is one of the commonly used methods in healthcare institution to monitor the heart condition. However, conventional ECG monitoring system is not suitable for longterm monitoring since it is bulky and experienced personnel is needed to interpret the ECG signal. In this study, flexible electrode and circuit using cotton fabric as the substrate material is proposed. Graphene-PEDOT:PSS ink which was synthesized via electrochemical exfoliation of graphite rod was used as the conductive material. The flexible electrode was fabricated using manual immersion of scoured fabric in the ink while wax patterning and pipetting methods were employed for fabrication of electrically conductive pattern for flexible circuit. Sheet resistance of the cotton fabric-based electrode coated with 5 layers of conductive ink is 75.9 Ω/sq. The ECG signal recorded using the cotton fabric-based electrode has similar features to that of using commercial silver/silver chloride electrode. On the other hand, the average resistance of as-fabricated 10 mm long and 1 mm wide conductive pattern is 128.68 Ω. The conductive pattern remained 42.1%, 41.1% and 53.6% of its conductance after 1000 bending cycles at bend radii of 0.50, 0.75 and 1.25 mm, respectively. Besides, the conductive pattern remained 70.4% and 50.8% of its conductance after 10 acute and obtuse folding cycles, respectively. A simple cotton fabric-based operational amplifier with gain of 1.67 was fabricated as an initial proof-of-concept for development of simple processing system on cotton fabric substrate.