Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet All organic graphene oxide and Poly (3, 4-ethylene dioxythiophene) - Poly (styrene sulfonate) coated knitted textile fabrics for wearable electrocardiography (ECG) monitoring Mahmuda Akter Shathi a,b,c , Chen Minzhi b,c, *, Nazakat Ali Khoso a,d , Hridam Deb a , Arsalan Ahmed a,e , Wang Sai Sai c a The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of the Ministry of Education, College of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou 310018, China 310018, PR China b Department of Fashion Design and Engineering, School of International Education, Zhejiang Sci-Tech University, Hangzhou, 310018, PR China c Department of Textile Engineering, College of Fashion, Zhejiang Sci-Tech University, Hangzhou, 310018, PR China d Department of Textile Engineering and Fashion Design, Faculty of Engineering & Architecture, Balochistan University of Information Technology, Engineering and Management Sciences (BUITEMS), Quetta 87100, Pakistan e Department of Textiles and Clothing, National Textile University, Karachi 74900, Pakistan ARTICLE INFO Keywords: Graphene Conductive polymers E-textiles Exhaust Dyeing Sensors Electrocardiograph ABSTRACT This research approach has been used to enhance and investigate the electrical performance of graphene-based textiles by using an exhaust dyeing method. We developed a highly flexible and wearable e-textile for smart clothing in general and electrocardiogram (ECG) biomedical applications in particular. One step dyeing and reduction of graphene oxide on the textile substrate was accomplished simultaneously at 90 °C in 2 h. After one bath dyeing and reduction of GO, the knitted fabric was coated with conductive polymer PEDOT: PSS via dip coating as a layer by layer (LBL) technique. The resultant knitted textile electrode showed a reduction in sheet resistance from 2.5 MΩ∼140KΩ with increasing (1∼10) dyeing cycles. The electrical conductivity was further the improved, as sheet resistance was decreased from 180KΩ∼120Ω when coated with PEDOT: PSS as compared to pristine PEDOT: PSS and rGO. The results showed that washing has an adverse effect on electrical con- ductivity. The textile electrode was stable up to 20∼30 washing and 120∼130 bending cycles. The developed electrodes were used as an ECG electrode, with low impedance and higher contact to human skin. The textile electrode showed the enhanced performance to detect the high-quality electrocardiograms (ECG) signals for heart rate in both wet and dry conditions. 1. Introduction Cardiovascular diseases provoke several deaths worldwide each year, increasing the mortality rate to 30 % caused by heart diseases [1]. During the last few decades, wearable e-textiles has been used to monitor and measure the body temperature, respiration, and biological signs such as pulse rate, electromyography (EMG) and electro- cardiography (ECG) [2]. These biomedical signals are widely detected by using metal electrodes such as silver, copper, aluminum, zinc, and gold. The use of these electrodes become limited due to their low per- formance, corrosion and degradation when exposed to moisture, body sweat and washing [3]. Such metal-based electrodes are complex arti- facts rigid and less flexible when embedded into wearable textiles. The metal electrodes are harsh and uncomfortable to wearer, causing skin irritation when directly contact with human skin [4]. Therefore, the development of textile-based metal-free electrodes is highly anticipated, as the textiles are highly flexible, breathable, and comfortable to the wearer. The measurement of the different vital medical signs such as EEG, EMG, EOG, and ECG signal can be attained at a broader range of potential difference of 0.001mV∼1.0 mV and frequency of 10∼50 HZ [5,6]. The graphene is considered as an alter- native and new material for wearable e-textiles as compared to metal- based electrodes and widely used in different health monitoring de- vices. In recent years, the demand for graphene-coated textiles is in- creasing for wearable sensors, energy storage & harvesting devices and Electromagnetic (EMI) protective clothing. Since the graphene-coated textiles are more comfortable due to higher flexibility, and breath- ability, as compared to their metal counterparts, therefore the https://doi.org/10.1016/j.synthmet.2020.116329 Received 16 December 2019; Received in revised form 19 January 2020; Accepted 8 February 2020 ⁎ Corresponding author. E-mail address: cmz_mail@zstu.edu.cn (C. Minzhi). Synthetic Metals 263 (2020) 116329 Available online 31 March 2020 0379-6779/ © 2020 Elsevier B.V. All rights reserved. T