Eco-Friendly Reduced Graphene e-Textile-Based Ergonomic Wearables Around-the-Neck and Behind-the-Ear for Vital Signs Monitoring

Wearable e-textiles have gained significant attention in recent years, particularly for long-term biopotential signal monitoring. In this study, we present two wearable electrode designs—a headband and a neckband—tailored specifically for ECG signal acquisition from behind the ear and around the neck regions. These designs were benchmarked against standard Ag/AgCl electrodes over 30 voluntary participants and demonstrated maximum correlation values as high as 98% and above for both designs, with an average correlation of 90.1% and 91.9% for the headband and neckband, respectively. A detailed investigation of six different electrode placements on the neck was also conducted to determine the optimal positions for recording ECG signals. The robustness of the designs was evaluated through 40-minute ECG recordings and under various intense movement conditions. Furthermore, to advance the development of sustainable and reliable wearable e-textile systems, we evaluated the real-life performance of textile electrodes reduced using two different agents: L-ascorbic acid, an eco-friendly, bio-based compound, and sodium borohydride, a commonly used but toxic chemical. While both agents are already known to effectively reduce graphene oxide, the primary objective was to comparatively assess the functional performance of the resulting electrodes under real-world conditions, specifically in scenarios relevant to wearable ECG monitoring applications. The reported results enhance the understanding of the efficiency and performance of the developed wearable e-textile designs for biopotential signal monitoring.