Improved Skin–Electrode Impedance Characteristics of Embroidered Textile Electrodes for Sustainable Long-Term EMG Monitoring

Textile-based electrodes offer several advantages such as washability, flexibility, and reusability. However, there are challenges when it comes to long-term, real-time continuous monitoring, particularly during self-administration situations which introduce severe motion artifacts. In response to these challenges, researchers have explored various moisture retaining filling textiles to enhance the sustainability of long-term EMG monitoring. This study focuses on comparing three alternative textile fillings: 3D knitted fabric, nonwoven fabric, and microfiber sandwiched between embroidered textile electrodes to evaluate their moisture retention performance and ability to record EMG. The developed electrodes are comprised of embroidered a polyamide-silver hybrid conductive thread, with the filling textiles sandwiched between this yarn and the support fabric and bobbin yarn. The support fabric is an elastic textile band. The creation of these electrodes utilized satin stitch techniques. Impedance characteristics were analysed using an IVI-UM setup with a two-electrode configuration. The electrodes were applied to the subject's bicep muscles using the elastic strap with a pressure of 12 mmHg. The developed textile filled embroidered electrodes using the satin stitch technique exhibited better dry and wet electrode skin-contact impedance performance compared to the normal satin stitch-based embroidered electrodes against to (Ag/AgCl) electrodes. Further evaluation focused on assessing the long-term stability and wettability of the wet electrode conditions with various drying time. The wet 3D knit (W3D) large satin stitched sandwiched electrodes displayed lower impedance characteristics than those made with wet nonwoven (WNW), wet microfiber (WMF), and the dry embroidered electrodes, with worst performing the normal satin stitch embroidered electrode. It was observed that increasing drying time increases skin-contact impedance, emphasizing the significance of selecting the appropriate filling materials capable of retaining moisture comfort over extended periods. This choice is vital for achieving long-term EMG monitoring and maintaining low contact impedance, which directly impacts the signal quality. The study evaluated the effects of moisture retention time for each textile filling type on sustainable long-term EMG monitoring. Among the tested electrodes, the wet ring satin stitch 3D knit (W3D) sandwiched embroidered electrode out-performed the others WNW, and wet MF based sandwiched electrode achieving a signal-to-noise ratio of 54.93 dB and a root mean square of 0.195 mV, respectively, at the parametric values identified in the experiments.