Abstract:

Objective This research aims to develop electrode products with high comfort and stability suitable for long-term dynamic surface electromyography (sEMG) monitoring, and to address the limitations of conventional Ag/AgCl gel electrodes in prolonged and dynamic use.

Method Flexible textile electrodes in three sizes (2 cm×2 cm, 3 cm×3 cm, and 4 cm×4 cm) were fabricated by knitting a silver-plated polyamide yarn and a polyamide fiber-polyurethane elastic fiber coated yarn using localized jacquard technology. A systematic evaluation was conducted to assess their electrochemical impedance, skin-electrode contact performance, and sEMG signal quality under different load conditions, as well as their stability during seven days of continuous use under various wearing scenarios.

Results The electrode features a textured surface with a jacquard design to ensure close skin contact. Electrical impedance increased as frequency decreased (182.7 Ω at 10 Hz and 99 Ω at 500 Hz). Contact impedance was reduced by higher applied pressure and moistened skin (using 75% medical alcohol). A 3 cm × 3 cm dimension of the electrode exhibited optimal electromyographic performance, showing signal-to-noise ratios (S_SNR) of 20.1 dB (no load) and 24.5 dB (3 kg load), root-mean-square values (R_RMS) of 0.046 mV and 0.07 mV, and mean power frequencies (f_MPF) of 182 Hz and 173 Hz, which were comparable to conventional Ag/AgCl gel electrodes. The signal remained stable during 40 h continuous wear, and no skin discomfort was reported after 7 d of use. In electromyography monitoring, the R_RMS value increased from 0.05 mV to 0.07 mV, while the f_MPF value decreased from 196 Hz to 179 Hz, consistent to gel electrodes.

Conclusion This study targets the need for comfortable and stable electrodes in long-term dynamic electromyography monitoring. Three sizes of silver-plated polyamide fiber knit electrodes, produced by a localized jacquard knitting process, were systematically evaluated for their electrochemical impedance, skin-electrode contact performance, signal quality under different loads, and long-term wear stability. Results show that the 3 cm × 3 cm electrode delivered the best overall performance. Its electromyographic signal metrics, including signal-to-noise ratio, root-mean-square amplitude, and mean power frequency, were comparable to those of conventional Ag/AgCl gel electrodes, while also offering superior wearing comfort, biocompatibility, and mechanical durability. Thus, the proposed electrode meets the requirements for long-term dynamic monitoring and holds broad application potential in rehabilitation medicines, sports science, and smart wearable devices.

Key words: knitted electrode, electromyography monitoring, wearable electrode, silver-plated polyamide fiber yarn, polyamide fiber /polyurethane elastic fiber-covered yarn, dynamic monitoring, smart textiles