Abstract:

Objective This study aimed to develop high-performance textile-based embroidery electrocardiogram (ECG) electrodes by investigating the influence of conductive yarn materials on their sensing properties. Conventional Ag/AgCl gel electrodes often cause skin irritation and performance degradation over prolonged use, necessitating the development of durable and comfortable alternatives. Four types of conductive yarns—nylon/silver, polyester/copper fiber, polyester/stainless steel fiber, and polyester/carbon fiber—were selected to fabricate embroidery electrodes. The research evaluated their structural characteristics, electrical properties, and ECG signal acquisition performance to identify the most suitable material for long-term monitoring.

Method Embroidery electrodes were fabricated using an elastic knitted fabric as the substrate and a bionic pattern inspired by tree frog toe pads to enhance the stability of skin-electrode contact. Four conductive yarns with identical linear density and metal content (15%-18%) were employed. Electrode thickness, flatness, surface resistance, skin-electrode interface impedance, and ECG signals were systematically measured. A standard limb lead system was used for ECG acquisition, and signal quality was evaluated using signal-to-noise ratio (SNR) and Pearson correlation coefficient, with medical gel electrodes as the reference. Martindale abrasion tests were conducted to assess durability under repeated friction.

Results The experimental results provided a comprehensive evaluation of how conductive yarn materials influence the structural, electrical, and functional properties of embroidery ECG electrodes. Among the four types tested, the nylon/silver electrode demonstrated the most favorable characteristics. It exhibited the lowest surface resistance across all measurement directions, with values significantly lower than those of the other electrodes. This can be attributed to its uniform silver coating and continuous conductive pathways formed during embroidery. The skin-electrode interface impedance for the nylon/silver electrode was also the lowest and remained the most stable over a 60-minute wearing period, indicating effective and consistent electrical coupling with the skin. In terms of dynamic signal acquisition, it achieved the highest signal-to-noise ratio (SNR) of 36.65 dB and the strongest Pearson correlation coefficient (0.97) with the standard Ag/AgCl gel electrode, confirming its superior accuracy in capturing ECG waveforms, including distinct P-waves, QRS complexes, and T-waves. The polyester/stainless steel fiber electrode ranked second in overall performance, which showed relatively low surface resistance and moderate skin-electrode impedance. Its rigidity, however, limited its ability to conform closely to skin during movement, leading to slight signal fluctuations. The polyester/copper fiber electrode suffered from discontinuous conductive networks due to fiber wear and breakage, resulting in higher resistance and unstable impedance. Meanwhile, the polyester/carbon fiber electrode, despite having the thinnest structure, displayed the highest electrical resistance and significant impedance variability, which led to poor signal stability and visible waveform distortion during ECG monitoring. Abrasion testing further differentiated the long-term usability of these electrodes. The nylon/silver electrode exhibited exceptional durability, maintaining a high SNR of 28.32 dB and a correlation coefficient above 0.8 even after 10 000 friction cycles. The polyester/stainless steel fiber electrode withstood up to 7 500 cycles before a noticeable decline in signal quality, benefiting from the inherent hardness of stainless steel fibers. In contrast, the polyester/copper fiber electrode experienced a rapid 181% increase in resistance after 10 000 cycles, while the polyester/carbon fiber electrode surged by 204% under the same conditions, indicating poor abrasion resistance. These mechanical limitations directly compromised their signal acquisition capabilities after repeated use. Overall, the combination of low initial electrical resistance, stable skin-electrode contact, high signal fidelity, and superior abrasion resistance makes the nylon/silver-based embroidery electrode a highly promising candidate for long-term, reliable ECG monitoring in practical wearable applications.

Conclusion This study confirms that the choice of conductive yarn material plays a critical role in determining the performance and durability of embroidery ECG electrodes. Nylon/silver yarn, with its uniform conductive layer and mechanical flexibility, provides optimal electrical properties, signal stability, and abrasion resistance, making it the most suitable material for long-term wearable health monitoring applications. Polyester/stainless steel fiber yarn offers a compromise between conductivity and durability but is limited by its rigidity. Polyester/copper fiber and polyester/carbon fiber yarns are less favorable due to their susceptibility to wear, high resistance variability, and poor dynamic response. These results provide a clear material selection guideline for developing high-performance textile-based electrodes, emphasizing the importance of both initial performance and mechanical resilience in practical use. Future work may focus on optimizing embroidery parameters and hybrid material designs to further enhance comfort and functionality.

Key words: smart wearable textile, embroidery electrode, conductive yarn, metal fiber, sensing performance, electrocardiogram signal, copper fiber, stainless steel fiber