针迹类型对表面肌电用刺绣型织物电极性能影响

Influences of stitch types on performance of embroidered fabric electrodesfor surface electromyography

为设计与开发高性能的表面肌电用刺绣型织物电极,优化其工艺参数,采用镀银纱线作为导电刺绣线,以弹性针织面料作为刺绣基底织物,制备了4种不同针迹类型的刺绣电极,测试了其皮肤-电极阻抗,并在行走和慢跑2种状态下使用刺绣电极与Ag/AgCl凝胶电极同步采集了小腿腓肠肌表面肌电信号,采用时域、频域及相关函数分析了刺绣电极与凝胶电极采集的肌电信号拟合性能。结果表明:针迹类型对刺绣电极的皮肤-电极阻抗有显著影响,其中放射状刺绣电极的皮肤-电极阻抗相对最小,而圆环状刺绣电极的阻抗最大;4种不同针迹类型的刺绣电极与Ag/AgCl凝胶电极的表面肌电信号采集效果较为相似,验证了刺绣电极的可行性;放射状刺绣电极的表面肌电信号拟合性能较优,更适合用于肌电信号监测。

Objective The aim of this study is to develop high-performance embroidered fabric electrodes for surface electromyography(sEMG)and optimize their process parameters.Four embroidered fabric electrodes with different stitch types were designed and produced to investigate the influence of stitch types on their conductivity properties and sEMG signal fitting performance,ultimately determining the optimal stitch type.Method Fabric electrodes were produced using embroidery techniques by virture of the advantage of tailored fiber placement in embroidery.Silver-plated yarn,known for its high conductivity,served as the conductive embroidery thread,and elastic knitted structure were used as the substrate to improve the fit of the electrodes to the skin.Four embroidered fabric electrodes with different stitch types,i.e.,tabby-stitch,box-stitch,annular-stitch and radial-stitch,were designed and produced.Skin-electrode impedance testing was conducted for each embroidered fabric electrode.In the states of walking and jogging,embroidered fabric electrodes and Ag/AgCl electrodes were aolopted to synchronously collect sEMG signal of the medial side of calf gastrocnemius muscle,and sEMG signal fitting performance of embroidered fabric electrodes and Ag/AgCl electrodes was evaluated in time-domain,frequency-domain and by correlation function analysis.Results 1)Through skin-electrode impedance testing,it was found that direct embroidery on elastic knitted fabric tends to cause wrinkling in the fabric,resulting in deformation of the embroidered fabric electrodes.Placing non-adhesive interlinings such as paper interlining or cloth interlining on the bottom layer of elastic knitted fabrics cannot effectively solve this problem.However,using hydrosol double-sided fuse interlinings to synthesize elastic knitted fabrics and paper interlinings into fabric substrate for embroidery can effectively prevent fabric wrinkling and electrodes deformation.2)Through skin-electrode impedance testing,it was found that stitch types significantly affect the skin-electrode impedance of embroidered fabric electrodes.During the test,the order of skin-electrode impedance was found to be annular-stitch electrode>box-stitch electrode>tabby-stitch electrode>radial-stitch electrode.The conductivity performance of embroidered fabric electrode with radial stitch is optima l.3)In the time-domain comparison diagram,sEMG signal of each embroidered fabric electrode was basically consistent with that of Ag/AgCl electrodes.The time-domain indices extracted include root mean square(RMS)and average rectifying value(ARV),while frequency-domain indices encompassed mean power frequency(MPF)and median frequency(MF).RMS,ARV,MPF and MF of each embroidered fabric electrode were close to those of Ag/AgCl electrodes.Therefore,the sEMG acquisition effect of embroidered fabric electrodes were similar to that of Ag/AgCl electrodes.4)The time-domain and frequency-domain characteristics of the sEMG signals collected by embroidered fabric electrode with radial stitch and Ag/AgCl electrodes were similar.Moreover,the ratio of information entropy of sEMG signal collected by embroidered fabric electrode with radial stitch and Ag/AgCl electrodes was the closest to 1,and the correlation coefficient between them was higher than 0.455 in the jogging state.So,it is believed that the sEMG signal fitting performance of the embroidered fabric electrode with radial stitch was better,and it was more suitable for sEMG monitoring.This result was related to the smaller skin-electrode impedance of embroidered fabric electrode with radial stitch,as generally speaking,the smaller the skin-electrode impedance of the electrode,the weaker the attenuation of the sEMG signal.Conclusion The sEMG signal acquisition effect of four embroidered fabric electrodes with different stitch types are similar to that of Ag/AgCl electrodes,which verifies the feasibility of embroidered fabric electrodes.The type of stitch affects the skin-electrode impedance and sEMG signal fitting performance of embroidered fabric electrodes.The embroidered fabric electrode with radial stitch has the smallest skin-electrode impedance and demonstrated optimal sEMG signal fitting performance,indicating that optimizing stitch can improve the performance of embroidered fabric electrodes.