Impedance Characteristics of the Skin-Electrode Interface of Dry Textile Electrodes for Wearable Electrocardiogram

Long-term dynamic Electrocardiogram (ECG) monitoring is considered as one of the main methods of preventing heart diseases. Ag/AgCl wet electrodes, although used clinically, are not suitable for long-time wearing. Dry textile electrodes, however, have won much attention for surmounting these drawbacks. This essay explains the impedance characteristics of the skin-electrode interface of wearable dry textile electrodes for measuring ECG. Specifically, through analyzing the characteristics of dry textile electrodes, the skin-electrode interface equivalent circuit models were built, the textile electrodes were made and the electrochemical impedance spectroscopy (EIS) for the skin-electrode interface was measured. Finally, the influence of each parameter to the interface was assessed. The research illustrated that interface of dry textile electrodes were more complicated than that of standard Ag/AgCl electrodes. The interface impedance |Z| and the interface phase were relevant to the signal frequency and the key of descending the interface impedance was to lower the polarization resistance. The textile electrodes have the Constant Phase Angle Element (CPE) behavior due to the dispersion effect of the time constant within the Frequency of ECG measuring.