Research On Preparation And Performance Of Wearable Textile ECG Electrodes

As a new electrode developed in the field of wearable electrocardiogram(ECG)monitoring,textile ECG electrode has attracted great attention.However,there are gaps between the fabric electrode and the skin interface,which will increase the impedance of the collection interface and lead to the poor quality of the collected ECG.Therefore,the gap and impedance can be reduced in two ways.Firstly,improving the electrode’s absorption of human skin surface sweat to reduce the void space and the contact impedance.Secondly preparing a raised textile electrode,depend on electrode surface fluffs can embed the skin hair into the fiber-fiber space,and the fluffs are in a tilted and disorderly distribution state,to reduce the gap between the electrode and the skin interface,and increase the effective contact,thus reduce the impedance.Based on this,two kinds of textile electrodes were prepared,one was cotton fabric electrode with good moisture absorption,the other was raised textile electrode based on chenille yarn.Both are obtained electrical conductivity by Silver plating process.Then,the contact impedance with skin,electrochemical impedance with simulated sweat,and the performance of the ECG were compared between the two kinds of textile electrode.The scan impedance of contact between silver-coated cotton textile and copper plate was tested to evaluate the effect of electric silver plating,because fabric structure and yarn density can affect the surface morphology of cotton fabric,and further affect the effect of electrical silver plating,evaluation by means of testing.In addition,there are two ways of electroless silver plating: static silver plating and ultrasonic silver plating,different ways will affect the binding force between the coating and the textile,which was evaluated by the quality loss of the textile after plain grinding.Moreover,the content of silver nitrate in the oxidation solution plays a decisive role in the contact impedance between the cotton textile electrode and the skin,which can be evaluated by testing the impedance between the two electrodes and the skin.The electrical silver plating process of the fluff textile electrode was the same as that of the cotton textile electrode.Finally,the properties of the two fabric electrodes were compared.On the influence factors of silver-plated cotton textile,the coating formed by ultrasonic assisted silver plating has good binding force to the textile;The scanning impedance of the 3/1 right twill silver-coated cotton fabric in contact with copper plate was between the plain weave and the bee nest textile,while the bee nest textile was the lowest,however,considering that the bee nest textile was easy to be damaged due to its long floating length,the 3/1 right twill was selected as the best organization structure;With warp density of 250 roots/10 cm silver-plated cotton fabric,the scanning impedance of contact with copper plate is minimum;Cotton textile electrodes made of 3 g silver nitrate had the lowest contact impedance with skin.On comparison of the two textile electrodes,the scanning impedance of the fluff electrode to the copper plate and the contact impedance to the skin are all lower than that of cotton fabric;The electrochemical impedance of fluff electrode in contact with electrolyte is better than cotton textile electrode,it mainly because the CPE-T value of fluff electrode is greater than that of cotton fabric electrode.The ECG obtained by the two textile electrodes under wet and dry conditions was similar to that obtained by the medical gel electrodes.The peak value of R wave in the wet state of the textile electrode is larger than that in the dry state,indicating that the wetting of the textile electrode can reduce the gap between the electrode and the interface,reduce the impedance and enhance the performance of the ECG.In addition,due to the presence of villi on the surface of the fluff textile electrode,the interface gap can be effectively reduced and effective contact area can be enlarged,and the electrochemical impedance between the fluff textile electrode and electrolyte is better than that of the cotton textile electrode,so the peak value of the ECG R wave of the fluff textile electrode in the dry and wet state is greater than that of the textile fabric electrode.