High electrical conductance poly(3,4-ethylenedioxythiophene) coatings on textile for electrocardiogram monitoring

• We functionalized fabrics of polyester for the making of textile electrodes, providing them with high electrical conductance characterized by a sheet resistance of 10 Ohm, by means of in situ synthesis of poly(3, 4 – ethylenedioxythiophene) PEDOT, using the vapor phase polymerization method.
• The polymer coated textile electrodes exhibited very good electrical conductance and showed improved washing resistance whereas detergent solutions having acid character and dopant properties were used in the laundering process.
• We made electrocardiogram (ECG) sensors from conductive fabrics by means of an embroidery method and characterized the sensors in terms of signal to noise ratio (SNR), under dry and moisture conditions, using a 16 – bit programmable data acquisition unit and a Matlab program.
• The characterization method and experimental results indicated that the surface morphology of the conductive fabrics play a role in the electrical contact sensor–skin, affecting the sensor’s SNR levels.
• This work indicated that textile electrodes have potential to replace standard metallic electrodes, with their performance optimized through the tailoring of fibre type, surface morphology and electrical conductivity.

In this article we present textile sensors for the continuous monitoring of electrocardiograms (ECG), made from fabrics coated with high electrically conductive poly(3,4-ethylenedioxythiophene) (PEDOT). Polymer coatings of PEDOT were in situ synthetized on plain weave fabrics of polyester by the vapour phase polymerization method, using aqueous oxidant solutions of Fe (III) chloride with a concentration of one molar, two polymerization layers and optimized process parameters. The coating provided fabrics with high electrical conductivity, characterized by a sheet resistivity of 10 Ω sq−1. PEDOT coated fabrics and commercial conductive fabrics were made into sensors using a digital embroidery method. The performance of the sensors was analyzed by measurements of signal to noise ratio (SNR) under dry and moisture conditions and compared to those obtained with gel electrodes. The PEDOT sensors exhibited good performance characterized by SNR levels of the order to those obtained with gel electrodes. ECG sensors made of different types of fabrics exhibit significant differences in the noise amplitude, suggesting that the textile fibres and surface morphology are relevant parameters to consider in the sensoŕs design, affecting the contact resistance electrode—skin. The sensor’s resistance to washing cycles was tested under various temperature and detergent conditions. The experimental results indicate that the lifetime of the electrodes can be considerably enhanced with detergent solutions of dodecylbenzenesulfonate (DBS).