Soft flexible conductive CNT nanocomposites for ECG monitoring

Abstract

With the continuing development and interest in wearable electronics and smart textiles, the need for a flexible conductive electrode for use in portable and wearable electrocardiogram (ECG) for long term monitoring rises. Here, we assess the efficacy and performance of various conductive composite polymers in collecting electrical signals from the heart. Thermoplastic polyurethane (TPU), ethylene-vinyl acetate (EVA), and styrene-butadiene-styrene (SBS) were blended with 1%, 2%, 5%, and 10% carbon nanotube (CNT) content using ultrasonication and compression molding techniques. The elastic modulus of the composites increased dramatically at 5% CNT and higher due to the high tensile modulus of the CNTs. The conductivity of each material also increased due to the formation of the conductive network past the percolation threshold. At 10% CNT, SBS, TPU, and EVA had conductivities of 257.9, 51.5, and 2.41 S m−1 respectively. TPU and SBS composites had better strain response due to their linearity between resistance and strain. On the acquisition of electrical signals from the heart, only 5% and 10% SBS-CNT composites were able to detect the ECG waves from the heart. The performance of the material met and even exceeded that of the commercial electrodes with slightly less high frequency noise.