Abstract
Textile electrodes, also called textrodes, for biosignal monitoring as well as electrostimulation are central for the emerging research field of smart textiles. However, so far, only the general suitability of textrodes for those areas was investigated, while the influencing parameters on the contact impedance related to the electrode construction and external factors remain rather unknown. Therefore, in this work, six different knitted electrodes, applied both wet and dry, were compared regarding the influence of specific knitting construction parameters on the three-electrode contact impedance measured on a human forearm. Additionally, the influence of applying pressure was investigated in a two-electrode setup using a water-based agar dummy. Further, simulation of an equivalent circuit was used for quantitative evaluation. Indications were found that the preferred electrode construction to achieve the lowest contact impedance includes a square shaped electrode, knitted with a high yarn density and, in the case of dry electrodes, an uneven surface topography consisting of loops, while in wet condition a smooth surface is favorable. Wet electrodes are showing a greatly reduced contact impedance and are therefore to be preferred over dry ones; however, opportunities are seen for improving the electrode performance of dry electrodes by applying pressure to the system, thereby avoiding disadvantages of wet electrodes with fluid administration, drying-out of the electrolyte, and discomfort arising from a “wet feeling”.
Highlights
The contact impedances were measured over the entire frequency range, and all measured frequencies were included in the analysis
Rs was calculated to be located in a range of 60–70 Ω on the agar dummy and 80–100 Ω on a human arm, which aligns with findings by Zhou et al (2015), who found similar Rs values with around 100 Ω for wet and dry textile electrodes on a human leg [31]
Indications were found that a higher yarn density reduces the impedance as well as an uneven surface structure in case of dry electrodes
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Smart textiles are textiles offering a plurality of functions that can be achieved by employing or integrating other technologies, foremost of these electronics [1,2]. Smart textiles find use in various application fields, including protection and security, energy, and transportation, and not least the healthcare sector. A wide variety of sensors and actuators based on textiles are possible today, most of which are based on incorporation of electrical conductivity, which can be realized by various means, e.g., by conductive particles in inks or coating pastes, or by conductive fibers or yarns to construct fabrics and nonwovens [3,4]
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