Study of anisotropic electrical resistance of knitted fabrics

Abstract

Knitted fabrics, due to their multifunctional characteristics in terms of flexibility, elasticity and pliancy, are suitable to be used in electro-thermal garments as monitoring sensors for body movement. The arrangement of fibers and yarns in textiles makes them, in the majority of cases, inhomogeneous and anisotropic materials. Five highly conductive plain weft knitted fabrics in which anisotropy of electro-conductive properties occurred were chosen. In order to assess the global degree of planar anisotropy of the knitted fabrics, a new measurement procedure was designed. The Van der Pauw electrode configuration was used. The determination of resistance at selected points on the sample surface allowed us to find the surface response for each sample. Based on the results, the assessment of the global degree of planar anisotropy of electro-conductive properties of knitted fabrics was possible. Moreover, the experiment was designed to simultaneously solve the problem of measuring the resistance at the sample edge. The quotients ratio used as a measure representing the degree of global anisotropy was found to range from 2.5 to 11.1. This quotient was higher compared to that determined on the basis of measurements conducted in multi-directions lying in the sample plane and at a constant distance from the electrodes and from the sample edge. The relatively wide range of resistance values obtained for three samples makes it possible to use them as strain sensors, for example. The narrow resistance range observed in two samples is suited for the development of medical sensors, such as electrocardiogram electrodes.