Failure modes of conducting yarns in electronic-textile applications

Abstract

Integration of electronic functionalities into textiles adds to the value of textiles. It allows measuring, detecting, actuating and treating or communicating with a body or object. These added values can render the smart textiles very useful, fun, supporting, protecting or even lifesaving. It is, however, important for the comfort, acceptance and functionality to have integration of electronics as unobtrusive as possible. One elegant unobtrusive method of integration is to have circuitry included in the textile and mount components to this circuitry. Conducting yarns introduced by weaving, knitting or embroidery are attractive candidates to compose the circuitry as they do not disturb the textile nature of the system and are processable by the mentioned conventional textile technologies. In the case that these smart textiles are worn by humans under dynamic circumstances, the system is exposed to mechanical stress. In this paper we report the results of studies on the failure modes of Ag-coated nylon yarns, which are applied on textile carriers by means of stitching or soutache embroidery. The test methods varied in combinations of mechanical stress, such as shearing, bending and tension, and support to better understand the process of deterioration of the yarns when these are mechanically stressed. The delamination of the Ag coating from the yarns leads to unstable resistance values in non-static conditions. The mechanical forces, such as shearing, bending and tension, cause progressively more damage to the filaments of the yarns. This leads to a reduction of the electrical conductivity.