Durability of screen printed electrical interconnections on woven textiles

Screen-printed interconnections are one example of interconnect technology that is currently being developed for e-textiles. The simplicity in the fabrication process and the high degree of design freedom it affords, allow electronic circuits to be easily realized on a textile host. Nonetheless, these interconnects often lose their electrical conductivities under external stresses such as bending or washing. This paper empirically demonstrates that electrical interconnects are more durable and reliable when printed on or close to the neutral axis (NA) of the e-textile where the internal stress is minimized. Piezoresistive strain gauges were screen printed on two different woven fabrics - Bari and PES (polyester), so as to locate the NA of these textile composites and evaluate the durability of the electrical interconnects under bending and washing stresses. Empirical results show that these mechanical effects significantly degrade the electrical conductivities of gauges positioned farthest from the NA. These gauges show resistance changes that were 34 times and 122 times more than those closest to the NA of their textile composites after five washing cycles and during negative bending curvature of 2 cm^-1. The implication of this result for screen printed e-textiles is that they will survive longer in their application environments if the interconnections and electronics integrated in them are in the proximity of the neutral axis of the e-textile.