Development of bimodal electrically conductive pastes with Ag micro- and nano-fillers for printing stretchable E-textile systems

Novel design concept to improve stability in electrical conductivity of elastomer-based conductive pastes (stretchable conductive pastes) during cyclic mechanical tension was proposed in this work. Silver (Ag) micro-flakes were selected as the main conductive fillers to prepare polyurethane-based conductive pastes. By modifying this single-modal conductive paste with Ag micro- and nanoparticles, two types of bimodal conductive pastes were prepared. After the single- and bimodal pastes were printed on an elastic textile substrate, the specimens were cured at 100°C for 1200s to prepared stretchable wire samples. A uniaxial cyclic tensile test with 10% strain was conducted using the specimens. Stability in electrical conductivity during the cyclic tensile test was significantly improved in the bimodal pastes than the single-modal paste containing only Ag flakes, although appropriate percentage of Ag particles within the total Ag loading was quite different depending on the particle size. In addition, fatigue damage introduced to the stretchable wire samples in the initial stage of the cyclic tensile test can be recovered by an annealing treatment.