Effect of filler morphology on fatigue properties of stretchable wires printed with Ag pastes

In this paper we examined the fatigue behavior of stretchable printed wires using electrically conductive pastes loaded with Ag flakes and microparticles, mixed into a polyurethane-based binder. The fatigue test damaged the stretchable wires by two different mechanisms, including cracking and binder softening (Mullins softening). The damage caused by binder softening could be recovered by annealing at 100 °C. The morphology and size of the fillers greatly affected the fatigue sensitivity of the electrical conductivity of the wires. Although flakes are suitable fillers for enhancing the fatigue lifetime of wires, their loading percentage and size distribution should be controlled to obtain reliable wires.