Controllable assembly of silver nanoparticles based on the coffee-ring effect for high-sensitivity flexible strain gauges

Abstract An effective and facile strategy was developed to assemble silver nanoparticle (AgNPs) into a series of close-packed silver nanoparticles wires (AgNWs), and successfully construct a high-sensitivity strain gauge on the flexible PET substrate. In this work, AgNPs were directly ink-jet printed onto the flexible PET substrate and assembled into paralleled twin lines induced by the coffee-ring effect. By regulating the coffee-ring effect, a series of well-organized AgNWs were controllably fabricated with a line width of 5–6 μm. Due to the exponential dependence of relative resistance variation to the applied mechanical strains, the assembled AgNWs-based strain gauge could achieve highly sensitive strain detection, exhibiting a high gauge factor approximately G  = 50–60 and a lowest strain level of 0.061% detection limit. Moreover, the AgNWs-based strain gauge demonstrated a reversible and reliable electrical response as a mechanical strain was periodically supplied at various frequencies. This simple, efficient and nonlithographic approach would be considered as an universal method to construct highly sensitive and reliable strain gauges for high resolution strain mapping fields.