Nacre-inspired highly stretchable piezoresistive Cu–Ag nanowire/graphene synergistic conductive networks for strain sensors and beyond

Abstract

Recently, it has become highly desirable but remains a challenge to design strain-sensing materials with rational geometric structures that endow the strain sensors with high sensitivity, large stretchability and a broad sensing range simultaneously. Herein, core–shell Cu–Ag nanowires (NWs) with tunable morphology and oxidation-resistance are achieved by an effective galvanic replacement reaction between Cu NWs and Ag(NH₃)₂⁺ without any additional heating, stirring or reducing agent. When the mass ratio of Cu NWs to AgNO₃ is 8 : 6, Cu–Ag NWs exhibit the best oxidation-resistance and electrical conductivity retention in harsh environments. Nacre-mimetic conductive composites are achieved by embedding porous conductive networks composed of Cu–Ag NWs/reduced graphene oxide (rGO) in a poly(styrene-block-butadiene-block-styrene) (SBS) matrix, enabling the process to be simple, energy-saving, and scalable. They can detect both tiny and large deformations with a wide sensing range (up to 374% strain), high sensitivity (a gauge factor up to 87 362), high break elongation (up to 660% strain), and excellent reliability and stability. This successful combination of huge sensing range and high sensitivity is attributed to the high stretchability of the SBS “mortar”, the hierarchical architecture and the synergistic effects of sensitive two-dimensional (2D) rGO, and the conductive stretchable one-dimensional (1D) Cu–Ag NW “brick”. In addition, the composites can be used as patterned conductive interconnects for light-emitting diodes.