Polypyrrole-coated copper nanowire-threaded silver nanoflowers for wearable strain sensors with high sensing performance

Abstract

• Core-shell copper-polypyrrole nanowires with tunable properties are achieved. • Cluster structure of Cu@PPy threaded Ag NFs is assembled. • Cluster structure endows the sensor with large stretchability and high sensitivity. • Diverse sensing mechanisms are proposed to explain the superiority. Although the development of wearable strain sensors with a wide sensing range (>50%) and high sensitivity (gauge factor (GF), > 100) is highly desirable, it also presents a grand challenge owing to the inverse relationship between sensitivity and sensing range in designing strain-sensing materials and geometric structures. In this study, we fabricate versatile conductive composites by embedding polypyrrole-coated copper nanowire (Cu@PPy NW)–threaded Ag nanoflowers (NFs) in a poly(styrene-block-butadiene-block-styrene) (SBS) matrix. The fabrication process is simple, energy–saving, and scalable. Moreover, the obtained cluster structures derived from Cu@PPy NW–threaded Ag NFs endow the composites with excellent electromechanical performance, which is demonstrated by its wide sensing range (up to 185% strain), high sensitivity (GF up to 1.28 × 10 6 ), as well as excellent reliability and stability. The superiority in sensing range and sensitivity is a result of the combination of the fracture–sensing mechanism, constrained crack–propagation mechanism by the matrix, slippage–sensing mechanism, and double bridge functions of Ag NFs and Cu@PPy NWs. The high performance allows the strain sensors to monitor full–range human motions.