Ultrastretchable and wearable conductive multifilament enabled by buckled polypyrrole structure in parallel

Abstract Stretchable conductive fibers have attracted much attention due to their potential use in wearable electronics. However, the ultra-high strain insensitive conductivity is hindered by mechanical mismatch in Young’s modulus and failure of stretchable structures under large deformation. This challenge is addressed with a conductive and elastic multifilament made of the polyurethane monofilaments that are surface-coated with buckled polypyrrole (PPy) of which flexibility is improved by sodium sulfosalicylate. Such parallel conductive monofilaments with PPy buckling on surface reduce the influence of cracks in the conductive coating on the overall conductivity, displaying an ultra-high strain insensitive behavior (quality factor Q = 10.9). Remarkably, various complex forms of wearable electronic textiles made by this conductive multifilament maintain the strain-insensitive behavior of the original multifilament, even upon the large deformation of human joint. This multifilament with wrinkled PPy has attractive advantages in the application of super-stretched wearable electronic devices.