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.

Maple Leaf Inspired Conductive Fiber with Hierarchical Wrinkles for Highly Stretchable and Integratable Electronics

“…As shown in Figure S1, the conductive PPy coating was obtained through the modified interfacial polymerization, as we previously reported. 41 First, PDA-coated fiber was placed in a Petri dish (diameter: 10 cm) containing a certain volume (20 mL) of a mixed solution of ferric chloride (0.36 M) and NaSSA (0.36 M), and then the Petri dish was frozen in a refrigerator (−5 °C). Subsequently, the same volume of cyclohexane solution containing pyrrole monomer was poured into the above solution.…”

Template-Free and Stretchable Conductive Fiber with a Built-In Helical Structure for Strain-Insensitive Signal Transmission

“…The process of the silver-plated conductive core fiber transforming into a spiral state is illustrated in Figure b,c. This process can be regarded as a continuous process of the prestretching and releasing strategy employed for the preparation of stretchable fibers. ,,, Because the speed of roller 2 ( V 2 ) is higher than that of roller 1 ( V 1 ), when the fiber passes the two rollers, the polyurethane sheath is prestretched and deformed due to the speed discrepancy; meanwhile, the silver-plated conductive fiber core cannot be stretched and just travels fast. As a result, the additional length of the silver-plated conductive fiber core is pulled into the sheath to adapt to the speed discrepancy between the two rollers.…”

“…The fibers with buckled structures are other strain-insensitive and highly stretchable conductive fibers. Moreover, continuous production of stretchable conductive fibers with a buckled structure has been achieved. ,, Besides, the fiber made up of buckled conductive polymer ribbons and an elastomer tube is created by combining coaxial spinning and segmented prestretching strategies . However, such a case does not address the issue of the slightly poor conductivity of the composite conductive layer.…”

Conductive fibers for biomedical applications

“…Muscle fiber bundles-inspired parallel conductive monofilaments were designed by in situ polymerization of PPy on pre-stretched PU multifilament, which attained a flexible conductive layer by doping PPy with plasticizer ( Fig. 3 C) [ 82 ]. Differentiated process of strain relaxation of the elastic PU fiber and plastic Cu fiber was utilized to fabricate helical PU/Cu fibers by fixing the pre-stretched PU fiber and a paralleled Cu fiber with cyanoacrylate coating ( Fig.…”

“…Despite these achieved elongation rates, along with large strain deformations always comes a reduction in conductivity, and the working strain range of conductive fiber still needs to be determined according to different applications. Inspired by the structure of the electroactive muscle fiber bundles, our group designed an ultrastretchable (>1000%) conductive multifilament with buckled PPy structure in parallel, which showed an excellent recoverability within 100% strain, and a small hysteresis within 200% strain [ 82 ]. Due to the flexible PPy doped with plasticizer and the paralleled buckles, the current paths in the multifilament were able to be stabilized even at 900% tensile strain ( Fig.…”