Strain-Durable High-Conductivity Nylon‑6 Fiber with 1D Nanomaterial Lamellar Cladding for Massive Production

Electrically conductive polymer fibers with high woven properties are in demand by broad application fields. The design of these materials for massive production requires high electrical conductivity, efficient fabrication yield, and economic accessibility. Here, we proposed a technique for fabricating continuous polymer fibers coated with 1D materials. By alternately coating conducting carbon black/polyurethane (PU) composites, single-walled carbon nanotubes (SWCNTs), and/or Ag nanowires (AgNWs) on Nylon-6 continuous fiber, lamellar cladding forms a compact conducting shell on the core fiber. The conductive fiber was continuously fabricated using the coaxial micro-painting technique of a 1D material solution. By keeping the size of the droplet constant at the vicinity of the tip of the flexible micro-painter, the Plateau–Rayleigh (P–R) instability of the wetting layer was depressed at fiber velocity far beyond inertial wetting. The fiber with a 2 μm-thick shell exhibits a conductivity of 53 ± 8 Ω/cm at a coating weight ratio of ∼6 wt % silver corresponding to a fiber conductivity of about 1665 S/cm. The much higher strain durability of the fiber coated with SWCNTs and AgNWs’ lamellar structure than the fiber coated with only silver nanowires was explained by the local interlayer conducting paths from the AgNW layer to the SWCNT layer. The fiber maintains 90% conductivity after 105 repeated folding or knotting on the monofilament. The conducting yarns were designed and fabricated into electric circuits in textile. As a typical biomedical and flexible electronic application, a low-frequency electrocardiogram (ECG) signal on these circuits was demonstrated.