Hierarchically Helical and Buckled Gold Leaf on TPU Fibers for Superelastic Electrodes and Multifunctional Sensors

Stretchable conductive fibers provide a practical format for wearable electronics because they can be incorporated into textiles without compromising low weight, softness, or air permeability. Here, we present hierarchically structured gold-leaf/WPU/TPU fibers prepared through a twisted coating route. With waterborne polyurethane (WPU) used as the adhesive interlayer, a strip of nano-gold leaf was transferred onto the surface of the pretwisted TPU fiber, and release of the stored twist converted the metal layer into a helical conductive path accompanied by surface buckling. The helical turn density governed both the wrinkle morphology and the strain-dependent resistance. After WPU encapsulation, the helical gold-leaf/WPU/TPU fibers (HGLWTFs) with a helical turn density of 0.5 turn/cm exhibited a stable and monotonic resistive response, with a gauge factor (GF) of 25.7 over 0-100% strain, response/recovery times of 192/243 ms, stable performance over 1000 stretching cycles at 30% strain, and an electrical conductivity of 5.70 × 106 S/m. The HGLWTFs were further thermoformed into superelastic electrodes, retaining an electrical conductivity of 4.62 × 106 S/m and reaching a Q value of 363.6 at 2000% strain. The DHGLWTF capacitive sensor exhibited a linear strain response with R2 = 0.997 and response/recovery times of 46/72 ms and detectable capacitance changes during finger approach. A smart textile glove assembled with HGLWTFs was further used for remote manipulation of a robotic hand. These results highlight the potential of hierarchical gold-leaf fiber conductors for wearable sensing, stretchable electrodes, and human-machine interfaces.