Piezoresistive nanocomposite fibers are essential elements for smart wearables and have recently become a research hotspot because of their high sensitivities at large deformations in the plastic regime. However, little attention has been paid to the electromechanical properties of such fibers at low strains where the resistance−strain (R−ε) relationship is reliably linear. In addition, prediction of the resistance signal stability for these materials during cyclic loading remains unreported. Here, we studied these two aspects using wet-spun piezoresistive nanocomposite fibers from polyether block amide (PEBA) composed of a hybrid conductive filler network of carbon black (CB) and carbon nanotubes (CNTs) in which the CB loading in the PEBA matrix was varied at a constant volume fraction of CNTs. We found the R−ε linear relationship (working factor, W) to increase with CB filler loading from 0.01 to 0.058. In addition, the gauge factors of these fibers varied inversely with W from 16.89 to 3.81. Using fatigue theory, we predicted the endurance limit of PEBA/CB-CNT fibers in the elastic regime to be ∼34.9 cycles. Although our fibers were extremely deformable, up to 500% strain, as is the case for most piezoresistive nanocomposite fibers, this work reveals the working range to be actually very small, comparable to rigid conventional strain gauges. We believe with PEBA/CB-CNT fibers' robust mechanical properties and the ease with which the electromechanical signal can be quantified with the fatigue model, they would be ideal materials to be integrated into textiles to perform as tough, finely tuned strain sensors for a range of rigorous bodily monitoring such as low-strain impacts and joint movements.

The combination of phase change materials (PCMs) with fibers can afford smart fibers with thermal management properties. However, the issues of easy leakage and poor thermal stability of PCMs often limit their use in hightemperature spinning. Herein, we report a form-stable PCM of spherical SiO 2 / PEG composite that was prepared through flash-drying using inorganic dendritic silica (D-SiO 2 ) as the core skeleton to support organic polyethylene glycol (PEG). The SiO 2 /PEG composite not only presents high crystallization enthalpy (101.35 J/g), but also maintains a superior phase change stability.Meanwhile, it exhibits a significant temperature hysteresis effect during heating and cooling, and the endothermic and exothermic time are 381.95 and 293.57 s, respectively. Because the degradation temperature of 300 C for SiO 2 / PEG is higher than the melt processing temperature of 240-270 C for the preparation of polyamide 6 (PA6) fibers, PA6/SiO 2 /PEG fibers were prepared using melt spinning. The prepared PA6/SiO 2 /PEG fibers exhibit high latent heat (17.14 J/g), outstanding thermal cycling stability and satisfactory temperature adjustment properties, and the temperature-adjustment time of 458.97 s and temperature difference of 10.68 C under the thermal environment. Moreover, the tensile strength of PCFs-20% reached 1.97 cN/dtex after drawing, which make PCFs meet the requirements of uses in textile industries.

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Microencapsulated core-shell structures are proved to be an effective means to realize high-enthalpy and shape-stabilized phase change materials (PCMs), but the low heat and shear resistance of the shell material...

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