One-Step Synthesis of Polar-Bear-Hair-Inspired Nanofibers for Multimodal Thermal Regulation

High-performance thermal regulators are essential for human survival in cold environments. However, conventional fibrous materials suffer from large diameters and low porosity, resulting in heavy weight and limited insulation. While aerogels are renowned for their low density and high porosity, their brittleness and poor mechanical properties severely hinder practical application. Herein, a porous-core/dense-shell nanofiber inspired by polar bear hair is engineered for multimodal thermal regulation via coaxial electrospinning based on fast-slow phase separation. Controlling polymer-solvent-water interactions within the coaxial jet induces rapid phase separation in the core and delayed phase separation in the shell, yielding porous-core/dense-shell nanofibers that self-assemble into aerogels (CSNA). The core/shell nanofibers and bonding networks endow CSNA with mechanical robustness, withstanding 20,000 times its weight without fracture. Meanwhile, the polar-bear-hair-inspired structure, featuring nanoscale fiber diameter, small pore size, and high porosity, synergistically achieves an ultralight density (5.5 mg cm^-3) and low thermal conductivity (26.45 mW m^-1 K^-1), enabling warmth retention that matches down at one-third the thickness. Furthermore, carbon-black-doped CSNA exhibits efficient Joule heating and photothermal conversion, enabling on-demand switching between passive and active warming modes under cold conditions. This strategy offers a promising approach for fabricating high-strength nanofibrous aerogels, showing great potential for next-generation thermal-regulation textiles.