Superelastic and Washable Micro/Nanofibrous Sponges Based on Biomimetic Helical Fibers for Efficient Thermal Insulation.

Extreme cold weather seriously harms human thermoregulatory system, necessitating high-performance insulating garments to maintain body temperature. However, as the core insulating layer, advanced fibrous materials always struggle to balance mechanical properties and thermal insulation, resulting in their inability to meet the demands for both washing resistance and personal protection. Herein, inspired by the natural spring-like structures of cucumber tendrils, a superelastic and washable micro/nanofibrous sponge (MNFS) based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation. By regulating the conductivity of polyvinylidene fluoride solution, multiple-jet ejection and multiple-stage whipping of jets are achieved, and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers, which are directly entangled to assemble MNFS. The resulting MNFS exhibits superelasticity that can withstand large tensile strain (200%), 1000 cyclic tensile or compression deformations, and retain good resilience even in liquid nitrogen (- 196 °C). Furthermore, the MNFS shows efficient thermal insulation with low thermal conductivity (24.85 mW m K), close to the value of dry air, and remains structural stability even after cyclic washing. This work offers new possibilities for advanced fibrous sponges in transportation, environmental, and energy applications.