Down-Feather-Inspired Cellulose/Chitin Coaxial Cryogel Fibers with Triple Barriers for Thermal Insulation Textiles

Biobased thermal insulation textiles are attractive for passive body temperature regulation, whereas current fillers and coatings remain relatively thick, fossil-derived, and insufficiently biocompatible. Inspired by down feathers, a biobased cellulose/chitin coaxial cryogel fiber (CCF) was fabricated by wet spinning followed by freeze-drying. The CCF comprises a triple-barrier structure consisting of a microporous regenerated cellulose sheath, a trapped-air interfacial layer, and a nanoporous chitin core, which collectively suppress heat transfer. The regenerated cellulose sheath provides sufficient strength and flexibility for weaving into fabrics. With similar thickness and lower areal density, CCF fabrics exhibit a low thermal conductivity of 0.033 W m^-1 K^-1 and outperform fabrics made from single-component regenerated cellulose or chitin cryogel fibers. They also show better thermal insulation than the representative commercial textiles tested in this study under both high- and low-temperature conditions. This strategy provides a potentially scalable route to biobased thermal insulation textiles without supercritical drying.