Nano–micro multiscale engineering of far-infrared cellulose acetate fiber aerogels for lightweight and flexible passive thermal health textiles

With the increasing incidence of knee osteoarthritis, the demand for personalized thermal-management orthoses is steadily growing, and aerogels are regarded as promising candidates because of their excellent thermal insulation. However, their single-mode insulation mechanism cannot effectively harness infrared radiation, and conventional functionalization strategies often compromise breathability, moisture permeability, and mechanical performance. Here, we propose a “nano–micro multiscale engineering” strategy that employs porous cellulose acetate (pCA) microfibers and nonporous cellulose acetate (npCA) nanofibers as aerogel building blocks. By introducing a blocked isocyanate (BIC) crosslinker and far-infrared ceramic powder (FICP), we fabricate a micro–nanofiber far-infrared thermal aerogel. In addition to intrinsic thermal insulation, the aerogel provides efficient radiative heating, achieving a combination of intrinsic insulation and radiative heat-management capability. When the mass ratio of pCA to npCA was 75:25, the mass ratio of BIC to cellulose acetate (CA) was 0.75, and the FICP loading was 15 wt% relative to the CA fiber mass, the aerogel exhibited outstanding insulation and an additional temperature rise of 17.44°C under external far-infrared irradiation (heating rate: 1.37°C min ^–1 ) in simulated-skin tests. Meanwhile, it maintained excellent air and moisture permeability, outperforming commercial knee pads and other fabrics. Overall, this work mitigates the long-standing trade-off among mechanical performance, thermal insulation, and wearing comfort, and offers a scalable pathway to customized multifunctional aerogels for wearable thermal management and thermotherapy applications.