Mixed-dimensional design for robust and knittable alginate/cellulose-based aerogel fibers for thermal insulation

Aerogel fibers with porous microstructure have shown great potential in the field of thermal insulation because of their flexibility and versatility. However, the production of aerogel fibers still faces challenges, including poor mechanical properties and high chemical requirements. Herein, continuous aerogel fibers derived from biodegradable sodium alginate (SA) and cellulose were successfully manufactured through a sequence of wet-spinning, solvent displacement, freeze-drying, and hydrophobic modification. A multiscale design was employed to enhance the mechanical properties of the aerogel fibers by incorporating cellulose with a high degree of fibrillation (referred to as SMCM) into bacterial nanocellulose (BNC). The synergistic effect of enhanced hydrogen bonding, facilitated by SMCM, and the physical entanglement provided by BNC contributed to a significant improvement in tensile strength of 2.8 MPa. The optimized fibers exhibited ultralight characteristics with a density of 95.8 mg/cm³ and an impressive porosity of 91.8 %, while assembled textiles demonstrated good thermal insulation with a thermal conductivity of 0.039 W·m^-1·K^-1. The utilization of SMCM and BNC eliminates the necessity for cellulose regeneration, thus reducing chemical consumption. This approach exhibits strong potential for scalable industrial production due to its simplified methodology.