Towards Biocompatible Cellulose Nanofiber Sponges with Tailored Pore Geometries

Cellulose nanofiber (CNF) sponges or CNF aerogels are promising biocompatible materials with applications ranging from biomedicine to environmental remediation. The highly porous architecture of these sponges - which is crucial for their functionality - is significantly influenced by the freezing step during fabrication. This review explores the critical role of freezing techniques in tailoring pore geometry and, consequently, the macroscopic properties of CNF sponges. We discuss conventional directional freezing methods and their limitations, highlighting the advantages of dynamic freezing for achieving isotropic pore structures. Furthermore, we examine various crosslinking strategies to enhance the stability and mechanical properties of CNF sponges. Finally, we present recent findings from our laboratory demonstrating the successful fabrication of biocompatible and crosslinked CNF sponges with tailored pore geometries using a dynamic freezing approach.