Free-form three-dimensional nanocellulose structure reinforced with poly(vinyl alcohol) using freeze-thaw process.

The free-form fabrication of networked bacterial cellulose (BC) structures was available using a particle matrix and a bioink embedding bacteria. However, the mechanical strength of such BC hydrogel structures does not satisfy the requirements for biomedical applications that require high toughness and elasticity. Here, we adopt the freeze-thaw process with a water-soluble polymer to form a crystalline structure around the BC nanofibers. The crystallization of polymer chains such as poly(vinyl alcohol) (PVA) occurs spontaneously during this process, which results in the unique and environment-friendly methodology of the composition. Crystallization enhances the mechanical strength of free-form BC hydrogels by filling the space between the nanofiber networks with crystalline polymeric fillers. Uniquely, a simple morphological variation can improve the mechanical strengths of BC/PVA cryogels, and this process may be broadly applicable as a tool for biomaterial design and fabrication.