Bacterial Cellulose-Based Inks: Enabling Mechanical Property Control in Sustainable 3D Printing

Advancements in sustainable materials are needed to combat pressing challenges posed by synthetic plastics, such as non-renewable sourcing, environmentally detrimental manufacturing processes, and end-of-life fates. Biopolymers are attractive alternatives to petroleum-derived polymers, offering a reduction in environmental impact across their entire lifecycle. In parallel, additive manufacturing has revolutionized the production of polymer-based materials for numerous applications, particularly those challenging to manufacture using conventional techniques, utilizing sustainability practices such as minimal material usage and limited waste generation. Currently, the materials used in 3D printing applications are rather limited and majority of them are synthetic polymers. There is a clear need to provide more sustainable materials for the ever-increasing 3D printing applications. In this study, we present an entirely biobased material platform designed for direct ink writing (DIW), with the aim of enabling precise control over the mechanical properties of 3D-printed structures, both at the hydrogel and solid foam states. Utilizing polymer network principles, we use lab-cultured bacterial cellulose (BC) as our primary, load bearing network element. We investigate the effects of chemical treatment with deep eutectic solvents on the BC fiber charge and degree of defibrillation, which ultimately exert a profound influence on ink rheology and hydrogel properties. BC holds particular promise due to its combination of high aspect ratio, molecular weight, and degree of crystallinity, and its capacity for scalable and tunable biosynthesis. Additionally, we explore the impact of introducing other biopolymers (e.g. proteins) and organic small molecules (e.g. lipids) on the rheological properties and mechanical integrity of the printed structures. By incorporating spatially modulated compositions, we open avenues for further fine-tuning of material properties. This comprehensive investigation aims not only to deepen our understanding of the structure-property relationships within BC-based networks but also to pave the way for tailoring the properties of resulting gels and foams for a diverse range of applications. These insights are poised to significantly advance our fundamental understanding of polymer physics and offer innovative solutions for sustainable material development.