Sheet-laminated additive manufacturing of bacterial cellulose nanofiber-reinforced hydrogels.

Three-dimensional (3D) printing of hydrogels offers promising potential for creating intricate, customizable structures with superior elasticity, softness, and biocompatibility. However, due to their high-water content, hydrogels often suffer from reduced mechanical strength, which is further decreased when they absorb water, limiting their use in environments requiring high mechanical durability. To address this, we developed a novel 3D printing technique to fabricate bacterial cellulose (BC) nanofiber-reinforced hydrogels, which we term sheet-laminated additive manufacturing (SLAM). SLAM is based on digital light processing (DLP) 3D printing technology and involves a process of sequentially layering BC nanofiber sheets impregnated with a photocrosslinkable monomer. The BC nanofiber sheets provide a unique 3D network, resulting in a significant enhancement of the mechanical strength of various photocrosslinkable hydrogels. A unique aspect of BC sheets is their ability to further improve mechanical properties by inducing nanofiber alignment or adjusting nanofiber density through stretching and compression pretreatments. The printed BC nanofiber-reinforced hydrogels maintained their strength after swelling and demonstrated exceptional performance in applications requiring high mechanical robustness. Our SLAM approach successfully created complex 3D structures, such as BC-reinforced hydrogel earthworm structures and pressure sensors, demonstrating its potential for advanced applications in high-stress environments.