(523e) 3D Printing-Directed Chiral Self-Assembly in Cellulose-Based Materials

The chiral or helical arrangement found in biomaterials including cellulose is known as the origin of the superior fracture resistance in wood and the vivid metallic colors in marble berries. In this work, we integrate the "bottom-up" molecular self-assembly with a "top-down" 3D printing technology to program nanoscale chiral arrangements of cellulose-based materials in intricate geometries. Our inks are designed based on cellulose colloidal particles enabling the formation of chiral nano/microstructures. We utilize the processing parameters of direct ink-writing (DIW) to manipulate the chiral nematic liquid crystalline phase in cellulose-based inks before deposition. This approach allows us to guide structural development from a specific initial condition. Through comprehensive rheological measurements, we have found that printing the chiral inks at a shear rate that induces a pseudonematic state in cellulose colloidal particles leads to consistent chiral recovery after the cessation of flow. This results in improved optical and mechanical properties in the final solid product. Our biomimetic concept will open the way to developing materials with programmable optical responses and enhanced mechanical properties, naturally emerging from their nanostructure, and transferred into the larger scale printed architectures, expanding 3D printing material technologies well beyond what has been conceived and attempted so far, into a new generation of composite and process design.