Construction of cross-scale hierarchical ordered biomimetic architectures enabled by a fluid shear force field-assisted sacrificial template method

Natural organisms contain tissues like pearl layers, muscles, and bones with multiscale, multilevel ordered structures, which are challenging for biomimetic material fabrication. This study introduces a versatile method combining cellulose nanocrystal (CNC) shear-induced orientation under fluid forces with DLP 3D printing to create 3D multilevel ordered biomimetic architectures. Using cancellous bone's trabecular branching geometry as a model, a DLP-printed GelMA sacrificial template-complementary to the target structure and enzymatically degradable-was filled with CNC/hyaluronic acid methacrylate (CNC/HAMA) bioink. Within the template's channels, CNCs and HAMA chains oriented along fluid shear forces, forming three-pronged macroscopic architectures mimicking bone trabeculae. Micro/nanoscale analysis showed a Hermans orientation factor of ∼0.76 for CNC/HAMA synergistic alignment, with CNCs achieving ∼70% orientation, enabling ordered nanoscale arrangement. Oriented CNC/HAMA fibers further established microscale order. This approach bridges a complex macroscopic geometry with a 3D cross-scale hierarchical ordered alignment, effectively replicating natural tissues' multilevel structure and enhancing mechanical properties compared to unstructured counterparts. It provides a robust strategy for effectively controlling the 3D molecular orientation within the confined 3D-printed macroscopic structures.