Scaling-Up of Nano-Architected Microstructures: A Mechanical Assessment

Nano- and micro-architected materials generated by ultra-high-resolution 3D printing techniques, such as two-photon polymerization direct laser writing (TPP-DLW) or projection micro-stereolithography (P mu SL), have garnered great interest due to their ability to achieve exceptional combinations of material properties. The scalability of these materials, however, remains a crucial challenge as larger high-resolution samples require stitching smaller blocks of the structure of interest together. Herein, scaling techniques and testing methodologies to investigate the effect of stitching on the integrity and mechanical behavior of TPP-DLW parts under tensile load are explored. Specifically, stitched log-pile I-beam specimens with relative densities of 21.5% and 54.7% are tested herein. The micro-tensile tests reveal that the higher-density log-pile samples exhibit brittle behavior with fracture loads at least four times higher than those of lower-density samples. The location of sample failure depends on the type of stitch introduced in the sample, as well as on the relative sample density. Overall, this study highlights the importance of stitching techniques and relative density for the design of nano- and micro-architected materials.