The effect of porosity on the mechanical properties of 3D-printed triply periodic minimal surface (TPMS) bioscaffold

Prevailing tissue degeneration caused by musculoskeletal maladies poses a great demand on bioscaffolds, which are artificial, biocompatible structures implanted into human bodies with appropriate mechanical properties. Recent advances in additive manufacturing, i.e., 3D printing, facilitated the fabrication of bioscaffolds with unprecedented geometrical complexity and size flexibility and allowed for the fabrication of topologies that would not have been achieved otherwise. In our work, we explored the effect of porosity on the mechanical properties of a periodic cellular structure. The structure was derived from the mathematically created triply periodic minimal surface (TPMS), namely the Sheet-Diamond topology. First, we employed a series of software including MathMod, Meshmixer, Netfabb and Cura to design the model. Then, we utilized additive manufacturing technology to fabricate the cellular structures with designated scale. Finally, we performed compressive testing to deduce the mechanical properties of each cellular structure. Results showed that, in comparison with the high-porosity group, the yield strength of the low-porosity group was 3 times higher, and the modulus was 2.5 times larger. Our experiments revealed a specific relationship between porosity and Young's modulus of PLA-made Sheet-Diamond TPMS structure. Moreover, it was observed that the high- and low-porosity structures failed through distinctive mechanisms, with the former breaking down via buckling and the latter via micro-fracturing.