The size effect on mechanical and permeability properties of porous bone structures fabricated by selective laser melting.

Porous structures are extensively utilized in bone tissue engineering for their lightweight nature, high strength-to-weight ratio, and superior energy absorption capacity. However, achieving optimal scaffold performance through precise dimension control remains a significant design challenge. This study systematically investigates the effect of unit-cell size on the mechanical and fluid transport properties of porous bone structures, aiming to provide guidance for scaffold design. Various porous structures with controlled unit cell sizes were fabricated via Selective Laser Melting (SLM) and evaluated under compressive loading. A complementary finite element (FE) model was developed to simulate mechanical responses and extract equivalent elastic modulus and compressive strength, while computational fluid dynamics (CFD) simulations were conducted on 4 × 4 × 4 arrays to calculate permeability. Results demonstrate that the Gyroid unit cell exhibited the most uniform stress distribution among the three studied architectures (Cube, Octa, Gyroid), and reducing unit cell size effectively mitigated stress concentrations to enhance structural stability. At a constant porosity, the compressive strength of uniform porous structures decreased with increasing unit-cell size, whereas the elastic modulus showed relatively low sensitivity to size variation. Meanwhile, permeability increased markedly with increasing unit-cell size. This study confirms that unit cell size profoundly impacts both the mechanical integrity and permeability of porous bone structures: smaller unit cells are recommended for applications prioritizing high compressive strength, whereas larger unit cells are more favorable for enhanced fluid transport.