Multi-parameter design of triply periodic minimal surface scaffolds: from geometry optimization to biomechanical simulation.

ABSTRACT

This study introduces a multi-parameter design methodology to create triply periodic minimal surface (TPMS) scaffolds with predefined geometric characteristics. The level-set constant and unit cell lengths are systematically correlated with targeted porosity and minimum pore sizes. Network and sheet scaffolds featuring diamond, gyroid, and primitive level-set structures are generated. Three radially graded schemes are applied to each of the six scaffold type, accommodating radial variations in porosity and pore sizes. Computer simulations are conducted to assess the biomechanical performance of 18 scaffold models. Results disclose that diamond and gyroid scaffolds exhibit more expansive design ranges than primitive counterparts. While primitive scaffolds display the highest Young's modulus and permeability, their lower yield strength and mesenchymal stem cell (MSC) adhesion render them unsuitable for bone scaffolds. Gyroid scaffolds demonstrate superior mechanical and permeability performances, albeit with slightly lower MSC adhesion than diamond scaffolds. Sheet scaffolds, characterized by more uniform material distribution, exhibit superior mechanical performance in various directions, despite slightly lower permeability. The higher specific surface area of sheet scaffolds contributes to elevated MSC adhesion. The stimulus factor analysis also revealed the superior differentiation potential of sheet scaffolds over network ones. The diamond sheet type demonstrated the optimal differentiation. Introducing radial gradations enhances axial mechanical performance at the expense of radial mechanical performance. Radially decreasing porosity displays the highest permeability, MSC adhesion, and differentiation capability, aligning with the structural characteristics of human bones. This study underscores the crucial need to balance diverse biomechanical properties of TPMS scaffolds for bone tissue engineering.