Abstract
Bone scaffolds are widely used as one of the main bone substitute materials. However, many bone scaffold microstructure topologies exist and it is still unclear which topology to use when designing scaffold for a specific application. The aim of the present study was to reveal the mechanism of the microstructure-driven performance of bone scaffold and thus to provide guideline on scaffold design. Finite element (FE) models of five TPMS (Diamond, Gyroid, Schwarz P, Fischer-Koch S and F-RD) and three traditional (Cube, FD-Cube and Octa) scaffolds were generated. The effective compressive and shear moduli of scaffolds were calculated from the mechanical analysis using the FE unit cell models with the periodic boundary condition. The scaffold permeability was calculated from the computational fluid dynamics (CFD) analysis using the 4×4×4 FE models. It is revealed that the surface-to-volume ratio of the Fischer-Koch S-based scaffold is the highest among the scaffolds investigated. The mechanical analysis revealed that the bending deformation dominated structures (e.g., the Diamond, the Gyroid, the Schwarz P) have higher effective shear moduli. The stretching deformation dominated structures (e.g., the Schwarz P, the Cube) have higher effective compressive moduli. For all the scaffolds, when the same amount of change in scaffold porosity is made, the corresponding change in the scaffold relative shear modulus is larger than that in the relative compressive modulus. The CFD analysis revealed that the structures with the simple and straight pores (e.g., Cube) have higher permeability than the structures with the complex pores (e.g., Fischer-Koch S). The main contribution of the present study is that the relationship between scaffold properties and the underlying microstructure is systematically investigated and thus some guidelines on the design of bone scaffolds are provided, for example, in the scenario where a high surface-to-volume ratio is required, it is suggested to use the Fischer-Koch S based scaffold.
Highlights
In recent years, due to the increased human life expectancy and the increased number of bone diseases and traumas [1], there has been an increasing demand for organ transplantations and a high demand for new artificial tissue substitutes [2]
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The effective compressive moduli of the Gyroid and Diamond-based scaffolds predicted from the Finite element (FE) analysis were compared to those obtained from the experimental testing (Table 2)
Summary
Due to the increased human life expectancy and the increased number of bone diseases and traumas [1], there has been an increasing demand for organ transplantations and a high demand for new artificial tissue substitutes [2]. The TPMS-based scaffolds have a mean curvature of zero [18], a high surface-to-volume ratio [19], the ease of functional grading [20] and a variable /tunable electrical/thermal conductivity [21], which can make their properties anatomical location-specific and subjectspecific and can largely increase their potentials in the applications in biomedicine and relevant fields [22]. When designing uniform or functionally graded scaffolds for a specific application, it is still unclear which scaffold topology is the best candidate among the vast TPMS scaffold topologies, e.g., Gyroid, Diamond, Schwarz P. This is because the relationship between the scaffold properties and the underlying topologies is still unclear
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