Finite element analysis of mechanical behavior, permeability and fluid induced wall shear stress of high porosity scaffolds with gyroid and lattice-based architectures

Abstract

Scaffold design necessitates the consideration of mechanical properties and fluid flow dynamics as the main factors in the development of such materials. The mechanical behavior of bone scaffolds is characterized by properties such as elastic modulus and compressive strength. In terms of fluid flow dynamics, within bone scaffolds, permeability is an important parameter that affects cells' biological activities, and flow-induced shear stress is used as a mechanical stimulant of cell growth. In this study, two scaffold architectures with gyroid and lattice-based rectangular unit cells were designed to analysis the effective elastic moduli, compressive strength, permeability and fluid flow-induced wall shear stress as functions of porosity. Six levels of porosity (65%, 70%, 75%, 80%, 85% and 90%) were assigned to the scaffold architectures, and 12 models were developed. Scaffold deformation under static loading, compressive strength based on von Mises criteria, pressure drop, and fluid flow-induced wall shear stress in the scaffolds were then determined by finite element analysis. In both the scaffold types, models with higher porosity exhibited lower mechanical properties. Under the same porosity, the lattice-based scaffolds exhibited a Young's modulus and a compressive strength higher than those achieved by the gyroid scaffolds. With reference to geometrical parameters and the derived pressure drop from the computational fluid dynamics (CFD) analysis, scaffolds permeability was calculated using Darcy's law. In both the scaffold architectures, high porosity increased permeability and decreased wall shear stress. In the same porosity, the lattice-based models exhibited higher permeability and lower wall shear stress than did the gyroid models. On the basis of the results on elastic modulus and permeability, the models that most effectively mimic the properties of cancellous bones were identified.

Keywords: CFD analysis; High porosity scaffolds; Mechanical properties; Permeability; Wall shear stress.