CFD Simulation on Permeability of Porous Scaffolds for Human Skeletal System

Abstract

Human skeletal system provides the protection of all organs and supports the loads from various daily activities. Therefore, the main objective of bone scaffold is to have mechanical strength to support the load and have the permeability that will have mass fluid transfer to enhance the healing of defects. In this study, we simulated the permeability of hexagonal unit cells at different pore sizes (1.0 mm, 1.5 mm and 2.0 mm) and at different inlet velocities (0.001 mm/s, 0.5 mm/s and 1 mm/s) by using Computational Fluid Dynamic (CFD) in Ansys software. Our finding shows that pressure drop from inlet to the outlet of the unit cell’s pore increased corresponding to the decreasing of pores diameter.  In contrast, increasing the velocities has increased the pressure drop from inlet to the outlet. The pressure drop at 0.001 mm/s, 0.5 mm/s and 1mm/s inlet velocities were 1.40×10^-4 Pa, 7.02×10^-2 Pa and 1.41×10^-1 Pa, respectively for 1.0 mm pore size.  The gradual decreased of the pressure will give the cell and nutrient to be diffused to the inner part of the scaffold. We calculated the permeability for each unit cell, and it can be acceptable based on the upper limit of human bone permeability. The variation in velocities did not gave significant differences for the scaffold permeability. However, the different of pore sizes gave significant effect in the scaffold permeability. The permeability value at 0.001 mm/s for 1.0 mm, 1.5 mm and 2.0 mm pore size were 2.900×10^-8 m², 4.863×10^-8 m² and 8.529×10^-8 m², respectively. By taking into accounts the pressure drop and permeability value, unit cell with 1 mm pore size is predicted to show a better performance in promoting cell growth due to the better flow characteristics in the scaffold. Permeability prediction will help in producing a functional bone scaffold that crucial in bone regeneration of the human skeletal system.