Computational fluid dynamics analysis of the fluid environment of 3D printed gradient structure in interfacial tissue engineering

Mass transport properties within three-dimensional (3D) scaffold are essential for tissue regeneration, such as various fluid environmental cues influence mesenchymal stem cells differentiation. Recently, 3D printing has been emerging as a new technology for scaffold fabrication by controlling the scaffold pore geometry to affect cell growth environment. In this study, the flow field within scaffolds in a perfusion system was investigated with uniform structures, single gradient structures and complex gradient structures using computational fluid dynamics (CFD) method. The CFD results from those uniform structures indicate the fluid velocity and fluid shear stress within the scaffold structure increased as the filament diameter increasing, pore width decreasing, pore shape decreased from 90° to 15°, and layer configuration changing from lattice to stagger structure. By assembling those uniform structure as single gradient structures, it is noted that the fluid dynamic characterisation within the scaffold remains the same as the corresponding uniform structures. A complex gradient structure was designed to mimic natural osteochondral tissue by assembly the uniform structures of filament diameter, pore width, pore shape and layer configuration. The results show that the fluid velocity and fluid shear stress within the complex gradient structure distribute gradually increasing and their maximum magnitude were from 1.15 to 3.20 mm/s, and from 12 to 39 mPa, respectively. CFD technique allows the prediction of velocity and fluid shear stress within the designed 3D gradient scaffolds, which would be beneficial for the tissue scaffold development for interfacial tissue engineering in the future.