Multiscale modelling in biomechanics

Rapid prototyping techniques have been widely used in tissue engineering to fabricate scaffolds with controlled architecture. Despite the ability of these techniques to fabricate regular structures, the consistency with which these regular structures are produced throughout the scaffold and from one scaffold to another needs to be quantified. Small variations at the pore level can affect the local mechanical stimuli sensed by the cells thereby affecting the final tissue properties. Most studies assume rapid prototyping scaffolds as regular structures without quantifying the local mechanical stimuli at the cell level. In this study, a computational method using a micro-computed tomographybased scaffold geometry was developed to characterize the mechanical stimuli within a real scaffold at the pore level. Five samples from a commercial polycaprolactone scaffold were analysed and computational fluid dynamics analyses were created to compare local velocity and shear stress values at the same scaffold location. The five samples did not replicate the computeraided design (CAD) scaffold and velocity and shear stress values were up to five times higher than the ones calculated in the CAD scaffold. In addition high variability among samples was found: at the same location velocity and shear stress values could be up to two times higher from sample to sample. This study shows that regular scaffolds need to be thoroughly analysed in order to quantify real cell mechanical stimuli so inspection methods should be included as part of the fabrication process.