Design and Fabrication of 3D Printed Tissue Scaffolds Informed by Mechanics and Fluids Simulations

Abstract

Advances in additive manufacturing are enabling the fabrication of lattices with complex geometries that are potentially advantageous as tissue scaffolds. Scaffold design for optimized mechanics and tissue growth is challenging, due to complicated trade-offs among scaffold structural properties including porosity, pore size, surface-volume ratio, elastic modulus, shear modulus, and permeability. Here, a design for additive manufacturing approach is developed for tuning unit cell libraries as tissue scaffolds through (1) simulation, (2) design automation, and (3) fabrication. Finite element simulations are used to determine elastic and shear moduli of lattices as a function of porosity. Fluids simulations suggest that lattice permeability scales with porosity cubed over surface-volume ratio squared. The design automation approach uses simulation results to configure lattices with specified porosity and pore size. A cubic and octet lattice are fabricated with pore sizes of 1,000μm and porosities of 60%; these lattice types represent unit cells with high unidirectional elastic modulus/permeability and high shear modulus/surface-volume ratio, respectively. Imaging suggests the 3D printing process recreates the form accurately, but distorts microscale features. Future iterations are required to determine how lattices perform in comparison to computational predictions. The developed approach provides the foundations of a design automation approach for optimized 3D printed tissue scaffolds informed by simulation and experiments.

Computationally designed lattices with tuned properties for tissue engineering using 3D printing

“…Elastic modulus and shear modulus were calculated using a beam analysis [ 2 , 29 , 62 ]. Each beam was composed of three finite elements with Abaqus software and 125 unit cells were patterned to fill a cubic volume.…”

“…Early iterations of this research were published and presented at the ASME International Design Engineering Technical Conference [ 62 ]. Xiuyu Wang aided with prototyping of 3D printed spinal cages.…”

Application of Computational Method in Designing a Unit Cell of Bone Tissue Engineering Scaffold: A Review

“…In a study conducted by Jahir-Hussain et al, they varied the pore shape of the scaffold, resulting in high mechanical strength but a low amount of porosity [ 29 ]. When the porosity of the scaffold is increased to be more than 50%, the square-shaped scaffold can exhibit mechanical properties similar to that of the host tissue [ 36 ]. Habib et al modified the square-shaped scaffold by increasing the porosity but could maintain the mechanical properties of the scaffold [ 19 ].…”

Geometry-Based Computational Fluid Dynamic Model for Predicting the Biological Behavior of Bone Tissue Engineering Scaffolds

“…A common solution is the use of Finite Element Analysis (FEA) and CFD is a popular approach in the field of bioengineering to predict the mechano-biological properties of scaffolds [ 23 , 24 , 25 ]. CFD is essential to understand the in vivo performance of a scaffold and to investigate its permeability characteristics, which strongly determine its biological performance [ 19 , 20 , 21 , 22 ].…”

“…CFD is essential to understand the in vivo performance of a scaffold and to investigate its permeability characteristics, which strongly determine its biological performance [ 19 , 20 , 21 , 22 ]. Haemodynamic metrics, such as WSS and fluid pressure, are known to impact the nitric oxide levels within the scaffold which is associated with the mechanical stimulus on cells [ 23 , 24 ]. WSS contributes to the differentiation of pluripotent stem cells into endothelial, cardiac, haematopoietic, and osteoblast phenotypes [ 25 , 26 , 27 , 28 , 29 ].…”