Optimal Design And Controllable Construction Of Porous Bone Tissue Engineering Scaffold

With the rapid development of computer aided design?CAD?and3D printing technology?3DP?,it is possible to design and manufacture bone tissue scaffolds with complex bionic structures.In this paper,the typical three-period miniaturized surface?TPMS?structure combined with the gradient structure and topology optimization were used to establish a porous scaffold design method for the objective of mechanical optimization.At the same time,scaffolds were controllably constructed based on the 3DP,and their mechanical performance was tested.The main work is as follows:?1?The construction of external shape and inner structures of porous scaffolds.The skeleton shape model was constructed by reverse engineering based on computed tomography?CT?.The TPMS function was used to construct three typical microstructures of P,G,and D.The gradient models of both single function and multi-model composite function were also constructed.The results show that the values of the equivalent stress and strain of the P,G,and D model are directly proportional to the loading force,and inversely proportional to the porosity.The range of elastic modulus is 1.1-6 GPa,which meets the requirement of bone elasticity modulus.The finite element analysis results show that the D structure model has the smallest stress and strain under the same load condition,which possesses better structural stability.Therefore,the D structure model and the previously obtained external shape were used to construct the TPMS femur shaped scaffold by boolean operation.The maximum equivalent stress of the scaffold is 23.452MPa,the equivalent strain is 2.56×10^-3mm/mm,the elasticity modulus is4.5GPa,the porosity is 60%,which induce that the porous scaffold model conform to the structure characteristics and mechanical strength of natural bone.?2?The design method of porous scaffolds based on topology optimization was proposed.The porous shell which is generated by the TPMS function is aimed at the lightweight design and the optimization of the complex shell structure,achieves the maximum porosity under the condition of the optimal strength,stiffness and stability.The longitudinal compression ultimate stress of the femur is 132.5MPa,so the D structural shell model has obtained the minimum wall thickness of 9.2mm and porosity of 62%after repeated topological iteration.This design method achieves light weight and large porosity of the scaffold.?3?The porous scaffolds were controllably manufactured by 3DP,and the mechanical properties were experimental studied.The SLA process was used to manufacture the designed bionics scaffolds.The compressive strength was tested by universal material testing machine.The results show that the three TPMS structures exhibit different fracture characteristics.The porous scaffolds with D structure has the highest compressive strength reaches 16±0.5 MPa,which is similar to the finite element analysis.Based on the finite element analysis and topology optimization,the optimum design of the porous scaffold is achieved.The scaffolds are controllably manufactured by SLA and tested by universal machine,which verify the optimum design of the scaffold.The results have a positive reference value for the research and application of bone tissue engineering.