Parametric Design Of Bone Tissue Porous Scaffold With Deformed Triply Periodic Minimal Surface Unit

Large bone defects caused by trauma,tumors,and osteoarthritis,have always been a challenging problem in modern medicine.With the development of bone tissue engineering and additive manufacturing technology,arbitrary personalized,complex,and refined porous scaffolds can be prepared,bringing new solutions to the problem of Large bone defects.Designing porous scaffolds of excellent structure and performance is the most critical step in bone tissue engineering.In the research of porous scaffolds designing,some scholars found that the porous structure based on Triply Periodic Minimal Surface(TPMS)is very suitable for the application of medical tissue engineering.There are many researches of bone tissue porous scaffold design based on normal TPMS units at home and abroad,but there are very few studies on deformed TPMS.Normal TPMS and deformed TPMS have their own advantages and disadvantages.For this issue,this paper establishes the relationship between the TPMS function parameters and the pore characteristics of porous structure,proposes the porous structure design method based on deformed TPMS,the design method of functionally graded porous scaffolds and the design method of fusion porous scaffolds.These methods can generate porous structures with controllable pore characteristics.The main work includes:(1)Research basic expression of deformed TPMS pore unit.The Marching Cubes(MC)algorithm is used to realize the visual expression of TPMS,design the deformed TPMS pore unit by dividing there Oriented Bounding Box(OBB),exploring the influence of TPMS function parameters on the modeling porous structures,which provides a theoretical basis for controlling the modeling porous structures in the parametric design algorithm.(2)Propose the parametric design method for deformed TPMS porous structure.By establishing the functional relationship between the TPMS function parameters and the porosity of the porous structure,a parameterized design method of the deformed TPMS porous structure is proposed,and the penalty function is used to optimize the design to deal with the fracture of the high porosity structure.(3)Propose the parametric design method of functionally graded porous structure.Research the characteristics of axial linear gradient and radial linear gradient porous structures,by using the linear variation of TPMS function parameters in the spatial uniaxial direction.Combined with the distance field,the thought of calibrating the direction of the spatial gradient by points,lines and planes,is used to propose a design method for the functionally graded porous structure in any direction in space.A more bionic performance of the gaussian graded porous structure design method was proposed,by using gaussian function.(4)Propose the parametric design method of porous structure based on fusion of different types of TPMS unit.Linear interpolation is used to describe the fusion transition of two different types of TPMS,and a sigmoid function method is proposed to optimize the transition structure,by adjusting the parameters of the sigmoid function.Using the sigmoid function as the weight function,by dividing the space sub-regions,a parameterized design method of porous structure fusion of any type of TPMS in space is proposed,which is verified by the design example.(5)Develop a parametric design system for bone tissue porous scaffolds and apply them to clinical case design.Based on the design platform Grasshopper of the threedimensional modeling software Rhinoceros,the algorithm was implemented and the parametric design system of the porous scaffold for bone tissue was developed.The feasibility and effectiveness of the proposed method were verified through clinical application.