Research On Modeling The Pore Distribution In Tissue Engineering Bone Scaffold Based On Shape Function

The definition"Tissue Engineering"was put forward at the proceedings held of a 1988 NSF-sponsored workshop: the application of principles and methods of engineering and life sciences toward fundamental understanding of structure-function relationships in normal and pathological mammalian tissues and the development of biological substitutes to restore, maintain, or improve functions. In order to regenerate the human tissues, scaffold, cells, signal transduction factor are three indispensable factors for tissue engineering.Based on the theories and techniques of CSG and solid modeling, a universe pore modeling approach for TE bone scaffold and a control approach for pore size distribution in the bone scaffold are proposed in this thesis. Firstly, a morphology-controllable pore modeling approach for TE bone scaffold is put forward based on the shape function in the finite element method: (1) the mapping relationship is established between the irregular elements and the cubic element (basic element) based on the iso-parametric method in FEM; (2) define the basic pore-making element; (3) construct a irregular pore controlled by a irregular hexahedral element based on the shape function in the finite element method; (4) generate the all-hexahedral mesh for a solid model by using the mesh mapping; (5) model various irregular pores after accessing the various irregular hexahedral elements; (6) TE bone scaffold modeling: construct the whole pore model by using the Boolean unit and bone scaffold model by using the Boolean difference; Secondly, based on the pore modeling approach by using the shape function and adaptive all-quadrilateral mesh refinement algorithm, a control approach for pore size distribution in the bone scaffold is proposed in this thesis: (1) expatiate the bone scaffold design approach based on the shape function; (2) describe the adaptive all-hexahedral mesh refinement algorithm; (3) describe the pore size distribution in the natural bone; (4) propose the bone scaffold design approach with defined pore size distribution. Additionally, the pore size distribution in the designed bone scaffold is calculated and interconnectivity in the bone scaffold is analyzed: (1) arrive at a conclusion after the pore size distribution calculation: the volume ratio between the irregular pore element and its control hexahedron is constant; (2) arrive at a conclusion after simulating the flow in the designed bone scaffold: a good interconnectivity in the bone scaffold which is designed based on the approach proposed in this thesis can be achieved. Finally, some aspects about how to fabricate the bone scaffold are discussed including the analysis of STL file errors, how to check STL file errors and repair the STL file errors. Compared to other methods such as 3D model assembled with discrete material cells, 3D pore-making method based on polyhedrons, computer modeling approach for microsphere-packed bone scaffold, multi-interior architecture design approach, the bone scaffold design approach proposed in this thesis can ensure the smooth surface for bone scaffold, natural pore morphology and gradient pore size distribution.This thesis is supported by a NSFC project: the solid modeling theory and its analysis for bone scaffold based on the geometric reasoning [50575139] and the Programme of Introducing Talents of Discipline to Universities [B06012].