Microporous Structure Design And Performance Analysis Of Bionic Bone Tissue Scaffolds

Bone tissue engineering is an important method for the treatment of hard bone defects.This method needs to make a degradable artificial bone scaffold model that matches the defect and implant it into the human bone defect.While the artificial bone scaffold is degrading in the body,the body grow new bone tissue,and finally realizes the repair of the bone defect.This thesis write an automatic modeling program to build the bone scaffold model.And study the relationship between the porosity,pore size,specific surface area,mechanical properties and permeability of bone scaffolds.The porosity distribution of the bone scaffold depends on the location of the bone defect,so this thesis write an automatic modeling program to build the microporous structure model with controlled porosity.For the three surface,Schwarz P,Diamond and Gyroid,using the one-sided filling method and the two-sided migration method build six solid models.Choosing the surface offset distance as design parameter,and establishing the relationship between porosity and offset distance to realize precise adjustment of porosity.In order to study the connectivity of the pores,the relationship between the minimum pore size and the offset distance is established.And then studying the relationship between minimum pore size,specific surface area and porosity.Analyzing the mechanical properties and degradability of bone scaffolds.Establishing the relationship between the equivalent elastic modulus,equivalent shear modulus and porosity by simulation.The results show that the tensile and compressive resistance capacity and the shearing resistance capacity are incompatible.Studying the symmetry of six structures,and getting the number of independent elastic constants of Schwarz P,Diamond,Gyroid is three,six,seven by coordinate transformation.The elastic constants are calculated by simulation,and the results show that the tensile-shear coupling and shear-shear coupling of the structure are very small.Calculating the equivalent elastic modulus in other directions by coordinate transformation,the results show that the elastic modulus of the two model generated from the same surface is opposite in size.Building the degradation model and fing that the degradation rate depends on the specific surface area of the model.As for Schwarz P,single-side filling method of equivalent elastic modulus and double-side migration method of equivalent elastic modulus are always the largest.As for Diamond,the double-sided migration method of initial elastic modulus the is large,but decline fastest.As for Gyroid,the one-sided filling method of initial shear modulus of is lower,but decline slowly.Analyzing the permeability of bone scaffolds.Studying the domain of pore of two methods by Boolean operations,and find that all domain of hole can be equivalent to the one-side filling method's domain of solid.Simulink unit cell based on laminar flow model,then establishing the relationship between the permeability coefficient and porosity for six structure.As for Diamond structure and Gyroid structure,there is a flow perpendicular to the pressure direction.Building the seepage model of the macroscopic bone scaffold.The Diamond structure has the largest permeability coefficient along the [111] direction,and the Gyroid structure has the smallest permeability coefficient along the [111] direction.The anisotropy of permeability coefficient has little effect on the total flow rate,and certain influence on the streamline.