Fabrication Of A Novel Biodegradable Vascular Stent By Three Dimensional Printing And Preliminary Study On Its Physical And Chemical Properties

Part ?:Finite Element Analysis and Hydrodynamic Simulation of Biodegradable Vascular StentPurpose:The three-dimensional model of vascular stent was evaluated by finite element mechanics analysis and hydrodynamic numerical simulation,which provided the basis for the design and optimization of scaffold structure.Methods:Through the three-dimensional modeling,the finite element analysis method was used to analyze the expansion process and the compression process of the scaffold unit.Then,the stent model was coupled with the blood vessel and blood flow,and the numerical simulation of mechanics was carried out to evaluate the wall shear stress changes of different scaffold models.Results:Through the finite element analysis of the scaffold model,it was found that the lower the height and the curvature of the stent model were,and the higher the expansion pressure and compressive pressure of the stent were.The behavior of the wall shear stress at each point of the different scaffold model was consistent with the change of the velocity of the blood flow,and the low wall shear stress region of the scaffold model 13 structure was smaller and potentially reduced the possibility of in-stent restenosis.Conclusion:In this study,the finite element analysis and hydrodynamic modeling of the vascular stent model could be used to optimize the scaffold structure from the perspective of mechanical mechanics and fluid mechanics of the vascular stent,respectively,and provided a sufficient theoretical basis for it.Part ?:Fabrication of a Biodegradable Vascular Stent by 3D Printing TechniquePurpose:The biodegradable vascular stent was prepared using a new three-dimensional printing technique.Methods:The poly-L-lactic acid powder was first subjected to a drawing process by a drawing system,and then the three-dimensional model was introduced into a FDM type three-dimensional molding apparatus to prepare a biodegradable vascular stent.Results:FDM-type three-dimensional molding device manufacturing biodegradable vascular stent surface finish was poor,and it could not achieve accurate printing.The innovative three-dimensional surface-forming device successfully prepared the biodegradable vascular stent with different curvature,and by controlling the extrusion amount of the three-dimensional printer nozzle in the unit time,the biodegradable vascular stent with different thickness of the stent bar was prepared.It achieved high precision,fast print molding.Conclusion:The new method of preparing the biodegradable vascular stent by the new three-dimensional printing process had the advantages of rapid prototyping and high precision.Part ?:Study on Mechanical Properties and Degradation Performance of Degradable Vascular StentPurpose:The mechanical properties and degradation in vitro performance of the stent were measured and evaluated.Methods:The mechanical properties of the stent with different structures of the stent and different extrusion amount of 150,200,250,300 per unit time were simulated by YISIDA digital push-pull tester DS-50N,which mainly included the test of radial force and flexibility performance.Stent Surface Coverage:Stent Surface Coverage =Stent Surface Area/Open Surface Area.Axial Shrinkage Coverage of Stent:Axial Shrinkage of Stent = Length of the Stent after Expansion/Length of the Stent before Expansion.Degradation experiments in vitro were performed on the biodegradable vascular scaffolds prepared by the three-dimensional molding process.The stent was evaluated in the presence of itself after 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 and 18 months' degradation.The molecular weight and molecular weight distribution of the polymer were also determined by gel permeation chromatography,and the mechanical properties(radial force)of the stent were measured at different time points in the degradation experiment.Results:Different structures of vascular stent radial support performance was different,low curvature of the stent supported better performance.When the extrusion of the three-dimensional printer nozzle was 250,the radial force of the stent was 128.7KPa,the flexibility was 0.54N,the stent surface coverage was less than 20%,the axial shrinkage was less than 5%,and the mechanical Performance met requirements.In the experiment of degradation of scaffolds in vitro,the trend of stent quality decline at different time points was slow and then slowed down.The molecular weight of the polymer decreased by about 54.4%after 6 months of scaffold degradation,about 69.7%after the 10th month,and then the degradation rate slowed down.The radial support force improved slightly after the first month of degradation,and then decreased gradually.And the radial force of the stent was 25.9%after the 11th month.Conclusion:In this study,the biodegradable vascular scaffolds prepared by the three-dimensional printing process had good mechanical properties and degradation properties,which could guarantee the effective radial force of the stent for a long time.