The Design Of Surface Texture In Vascular Stent And Its Effect On Blood Flow

In recent years, as the aging of population continues to increase, the morbidity ofcardiovascular disease has been increasing. The dead toll caused by cardiovasculardisease increase from one-tenth surge at the start of20th century to one-third in early21st century, has become the world’s first cause of death，however, the trend is rising.At present, the methods of surgery for the treatment of cardiovascular diseasesare operation treatment, drug treatment, and intervention, and so on. Among them,interventional therapy with minimal trauma, less complications, safe operation andhigh success rate, has been widely used in the treatment of cardiovascular diseases.However, after using Endovascular stent, the possibility of vascular restenosis will bevery high, about10%of the patients required re-implantation of the stent, which willbring great physical and mental burden and economic losses to the patients.Surface texture is to process a series of certain rules of micro pit or groove,making the surface processed has different physical properties with the unprocessedsmooth surface, so as to achieve the purpose of surface modification. Therefore,biomedical material with reasonable designed surface texture can surely improve theblood thinning properties.In this dissertation, the author used ANSYS CFX to make direct NumericalSimulation on unsteady circular channel with a rigid surface texture. And from theblood flow, wall shear stress, pressure and other parameters to analyze the effect ofthe blood flow caused by different surface texture. The main conclusions are asfollows:Firstly, a circular channel blood flow model is established to investigate thedifferent area ratio and different depth effect of cylinder micro-dimple surface texturewith different area ratio of8.67%,12%,15.87%and non-textured surface texture onthe pressure and flow rate generated between conformal contacting surfaces. It showsthat cylinder micro-dimple surface texture has little influence on the flow rate andpressure of blood, but has significant influence on the wall shear stress. The optimumratio of the depth to the diameter is0.0875, and the optimum area ratio of these three area ratios is12%.Secondly, a circular channel blood flow model is established to investigate thedifferent area ratio and different depth effect of cylinder micro-convex surface texturewith different area ratio of8.67%,12%, and15.87%on the pressure and flow rategenerated between conformal contacting surfaces. It shows that cylindermicro-convex surface texture has little influence on the flow rate and pressure ofblood, but has significant influence on the wall shear stress. The optimum ratio of thedepth to the diameter is0.0875, and the optimum area ratio of these three area ratiosis12%.Thirdly, a circular channel blood flow model is established to investigate thedifferent area ratio and different depth effect of square micro-convex surface texturewith different area ratio of8.67%,12%, and15.87%on the pressure and flow rategenerated between conformal contacting surfaces. It shows that among these threedifferent area of surface texture, the optimum height is0.04, and the optimum arearatio is12%.Lastly, comparative analysis of the simulation results of cylinder micro-dimplesurface texture, cylinder micro-convex surface texture and square micro-convexsurface texture on the effect of blood flow. We can draw a conclusion that cylindermicro-convex surface texture is more conductive than cylinder micro-dimple surfacetexture to promote the flow of blood and to hinder the formation of blood clots. Andsquare micro-convex surface texture is more conducive than cylinder micro-convexsurface texture to hinder the formation of blood clots in the stent.