The Basic Research Of Bionic Artificial Valve Based On The Super-hydrophobility And Rheology Reduction Theories

The replacement of artificial heart valve is one of the most effective way,also is a last way to save live of the patient whose heart valve is badly pathologically changed.Although the mechanical valve becomes the most widely used clinically as an artificial heart valve because of its longer life,it has poor hemo-compatibility.In order to decrease the risk of thrombosis complication,the patient who is implanted the mechanical valve should be treated with anticoagulant every day.Even if they are treated with sufficient anticoagulant,thromboembolism and anticoagulation-related complications such as bleeding are still founded.Accordingly,the solution improving the hemocompatibility of the mechanical valve is currently the center of research.It not only has important scientific significance,but also has the great economic value and social significance.In this paper,the aortic and mitral valve of the mouse and the tricuspid vavle of the rabbit are studied using scanning electron microscopy(SEM).On the animal's heart valve surface,there are some regular micro cobblestones-likes with the nano tenuous villus.This hierarchical structure on the surface of the heart valve,which is similar to that of lotus leaf surface,may be very useful to modify the wettability of heart valve surface,decrease the flow resistance of the blood and reduce the amount of adsorbed platelet on the surface,thus decrease the form of thrombus on the heart valve surface.In addition,the size and shape of microstruture of insect wings surface are different from each of other.The super-hydrophobic property of the solid surface depends not only on the surface chemical composition,but also by the surface micro-strcture.According to the classical wettebility theories——Wenzel theory and Cassie theory,the theoretical model of apparent contact angle of the droplet on the parallel two-dimensional gratings,three-dimensional periodic square pillar,square pit,as well as micro-structure of mastoid are set up.The effect of the parameters of surface micro-structure on the wetting propertie and the transition between two super-hydrophobic states on different micro-structure is discussed initially s.Different micro-structures on the surface of K9 glass,polyurethane(PU), Pyrolytic Carbon(PyC) are fabricated by femo-second technology and the apparent contact angle of droplet on those surfaces are measured.The effect of the laser parameters on the microstructure and superhydrophobility is also discussed.The regular array square columns and square holes micro-structure on the PDMS surface are manufactured using soft lithography.The hydrophobic properties of the microstructure of square columns and square hole in the same size and complementary shape are also complementary to each other.The rheological drag reduction of super-hydrophobic micro-structure solid surface is studied using rheometer.First of all,the formulae for calculating the slip length and the drag reduction rate of the superhydrophobic surface are derived and the existence of slip on the superhydrophobic surface is verified.The properties of drag reduction of the super-hydrophobic surface are studied by testing the torques with fresh blood,plasma and water respectively on the PU surface with mastoid micro-structure at different periodic space.The results showed that at a certain range, the greater the periodic space of the mastoid micro-structure,the better the drag reduction of the surface.But when the periodic space increased to a certain extent,the effect of drag reduction will reduce with the increase of the periodic space.This is because that the superhydrophobic status of droplets on the surface change.The micro-structures with the different shape and size are fabricated on the surfaces of PDMS,PU,PyC.The effect of fine structure on the hemo-compatibility is studied through the platelet adhesion experiment,dynamic coagulation and hemolysis test experiment.The results show that the periodic space of the micro-structure has significant effection on blood compatibility.At a certain range,the greater the periodic space,the better the blood compatibility,but more than this range,the blood compatibility of the material surface will be worse with the increase of the periodic space.