The Studies Of Ti-O/Ti-N Gradient Film On Artificial Heart Valve

At present,a large number of studies have shown that the blood compatibility of TiO₂ is superior to that of LTIC(which has been widely applied to anti- thrombin material for artificial heart valve).In order to apply TiO₂ to surface modification of artificial heart valve to improve the blood compatibility,we proposed to apply TiN/TiO₂ to surface modification of the artificial heart valve.In this way,we both improved the blood compatibility and mechanical properties of the artificial heart valve.Four transitional modes form TiN to TiO₂ had been designed,and TiN/TiO₂ composite films had been deposited on Ti6A14V by unbalance magnetron sputtering as well.The result indicated that after the deposition of TiN film,the N₂ flow was gradually decreased to Osccm and deposited Ti,then gradually increased the O₂.By this method,compared to TiO and Ti/TiO films,we found the TiN/Ti-O composite film had the best mechanical property.Afterwards Ti/TiN multilayer films and Ti-O films were prepared on the valve ring.We studied the influence on the properties of Ti/TiN multilayer films by different deposition time of the Ti,TiN in each period. The results showed that the deposition time in each period would determine the formation of multilayer films and the mechanical properties. when the deposition time of the Ti,TiN was respectively 72s,180s,the Ti/TiN multilayer films,which have obvious multilayer structure and are composed of Ti₂N and TiN phases with modulation period of 100nm, show high hardness and wear resistance.The titanium films with different microstructure and properties were synthesized at different O₂ flow by unbalance magnetron sputtering.When the O₂ flow is 14sccm,the film, which is rutileTiO₂ crystal,possesses semiconducting behavior and water contact angle is 57.5°.The PLT adhesion experiment indicated this kind of film possessed the best blood compatibility.Finally,TiN/TiO₂ composite film was synthesized on valve ring by unbalance magnetron sputtering.We researched its mechanical properties (hardness,wear resistance,film-substrate cohesion),and found that the mechanical properties of TiN/TiO₂ composite film were much better than that of TiO₂ film.In order to simulating the artificial heart valve working in human body,we did the wet rubbing experiment in SBF solution.The test indicated the main wear mechanism of the film is fatigue abrasion. First,the Ca,P salt deposited on the surface of the film and were compacted by the sliding of the SiC ball.Then the crackle occurred and extended during cyclic loading of the contact stress.Finally,the film dropped.We have prepared TiO₂ film which has good blood compatibility and TiN/TiO₂ composite film with both good blood compatibility and excellent mechanical capability.Those researches have important significance for the surface modification of the artificial cardiovascular material.The Ti/TiN multilayer film which we deposited on the workpiece with complex shape shows good mechanical properties.This result will improve the manufacture level of industry and will produce many economic and social benefits.