【作者】 叶霞；

【导师】 蔡兰；

【作者基本信息】 江苏大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 置换人工心脏瓣膜是治疗心脏瓣膜疾病的最有效的方法之一,也是临床治疗的最后一步。机械瓣虽然因其具有较长的使用寿命而成为目前临床上使用最为广泛的一种人工心脏瓣膜,但由于其不具有天然心脏瓣膜最优化的血流动力学性能,置入人体后即使患者终身服用抗凝药物,却仍会出现瓣膜血栓形成、血栓栓塞和抗凝相关出血等并发症。因此,解决机械瓣的血液相容性问题是目前机械瓣膜研究工作的中心内容,这项工作不仅具有重要的科学意义,而且具有重大的经济价值和社会意义。师法自然,本文首先研究了老鼠的主动脉瓣、二尖瓣以及白兔的三尖瓣表面的微细结构,发现动物心脏瓣膜表面均匀分布着微米级的“鹅卵石”和许多纳米纤毛。这种与荷叶表面相似的微纳复合阶层结构使得血液流经瓣膜表面时流动阻力减小,血小板在瓣膜表面的粘附也随之而减少,从而最终降低了血栓的形成。同时发现,生物界具有超疏水性能的昆虫翅膀表面的微结构形状和尺度也各不相同。受此启发,为制备具有超疏水性能的仿生人工心脏瓣膜表面,首先构建了二维平行光栅、三维周期方柱、方形凹坑以及乳突微结构,同时根据两种经典超疏水理论——Wenzel理论和Cassie理论,分析了超疏水发生的条件,并分别建立了四种微结构的表观接触角理论模型,初步探讨了表面微结构参数对其疏水性能的影响以及不同微结构形状下两种状态之间的转换。仿生超疏水心脏瓣膜表面微细结构的制备是其性能研究的前提和基础。本课题利用飞秒激光加工技术分别在K9玻璃、聚氨酯、热解炭等心脏瓣膜材料表面加工二维光栅和三维乳突微结构,并进行疏水性能的表征,探讨了加工用激光参数对表面微细结构及疏水性能的影响;同时用软刻蚀法在PDMS表面加工出周期方柱和方孔微结构,通过比较其超疏水性能发现参数相同、形状互补的方柱和方孔微结构的疏水性能也互补。滑移减阻是超疏水微结构人工心脏瓣膜表面的一个重要特性,也是其表面能减少血栓形成的主要因素。本课题利用流变仪研究了超疏水微结构固体表面的流变减阻特性,在验证超疏水表面存在滑移的基础上,推导了超疏水表面滑移长度与减阻率的计算公式。分别用新鲜血液、血浆和水在不同周期间距的乳突微结构聚氨酯表面研究了超疏水表面的流变减阻性能。结果表明,在一定范围内,乳突微结构周期间距越大,其表面减阻性能越好,但当周期间距增大到一定的程度时,减阻效果反而降低了,这是因为液滴在表面的超疏水状态发生了转变的缘故。血液相容性的好坏是衡量人工心脏瓣膜质量高低的关键因素,通过在PDMS、聚氨酯、热解炭三种材料表面构建形状不同、参数不同的微细结构,并通过血小板粘附实验、动态凝血实验以及溶血实验来研究表面微细结构对血液相容性的影响。结果表明,微结构周期间距同样对血液相容性有很大的影响,在一定范围内,周期间距越大,血液相容性越好,但超过这个范围时,材料表面的血液相容性反而会随着周期间距的增大而降低。更多还原

【Abstract】 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.更多还原