Study On The Blood Lubrication Properties Based On The Viscoelasticity Model

The wearing abrasion of the research and use of artificial organ mechanical parts, Such as mechanical heart and heart-lung machine, badly affects their longevity and reliability. Favorable lubrication can not only reduce abrasion of the artificial organs, but also guarantee the patient's life safety and improve the life quality. Using the patient's blood as the friction lubricant between the movement parts is an effective way to solve the difficult problem. Blood is a physiological activity fluid, with its complex components and special fluidity,which brings advantage and disadvantage effect of the blood lubrication. Besides, researchers principally concentrated their blood researches on the clinical medicine domain formerly, such as physiology and pathology and so on. There are very few predecessors in literature who attempted to explore the blood lubricating as mechanical parts lubricant.Based on blood hemorheology theory, several physiological and biochemical indexes of the blood were discussed in this paper. Considered the special properties, the linear viscoelastic model of Maxwell Model was used to describe non-newtonian fluid properities of blood in macrocosmic and microcosmic viscoelastic of blood cell. Based on the Maxwell model, the lubricating properties were investigated both from macrocosmic and microcosmic aspects.According to special properties of blood, these factors including deformation,aggregation of blood cell, the component variation, properties of friction interfacial, temperature and so on, these affect the lubricating properties of blood were investigated. According to special lubricating properties of blood, on basis of those factors, a framework of blood lubrication evaluation indexes are proposed:(1)the biological compatibility indicators of the friction interface—thrombus;(2)the biological restrictions indicators—hemolysis;(3)the loading and bearing capacity confine which is evaluation the lubricant;(4)the temperature of the interfacial friction is confined in the range of body temperature of human. The adsorption characters and morpholgy of blood cell and the lubrication properties were decided by the surface properties. The adsorption of blood cell on the surface can affect the lubrication performance. The AFM, in this paper, was used to research the microcosmic morphology and mechanical characters of blood cells, which were absorded on surface Ti alloy and mica. The absorption properties and micromechanical behaviors were investigated from the aspect of micromechanics. Based on the cellar mechanics, the absorption model of blood was build too. On basis of micro-tribology, the micro-friction mechanism of blood cell's suface was discussed. For the first time,the friction force and friction coefficient of blood cell's surface were investigated, and then the principle of friction on the surface of biological cells were researched by AFM. All of these works lay the foundation for improving the blood lubrication effect and decreasing the damage for blood cell.From the viscoelastic characteristics of the blood to the analysis of blood components, the experimental results show that the blood cell hematocrit influences the blood mechanical loading capacity. That is, the greater hematocrit is, the stronger blood loading capacity is. Through macro-friction experiment, the original established macro viscoelastic models of the blood are amended. On the basis of these, relational models between hematocrit of the blood red cells and blood loading capacity are set up. With the dynamic change of blood components and the dynamics of lubrication gap, lubrication state change of the blood lubrication was researched. In view of the blood lubrication, under different lubrication case, different blood lubrication state models were also established.Based on this, Reynolds equations suitable for Maxwell equation were deduced, and then the Reynolds equations were applied to the emulation analysis in the minimal axial blood pump. The corresponding conclusions drawn will provide a basis for further studying the blood lubricating and the optimization of the blood pump structure.