【作者】 王泽；

【导师】 周明；

【作者基本信息】 江苏大学 ， 机械制造及其自动化， 2013， 博士

【摘要】 消化道是人体主要的消化吸收器官,随着环境污染加剧、工业生产的加快、饮食结构的改变,食道癌、肠道肿瘤等消化道疾病发病率逐年增加。消化内镜检查是消化道疾病诊断、治疗的重要手段,内插式内镜需要借助外力推入人体内病人承受巨大痛苦甚至造成咽喉擦伤、食道黏膜层撕裂、肠胃穿孔等并发症。胶囊式内镜吞服后靠蠕动进入人体内,但存在电量供应不足、无法定位、运动不能控制、体内停滞等问题。主动式微机器人在顺滑消化道内自主行走必须要有足够大的摩擦力,才能为其运动提供驱动力。因此,开展消化道的生物摩擦学研究,为解决消化道组织擦伤、胶囊滞留、微机器人运动方式控制以及内镜结构优化设计具有重要的理论研究意义和学术价值。本文以家兔消化道为研究对象,通过表征其内表面微结构、蠕动时内表面形貌变化、力学性能、肠黏液润滑性和流变性,采用边界润滑理论探索摩擦力变化机理。将肠蠕动简化为正弦波,采用薄壳理论、边界润滑理论和五元粘弹性模型建立摩擦力预测模型。采用Matlab模拟出在肠蠕动条件下,肠道粘弹性变形、肠黏液、内镜尺寸、材料与摩擦力的关系,为无损诊断内镜的设计奠定实验基础推动医用微机器人的研制。摩擦学中表面形貌是影响其摩擦性能的重要因素,本文采用环境扫描电镜对家兔整个消化道内表面的微结构进行观察,结果表明食道、胃、小肠、大肠内表面结构差异很大。食道内表面沿环向分布着不连续的脊状结构,小肠内表面分布着皱襞、绒毛和微绒毛,并且不同肠段绒毛的形状和稀疏程度均不同,胃内表面分布着皱襞和胃小凹,大肠与小肠不同没有绒毛。摩擦学中除了表面形貌外,表面的物理、化学和力学性能对摩擦性能影响也很大。本文采用微摩擦仪和流变仪对肠黏液的流变性、润滑性进行测试,结果表明肠黏液为非牛顿流体具有剪切稀化性,随着剪切率增大粘度降低并趋于一常数,变为牛顿流体。分析认为是肠黏液中的蛋白大分子受到破坏造成的；PDMS塑料薄膜在干摩擦、去离子水、肠黏液条件下摩擦,肠黏液使摩擦系数降低到10-2数量级肠黏液具有良好的润滑性,分析认为肠黏液中的磷脂层具有疏水性覆盖在弹性凝胶层上,可降低吸附力起到滑移减阻的作用。采用微电子拉伸仪对食道、气管、小肠、大肠进行了轴向和环向拉伸,结果表明食道、气管、小肠、大肠的力学性能不同,并且都是各向异性材料,环向伸长比大于轴向伸长比,提出了消化道黏膜层的微结构是影响其力学性能的重要因素。设计了一种新的测试方法能排除粘弹性变形的影响,测试肠道表面形貌的变化与摩擦性能的变化规律。该测试方法制造了五个直径不同的半圆柱体,依次比被测5个样品直径增大0%,20%,40%,60%,80%,将肠道内表面朝外套在半圆柱体上,使5个肠段环向应变率依次为0%,10%,20%,30%,40%,然后测不同应变条件下摩擦系数的变化,结果表明：当环向应变率小于10%,随着速度和载荷的增大摩擦系数上下波动较小基本不变；当环向应变率大于10%,随着速度和载荷的增大摩擦系数上下波动较大,增幅明显。提出了摩擦系数变化的机理：当肠道环向应变率小于10%,润滑形式为混合润滑；环向应变率大于10%,润滑形式转化为边界润滑。建立了肠道产生粘弹性变形和不产生粘弹性变形时的两种摩擦力预测模型,并采用Matlab进行了数值模拟。第一种模型利用薄壳理论和肠道粘弹性变形模型建立肠道蠕动的动力学模型,将蠕动波简化为正弦波,利用五元粘弹性模型和基本摩擦定律推导出摩擦力计算表达式。第二种模型考虑了内镜微型化后,不受肠道粘弹性变形影响仅由内表面形貌和物理化学性质决定,采用边界润滑理论和分形理论推导出了摩擦力计算表达式。仿真结果表明：有蠕动比没有蠕动时胶囊产生的摩擦力大；摩擦力随着胶囊内镜半径、长度、速度增大而增大；半径比长度产生的摩擦力增量大；前进端与驱动端接触角产生的摩擦力增量相当,相同的接触角前进端比驱动端产生的摩擦力大,重力产生的摩擦力可以忽略不计。更多还原

【Abstract】 The digestive tract is the main digestion and absorption organ of human body. With the exacerbating of the severe pollution of the environment, speeding up of the industrial production, changing of the dietetic structure, digestive tract diseases such as esophageal cancer, intestinal cancer incidence increased year by year. Digestive endoscopic checking is an important means of the digestive tract disease diagnosis and treatment, interpolation endoscopic pushed into the patients’body with the aid of outside force may cause great pain to patients and even cause postoperative complications such as throat bruises, perforation of the esophageal mucosa tear and gastrointestinal perforation. Capsule endoscopy, after swallowing, moves into the body by creeping, and it exists some other problems such as shortage of power supply, unable to locate, motion out of control, and stagnation in the body. Active decay robot, if wanting to walk smoothly in the digestive tract, must have enough frictions so as to provide driving force for its movement. So, the biological tribology research on the digestive tract, in order to solve the digestive tract tissue bruise, capsule retention, endoscopic micro robot motion control and structure optimization design has very important theoretical research significance and academic value.Taking rabbit digestive tract as the research object, this paper explores the friction mechanism by adopting the boundary lubrication theory through the characterization of surface topography change within its surface microstructure and creep, rheology, mechanical performance, intestinal mucous lubricity. The paper Simplifies the bowel movements to sine wave and uses the thin shell theory, the boundary lubrication theory and five-elements viscoelastic model to establish the friction force prediction model. The paper uses Matlab to simulate the relationship between intestinal viscoelastic deformation, endoscopic intestinal mucous, size, material and the friction under the condition of intestinal peristalsis, which will lay a solid experimental foundation for the non-destructive diagnosis so as to promote the development of medical micro robots. Tribology in surface morphology is one of the important factors affecting the friction performance, this paper uses the environmental scanning electron microscope to observe the entire inner surface of the digestive tract of rabbit microstructure, the results show that surface structure between esophagus, stomach, small intestine and large intestine is greatly different. Inner surface of esophagus distributes with discontinuous ridge structure, Inner surface of small intestine distributes with fold, small intestine villi and microvilli, and different shapes of the intestine villi with different sparse degree, stomach surface distribute with fold and gastric pit, large intestine different from small intestine has no villi.In addition to surface morphology, in the tribology, the impact of the physical, chemical and mechanical properties on friction is very big also. This article uses the micro friction tester and rheometer to test the rheological properties of intestinal mucous, lubricity, and the results show that intestinal mucous for non-newtonian fluid with shear thinning, along with the increasing of the shear rate, viscosity tends to a constant and becomes into a Newtonian fluid. Analyst say that it was caused by the damage of the protein molecules in intestinal mucous; PDMS plastic film rubs under the condition of dry friction, deionized water, and intestinal mucous, then intestinal mucous will reduce friction coefficient to10-2orders of magnitude, and intestinal mucous has good lubricity. It was showed that the phospholipids layer covering on the elastic gel in intestinal mucous has the dewatering property, and can decrease the adsorption force to have the effect of sliding friction reduction.By adopting micro-electronic stretcher to the esophagus, trachea, small intestine, large intestine, axial and radial tensile, the paper get the results that the mechanical properties of the esophagus, trachea, small intestine, large intestine are different and possess the anisotropic material, and radial elongation ratio is greater than the axial elongation ratio, then it is proposed that the digestive tract mucosa of microstructure is one of the important factors affecting its mechanical performance.We design a new test method which can eliminate the effects of viscoelastic deformation and test the intestinal changes of surface morphology and the change law of friction performance. This test method produces five different semi-cylinders with different diameter which are0%,20%,40%,60%,80%, larger than the diameter of5samples to be tested. To put the inner surface of the intestinal surface on the semi-cylinder and make five bowel radial strain rate was0%,10%,20%,30%,40%, and then test the change of the friction coefficient under different conditions of strain measurement, we got the results that, when the radial strain rate is less than10%, with the increase of speed and load fluctuating smaller, friction coefficient basically remain unchanged; When the radial strain rate is more than10%, coefficient of friction, with the increase of speed and load fluctuation volatile, increases significantly. The paper puts forward the mechanism of the friction coefficient change:when the intestinal radial strain rate is less than10%, lubrication form is liquid lubrication; when the radial strain rate is more than10%, lubrication form becomes into thin film lubrication.The paper established two kinds of friction prediction models of the deformation of intestinal producing viscoelasticity and the deformation of intestinal producing no viscoelasticity respectively, and carried on the numerical simulation by using Matlab. The first model uses the thin shell theory and intestinal dynamic model of viscoelastic deformation model to establish the dynamic model of the intestinal peristalsis, and simplifies the peristaltic wave to sine wave, and uses five-elements viscoelastic model and the basic law of friction friction to deduct the calculation expressions. The second model, after endoscopic miniaturization, has taken into account that no effect by the intestinal viscoelastic deformation is only determined by the surface morphology and the chemical and physical properties, and deduced the friction calculation expression by using boundary lubrication theory and fractal theory. The simulation results show that there are more frictions when squirming than those when not squirming; the friction increases with the capsule endoscopy radius, length, speed; radius produces bigger incremental friction force than length; contact angles of the forward end and drive end produce the same amount of friction; forward end produces more frictions than drive end with the same contact angle, friction gravity produced by gravity is negligible.更多还原