基于柔顺机构的人工晶状体设计、制备及实验研究

发布时间：2018-04-28 22:42

本文选题：人工晶状体 + 柔顺机构　；参考：《北京工业大学》2016年博士论文

【摘要】：柔顺襻人工晶状体是人工晶状体(intraocular lens,IOL)与柔顺机构相融合形成的新型IOL,由于使用柔性铰链传递机构运动,结合柔顺微位移放大机构设计,可从根本上解决传统襻结构调节力不足的问题,从而有效提高IOL的屈光能力。目前,国内外研究主要集中在IOL光学部可以产生超大形貌变化的生物医学材料的开发研制以及具有微调节作用的IOL襻结构的构型设计和形变分析上,而结合机构学理论的IOL构型设计这一交叉研究新方向尚未被提出,使用柔顺微位移放大机构替代传统襻结构所带来的优越性也尚未被揭示出来。因此,开展基于柔顺机构的IOL襻结构研究具有重要的理论意义和广阔的应用前景。本文以IOL为研究对象,围绕IOL的建模、设计、制备以及实验四个方面,开展了系统的理论和实验研究。在建模方面:建立了新型人眼晶状体和IOL的结构参数化模型与屈光有限元模型。根据不同来源、不同个体的活体眼晶状体及其周围组织的形态和生理特点,以患者年龄为自变量,以晶状体囊膜和核的直径、厚度、前后极点曲率半径为因变量,并进一步考虑了赤道部脊的宽度以及囊膜在极点处厚度情况,建立了人眼晶状体结构的三维参数化模型,并依此设计了IOL光学部的结构参数。这些工作为开展IOL光学部的设计及实验研究提供了有效工具。在设计方面:首先,基于晶状体皮质的折射率梯度模型和屈光有限元模型,首次提出使用聚二甲基硅氧烷(polydimethylsiloxane,PDMS)生物医学材料作为IOL光学部材料,研究了不同调节幅度对光学部形貌变化及屈光力的影响。其次,基于杠杆原理和三角原理分别开展了IOL襻结构的研究。针对IOL调节力不足的问题对柔性关节进行了设计,通过定义中间参数,推导出了椭圆弧型柔性铰链在平面受力状态下的柔度计算公式,分析了切口处几何形状、尺寸及最小厚度与铰链性能之间的关系,通过有限元分析多个不同尺寸的椭圆弧型柔性铰链,印证了理论分析的正确性。采用多个单级放大机构叠加的组合方式,分别设计了适用于囊袋内的基于杠杆原理和三角原理的柔顺微位移放大机构,两种机构的末端输出位移分别放大约10倍和25倍,大幅度提高了输出位移,表明了设计方案的有效性。再次,基于结构拓扑优化技术开展了IOL襻结构的设计。利用拓扑优化技术和有限元方法,以结构末端输出端位移最大化和质量最小化为优化目标,建立了优化数学模型,结合Hypermesh拓扑优化模块建立拓扑优化结构模型,分别进行刚性几何模型和柔性几何模型的重建及仿真分析。通过改变设计域高度,获得了满足不同设计域的结构,并探寻到构型与设计域之间的变化规律;通过对相同设计域内的结构进行对比分析,总结了机构各部件的几何参数与放大比之间的规律,设计了可满足于不同设计域,实现不同倍数放大的初始微位移放大机构的参数化模型。在制备方面:提出了IOL光学部和襻结构的新型制备工艺。基于液体表面张力现象,考虑材料间的浸润性问题,采用PDMS材料,通过控制温度、体积、时间的变化,以悬滴的方式三步成型制备双凸透镜,形成多种表面曲率组合的双凸透镜。基于3D打印技术,通过Solid Edge三维模型转换成STL文件格式,导入切片软件后,调整操作参数,整体放大结构比例(5倍),完成四种微位移放大机构的制备。测量结果表明,柔性铰链部分的制造误差不超过5%。在实验方面:进行了IOL光学部光学性能、光襻结构的形貌及位移变化和IOL屈光调节的实验研究。基于文中建立的驱动系统平台,使用焦距测量系统测得PDMS透镜的屈光力约为277.001D,与理想结果相差仅为2.2%,表明了建立的焦距测量系统的可行性和准确性。进行光学部屈光力测量和襻结构输出放大比的测量,结果表明,与未发生调节作用时相比,PDMS透镜的焦距最大可减小至约3.01mm,在空气中的最大屈光能力可以达到约327.226D。杠杆机构和三角机构的实际位移放大比比理想值降低了约50%,而采用拓扑优化方法设计的机构的实际放大比与理想放大比较为相近。基于人眼光学系统的工作原理,建立了IOL的光学系统模型,IOL在蒸馏水中的最高屈光能力约23.02D,达到并超过了预期设计目标(8.0D的正常生理调节水平),显著提高了IOL的调节幅度,验证了本文提出的通过改变IOL光学部形貌来增加调节幅度的方法的有效性,以及在有限操作域内以柔顺微位移放大机构替代传统单一襻结构进一步增加调节幅度的可行性和有效性。
[Abstract]:The flexible loop IOL is a new type of IOL which is formed by the fusion of intraocular lens (IOL) and the compliant mechanism. Due to the use of flexible hinge transfer mechanism and the design of compliant micro displacement amplification mechanism, it can fundamentally solve the problem of insufficient regulating force of the traditional loop structure, thus effectively improving the refractive power of IOL. The internal and external research focuses on the development and development of biomedical materials which can produce ultra large morphologies in the IOL optics, and the configuration design and deformation analysis of the IOL loop structure with micro regulation. The new direction of the cross study, which combines the IOL configuration design of the mechanism theory, has not yet been put forward, and the flexible micro displacement amplification mechanism is used. The advantages of replacing the traditional loop structure have not been revealed. Therefore, it is of great theoretical significance and broad application prospect to carry out the research on the IOL loop structure based on the compliant mechanism. This paper takes IOL as the research object, and carries out the theoretical and Experimental Research on the modeling, design, preparation and experiment of IOL in four aspects. In the modeling aspect, the structural parameterization model and the refractive finite element model of the new human eye lens and IOL were established. According to the different sources, the morphological and physiological characteristics of the lens and the surrounding tissues of the living eye of the different individuals were based on the patient's age as the independent variable, the diameter of the capsule and nucleus of the lens, the thickness, the radius of the radius of the curvature of the pole and the pole. In addition, the width of the equatorial ridge and the thickness of the capsule at the pole are considered. A three-dimensional parametric model of the lens structure of the human eye is established, and the structural parameters of the IOL optical part are designed. These work provide an effective tool for the design and experimental research of the IOL optics. The refractive index gradient model and the refractive finite element model of the cortex have been proposed for the first time using polymethylsiloxane (polydimethylsiloxane, PDMS) biomedical materials as IOL optical materials. The effects of different amplitude of adjustment on the change of optical morphology and the refractive power are studied. Secondly, the IOL haptics are carried out based on the principle of lever and the principle of trigonometry. The flexible joint is designed for the lack of IOL regulation force. By defining the intermediate parameters, the flexibility calculation formula of the elliptical arc flexure hinge under the plane force is derived. The relationship between the geometric shape, the size and the minimum thickness of the notch and the performance of the hinge chain is analyzed, and a number of finite element analysis is used to analyze the joint. The correctness of the theoretical analysis is confirmed by the different sizes of the flexible hinges of elliptical arc type. The flexible micro displacement amplification mechanism, based on the principle of lever and the trigonometric principle, is designed, using the superposition method of multiple single stage magnifying mechanisms. The end output displacement of the two mechanisms is about 10 times and 25 times respectively. The output displacement is improved and the effectiveness of the design scheme is demonstrated. Thirdly, the design of the IOL loop structure is carried out based on the topology optimization technology of structure. By using the topology optimization technique and the finite element method, the optimization mathematical model is established with the optimization goal of the maximum output end displacement and the quality minimization of the structure, and the Hypermesh topology optimization model is established. The block topology optimization structure model is set up to reconstruct and simulate the rigid geometric model and the flexible geometric model respectively. By changing the height of the design domain, the structure which satisfies the different design domains is obtained, and the changes between the configuration and the design domain are explored. The structure of the same design domain is compared and analyzed, and the machine is summarized. The parameters between the geometric parameters and the magnification ratio are constructed, and a parameterized model for the initial micro displacement amplification mechanism with different magnification is designed. In preparation, a new preparation process of the IOL optical and loop structure is proposed. Based on the liquid surface tension, the wettability of the material is considered. By using PDMS material, by controlling the change of temperature, volume and time, the double convex lens is prepared by three steps of hanging drop, and a variety of double convex lens with surface curvature combination is formed. Based on 3D printing technology, the Solid Edge 3D model is converted into a STL file format, and the operation parameters are adjusted, and the overall amplification structure ratio (5) is adjusted. The measurement results show that the manufacturing error of the flexure hinge part is not more than 5%. in the experiment: the optical properties of the IOL optics, the change of the shape and displacement of the loop structure and the experimental study of the IOL diopter are carried out. Based on the driving system platform established in this paper, the focal distance measurement system is used. The refractive power of the PDMS lens is about 277.001D, and the difference between the ideal result is only 2.2%, indicating the feasibility and accuracy of the established focal length measurement system. The measurement of the optical refractive power and the loop structure output amplification ratio is measured. The results show that the focal length of the PDMS lens can be reduced to about 3.01mm, as compared with the non regulation effect. The maximum refractive power in the air can reach about 50% of the actual displacement amplification ratio of about 327.226D. lever mechanism and trigonometric mechanism, and the actual amplification ratio of the mechanism designed by topology optimization is similar to that of the ideal amplification. Based on the working principle of the human eye optical system, the optical system model of IOL is established, I The maximum refractive power of OL in distilled water is about 23.02D, reaching and exceeding the expected design target (the normal physiological regulation level of 8.0D), which significantly improves the adjustment range of IOL. The validity of the method proposed in this paper is proposed by changing the morphology of the IOL optics to increase the amplitude of the adjustment, and the flexible micro displacement is placed in the limited operating domain. Large organizations replace traditional single loop structures to further increase the feasibility and effectiveness of adjustment.

【学位授予单位】：北京工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH112

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