基于形状记忆聚合物的柔性内镜变刚度设计与性能研究

     对于柔性内镜而言，微创手术需要内镜经人体自然腔道进行，针对人体内自然腔道狭窄多曲、操作空间有限、手术器械自由度不足、进行手术操作时提供的刚性支撑低、机器人集成程度要求极高等内镜手术的核心问题，研发出具有变刚度特性的柔性连续体手术操作臂，实现操作臂的刚柔转化，是保障微创手术人机交互安全、提升稳定性、兼顾操作精度和力输出的关键。针对上述问题，本文制备了一个应用于柔性内镜的变刚度外鞘结构。将该结构装配于柔性内镜上，可在不同温度刺激下完成较大范围的刚度变化。

     形状记忆聚合物是一种能够通过外界刺激产生变化，使其性能参数随之改变的一类材料，具有可回复形变量大、形变响应温度容易调节、形状记忆效应种类多等优点。本文使用了一种商用形状记忆聚合物材料作为变刚度功能材料，并基于该材料设计了一种集成有冷却层和形状记忆聚合物层的变刚度外鞘，由形状记忆聚合物承担结构的变刚度功能，冷却层承担对形状记忆聚合物的温度控制功能。根据对变刚度外鞘进行传热仿真与不同温度工况下的刚度特性仿真分析与测试结果表明，该变刚度结构可以在较短时间内经温度变化刺激完成柔性内镜的刚度转化，刚度变化最大可达约 140 倍。该变刚度外鞘可以有效改善目前柔性内镜在进行手术操作时刚度不足、稳定性较差的问题，提升手术效率，且结构简单，适用于大部分柔性内镜，在微创手术领域有良好的应用前景和价值。

    For flexible endoscopy, Minimally Invasive Surgery requires the endoscope to be carried out through the natural human cavity. In view of the core problems of narrow and curved natural cavity in the human body, limited operating space, insufficient freedom of surgical instruments, low rigid support during surgical operation, and extremely high requirements for robot integration in endoscopic surgery, a flexible continuous operating arm with variable stiffness cha racteristics has been developed and issued. The rigid-flexible transformation of the manipulator arm is the key to ensure the safety of human -computer interaction in Minimally Invasive Surgery, which can improve the stability, and take into account the operation accuracy and force output. To solve above problems, a variable stiffness sheath structure for flexible endoscopy was designed. When the structure is installed on the flexible endoscope, a wide range of the stiffness changes can be achieved under different temperature stimulation.

    Shape Memory Polymer is a kind of material which can change its performance parameters by external stimulation. It has the advantages of large shape recovery variable, easy adjustment of deformation response temperature and variety of shape memory effect. In this paper, a commercial Shape Memory Polymer material is used as a variable stiffness functional material, and based on this material, a variable stiffness outer sheath with an integrated cooling layer and a Shape Memory Polymer layer is designed. The Shape Memory Polymer is mainly used for the variable stiffness function of the structure, and the cooling layer is used for the temperature control function of the Shape Memory Polymer. According to the heat transfer simulation of the variable stiffness sheath and the simulation analysis and test results of the stiffness characteristics under different temperature conditions, the variable stiffness structure can complete the stiffness transformation of the flexible endoscope in a relatively short time by the stimulation of temperature change, and the maximum stiffness change can achieve about 140 times. The variable stiffness sheath can effectively improve the insufficient rigidity and poor stability of flexible endoscopes during surgical operations, and improve surgical efficiency. Besides, the structure is simple, which is suitable for most of the flexible endoscopes,and has a good application prospect and value in the field of Minimally Invasive Surgery.

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