【作者】 张然；

【导师】 褚金奎；

【作者基本信息】 大连理工大学 ， 微机电工程， 2013， 博士

【摘要】 随着MEMS技术的不断发展及对物质在微/纳尺度特性研究的深入,研究和开发适用于复杂MEMS器件微装配及对各种具有微/纳尺度研究对象进行微操作的微夹持系统,能够很好地促进这些领域的发展。作为末端执行部分的微夹持器是微夹持系统与被夹持对象之间的接口,其夹持效果直接决定微夹持系统的性能,因此微夹持器已成为目前的研究热点。对目前微夹持装置的研究现状进行分析可知,电热驱动微夹钳具有结构紧凑、控制容易及输出力较大等优点。而SU-8胶材料具有高热膨胀系数、低热导系数、良好的生物兼容性和较好的工艺性等特点,特别适合制作电热微夹钳。基于以上原因,本文以电热驱动SU-8微夹钳为研究对象,对其设计、制作及测试等相关问题进行了深入研究。在设计方面,针对目前设计方法的不足,提出了一种电热驱动微夹钳柔性机构的系统设计方法。首先归纳及推导了明确的用于微夹钳柔性机构拓扑结构设计的选择准则。利用选择准则对用于微夹钳拓扑结构设计的六杆、八杆及十杆对称单自由度刚性机构进行了综合,得到了66种备选机构。为避免在几何优化过程中对设计者经验的依赖,提高优化效率,基于刚度矩阵方法建立微夹钳参数化刚度模型,利用所建模型对微夹钳几何尺寸进行优化。采用该系统设计方法,设计出一种钳口常闭型(A型)及一种钳口常开型(B型)电热驱动SU-8微夹钳,由ANSYS软件仿真结果可知,优化结果满足设计要求,性能优于经验设计,A型及B型微夹钳的放大倍数分别为30.4和14.8。基于拓扑优化方法及伪刚体模型方法对具有纳米级钳口结构电热驱动微夹钳进行了设计。提出了一种具有三层对称三明治结构的新型SU-8胶V形电热驱动器,考虑了聚合物材料电、热耦合及多材料结构热膨胀分布不均问题,能够有效避免驱动过程中的平面外运动,并具有驱动电压低、工作温度低及结构紧凑等特点。采用整体释放及双面溅射工艺对设计的电热驱动SU-8微夹进行了成功制作,并对影响加工质量关键工艺参数进行了优化。针对所设计具有纳米级钳口结构电热驱动微夹钳的结构特点,提出了一套采用纳米压印工艺与微加工工艺相结合的制作工艺,并对该工艺进行了初步探索。搭建了一套微夹钳微操作及性能测试系统,在25℃的洁净实验室环境下,对制作出的A型及B型微夹钳进行了钳口位移输出特性及驱动器温度特性测试。由测试结果可知：A型微夹钳需73.6mV的驱动电压(此时输入功率25.61mW,驱动器平均温升45℃),可输出107.5μm的钳口距离变化量,其钳口响应时间均约为0.3s。对于B型微夹钳,施加195mV的驱动电压(此时输入功率为111.1mW,驱动器平均温升为53.7℃)可使钳口闭合,钳口距离变化量为-71.51μm,其钳口响应时间均约为0.23s。在测试过程中,两型微夹钳钳口的平面外位移小于500nm,证明了电热驱动器结构的合理性。A型微夹钳的驱动效率为4.18μm/mW,在已报道的同类微夹钳中最大。同时,A型及B型微夹钳所需驱动电压在同类微夹钳中最低。提出了一种基于SU-8胶压阻式微悬臂梁微力传感器的微夹钳夹持力直接测量方法,并研制了相应的测量装置,实现了对微夹钳夹持力的直接测量。基于该测量装置,对制作出的两种微夹钳进行了夹持力测量及钳口刚度标定。由实验结果可知：A型及B型微夹钳的钳口刚度分别约为2.83N/m及7.22N/m,满足设计要求。该方法所用传感器结构简单,成本低,精度与尺寸满足微夹钳夹持力测量需要。为验证微夹钳的夹持效果,在25℃的洁净实验室环境下,采用A型及B型微夹钳成功地进行了毛发和长耳鸮覆羽羽小枝微拉伸测试试样的微装配实验,又成功地对PS小球、微血管标本和蓝藻细胞进行了微操作实验。实验结果说明这两种微夹钳可以很好地完成多种形状及尺寸的微小生物试样及微小物体的微操作及微装配。更多还原

【Abstract】 To promote the MEMS technologies and the studies of microscale and nanoscale effects, it’s necessary to develop the micro-gripping system which is suitable for the micro-assemblies of complicated MEMS devices and the micro-manipulations of microscale and nanoscale objects. As the end execution part of the micro-gripping system, the microgripper is the interface between the micro-gripping system and the gripped object. Therefore, the performances of the micro-gripper system are directly determined by the clamping capacity of the microgripper which has become a reseach focus currently. Based on the analysis of the current research achievements of micro-gripping devices, it can be known that electrothermal microgrippers have many advantages such as compact structure, easily control and relatively large gripping force. And with the characteristics including a relatively high coefficient of thermal expansion, low coefficient of thermal conductivity, good biocompatibility and simple processing, SU-8is suitable to be the material of electrothermal microgrippers. For these reasons, the design method, fabrication processes and performace tests of the electrothermal SU-8microgripper is studied in this thesis.A new systematic design procedure for the compliant mechanisms of electrothermal microgrippers is presented. The explicit selection terms for the compliant mechanisms topology design are summarized and proofed firstly. Based on the selection terms, the structural synthesis of the symmetrical one-DOF6-bar,8-bar and10-bar rigid-body mechanisms for the microgripper compliant mechanism topology design is carried out, and66reasonable mechanisms are obtained. In order to avoid the reliance on designer’s experience and improve the design efficiency, the stiffness parametric modeling of microgripper is carried out based on the stiffness matrix model method. And then the geometric size optimizes are implemented based on the proposed models. A normally closed type (A type) and a normally open type (B type) electrothermal SU-8microgripper are designed using the systematic design procedure. According to ANSYS software simulation results, the obtained microgrippers meet the design requirements, and their performances are better than the empirical designs. The amplification ratios of A type and B type microgripper are respectively30.6and14.8. Then, the SU-8electrothermal microgripper with nanoscale jaws is designed based on the topology optimization method and the pseudo-rigid model method.Considering the polymer electricity and thermal coupling and the thermal expansion uneven distribution of multi-material structure, a novel SU-8chevron electrothermal micro-actuator with three-layer symmetrical sandwich structure is proposed. Without the out-of-plane actions, the novel micro-actuator has the advantages of low driving voltage, low working temperature and compact structure. Then, the designed microgrippers are successfully fabricated using the entire piece releasing process and two-sided sputtering process process. And the critical process parameters affecting the processing quality are optimized. A fabrication process combining micro fabrication process and nanoimprint process is proposed for the fabrication of the designed microgripper with nanoscale jaws. A preliminary study of the proposed process is carried out.A micro-manipulation and performance test system of fabricated A type and B type microgripper is developed for the measurements of jaw displacement output characteristics and the actuator temperature characteristics. The test experiments are carried out at25℃in clean laboratory. The experimental results demonstrate that for A type microgripper, a jaw gap change of107.5μm requires only73.6mV,25.61mW and only44.92℃average temperature increase at the actuator, and the jaws response time is about0.3s. For B type microgripper, with195mV,111.1mW and53.7℃average temperature increase at the actuator, a71.5μm jaws gap change is obtained, making jaws to be cloesd. The jaws response time of B type microgripper is about0.23s. During both performance tests, the out-of-plane actuations of jaws are less than500nm, which verifies the rationality of the micro-actuator structure. It can be known that A type microgripper has the maximum driving efficiency (4.18μm/mW) in the reported SU-8electrothermal microgrippers. And A type and B type microgripper require lower voltages than others.This thesis presents a direct measuring method of microgripper gripping force based on SU-8micro-cantilever sensors with integrated copper piezoresistive strain gauge. The corresponding measuring device is developed and the direct measurements of microgripper gripping forces are implemented. Then, the micro gripping forces of two developed microgrippers are measured by the developed device and the jaw stiffness calibrations are also carried out. According to the experiment results, A type microgripper has a jaw stiffness of about2.83N/m and the jaw stiffness of B type microgripper is about7.22N/m. The calibration results meet the design requirements. With a simple structure, appropriate size and measurement accuracy, the low cost micro-cantilever sensor is suitable for the microgripper gripping force measurements.In order to test the gripping performances, micro-assembly experiments of specimen of fine hair and asio otus covert feather barbule for micro-tensile testing, and micro-manipulation of PS balls, micro blood vessel specimen and cyanobacteria cell are successfully implemented using A or B type microgripper. The test experiments are carried out at25℃in clean laboratory. The experiment results demonstrate that the developed microgrippers can accomplish many micro-manipulation and micro-assembly experiments of microscale objects and biological samples with a variety of shapes and sizes.更多还原