考虑获知SU-8胶的光弹性性能有利于拓展其在微纳米领域中的应用范围, 本文设计了材料应力光学系数显微测量光路, 完成了SU-8胶应力光学系数的测量实验。首先, 基于光弹性原理设计了测量光路, 推导了求解应力光学系数的计算公式; 然后, 根据所设计的光路搭建了应力光学系数显微测量实验装置, 在SU-8胶试样光弹性条纹的单个半级数范围内进行了单向拉伸实验; 最后, 利用Matlab提取实验照片组中光强值信息, 得到了不同拉力下透过SU-8胶试样的单色光光强值, 计算求解出了SU-8胶的应力光学系数。实验结果以及测量公式计算显示, SU-8胶的应力光学系数为(3.007±0.149)×10–11 m2/N, 大于光学玻璃等材料的应力光学系数, 也远大于二氧化硅等MEMS领域常用材料的应力光学系数。实验结果可为以SU-8胶为材料, 通过光弹性原理进行微力测量的微探针、微夹钳等的设计与制作打下基础。

The photoelastic performance of SU-8 photoresist is related to extending its applications to the field of MEMS(Micro-electronic-mechanical System). Therefore, this paper designs a micro-measuring path to obtain the stress-optical coefficient of the SU-8, and implements the measurement experiment of SU-8 photoelastic performance. Firstly, based on the photoelastic mechanism, the micro-measuring optical path was designed and the formulas for the calculation of SU-8 stress-optical coefficient were deduced. Then,, the experiment devices for photoelastic microscopic measurement were built according to the designed optical path, and the tensile test of SU-8 specimen was conducted in the scope of the half order of a single photoelastic fringe. Finally, through extracting the values of the light intensity from the experimental photographs by Matlab, the light intensity of monochromatic light penetrated throught the SU-8 specimen under different tensile forces were measured and the value of SU-8 stress-optical coefficient was calculated. The experimental results and the calculation of measurement formulas show that the stress-optical coefficient of SU-8 is (3.007±0.149)×10–11 m2/N, greater than that of normal optical glass and other materials commonly used in MEMS fields, such as silica. The experimental results can lay a foundation for the design and manufacturing of micro-grippers and micro-probes made from the SU-8 materials and used for the force measurement through photoelastic mechanisms.