| With the development of the research on micro/nano science, it has bacome a hot issue to obtain the force information of the objects under micro/nano-scale. As one of the most important micro-sensors in MEMS field, micro-force sensor can measure the force of the objects in micro/nano scale effectively, and plays a very important role in biomedical, material chemistry and other areas, which can promot the development and innovation of these fields significantly. Therefore, designing and manufacturing a new micro-force sensor, with properties of sample process, short production cycle, low-cost and high sensitivity, good biocompatibility, low power consumption, have great significance.SU-8 is a kind of photoresist, which belongs to epoxy resin. Because of the excellent mechanical properties, processing characteristics and biocompatibility, SU-8 is used in the field of MEMS widely. In addition, as one of the photoelastic materials, SU-8 has good photoelastic property. When light penetrates the SU-8 meteiral with internal stress, double refraction phenomenon will happen because of the photoelastic effect. As a kind of non-contact experimental measurement method, photoelasticity can be used to analyze and solve the problems of sapce stress distribution of the photoelastic materials effectively, which has been applied to engineering, materials, medicine and other macro fields. But in the micro fields, researches on the photoelasticity are rarely reported.This paper proposes a novel micor-force measurement solution based on photoelastic mechanism. Through this solution, a new type of micro-force sensor, whose material is SU-8, is designed and fabricated.Firstly, the principle of photoelasticity is analyzed, and the theoretical verification of above-mentioned micor-force measurement solution based on photoelastic mechanism is conducted. Then, the optical path of micro-force measuring system for SU-8 micro-force sensor is designed.Secondly, the photoelastic performance of SU-8 material is studied. During the study, it is important to obtain the stress-optic coefficient in order to analyze the photoelastic property of SU-8. Thus, in this paper, the optical path of SU-8 material stress-optical coefficient micro-measuring system is designed and set up, and the formulas for the calculation of SU-8 stress-optical coefficient are derived. Then, the tensile test of SU-8 specimen that is produced by MEMS technology is carried on and the measurement of SU-8 material stress-optic coefficien is completed. According to the experimental results, the stress-optical coefficient of SU-8 material is (3.007±0.081)×10-11 m2/N. which lays a foundation for the design and manufacturing of the micor-force sensor.Finally, according to the propsoed micro-force measurement solution, the whole structure of SU-8 micro-force sensor is designed and the finite element simulation analysis is conducted. Then, the micro-force sensor is fabricated by MEMS technology based on the above-mentioned work and the process parameters are optimized. After building the relationship between the received optical signal and micro force that is applied to the sensor, the experimental measurement devices for micro-force sensor are set up. and the performance test of SU-8 micro-force sensor is conducted within the scope of the half order of single photoelastic fringe. According to the experimental results, the measurement range of SU-8 micro-force sensor is 0?3000?N, the force sensitivity is 1.26667×10-6/?N, the linearity error is 8.64%, the repeatability error is 4.59% and the resolution is better than 30?N.The experimental results indicate that the designed micro-force sensor can realize the measurement of micro-force. At the same time, SU-8 micro-force sensor has advantages of sample process and short production cycle. In addition, due to the good biocompatibility of SU-8 and the non-contact measurement of photoelasticity, this sensor has potential values and wide applications in biomedical and material chemistry researches. |
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