Theoretical Study on Micro-scaled Optical Stress Sensors

微尺度光學壓力傳感器的理論研究

Student thesis: Doctoral Thesis

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Award date25 Aug 2023

Abstract

With the development of robotic science, stress sensors become more and more important. The advancements of artificial intelligence (AI) and Internet of Thing (IoT) makes the miniaturization and integration of sensors become a significant development direction, for example, to build sensors on one chip. The optical stress sensor is a very important category of the stress sensor, and the microbend optical stress sensor and the optical stress sensor based on the stress-optical effect are also important members in optical stress sensor family. However, most of the existing microbend optical stress sensor and the optical stress sensor based on the stress-optical effect in the literatures have relatively large sizes, and some of them have the intricate structures. It is difficult for them to be miniaturized and integrated. In addition, the simulation methods for these two types of optical stress sensors in the literatures are not fruitful, and some of them have complex calculation. In this project, the micro-scaled microbend optical stress sensor and micro-scaled optical stress sensor based on the stress-optical effect with the sizes from dozens of micrometers to one hundred and more micrometers were modeled and simulated with convenient and efficient methods. The force field and the electromagnetic wave field were coupled together to solve the models. The simulation results in this project were validated by the similar existing experimental and simulation results in the literature. These two types of micro-scaled optical stress sensors in this project represent the dynamic sensor and the static sensor in this project, respectively.

For the micro-scaled microbend optical stress sensor, the SU8 and Ag film were first introduced into the microbend optical stress sensor, and the micro-scaled multilayered fiber structures of the microbend optical stress sensor were modeled and simulated after the experimental tests of the microbend optical stress sensor units in principle. The Glass/Ag/SU8/PDMS model has good comprehensive performances of sensitivity, linearity, and detectable range among the three models in this part.

For the micro-scaled optical stress sensor based on stress-optic effect, the models with different structures and materials were modeled and simulated. The fiber-like structure and the straight structure had their respective advantages. The models with glass material shown the higher sensitivity compared with other models. The variation trend of the amplified difference of normalized output power will be changed due to the different materials, and the material selection has the significant effects on the sensitivity of the models, which is very valuable for the model design. All the models in this part shown the good performance and high-linear responds to the applied force.

The works in this project provide the routes and possibilities for the design and fabrication of optical stress sensors, especially in the micro-scaled size, on the aspects of both structure and material. This project will promote the development of optical stress sensors with the direction of miniaturization and integration in the future.

    Research areas

  • Optical stress sensor, Micro-scaled, Microbend, Stress-optical effect, Simulation