| Micro/nano-technique represents the research tendency of future science and technology; it has been counted as the advanced field for priority development by more and more countries. One of the micro/nano-technique development foundations is micro/nano structures and devices fabrication, which has the laser-induced fabrication technique as an important branch. The common feature of current laser-induced microfabrication, like photolithography, excimer laser technology, femtosecond pulse microfabrication etc, is utilizing laser-induced etching effect on material surface to perform the depressed microstructure fabrication. In order to get a convex micro-projection, a novel microstructure fabricating method based on laser-induced thermoplastic formation is introduced in this dissertation for the first time. It can complete real-time fabrication of micro-dot,-pillar,-line,-wall,-bulk etc in various forms and sizes. It has advantages of novel principle, simple equipment, easy operation, no masking, and real-time manufacture. It has an extraordinary scientific meaning and comprehensive application prospect in micro/nano-technique field.This dissertation carries out complete and systematic research on laser-induced thermoplastic formation mechanism, discloses the qualification of dynamic balance in three-dimensional (3D) microstructure manufacturing process. We analyze the photo-thermal effect on material surface generated by laser irradiation, and build a two-dimensional (2D) static model of temperature rising distribution on material surface. This temperature rising distribution generates phase change process, surface tension towards particular direction and circulation inside melt material. These end up with thermoplastic formation above material surface. Then we study the variation of melt material circulation; discuss the balance between melting velocity and solidifying velocity of melt circulation. An equation of dynamic balance in thermoplastic formation process is provided, which has been proved to be the foundation of getting a continuous and stabile thermoplastic formation results. We analyze the main fabricating parameters, and discuss their influences to the thermoplastic formatted microstructures.According to above theoretical analyses, we present and develop the micro-fabrication method based on laser-induced thermoplastic formation. Revolving around this method, an overall scheme of microstructure fabrication based on laser-induced thermoplastic formation is designed. About important influences in microstructure formation process, such as thermoplastic material, temperature of liquid environment and laser irradiation time, systematic researches has been carried out, including selecting thermoplastic material, preparing samples, controlling the temperature of distilled water and manipulating the proper time of thermoplastic formation. Scanning control method is employed to move the sample in three dimensional relatively to laser beam, in order to get microstructures corresponding to the scanning route, and make preparations for fabricating graphic or more complicated microstructures.A 3D microstructure fabricating system based on laser-induced thermoplastic formation has been built up. It consists of laser and its beam path, substrate material, liquid environment and its container, microscopy monitor unit with charged couple device (CCD), step scanning stage. and computer hardware with dependent program. The laser beam path is responsible for laser beam adjusting and focusing, with a shutter to control the fabricating laser beam on and off. As the focal spot irradiated on the substrate material placing in liquid environment, a micro-dot or-pillar is fabricated there. While laterally moving the substrate relatively to the focal spot by a step scanning stage, desire shapes of microstructures can be obtained. To monitoring the laser focusing and observing the formation results instantly, we modify a microscopy monitor unit, displaying the lateral view of laser irradiated zone on substrate surface. The controlling message of laser shutter and scanning path in microstructure fabrication process is output from the computer system.We carry out experimental study of laser-induced thermoplastic micro-fabrication, complete the fabrication of micro-dot,-pillar,-line,-wall,-bulk and other kinds of complicated microstructures. The liquid environment has been proved to be determinant for fabricating results through experiment. Laser diode source and solid laser source have been compared on thermoplastic formation effects. We carry out fabrication experiments on different thermoplastic materials. Micro scale structures can be obtained on polythene (PE) material, while microstructures with better appearance can be obtained on paraffin mixture. The relation between microstructure shape and laser irradiation time has been studied through experiments. We carry out the fabricating parameter optimization study for micro-pillar. For the requirements of high height-width (HW) ratio and small diameter, micro-pillar with HW ratio of 8 and micro-pillar with diameter of 50μm has been achieved. Microstructure arrays have been fabricated, including dot array and pillar array. We study the thermoplastic formation of micro-lines with different laser power and different scanning velocity, analyzing their influences for fabrication results. We also explore the fabrication of complicated microstructures; complete the laser-induced thermoplastic formation of various kinds of complicated microstructures.The achievements of this whole subject are concluded at the end:studying the mechanism of laser-induced thermoplastic formation in both theoretical and experimental ways, approving feasibility of microstructure fabrication based on laser-induce thermoplastic formation, optimizing the fabricating parameters and accomplishing fabricating experiments of different types of microstructures. Besides, we point out some inadequacy of this work, and give some advices on the future research.
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