Stu Dy Of Ultrasonic Imprinting For Polymer Microstructure

With the rapid development of the micro and nanotechnology, polymer micro devices are widely studied in various fields for their high performance. The fabrication of microstructure is one of the key issues in commercialization of MEMS devices. Ultrasonic imprinting is a promising method with the advantage of rapid, clean, short imprinting cycle, and efficient forming. However, it is still in its early stage, so there are still many problems in microstructure forming process, such as undefined impacts on forming from different process parameters, poor replicating forming uniformity of on large area.Take forming the microchannels of microfluidic chip as an example, an ultrasonic imprinting system was built. Based on the combination of function and manufacture, accessory imprinting structures for pressurizing were introduced and mold based on silicon wet etching was made to satisfy the functions of microfluidic chip. Parameters of the imprinting that influence the microstructure forming were studied by finite element simulations and orthogonal experiments. Forming quality and uniformity were analyzed with different ultrasonic imprinting process parameters. High replication accuracy of were reached by the optimized the processing parameters and accessory imprinting structures.The process of ultrasonic imprinting on both surface of microstructure was studied, which improved the efficiency by forming on both sides of the structure. Soda-lime glass molds were fabricated by photolithography and wet etching. Mold-substrate-mode style was selected. The simple variable method was introduced in the experiments to find the relationship between and ultrasonic process parameters and power. Focusing in the defects in the experiments, the method of heat-assisted ultrasonic imprinting was proposed to accomplish replication on both surfaces. The forming quality of substrate was obviously improved after using heat-assisted imprinting method.The impacts of heat-assisted ultrasonic imprinting process parameters on forming were researched using orthogonal method. The experimental results showed that the lower surface was better formed than the upper surface. Different polymer materials, such as PMMA, PVC, PC and COP, were studied and the results shown that the PMMA substrate is the most ideal one.The replicating difference between the two imprinting surfaces in the imprinting experiments indicates that there exists temperature difference between them in imprinting process. A temperature testing system was built to measure the changing of the temperature field in the imprinting process and the temperature curves were analyzed. Comparison to common ultrasonic imprinting, the thermal assisted ultrasonic imprinting has quicker heat generation speed and energy accumulation. So the proper pre-heat temperature can help the heat generation in the ultrasonic imprinting and further improve the replication quality.