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TY - THES AU - Peng, Yujiang TI - Ultraschallthermoformen PB - Rheinisch-Westfälische Technische Hochschule Aachen VL - Dissertation CY - Aachen M1 - RWTH-2021-08544 SP - 1 Online-Ressource : Illustrationen PY - 2021 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University N1 - Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2021 AB - Ultrasonic thermoforming is a novel process to generate three-dimensional micro structures in the production of thermoplastic microfluidic systems. This thesis focuses on basic investigations of thermoforming with ultrasound. Ultrasonic fabrication techniques are also discussed. For ultrasonic thermoforming, polymer layers are enclosed between two tools and heated up by the vibrations of ultrasound. This way, the polymer adapts to micro structures on the tools within seconds. In the first part of this thesis, basic investigations of ultrasonic thermoforming were launched. Test tools were designed containing micro structures of varied shapes and edge roundings to find out the process window and to better understand the limits of ultrasonic thermoforming. The dimensions of the micro structures fabricated by ultrasonic thermoforming were measured and compared to the dimensions of the tool. No obvious shrinkage of the polymer caused by the process was observed. Experiments showed that rigid tools from aluminum are superior compared to tools from softer material. When using a rigid tool, the process window is much larger. Extra thin foils, 16 to 20 µm in thickness, were successfully thermoformed by a rigid tool with the aid of buffer foils. Measurements showed that the tool fixed on the sonotrode got tens of degrees hotter than the one fixed on the anvil. Both tools got several degrees hotter if the tool with convex microstructures was fixed on the sonotrode compared to fixed on the anvil. On each tool, the temperature in the center was generally higher than in the surrounding area and the difference was about several degrees. The temperature of the thermoformed foils was not homogeneously distributed; it correlated to the shape of the structures. In further developments, electrical elements were integrated into ultrasonically fabricated microsystems. Micro channels and cavities with different dimensions, geometry, and connection were successfully thermoformed into PET-G foils (3 × 5 cm). LEDs were integrated into it by ultrasonic welding with a flat foil. Furthermore, a micro flow sensor with a cylindrical flow channel was fabricated by welding two semi-cylindrical channels onto each other. The flow sensor was tested with three kinds of liquids. Additionally, a variable focus lens was fabricated. Three foils for the lens were ultrasonically fabricated in a single step by combining ultrasonic thermoforming, ultrasonic hot embossing, and ultrasonic punching. After filling with pure water, the focal length of the lens was varied according to the magnetic field generated by an integrated coil. In the last part of this thesis, single-layer PEEK microdiaphragms and composite microdiaphragms were fabricated by ultrasonic thermoforming and welding. Their resonance frequencies were successfully measured and analyzed. LB - PUB:(DE-HGF)11 DO - DOI:10.18154/RWTH-2021-08544 UR - https://publications.rwth-aachen.de/record/825827 ER -