% IMPORTANT: The following is UTF-8 encoded. This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.
@PHDTHESIS{Peng:825827,
author = {Peng, Yujiang},
othercontributors = {Schomburg, Werner Karl and Schnakenberg, Uwe},
title = {{U}ltraschallthermoformen},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2021-08544},
pages = {1 Online-Ressource : Illustrationen},
year = {2021},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, Rheinisch-Westfälische Technische
Hochschule Aachen, 2021},
abstract = {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.},
cin = {417420},
ddc = {620},
cid = {$I:(DE-82)417420_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2021-08544},
url = {https://publications.rwth-aachen.de/record/825827},
}
guest ::