Stuttgart, Univ., Diss., 2007.

Stuttgart, Univ., Diss., 2008.

Konstanz, Univ., Diss., 2006.

Zugl.: Hamburg, Techn. Univ., Diss., 2009

Zugl.: Freiburg (Breisgau), Univ., Diss., 2004.

Zugl.: Karlsruhe, Univ., Diss., 2008 / Hergestellt on demand

Der 3D-Druck ist ein elementarer Bestandteil der Biofabrikation. Beispielsweise wird mittels Biotinten und einem geeigneten 3D-Druckverfahren Schicht für Schicht eine Geometrie aufgebaut. Durch die Gestaltung von mikrofluidischen Druckköpfen wird eine Möglichkeit geschaffen multiple Materialansätze im Druckkopf zu vermischen und so in einem bestimmten Mischungsverhältnis zu drucken. Mit dem DLP-SLA-Drucker Vida HD Crown and Bridge (EnvisionTEC) und dem Harz E-Shell 600 (EnvisionTEC) wurden zunächst die Auflösungsgrenzen des Druckers ermittelt sowie Komponenten für die Realisierung eines mikrofluidischen Druckkopfes prozessiert. Bei den Komponenten handelt es sich zum einen um Geometrien, die beispielsweise als Mischeinheit im Kanal dienen können und des Weiteren um senkrechte Kanäle die Biotinten führen können, sowie um Kanäle, die als Zuläufe für den Hauptkanal des mikrofluidischen Druckkopfs dienen können. Die Eigenschaften und die technische Realisierbarkeit der gedruckten Objekte wurden eruiert. Dabei wurden die jeweiligen Geometrien und Kanalöffnungen vermessen, große Aspektverhältnisse der Geometrien untersucht und die Durchgängigkeit der Kanäle geprüft. Zukünftig können die prozessierten Komponenten für einen mikrofluidischen Druckkopf variabel kombiniert werden und auf dieser Basis weiterführende Experimente stattfinden. / 3D printing is an essential part of biofabrication. For example, geometries are built up layer by layer using bio-inks and a suitable 3D printing process. New options are given by the fabrication of a microfluidic print head. The design of microfluidic print heads creates the possibility of mixing multiple materials inside the print head and thus start printing certain mixing ratios. The resolution limits of the DLP-SLA printer Vida HD Crown and Bridge (EnvisionTEC) using the resin E-Shell 600 (EnvisionTEC) were first determined and components for the layout of a microfluidic print head were processed. The components are, on one hand, geometries that can serve as a mixing device inside the channel, and on the other hand, vertical channels that can carry bio-inks and channels that serve as inlets for the main channel of the microfluidic print head. The properties of the printed objects were examined, the respective geometries and channel openings were measured, large aspect ratios of the geometries were examined and the consistency of the channels investigated. In future, the processed components for a microfluidic print head can be combined variably and further experiments can take place on this basis.

Zugl.: Freiburg (Breisgau), Univ., Diss., 2009

The mechanical parameters of biological cells are relevant indicators of their function or of disease. For example, certain cancerous cells are more deformable than healthy cells. The challenge consists in developing methods that can measure these parameters while not affecting the cell. The Optical Stretcher is a microfluidic system that deforms single suspended cells without contact using lasers and determines the cells’ viscoelastic properties. The advantage compared to standard methods of molecular biology is that cells do not need to be treated with additional markers. Basic versions of the Optical Stretcher have existed for some years. These allow the measurement of homogeneous cell populations. Up until now, it was only possible to calculate average population values of compliance. To characterize inhomogeneous populations however, it is necessary to consider each single cell and measure additional mechanical or optical parameters such as the refractive index. This work highlights various extensions of the Optical Stretcher. A novel procedure, including an improved image processing algorithm, is presented to analyze mechanical data in real time. In combination with measurements of the optical refractive index, single cells can now be characterized in more detail. Moreover, it is now possible to extract interesting subpopulations that can be further examined with molecular biology techniques. Depending on the intended purpose, novel devices for cell measurements, based on microfluidic and optical considerations, are presented. The fundamental concept involves microstructured chips that can be integrated into a commercial microscope. These chips offer the possibility of separating measured cell populations according to their mechanical properties. This separation, including mathematical classification, is demonstrated. These methods are tested with cell types of differing mechanical properties to prove their applicability in practice. Single cells are sorted into their respective population of origin. These novel methods offer the possibility of a versatile device to be applied in biophysical research.

Zugl.: Dresden, Techn. Univ., Diss., 2008