TY - THES A1 - Gruber, Julia T1 - Gefrierstrukturierung von Biopolymer-Keramik-Kompositen T1 - Freeze-Structuring of Biopolymer-Ceramic-Composites N2 - Das Ziel der vorliegenden Arbeit war, die Gefrierstrukturierung von Biopolymer-Keramik-Kompositen zur Nachahmung von osteochondralem Gewebe zu untersuchen. Dies diente der Forschung an alternativen Therapiemethoden zur Regeneration von osteochondralen Defekten, da durch derzeitige Therapien oftmals nur ein minderwertiger Reparaturknorpel gebildet wird und keine langfristigen Erfolge erzielt werden. Die Herstellung der Proben zur Nachahmung von osteochondralem Gewebe erfolgte mit der Technik der Gefrierstrukturierung, wodurch anisotrope und hoch geordnete Systeme erhalten wurden. Im Rahmen einer systematischen Untersuchung wurden mehrere Parameter, wie beispielsweise der externe Temperaturgradient, variiert und deren Auswirkungen auf die Proben untersucht. Im ersten Versuchsteil wurde die bidirektionale Gefrierstrukturierung untersucht, um die Morphologie der hergestellten Proben zu optimieren. Anschließend wurden zweischichtige Alginat- bzw. Kollagen-Bruschit-Systeme zur Nachahmung von osteochondralem Gewebe hergestellt. Die erste Schicht sollte Knochen imitieren, während die zweite Schicht Knorpel nachahmte. Die Morphologie der hergestellten Proben wurde unter dem Stereo- und Rasterelektronenmikroskop untersucht. Zur Untersuchung des mechanischen Verbundes zwischen den Schichten wurden Zugversuche durchgeführt. Alle hergestellten Systeme waren hoch geordnet und anisotrop. Die zweischichtigen Systeme wiesen einen Verbund beider Schichten auf und durch die Variation verschiedenster Parameter konnte ein näheres Verständnis des Einflusses dieser auf die Probenmorphologie erlangt werden. N2 - The aim of the present work was to investigate the freeze-structuring of biopolymer-ceramic-composites to mimic osteochondral tissue. This served to research alternative therapy methods for the regeneration of osteochondral defects, as current therapies often do not achieve long-term success. The preparation of samples to mimic osteochondral tissue was performed using the technique of freeze-structuring, obtaining anisotropic and highly ordered systems. As part of a systematic investigation several parameters, such as the external temperature gradient, were varied and their effects on the samples were studied. In the first part of the experiment, bidirectional freeze-structuring was investigated to optimize the morphology of the prepared samples. Subsequently, two-layered alginate- or collagen-bruschite-systems were prepared to mimic osteochondral tissue. The first layer was intended to mimic bone, while the second layer mimicked cartilage. The morphology of the prepared samples was examined under the microscope. Tensile tests were performed to investigate the mechanical bond between the layers. All the fabricated systems were highly ordered and anisotropic. The two-layered systems had a composite of both layers and by varying a wide range of parameters, a more detailed understanding of the influence of these on the sample morphology could be obtained. KW - Gerichtete Erstarrung KW - Gefrierstrukturierung KW - Freeze-Structuring KW - Osteochondrales Gewebe Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259533 ER - TY - JOUR A1 - Seifert, Annika A1 - Gruber, Julia A1 - Gbureck, Uwe A1 - Groll, Jürgen T1 - Morphological control of freeze‐structured scaffolds by selective temperature and material control in the ice‐templating process JF - Advanced Engineering Materials N2 - Herein, it is aimed to highlight the importance of the process parameter choice during directional solidification of polymer solutions, as they have a significant influence on the pore structure and orientation. Biopolymer solutions (alginate and chitosan) are directionally frozen, while systematically varying parameters such as the external temperature gradient, the temperature of the overall system, and the temperatures of the cooling surfaces. In addition, the effect of material properties such as molecular weight, solution concentration, or viscosity on the sample morphology is investigated. By selecting appropriate temperature gradients and cooling surface temperatures, aligned pores ranging in size between (50 ± 22) μm and (144 ± 56) μm are observed in the alginate samples, whereas the pore orientation is influenced by altering the external temperature gradient. As this gradient increases, the pores are increasingly oriented perpendicular to the sample surface. This is also observed in the chitosan samples. However, if the overall system is too cold, that is, using temperatures of the lower cooling surface down to −60 °C combined with low temperatures of the upper cooling surface, control over pore orientation is lost. This is also found when viscosity of chitosan solutions is above ≈5 Pas near the freezing point. KW - unidirectional freezing KW - anisotropic porous structures KW - morphology controls KW - systematic investigations Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256330 VL - 24 IS - 3 ER -