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Characterization of surface and mechanical properties of microbial cells
Khýrová, Markéta ; Lukeš,, Jaroslav (referee) ; Plichta, Tomáš (advisor)
The subject of this diploma thesis is the characterization of bacterial strains capable of polyhydroxyalkanoates (PHA) production in terms of morphology and mechanical properties. With this aim, an atomic force microscope (AFM) was used together with a nanoindentation instrument to perform microcompression tests on selected microorganisms. The model bacterial strains, Cupriavidus necator and Rhodospirillum rubrum, were tested in their PHA-producing form and in their mutant non-producing variant, in order to study the effect of PHA amount on bacterial morphology and mechanical properties. In the experimental part of this work, the preparation of native bacterial samples for both techniques were first optimised. Glass substrates were treated with plasma and the cells were subsequently fixed with poly-L-lysine. In addition, sample preparation including fluorescent staining was optimized for the microcompression tests in order to easily detect cells and determine their size. Finally, the impact of different measurement parameters and mathematical models for calculating Young's modulus on the AFM data were evaluated. The results revealed the effect of PHA on bacterial cell morphology and showed that PHA producers exhibit higher Young´s modulus on average compared to their mutant. It was also shown experimentally that microcompression tests provide significantly higher Young's modulus values than those obtained by AFM.
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Development of Nanofabrication Methodology for Study of Mechanical Properties of Thin Films using Focused Ion Beams
Kuběna, Ivo ; Švejcar, Jiří (referee) ; Kruml, Tomáš (advisor)
The main goal of this work is to find a methodology of the fabrication of microcompressive specimens (pillars) from thin metallic film prepared by means of PVD. The studied film was prepared by the ON Semiconductor company, Roznov pod Radhostem. Its chemical composition was Al-1.5 wt.% Cu; such films are used for electric connections on integrated circuits. At first, a thin intermediate layer of W-10 wt.% Ti was deposited on the Si single crystalline substrate with the purpose of improving adhesion properties of the studied film. The geometry of the microcompressive specimen should be as close to the cylindrical shape as possible. The height of the cylinder is given by the film thickness, its diameter is approximately 1 m. Such specimens were prepared in Quanta 3D FEG Dual BeamTM facility using focused ion beams technology. Experiments were done at FEI Company in Brno. In total, 39 microcompressive specimens were prepared at various ion milling conditions. The required geometry was finally attained by the optimization of processing parameters, in particular the parallelism of lateral faces was improved, the bottom of the removed zone in the vicinity of the pillar was almost flat and the transition pillar – flat bottom was regular. The prepared pillars are suitable for the microcompression tests; the first of them have been already performed within the cooperation with the Institut of Physics, Academy of Sciences of the Czech Republic, Praha.
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Development of Nanofabrication Methodology for Study of Mechanical Properties of Thin Films using Focused Ion Beams
Kuběna, Ivo ; Švejcar, Jiří (referee) ; Kruml, Tomáš (advisor)
The main goal of this work is to find a methodology of the fabrication of microcompressive specimens (pillars) from thin metallic film prepared by means of PVD. The studied film was prepared by the ON Semiconductor company, Roznov pod Radhostem. Its chemical composition was Al-1.5 wt.% Cu; such films are used for electric connections on integrated circuits. At first, a thin intermediate layer of W-10 wt.% Ti was deposited on the Si single crystalline substrate with the purpose of improving adhesion properties of the studied film. The geometry of the microcompressive specimen should be as close to the cylindrical shape as possible. The height of the cylinder is given by the film thickness, its diameter is approximately 1 m. Such specimens were prepared in Quanta 3D FEG Dual BeamTM facility using focused ion beams technology. Experiments were done at FEI Company in Brno. In total, 39 microcompressive specimens were prepared at various ion milling conditions. The required geometry was finally attained by the optimization of processing parameters, in particular the parallelism of lateral faces was improved, the bottom of the removed zone in the vicinity of the pillar was almost flat and the transition pillar – flat bottom was regular. The prepared pillars are suitable for the microcompression tests; the first of them have been already performed within the cooperation with the Institut of Physics, Academy of Sciences of the Czech Republic, Praha.
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