Browsing by Subject "sol-gel"

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    Engineering Biocatalytic Materials: Encapsulation Systems for Biotechnology
    (2018-09) Sakkos, Jonathan
    My dissertation presents scientific and engineering contributions. Both sol-gel and layer-by-layer technologies were used to study prokaryotic cells under confinement and the role that the encapsulation material plays in affecting these cells. My work focused on the development, synthesis, and use of biologically active materials for water treatment based on silica gel bioencapsulation. Silica gels were developed with improved mechanical properties while ensuring that these materials were cytocompatible. The ratio of the silicon alkoxide crosslinker to silica nanoparticles was crucial in adjusting the maximum stress at failure. I demonstrated a 6-fold improvement in the compressive stress at failure in a silica bioencapsulation matrix containing metabolically active cells. These gels were organically modified to study the effect of encapsulation matrix hydrophobicity on the relative adsorption and biodegradation of organic pollutants. The ratio of biodegradation to adsorption was a strong function of the hydrophobicity of the pollutant. A layer-by-layer approach was used to minimize the diffusion length and protect the encapsulated biocatalyst from environmental stressors. I showed that targeting the cytoplasmic membrane with detergents increased its permeability and enabled a 15-fold enhancement in the rate of biocatalysis. To demonstrate the protective effects of the microbial exoskeleton, the coated cells were exposed to environmental stressors ranging from heat shock and desiccation to enzymatic attack and predation by protozoa. With a minimum of 4 layers, the biocatalytic activity was preserved for all cases examined. The translational application of cyanuric acid hydrolase (CAH) was also studied. By treating the cells with glutaraldehyde to crosslink the membrane-bound proteins, the cell was stabilized and CAH was retained within the whole cell biocatalyst.
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    Photonic Curing Solution-Processed Metal Oxide Semiconductor Thin-Film Transistors
    (2021) Weidling, Adam
    Metal oxide semiconductors such as InGaZnO and its derivatives are a promising group of materials with high mobility, low cost, and optical transparency. As the development of flexible electronics continues, these materials have several advantages for thin-film transistors over amorphous silicon such as high field effect mobility, and the ease of synthesis and deposition. The ability to create high-quality semiconductor materials compatible with low-temperature processing has been an emerging area of research over the past few decades. This research has included alternative synthesis routes, processing methods, and substrate materials. The ability to develop high-quality flexible devices has vast societal impact in leisure with applications such as next generation flexible displays, as well as in conformal medical devices for health monitoring. In this work, photonic curing is introduced as a method to rapidly and efficiently create high-quality thin-film transistors. This work addresses the importance of material parameters on the transient curing response and design guidelines for developing high-quality devices. Photonic cured metal oxide TFTs were compared with a thermally annealed baseline to study the TFT performance and chemical composition. Despite the short time scale in which the photonic curing process operates over, the photonic cured devices had a higher field effect mobility than the thermally annealed devices having mobilities of 21.8 cm^2V^-1s^-1 and 17.1 cm^2V^-1s^-1 respectively. A 3D model was developed to simulated the photonic curing process and to explore the impact of different materials and device layouts on the thermal profiles. The development of a robust fabrication platform for flexible electronics has been a challenge in the development of higher-complexity flexible circuits. To overcome this, a robust photonic lift-off process using a light absorber layer was developed using a low-CTE polymer. The large area and uniformity of the lamp energy allows for rapid and large area polymer delamination. In addition to providing a robust platform for fabrication, this process allows for fully-photonic processed fabrication including both semiconductor processing and substrate lift-off. The ability to use photonic curing for both semiconductor processing and polymer delamination allows for process times to be greatly reduced, and provides a new pathway towards fabricating next-generation high-performance flexible electronics.