M.Ing. / Please refer to full text to view abstract

Excess fluoride in groundwater used for drinking can pose serious health hazards, especially in poor, rural areas of the developing world lacking water treatment. The World Health Organization recommends a maximum fluoride contaminant level of 1.5 mg/L in drinking water [1]. Over 200 million people in low- and middle-income countries currently drink groundwater over that limit [2]. Current field detection of fluoride typically uses HACH kits, with several groups developing smartphone based alternatives [3]. These methods are based on colorimetry. The HACH kit is limiting because appropriate training is required, results are sensitive to competing ion contamination and chlorine, the glassware must be clean, and repetition is needed to ensure reliability [4]. The use of a smartphone for in-field detection of fluoride is promising and takes a strong step towards quick, easy, reliable, and portable fluoride detection. Our research takes the concept of a portable device one step further by using a fundamentally different, and simpler, mode of detection. We have demonstrated the use of optical fibers as an alternative, non-colourimetric fluoride detection method. The tip of a single mode optical fiber is coated with a thin film of Al and is immersed in an aqueous fluoride solution. The reaction between fluoride and the Al coating changes internal reflection proportional to fluoride concentration which is measured by a photodetector as an output voltage. We made great steps in optimizing the methods, materials, and code required for this sensor. Additionally, we built a device to allow approximate standardization of Al thickness as a function of the distance from the target and time of sputtering. We established the best practical thickness of Al coating, improved repeatability between sputter deposition events, and implemented an optical switch into the experimental set-up. / Graduate / 2021-07-28

In recent years super-hydrophobic micro-patterned substrates (SHS) have been successfully used for the suspension of a few biological molecules, allowing the further characterization in a background-free environment by label-free techniques such as Raman spectroscopy, SEM and TEM in one device. This result is due to the combined action of laminar flow and shear stress exerted on the molecules contained in a drop that is spotted on top of the SHS and slowly evaporates. This new method is here proposed for the label-free formation and background-free characterization of amyloid fibers. Amyloids are insoluble aggregates formed by proteins that convert from a misfolded form into highly-organized β-sheet structures that could accumulate in different organs and compromise their normal physiological functions. Known amyloid-related diseases, named amyloidosis, are for instance Alzheimer, Parkinson, and type 2 diabetes. In classical crystallography, the study of the amyloid aggregates structure is often hampered by the laborious and time consuming sample preparation techniques. Therefore the need of a quick reproducible technique, has emerged. The amyloid fibers investigated in this work are derived from a lysozyme protein and a Tau-derived short peptide, both known to be related to two forms of amyloidosis. With this technique we demonstrate that threads of protein fibers are deposited on the substrate helped by the patterning of the SHS and its properties, and by characterizing them with Raman spectroscopy technique we revealed that they are anisotropic structures of amyloid nature. This type of sample preparation technique arises from the effect of the evaporation on the SHS, and opens up new possibilities for the formation of oriented fibers of amyloids and more in general, of proteins, ready for a substrate-free characterization, while classic crystallographic methods could have a limitation.

Using silkworms as the potential host to spin spider silk-like fibers is an area of intense research world-wide. The conventional methods used to create transgenic silkworms hosting spider silk-like gene limits the incorporation of spider silk-like protein and do not improve the mechanical performance of the composite silkworm/spider silk fibers. In this dissertation, synthetic spider ampullate genes were incorporated into the precise site of the fibroin heavy chain or light chain using the latest genome editing technology CRISPR/cas9 guided non-homologous end joining as opposed to conventional random integration using transposon-based piggyBac system. These protocols, with extensive applicability to other silkworm researches, improved the content of spider silk-like protein in the transgenic silkworm/spider silk fibers, increases genetic stability in offspring, and improves the mechanical performance of the transgenic fibers compared to traditional methods. In addition, an enhanced green fluorescence protein (eGFP) was successfully incorporated into the fibroin light chain of silkworms using CRISPR/C as 9 initiated homologous recombination. The transgenic silkworm/spider fibers emitted strong green fluorescence under excitation. These results demonstrate that the we successfully developed a protocol to make silkworm as a host to spin spider silk-like fibers.

Recently, in communication system, fiber optics has become a most interesting development tool as a transmission medium. It first appeared as a feasible transmission medium in 1970. The reason for the development in fiber optics comes from the overwhelming advantage in technology and economy compared to wires and coaxial links. For technology progress, typically, optical fiber has a wide transmission band-width (0.1-1000 GHz), lower loss per unit length (0.15 – 5 dB km ^-1[1]), and does not allow electromagnetic interference. For example, signal transmitted over commercial silica-based fiber must be reamplified every 10 to 50 kilometers, whereas signals transmitted over copper wires must be reamplified every 4 to 6 kilometers. The economical advantage are as follows: a typical cable fiber weighs only about 3 kg/km; cost under $500/km or less, and has a longer repeater spacing of up to 100 km or more at a data rate of at least several hundred megabits per second. Because the optical fibers meet both demands, it has enabled us to construct high bit-rate and long haul communication systems in metropolitan area.

The objectives of this work were (i) to develop a new methodfor the preparation of thin cellulose model films, (ii) to usethese model films for swelling measurements and (iii) to relatethe swelling of fibers and films to the dry strength ofpaper. In the new film preparation method, NMMO(N-methylmorpholine-N-oxide) was used to dissolve cellulose andDMSO (dimethyl sulfoxide) was added to control the viscosity ofthe cellulose solution. A dilute solution of the cellulose wasspin-coated onto a silicon oxide wafer and the cellulose filmthus prepared was then precipitated in deionised water. Asaturated layer of glyoxalated-polyacrylamide was used toanchor the film onto the silicon oxide wafer. This proceduregave films with thicknesses in the range of 20-270 nm. Thefilms were cleaned in deionised water and were found by ESCAanalysis and contact angle measurements (θ&lt;20°)to be free from solvents. Solid state NMR measurements onfibers spun from NMMO also indicated that the model filmconsisted of about 50% crystalline material and that thecrystalline structure was of the cellulose II type.Determination of the molecular weight distribution of thecellulose surface material showed that the NMMO treatmentcaused only a minor breakdown of the cellulose chains and thatlow molecular mass oligomers of glucose were not created. It was further shown that atomic force microscopy (AFM)measurements could be used to determine the thicknessof thecellulose films, in both the dry and wet states. The thicknesswas determined as the height difference between the top surfaceand the underlying silica wafer measured at a position where anincision had been made in the cellulose film. The cellulosesolutions were also directly spin-coated onto the crystal usedin the Quartz crystal microbalance (QCM-D), pre-treated withthe same type of anchoring polymer. With this application,these model surfaces were shown to be suitable for swellingmeasurements with the QCM-D. The extent of swelling and theswelling kinetics in the presence of electrolytes, such asNaCl, CaCl2 and Na2SO4, and at different pH were measured inthis way. The films were found to be very stable during thesemeasurements and the results were comparable to the swellingresults obtained for the corresponding pulps. The swelling ofboth fibers and films followed the general behavior ofpolyelectrolyte gels in the presence of electrolytes and was inaccordance with the Donnan equilibrium theory. The films havebeen shown to differ from fibers with regard to the absence ofa covalent interior network. This influences the evaluation ofthe deswelling effects measured on the model films. Theswelling effect seen with different electrolytes has also beenconsidered in relation to the tensile strength of paperprepared from a kraftliner-pulp. In this study, it was foundthat there was no direct relationship between the swelling ofthe fibers, measured as WRV, and the strength of the paper inthe presence of different electrolytes at pH 5. KEYWORDS:absorption, carboxymethyl cellulose,cellulose, cellulose fibers, dissolving pulps, donnanequilibrium, electrolytes, film, ion exchange, ionization,kinetics, liner boards, microscopy, spinning, surfaces,swelling, tensile strength, water, water retention value. / <p>NR 20140805</p>

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