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<p>Sample preparation is a crucial processing step required for molecular biological analysis of environmental samples like water that has a variety of constituents in it. Furthermore, large volumes of sample need to be processed as the prescribed limits of pathogens in water are extremely low. However, microfluidic biosensing devices that can perform rapid molecular biological analysis in the field are designed to handle small sample volumes. In such cases, there is a need for a sample processing device that can reduce (concentrate) a large sample volume into a small one while retaining the biological species present in it. Hollow fibers are appropriate for this purpose of sample reduction and serve as a macro to micro interface for the microfluidic device. The received concentrate from the hollow fiber device requires be further concentrated to several microliters and separated and sorted to various modular components within the microfluidic device. This requires a second stage microfiltration where an integrated membrane can sort based on particulate size. In this thesis, a two stage filtration was designed. A first stage hollow based fiber pre-concentration device is developed that is portable, low cost, has high retention efficiency, low elution volume and is rapid. The hollow fiber device has low elution volume of ~1-3 ml. Controlled experiments were performed to validate the recovery of the hollow fiber device. Simulated 250 ml E.coli contaminated samples were filtered to <5 ml from an original sample volume of 250 ml. No bacteria were present in the filtrate and nearly 100% was recovered at high bacterial concentrations. At low concentrations (~200 cells in the sample) the recovery was less (~50%). A second stage microfiltration device that can be integrated with the microfluidic device and that can reduce the sample still further from ~ 5 ml to 5 μl was designed. Plasma bonding of ultrafiltration and microfiltration membranes using fluorine ions was investigated for fabrication of this device. The bonding of PDMS channels with polysulfone membranes via SF6 plasma was tested via tensile pull tests, burst pressure tests, and analyzed through scanning electron microscopy and electron dispersive x-ray spectroscopy. Quantitative tests on 10kDa and 70kDa polyethersulfone membranes demonstrated increased operational bonding strength of 86.6 and 146.9 kPa increases with three hour plasma application. Microfiltration membranes (0.2 micrometer pore size polyethersulfone) bonded in such a way that was easier to permeate as compared to ultrafiltration membranes. This bonding technique is generic in nature and can be used for integration of other commercially available polyethersulfone membranes with microfluidic devices for applications such as bio separations. No filtration testing was performed with E.coli samples.</p> / Master of Applied Science (MASc)

Fused deposition modeling (FDM) is gaining an ever increasing attention for its ability to fabricate complex geometry parts and prototypes at lower cost. The technology is striving to produce parts with high mechanical resistance that can withstand and perform under high stress environment. The adhesion strength between layers, transverse strength, is a limiting factor that need to be quantitatively evaluated to further understand and improve the bonding behavior of thermoplastic polymer in FDM. This interfacial adhesion is derived by the diffusion and penetration of polymer chains across the interface allowing the chain entanglement to form a bonding medium. This study investigates the bonding behaviour of polylactic acid (PLA) as a function of chain branching. The adhesion strength is quantitatively evaluated by developing and performing a peel test of a two-printed layer samples. It is possible to increase chain branching of PLA by bulk modification with epoxy chain extender. The modification of PLA was carried out using an internal batch mixer with four different concentrations of chain extender. The modified PLA was processed into print filament and characterized by parallel plate rheometry and DSC. It was found that the addition of chain extender increased molecular weight and degree of branching of PLA and in return the peel testing results reflected a significant increase in adhesion strength. Such improvement can be attributed to the long branched chains of PLA and its ability to create entanglements between layers. These findings can help in producing better PLA filaments to provide a higher stress resistance for FDM fabricated functional parts. / Thesis / Master of Applied Science (MASc) / Fused Deposition Modeling (FDM) is a recent popular method of plastic 3D printing technique, in which plastic filament is heated to a molten state to be then deposited through a layer-by-layer fashion to successfully fabricate parts. One of the drawbacks of that technology is the low bonding strength developed between layers as compared to strength along the length direction of layers. This study focuses on developing a testing methodology to evaluate the adhesion strength between layers and altering the material structure to maximize such strength. Four types of polylactic acid with different degrees of chain branching were successfully processed, printed and tested. Material with higher degree of branching yielded higher adhesion strength.

Lead (Pb) levels in tap water below the established water safety guideline are now considered harmful, thus detecting sub-parts-per-billion level Pb is important. This thesis reports on a miniaturized Copper (Cu)−based electrochemical sensor fabricated from thick film electrodes for their superior sensing performance. These thick film electrodes are based on highly conductive rolled-annealed Cu foil that has a compact bulk structure, but these advantages are often offset by the fact that RA Cu foil is difficult to bond to a substrate due to poor film-adhesion property and lack of mechanical interlocks. For this reason, we develop a direct bonding process for Cu/polymer. An integrated three-electrode planar configuration is then fabricated on the bonded specimen to achieve a fully-functional sensor that can detect 0.2 μg/L (0.2 ppb) Pb2+ ions from a 100 μL sample in only 30 s. This is the most rapid detection of Pb featured to date by an all Cu-based sensor. This thesis first focuses on improving substrate adhesion of RA Cu foil to liquid crystal polymer (LCP). This is achieved by a surface activated bonding process where Cu and LCP surfaces are treated with low-power reactive ion etching oxygen plasma followed by low-pressure contact at 230 °C. This treatment produces hydroxyl (OH−) groups on Cu and LCP surfaces making them highly hydrophilic. When Cu and LCP are contacted and heated, the OH− chains condense by dehydration and form an intermediate oxide layer. This layer mainly develops as Cu2O nanoparticles from the plasma-treated Cu side due to thermal oxidation in air. These nanoparticles diffuse into the polymer substrate when heated under mechanical pressure, resulting in a strongly bonded flexible specimen for the sensor. A simple, inexpensive, and production-friendly fabrication process is then developed for these sensors. Following direct bonding, flexible Cu/LCP is fed into a LaserJet printer for a one-step transfer of polyester resin−based electrode mask on Cu. This is followed by etching, packaging, and a chlorinating process to achieve a fully-functional integrated sensor. The sensing performance of directly bonded Cu/LCP is comparable to that of commercially available Cu/polyimide (PI) laminate. Our approach holds promise towards realizing low-cost integrated water quality monitoring systems. / Thesis / Master of Applied Science (MASc) / Lead contamination in tap water has major health risks for which monitoring of its levels is important. In this thesis, we develop a low-cost copper/polymer-based lead sensor. The sensor is fabricated from high-quality metal foil electrodes that are integrated to a polymer substrate by a direct bonding process. This enables strong adhesion of foil-based electrodes to the substrate that is crucial to the sensor performance and packaging integrity. We investigate the bonding mechanism between copper and polymer to understand the fundamentals of materials integration. These findings will lead to the development of polymer-based sensors and integrated systems. The bonded sensor bases are mechanically flexible, which facilitates a rapid and low-cost fabrication process using a laser printer. The developed sensor has a fast response time (30 s) and can detect very low levels of lead, thus making it suitable for water quality monitoring applications in under-developed and developed countries with legacy water systems that have not been upgraded yet.

This thesis extends our fundamental knowledge in the area of high oxidation state chemistry of xenon trioxide, XeO3. Oxygen coordination to the Xe(VI) atom of XeO3 was observed in its adducts with triphenylphosphine oxide, [(C6H5)3PO]2XeO3, dimethylsulfoxide, [(CH3)2SO]3(XeO3)2, pyridine-N-oxide, (C5H5NO)3(XeO3)2, and acetone, [(CH3)2CO]3XeO3. The crystalline adducts were characterized by low-temperature single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO3, which detonates when mechanically or thermally shocked, the solid [(C6H5)3PO]2XeO3, [(CH3)2SO]3(XeO3)2, and (C5H5NO)3(XeO3)2 adducts are insensitive to mechanical shock, but undergo deflagration when exposed to a flame. Both [(C6H5)3PO]2XeO3 and (C5H5NO)3(XeO3)2 are air-stable at room temperature. The xenon coordination sphere in [(C6H5)3PO]2XeO3 is a distorted square pyramid and provides the first example of a five-coordinate Xe center in a XeO3 adduct. The xenon coordination sphere of the remaining adducts are distorted octahedral comprised of three equivalent Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO3. Hirshfeld surfaces of XeO3 and (C6H5)3PO in [(C6H5)3PO]2XeO3 show the adduct is well-isolated in its crystal structure and provide a visual representation of the secondary Xe---O bonding in this adduct. Crown ethers have been known for over 50 years, but no example of a complex between a noble-gas compound and a crown ether or another polydentate ligand had been reported. Xenon trioxide is shown to react with 15-crown-5 to form the kinetically stable (CH2CH2O)5XeO3 adduct which, in marked contrast with solid XeO3, does not detonate when mechanically shocked. The crystal structure shows that the five oxygen atoms of the crown ether are coordinated to the xenon atom of XeO3. The gas-phase Wiberg bond valences and indices and empirical bond valences indicate the Xe---Ocrown bonds are predominantly electrostatic, σ-hole, bonds. Mappings of the electrostatic potential (EP) onto the Hirshfeld surfaces of XeO3 and 15-crown-5 in (CH2CH2O)5XeO3 and a detailed examination of the molecular electrostatic potential surface (MEPS) of XeO3 and (CH2CH2O)5 reveal regions of negative EP on the oxygen atoms of (CH2CH2O)5 and regions of high positive EP on the xenon atom that are also consistent with σ-hole bonding. Reactions of crown ethers with HF acidified aqueous solutions of XeO3 at room-temperature yielded adducts of 12-crown-4, (CH2CH2O)4XeO3, and 18-crown-6, [(CH2CH2O)6XeO3∙2H2O]2∙HF, whereas slow cooling of a solution of XeO3 with 18-crown-6 in acetone yielded (CH2CH2O)6XeO3∙2H2O. The adducts (CH2CH2O)4XeO3 and (CH2CH2O)6XeO3∙2H2O are shock-insensitive whereas the former adduct is air-stable at room temperature. The low-temperature, single-crystal X-ray structures show the Xe atom of XeO3 coordinated to the oxygen atoms of the crown ether ring. Uncharacteristic xenon coordination numbers exceeding six (including the three primary bonds of XeO3) were observed for all crown ether adducts. Raman spectroscopy frequency shifts are consistent with complex formation and provided evidence for the 2,2,1-cryptand adduct of XeO3. Gas-phase Wiberg bond valences and indices and empirical solid-state bond valences confirmed the electrostatic nature of the Xe---O bonding interactions. Comparisons between the XeO3 and SbF3 18-crown-6, 15-crown-5, and 12-crown-4 complexes are made. Incorporation of xenon trioxide, XeO3, into inorganic polyatomic salts under ambient conditions has been observed in several mixed xenate salts; K[XeO3XO3] (X = Cl, Br), K2[XeO3SeO4]∙HF, K[(XeO3)nZO3] (Z = I, N), and M2[(XeO3)nCO3]∙xH2O (M = Na, K, Rb, Ba). Raman spectroscopy was used to identify the aforementioned compounds and K[XeO3ClO3], K[XeO3BrO3], K2[XeO3SeO4]∙HF, and Rb2[(XeO3)2CO3]∙2H2O were also characterized by low-temperature, single-crystal X-ray diffraction. The xenon atom of XeO3 is seven coordinate in K[XeO3ClO3] and six coordinate in all other compounds with Xe---O distances that are significantly less than the sum of the Xe and O van der Waals radii. These salts provide examples of XeO3 coordinated to inorganic compounds and may provide insights into the inclusion of xenon oxides in minerals. / Thesis / Master of Science (MSc)

Low molecular weight liquid polybutadienes (1000 – 2000 g/mol) consisting of 60 mol% 1,2-polybutadiene repeating units were synthesized via anionic telomerization and conventional anionic polymerization. Maintaining the initiation and reaction temperature less than 70 °C minimized chain transfer and enabled the telomerization to occur in a living fashion, which resulted in well-controlled molecular weights and narrow polydispersity indices. MALDI-TOF mass spectrometry confirmed that the liquid polybutadienes synthesized via anionic telomerization contained one benzyl end and one protonated end. Subsequently, 2-ureido-4[1H]-pyrimidone (UPy) quadruple hydrogen-bonding was introduced to telechelic poly(ethylene-co-propylene), and mechanical characterization of the composites with UPy-functionalized carbon nanotubes was performed. The composites enhanced the mechanical properties and the UPy-UPy association between the matrix polymer and carbon nanotubes prevented the decrease of an elongation at break. The matrix polymer was also reinforced without sacrificing the processability. Additionally, UPy groups were introduced to styrene-butadiene rubbers (SBRs). Introducing UPy groups to SBRs drastically changed the physical properties of these materials. Specifically, the SCMHB networks served as mechanically effective crosslinks, which raised Tg and enhanced the mechanical performance of the SBRs. Novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(tert-butyl styrene)), poly(methyl methacrylate)-g-(poly(tert-butyl styrene)-b-poly(sulfonic acid styrene)), and the corresponding sodium sulfonate salts were successfully synthesized via living anionic polymerization, free radical graft copolymerization, and post-sulfonation strategies. The graft copolymers contained approximately 9 – 10 branches on average and 4 wt% of sulfonic acid or sodium sulfonate blocks adjacent to the backbone or at the branch terminus. The mobility of the sulfonated blocks located at the branch termini enabled the sulfonated blocks to more readily interact and form ionic aggregates. The glass transition temperatures (Tg) of the sulfonated graft copolymers with sulfonated blocks at the branch termini were higher than that of copolymers with sulfonated blocks adjacent to the backbone. More facile aggregation of sulfonated blocks at the branch termini resulted in the appearance of ionomer peaks in SAXS whereas ionomer peaks were not observed in sulfonated graft copolymers with sulfonated blocks adjacent to the backbone. In addition, similar analogues, novel site-specific sulfonated graft copolymers, poly(methyl methacrylate)-g-(poly(sulfonic acid styrene)-b-poly(ethylene-co-propylene)) (PMMA-g-SPS-b-PEP), poly(methyl methacrylate)-g-(poly(ethylene-co-propylene)-b-poly(sulfonic acid styrene)) (PMMA-g-PEP-b-SPS), and the corresponding sodium sulfonate salts were successfully synthesized. Estimated ï £N values predicted the phase separation of each block and differential scanning calorimetry (DSC) and dynamic mechanical analysis confirmed the phase separation of each block component of the graft copolymers. The aggregation of sulfonic acid or sodium sulfonate groups at the branch termini restricted the glass transition of the PEP block. This lack of the glass transition of the PEP block resulted in higher storage modulus than a sulfonated graft copolymer with sulfonated blocks adjacent to the backbone. The location of sulfonated blocks in both sulfonic acid and sodium sulfonate graft copolymers significantly affected the thermal, mechanical and morphological properties. Lastly, symmetric (16000 g/mol for each block) and asymmetric (14000 g/mol and 10000 g/mol for each block) poly(ethylene-co-propylene)-b-poly(dimehtylsiloxane) (PEP-b-PDMS) were synthesized using living anionic polymerization and subsequent hydrogenation. The onset of thermal degradation for the PEP-b-PDMS diblock copolymer was higher than 300 ºC and PEP-b-PDMS was more thermally stable than the precursor diblock copolymer, polyisoprene-b-PDMS. DSC analysis of PEP-b-PDMS provided Tg of PDMS -125 ºC, Tg of PEP -60 ºC, Tc of PDMS -90 ºC, and Tm of PDMS -46 and -38 ºC, respectively. Appearance of thermal transitions of each PEP and PDMS block revealed the formation of phase separation. Estimated Ï N also supported the phase separation. / Ph. D.

Structural adhesive bonding offers several advantages over other types of joining. These include improved stress distribution and increased design flexibility. Adhesive bonding is important in aerospace, automotive, and packaging applications. However, the full potential of the technology has not been exploited because the understanding of the basic mechanisms of adhesion and adhesion failure is incomplete. This investigation elucidates the chemical and mechanical mechanisms responsible for durable adhesion of epoxy resins to phosphorus oxo acid treated aluminum alloys. By systematically altering the adherend surface chemistry, surface topography, and adhesive formulation, combined with accelerated testing, the chemical and mechanical factors that influence the properties of adhesively bonded aluminum are isolated and assessed. It is postulated that a combination of two factors determines the strength and environmental durability of epoxy-bonded aluminum. One is the formation of hydrolytically stable, primary bonds between the adhesive and the adherend, and the second is the hydrolytic stability of the surface oxide, which is always present on the surface of aluminum and aluminum alloys. These conditions can best be met by chemical pretreatment of the oxide surface, which renders the oxide insoluble and creates, at the same time, functional surface sites. These sites can form chemical bonds with reactive components of the adhesive. Morphological and mechanical alteration of the metal surface oxide through hydroxide formation requires liquid water. Liquid water can only form by capillary condensation in interfacial gaps from molecularly diffusing water. A hydrolytically stable oxide will prevent bond failure due to mechanical weakening of the substrate surface, while a high density of hydrolytically stable surface bonding sites will minimize the occurrence of capillary gaps at the interface, thus decreasing the formation of liquid water. It is shown that highly chemically active, although not inherently stable, oxide surfaces can provide environmentally stable adhesive bonds. Conversely, certain highly stable oxide surfaces with few chemically active sites provide no environmental stability to adhesive joints, regardless of the topography of the surface. / Ph. D.