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Surface science is a multidisciplinary subject which affects us on a daily basis. Surfaces are of particular interest because the chemical bonding and atomic structure is different at the surface compared to the bulk properties of a material. This interface is of great significance because it is where charge exchange, or new chemical bonds occur. One essential aspect of surface science is surface wettability, which can be harnessed to produce self-cleaning surfaces. This very lucrative notion, where surfaces with low adhesion to liquids, can result in quick and autonomous shedding, has inspired a multitude of device fabrication and implementation. Over the past decade, several self-cleaning surfaces have been fabricated from superhydrophobic surfaces, which depends on a stable interface between solid, liquid and gas. These surfaces, however, are restricted in their applications and fail to operate upon mechanical damage or nonhomogeneous fabrication processes. Recent advances in wettability science have produced omniphobic lubricant-infused surfaces (OLIS). These surfaces are created by tethering a liquid to a surface, providing a stable liquid interface, which results in excellent aqueous and organic liquid repellency, and high robustness toward physical damage. This thesis will encompass an overview of the classical models for surface wettability, new models for liquid mobility, the criteria required to obtain OLIS, as well as some of the biomedical engineering applications fabricated from this technology. Herein, a novel manufacturing process was developed to produce smooth channeled polymeric microfluidic devices from rough 3D printed molds. Additionally, we integrated OLIS technology with electroconductive sensors to create high surface area electroactive material with self-cleaning properties, ideal to combat non-specific adhesion of biomolecules. Furthermore, our fabrication methods are inexpensive and have the potential to be easily integrated into manufacturing processes to create highly functional microfluidic devices, optimal for lab-on-chip diagnostic platforms. / Thesis / Master of Applied Science (MASc) / Recent advances in wettability science have produced omniphobic lubricant-infused surfaces (OLIS) inspired by the Nepenthes pitcher plant. These surfaces are created by tethering a liquid to a surface, providing a stable liquid interface, which results in excellent aqueous and organic liquid repellency, as well high robustness toward physical damage and high pressure dispensing scenarios. The motivation for this thesis is to expand on the applications for OLIS devices. Herein, a novel manufacturing process was developed to produce smooth channeled polymeric microfluidic devices from rough 3D printed molds. Additionally, we integrated OLIS technology with electroconductive sensors to create high surface area electroactive material with self-cleaning properties, ideal to combat non-specific adhesion of biomolecules.

This study demonstrates that the surface motility of the bacterium Pseudomonas aeruginosa is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing tryptic soy broth growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of "walking" bacteria on the hydrophobic surface. Sensitivity to the substrate surface chemistry occurs despite the presence of a complex mix of substances in the growth medium and offers hope that surface chemistry can be used to tune motility and the progression to biofilm formation. Additionally, the effect of reducing the near-surface Young's modulus of the PDMS from 7000 to 70 kPA is investigated. For the lower modulus material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low modulus materials. Consequently, except over very short time intervals, Young's modulus in the surface region is not effective as a means of modulating motile behavior. / Master of Science / This study demonstrates that the ability of the bacterium Pseudomonas aeruginosa to move on a solid surface is dependent on the surface chemistry of the underlying substrate. In particular, cells on hydrophobic polydimethylsiloxane (PDMS) have a speed that is on average 38% greater than on hydrophilic PDMS. These results were obtained using time-lapse microscopy of bacteria exposed to continuously flowing growth medium at 37 ⁰C. Not only are the mean speeds different, the distributions of speeds are also different: on the hydrophobic substrate, a smaller proportion of bacteria move by less than about one body-length (~3 µm) in 60 minutes. In addition, the surface chemistry affects the orientation of the cells: there is a greater fraction of vertically-oriented bacteria on the hydrophobic surface. Additionally, the effect of reducing the stiffness of the PDMS from 7000 to 70 kPA is investigated. For the less stiff material, there is an increase in the likelihood of a bacterium executing sudden, high angle turns. This is evident in images with a framerate of one frame per 0.22s. However, the impact of these turns is averaged out over longer times such that the mean speed over periods of more than about one minute is the same for bacteria on both the high and the low stiffness materials. Consequently, except over very short time intervals, stiffness in the surface region is not effective as a means of changing patterns of surface-bound P. aeruginosa movement.

Soilless substrates, such as peat, pine bark, and coir, are widely used as growing media in containerized crops for their favorable characteristics, including low bulk density, balanced air exchange and water retention, disease resistance, and low pH and salinity. However, improper irrigation of these media can have negative outcomes such as root asphyxia, pathogen development, and reduced plant growth. Understanding pore size distributions, water dynamics, and gas diffusivity of these substrates is essential to promote plant growth. The effects of different particle sizes of soilless media on processes such as infiltration, hydraulic conductivity, and gas diffusivity are also not well understood. The characterization of these effects is important for the overall improvement of container crop production. This thesis presents three studies that aimed to characterize the physical and hydraulic properties of pine bark substrates, both unamended and amended with peat or coir. The first study looked at three substrate types: unamended, unscreened pine bark, peat-amended pine bark, and coir amended pine bark. Three methods were employed to quantify pore distributions: non-equilibrium infiltration measurements, equilibrium water retention characterization, and scanning electron microscopy. We characterized pore distributions during wetting and drainage for the three substrates. Coir-amended bark had the largest water-conducting porosity, highest hydraulic conductivity, and most water retention. Unamended pine bark had the highest microporosity, and the addition of peat and coir lowered macroporosity, with peat having the greater effect. The total porosity inferred from the infiltration method was significantly smaller than that inferred from drainage experiments due to assumptions related to pore shape. The second study focused on defining hydraulic conductivity and water retention for pine bark substrates of five different particle sizes, <1 mm, 1-2 mm, 2-4 mm, 4-6 mm, and an unscreened fraction. We utilized the same methods from the first study. The resulting data showed that the smallest particle sizes (i.e., <1 mm and 1-2 mm) had the highest hydraulic conductivity and greatest water retention. The three larger sizes had lower hydraulic conductivity and poor water retention, including the unscreened fraction, which more closely followed the results of the 2-4 mm size. The final study examined gas diffusivity of the five pine bark particle sizes at different moisture levels: 60% moisture content (initial conditions), saturated at the bottom of the sample, near-saturated at the sample bottom, and drained from saturation to container capacity. We used a one-chamber gas diffusion setup to find gas diffusion coefficients (Ds). The results displayed an inverse relationship between Ds values and substrate water content. In addition, the larger particle sizes were less sensitive to changes in water content due to their well-draining large pores. Proper balance of aeration and water retention is necessary for the success of soilless growing media. Overall, the smaller particle size fractions had the best water retention and hydraulic conductivity rates while the larger fractions had the largest Ds coefficients. This work contributes valuable knowledge on the physical and hydraulic properties of different size fractions of pine bark substrates, which can assist nursery growers in optimizing water usage for sustainable container crop production. / Master of Science / Since the 1950's soilless substrates have been an important resource for growing a variety of fruits, vegetables, flowers, and ornamental plants. Soilless growing media have become more popular choices for containerized plant production compared to natural soils due to improved air exchange, increased disease resistance, and more plants per acre. They are also favored because they help conserve resources, reduce agricultural waste, and minimize transportation requirements as compared to traditional cropping methods. The most popular types of soilless media include peat, coir, compost, and pine bark. In the U.S., pine bark is the main substrate used, as it is renewable and widely available. Growers still face many issues when using containerized crop production. For example, pine bark is susceptible to water runoff which can cause environmental problems and increase costs from this loss of water and fertilizer. Further characterizing of water and gas dynamics in of pine bark growing media is important for conserving water and fertilizer resources while optimizing plant growth in this container cropping industry. Pore characteristics, aeration, and water movement are key factors of substrates to be described to solve these challenges. This project aimed to apply soil physics strategies to soilless media, focusing on describing pore sizes, water movement, water holding capacity, and air movement in pine bark substrates. We utilized three methods throughout this study. For the first method, we took infiltration measurements to examine how water moved into the media, while the second utilized controlled drainage experiments to observe how water moved out of the media. The final method was characterizing gas movement through the substrates at different water contents and particle sizes. The results found showed that the smaller particle sizes and pine bark mixed with peat and coir had increased ability to retain water and allow water movement as compared to the larger particle sizes and unamended pine bark. In contrast, the larger particles had less water retention but improved gas movement. These results could be applied by stacking different particle sizes or mixes over one another could optimize water retention in the top of the container and drainage and gas movement in the bottom of the container. Overall, the application of this work is to create best management practices for growers to be able to balance water retention and gas movement in order to optimize plant growth.

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This thesis is concerned with the study of morphology and properties of sub-micron thin Nafion® films. The motivation of the work arises from the need to characterize the 4 -10 nm thin ionomer films in the catalyst layer of polymer electrolyte fuel cell (PEFC). A protocol for the fabrication of self-assembled ultra-thin Nafion® films on planar substrates was successfully developed. Films of thickness ranging 4 nm-300 nm, determined by three different techniques - variable angle spectroscopy ellipsometry (VASE), atomic force microscope (AFM) and x-ray photo-electron spectroscopy (XPS), could be reproducibly generated on SiO2/Si wafer. The 4 nm thin film is one of the thinnest, continuous film of Nafion® ever reported. This is the first time that the structure/properties of such thin Nafion® film have been investigated. An interesting finding is the thickness-dependent structure and property of these films. Films with thickness <55 nm exhibited hydrophilic-free surface but thicker films (>55 nm) had hydrophobic surface. Similarly, sub-55 nm films had a lower and thickness-independent protonic conductivity compared to thicker films that exhibited thickness-dependent conductivity. Anomalously high water uptake (by quartz crystal microbalance) and swelling (by ellipsometry) of sub-55nm films indicate that low conductivity is not due to low water content However, differences in surface morphology were observed by the AFM phase contrast analysis. The lack of ionic domain was also observed in the thinner films (4-30 nm) from the grazing incidence small x-ray scattering (GISAXS) experiments. Thermal annealing over a range of temperature (110-160 oC) revealed a dramatic switching of the film surface from hydrophilic to hydrophobic was observed for sub-55 nm films with lower thickness film requiring higher annealing temperature. Bulk proton conductivity was significantly reduced after annealing for all films. An interesting finding was the regeneration of conductivity after to prolonged liquid water exposure and a corresponding switching back of the surface to hydrophilic. The thickness-dependent structure/property of ultra-thin Nafion® films is attributed to substrate induced confinement effect. Self-assembly of Nafion® on various substrates (SiO2, carbon, Pt and Au) was studied. The ionomer/substrate interaction and resulting film morphology followed a trend with respect to substrate surface energies and Nafion® dispersion compositions. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2013-09-29 12:36:19.05

De nombreuses applications industrielles mettent en évidence l’importance des propriétés de mouillage des surfaces métalliques que ce soit directement pour les propriétés d’écoulement de fluides sur ces surfaces ou indirectement pour leur lien avec les phénomènes d’adhésion. Les travaux de Wenzel (1936) et de Cassie -Baxter (1944) ont montré que cette mouillabilité dépendait à la fois de la tension superficielle du solide mais aussi de sa topographie de surface. Ainsi la maîtrise et l’optimisation de ces propriétés nécessitent le contrôle de ces deux aspects, à l’image de la feuille de lotus dont le caractère super-hydrophobe réside à la fois en la présence d’une cire hydrophobe et d’une rugosité multi-échelle. Ces observations sont à l’origine, cette dernière décennie, du développement des techniques de gravures chimiques pour réaliser des texturations superficielles de matériaux et contrôler leur mouillabilité. Afin de surmonter certaines limitations de ces techniques et privilégier un procédé par voie sèche, nous avons envisagé de structurer la surface d’alliages métalliques de titane, d’aluminium, et de différents aciers inoxydables, au moyen d’un traitement de surface par laser femtoseconde. L’analyse topographique de la surface des matériaux (profilométrie optique, AFM, MEB) en fonction des paramètres d’irradiation du laser comme la densité de puissance laser, le nombre d’impulsions et le décalage latéral du faisceau en configuration balayage, a montré l’efficacité de ce procédé pour générer des texturations multi-échelles. Les différentes morphologies de textures peuvent être associées à des transitions de régimes dans l’interaction laser - matière (ripples, spikes, …). L’analyse chimique et structurale (DRX, XPS) des surfaces traitées a mis en évidence des modifications microstructurales dues aux effets thermiques du laser ainsi qu’une évolution de l’état chimique de la surface dont les effets sur la mouillabilité sont importants. L’hydrophobie des surfaces métalliques a été considérablement accentuée par le traitement laser. Ces résultats pourront être exploités pour différentes applications industrielles notamment comme moyen de contrôler l’état de surface des moules de plasturgie. / Many industrial applications highlight the importance of the wetting properties of metallic surfaces related to their adhesion phenomena. Wenzel’s (1936) and Cassie – Baxter’s (1944) independent works showed that the wettability depended on both the surface tension of the solid but also on its surface topography. Thus the control and optimization of these properties require control of both aspects, like the lotus leaf whose superhydrophobic character lies in the presence of a hydrophobic wax and a multi-scale roughness. These observations are at the origin of the development of chemical etching techniques to produce surface texturing of materials and control their wettability. To overcome some limitations of these techniques and focus on a dry process, we considered the surface texturing of metal alloys of titanium, aluminum, and various stainless steels, using a femtosecond laser surface treatment. The analysis of the topography of the textured surfaces using different techniques (optical profilometry, AFM, SEM) showed the effectiveness of this method for generating multi-scale texturing. The different morphologies of textures can be associated with regimes transitions in the laser - matter interaction (ripples,spikes ...). The chemical and structural analysis (XRD, XPS) of the treated surfaces revealed microstructural changes due to thermal effects of laser, and a shift in the chemical state of the surface whose effects on the wettability are important. The hydrophobicity of metallic surfaces was significantly enhanced by laser treatment. These results may be used for various industrial applications, including the control of the surface state of plastic molds.

Une des méthodes de récupération assistée du pétrole les plus utiliséesest l'injection de polymères. L'efficacité de cette méthode est attribuée principalement à laréduction de la mobilité de la phase aqueuse et à la viscoélasticité des polymères. Cetteefficacité dépend de plusieurs paramètres comme la perméabilité, la température, la salinité,l'hétérogénéité, la mouillabilité, le nombre capillaire, etc. De nombreuses connaissances ontété accumulées s’agissant du rôle des polymères dans la récupération du pétrole. Néanmoins,il subsiste encore des questions importantes:• Quel est le meilleur moment pour l’injection de polymère?• Quel rôle joue la mouillabilité dans la récupération ultime de pétrole?• Comment les effets viscoélastiques influencent-ils la récupération?• Quel est le rôle l’adsorption du polymère dans le processus de récupération?Cette thèse, expérimentale, a pour but de fournir des données concernant ledéplacement diphasique (en conditions de mouillabilité intermédiaire et de mouillabilité francheà l’eau) et d’investiguer l’impact réel de la rhéologie sur l’efficacité de déplacement de l’huile.Des injections de polymères sont réalisées à différents stades de précocité (c’est àdire, à différents moments après l’injection d’eau). Les résultats montrent un impact significatifde la précocité du balayage de polymère sur les taux de récupération finale et apparait commeun facteur déterminant à prendre en compte. D’autre part, on observe une récupération plusfaible pour une mouillabilité franche à l’eau que pour une mouillabilité intermédiaire etl’adsorption et la viscoélasticité de la solution de polymère ne sont pas déterminants dans letaux de récupération (dans nos conditions) alors que nos résultats indiquent un changementde mouillabilité durant l’injection de polymère.Des expériences complémentaires de dispersion diphasique ont ensuite mis enévidence un lien direct entre la dispersivité et le taux de récupération final. / Polymer flooding is one of the most developed chemical enhanced oil recoverymethod that has been used successfully since decades. In this chemical EOR method, thepolymer is adding to a waterflood to decrease its mobility. The resulting increase in viscosityas well as a decrease in aqueous phase permeability improve macroscopic oil sweepefficiency. At the pore scale, viscoelasticity is known to be also a key parameter that controlsthe microscopic sweep efficiency. However this sweep efficiency depends on several factorslike the permeability, temperature, salinity, wettability, capillary number, heterogeneity, etc.Therefore several studies are still necessary to have a better understanding of the behaviourof the polymer inside porous media and to optimize the process.• What is the best moment to inject polymer?• What is the role of wettability in final recovery?• How do viscoelastic effects influence recovery?• What is the role of adsorption of the polymer in the recovery process?In our interest to optimize and to understand polymer flooding process we have analysed thedependence of the sweep efficiency with the moment of the polymer injection duringwaterflooding and wettability (Water wet and intermediate wet). The polymer solution isinjected in the core at different maturity times (0PV, Breakthrough, 1PV, 2PV, 3PV, 4PV and6PV).The main results can be summarized in three points .The results show oil recoveryfinal for water wet corefloods is lower than intermediate wet corefloods. On the other hand, theproduction of oil with the injection of polymer is higher than the injection of water due to afavorable mobility ratio. Finally, the final recovery rates are lower when the polymer injectionis late. These results suggest that the history of sweeping can lead to different distributions ofphases (oil/brine) at the end of the waterflood. The sweep efficiency is related to the ability ofthe polymer to disperse throughout the accessible portal space. We have analysed this aspectfrom the point of view of the diphasic dispersion by showing that the dispersivity of the phasesis different at each time of the water injection. The complementary diphasic dispersionexperiments showed a direct link between dispersivity and the final oil recovery.

Many of Brazil\'s pre-salt basins are located in ultra-deep waters, and the high heterogeneities of its offshore carbonate reservoirs make the extraction of representative rock samples difficult, risky and expensive. Synthetic plugs are required to understand oilfield properties and the behavior of oil in reservoirs where natural plugs cannot be extracted. Specifically, in cases where it is necessary to reproduce representative mineralogical and petrophysical characteristics from carbonates reservoir, it is evident that there are a lack of publications focusing on synthetic plug construction. In this work, the construction of synthetic plugs is studied, using a combination of published methodologies to achieve an alternative construction of synthetic carbonate plugs for laboratory scale studies. The obtained plugs used a procedure based on disintegrated rock matrices with known particle sizes and particle size ratio, uniaxial compaction with controlled load force and velocity, CaCO3 solubility control by changing temperature and pH and bonding material. Consolidation, wettability and petrophysical properties of the synthetic plugs were evaluated to characterize them. Generally, it was observed that the porosity and permeability features of the synthetic plugs were within the range of carbonate reservoirs. However, without reproducing a heterogeneous pore structure normally present in natural samples. On the other hand, wettability properties of the resulted synthetic plugs were similar to the natural carbonate plugs. Further studies are necessary to obtain more similar chemical and petrophysical properties to the natural samples. / A localização em águas ultra profundas das reservas petrolíferas do pré-sal brasileiro e a alta heterogeneidade dos seus reservatórios carbonáticos dificultam a aquisição de uma amostra de rocha representativa, além de ser uma operação de risco e de alto dispêndio. Plugues sintéticos são utilizados para compreensão das propriedades dos campos petrolíferos e para avaliação do comportamento dos hidrocarbonetos em reservatórios onde plugues reais não podem ser adquiridos. Especificamente, nos casos onde são necessários reproduzir características representativas mineralógicas e petrofísicas dos reservatórios carbonáticos, sendo notório a falta de publicações voltada para construção de plugues sintéticos. No presente trabalho, estudou-se a construção de plugues sintéticos empregando metodologias já difundidas, visando a construção de plugues carbonáticos sintéticos para utilização em escala laboratorial. Os plugues obtidos foram construídos utilizando matrizes de rochas desintegradas com tamanhos e proporções de partículas conhecidos, compactação uniaxial com força e velocidades controladas e controle de solubilidade de CaCO3, variando apenas temperatura, pH e proporções de material cimentante. Foram avaliadas as propriedades petrofísicas, a molhabilidade e a consolidação dos plugues sintéticos para posterior caracterização dos mesmos. Comumente, observou-se que os valores de porosidade e permeabilidade dos plugues sintéticos se encontravam dentro do intervalo de valores obtidos em reservatórios carbonáticos reais. No entanto, não reproduziram a estrutura heterogênea dos poros, normalmente presente em amostras de rochas naturais. Em contrapartida, as propriedades de molhabilidade dos plugues sintéticos se apresentaram análogas aos plugues de rochas carbonáticas naturais. Estudos complementares são necessários para obtenção de propriedades químicas e petrofísicas mais próximas das amostras reais.