A microbubble dispersion (MBD) was used to supply oxygen for an aerobic fermentation of Baker's yeast. The 1-liter microbubble dispersion generator supplied bubbles for 20-liter and 50-liter working volume fermentations in a 72-liter pilot scale fermenter. The microbubbles were stabilized by the surfactants naturally present in the culturing broth medium. The growth patterns of yeast Saccharomyces cerevisiae, cultured at agitation speeds of 150 rpm and 500 rpm, were compared for oxygen supplied by ordinary air sparging and by MBD sparging. Both air sparged and MBD systems were supplied air at equivalent volumetric flow rates. The volumetric oxygen transfer coefficients (KLa) were estimated by the yield coefficient method. The KLa values increased from 142.5 to 458.3 h-1 and from 136.1 to 473.3 h-1 for 20- and 50- liter runs, respectively, as the agitation speed was increased from 150 to 500 rpm in the ordinary air sparged fermentations. The oxygen transfer coefficients in the MBD sparged fermentations were found to be independent of the fermenter agitation speed at approximately 480 h-1 for 20-liter runs and 340 h-1 for 50-liter runs. The growth rates for MBD at 150 rpm were essentially equivalent with air sparged fermentations at 500 rpm. The total power consumption per unit volume of broth for the 150 rpm, MBD fermentation was 68% lower than the 500 rpm, air sparged run for the 20-liter fermentations and was 55% lower for the 50-liter fermentations. / Master of Science

Colloidal particles provide the ideal building blocks for the next generation of microdevices, such as advanced sensors and precision drug delivery systems. However, many such applications require the use of top-down (i.e. humanly controllable) forces to manipulate colloidal particles with single-particle precision, and current methods can only achieve such precision for small numbers of particles at a time. To address this challenge, we propose using chemical forces in combination with existing top-down techniques to enable the control of larger numbers of particles simultaneously. Controlling colloids using chemical reactions is a novel technique not typically utilized. Due to its distinct difference from other control methods, it provides new degrees of freedom to work with which offer new opportunities for designing colloidal devices. In this dissertation, we show how modern control theory can be used to implement the control of colloidal particles using chemical forces. We use Brownian dynamics simulations to test control strategies for three different situations: directly controlling chemical reactions to produce a desired concentration gradient, controlling a reactive colloidal particle that interacts chemically with other colloids to move them to desired locations, and controlling the dynamics of active colloidal particles to manipulate their collective behavior. The results obtained in this work will demonstrate the plausibility of each of these three control strategies and provide insights into the choices of physical parameters that can be used in future experiments.

This study seeks to develop smart hydrogel formulations for injectable controlled drug delivery from Pluronics to enhance patients compliance, decrease side effects, reduce dose and frequency. A biocompatible copolymer, Pluronic F127 was probed as the main ingredient for the injectable systems owing its low gelation concentration and ease of modification the system properties through excipients addition. The matrix properties were studied through a series of thermal, rheological and structural (SAXS/SANS) experiments as a function of concentration and shear rate, covering both static and dynamic environments. It has shown that gelled viscosity (and structure) can be critically controlled by shear rate and the structures recorded do not match those predicted for sheared colloids. Two further Pluronics F68 and F108, were studied showing similar but shifted gelation properties to F127. Effects of additives were studied by introducing different Mw PEGs and a model hydrophobic drug ‘ibuprofen’ to a F127 20% formulation. PEGs addition effects on the system properties and gelation transition were largely dependent on the Mw used in the blend, which became more prominent with increasing chain length. Ibuprofen’s addition has resulted in reduced gelation temperature and smaller hard spheres without having a great effect on the system rheological properties compared to neat gels. Blends containing both additives PEG and ibuprofen exhibited a synergistic effect, where comparisons show that Ibuprofen had the largest effect on the blends lowering gelation boundaries and slightly increasing the size of the hard spheres indicating the necessity of full characterisation of the formulation with any API.

O presente trabalho teve como objetivo verificar a influência dos parâmetros tecnológicos do processo de secagem por aspersão sobre as características do produto obtido a partir de extrato seco de Maytenus ilicifolia. Para tanto, foi realizado um estudo exploratório, utilizado um desenho experimental fatorial, analisando quatro parâmetros: a concentração de dióxido de silício coloidal (10 e 30 %), o tempo de dispersão em meio líquido das matérias-primas (0,5 e 4 horas), a temperatura de entrada do ar de secagem na torre de aspersão (150 e 180 ºC), e a velocidade de rotação do disco aspersor (9.500 e 11.000 rpm). O teor de umidade residual, a morfologia, a distribuição granulométrica e o fluxo dos pós obtidos, assim como o rendimento do processo e a concentração do marcador catequina foram considerados como respostas ao desenho fatorial. O aumento da temperatura de entrada conduziu a produtos com umidade reduzida e a maior eficiência do processo. A concentração do dióxido de silício coloidal afetou principalmente as propriedades de fluxo e o teor de catequina nos pós produzidos. A maior velocidade de rotação influenciou de modo positivo somente sobre o rendimento do processo. / The present study aimed to evaluate the influence of technological parameters related to the spray drying process over the product obtained from a Maytenus ilicifolia spray dried extract. Therefore, an exploratory study was carried out using an experimental factorial design assessing four parameters: colloidal silicon dioxide concentration (10 – 30 %), dispersion time of the feed material (0.5 – 4 h), air inlet temperature in the spray dryer (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). According to an experimental factorial design four parameters were assessed: colloidal silicon dioxide concentration (10 – 30 %), mixing time (0.5 – 4 h), inlet temperature (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). Moisture content, morphology, particle size, flow, process yield and catechin concentration were considered as responses of the factorial design. Increasing inlet temperature led to dried products with reduced moisture content and higher process yield. Aerosil content mainly affected flow properties and catechin content in the powders. Atomizer speed at high level only enhanced process yield.

O presente trabalho teve como objetivo verificar a influência dos parâmetros tecnológicos do processo de secagem por aspersão sobre as características do produto obtido a partir de extrato seco de Maytenus ilicifolia. Para tanto, foi realizado um estudo exploratório, utilizado um desenho experimental fatorial, analisando quatro parâmetros: a concentração de dióxido de silício coloidal (10 e 30 %), o tempo de dispersão em meio líquido das matérias-primas (0,5 e 4 horas), a temperatura de entrada do ar de secagem na torre de aspersão (150 e 180 ºC), e a velocidade de rotação do disco aspersor (9.500 e 11.000 rpm). O teor de umidade residual, a morfologia, a distribuição granulométrica e o fluxo dos pós obtidos, assim como o rendimento do processo e a concentração do marcador catequina foram considerados como respostas ao desenho fatorial. O aumento da temperatura de entrada conduziu a produtos com umidade reduzida e a maior eficiência do processo. A concentração do dióxido de silício coloidal afetou principalmente as propriedades de fluxo e o teor de catequina nos pós produzidos. A maior velocidade de rotação influenciou de modo positivo somente sobre o rendimento do processo. / The present study aimed to evaluate the influence of technological parameters related to the spray drying process over the product obtained from a Maytenus ilicifolia spray dried extract. Therefore, an exploratory study was carried out using an experimental factorial design assessing four parameters: colloidal silicon dioxide concentration (10 – 30 %), dispersion time of the feed material (0.5 – 4 h), air inlet temperature in the spray dryer (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). According to an experimental factorial design four parameters were assessed: colloidal silicon dioxide concentration (10 – 30 %), mixing time (0.5 – 4 h), inlet temperature (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). Moisture content, morphology, particle size, flow, process yield and catechin concentration were considered as responses of the factorial design. Increasing inlet temperature led to dried products with reduced moisture content and higher process yield. Aerosil content mainly affected flow properties and catechin content in the powders. Atomizer speed at high level only enhanced process yield.

O presente trabalho teve como objetivo verificar a influência dos parâmetros tecnológicos do processo de secagem por aspersão sobre as características do produto obtido a partir de extrato seco de Maytenus ilicifolia. Para tanto, foi realizado um estudo exploratório, utilizado um desenho experimental fatorial, analisando quatro parâmetros: a concentração de dióxido de silício coloidal (10 e 30 %), o tempo de dispersão em meio líquido das matérias-primas (0,5 e 4 horas), a temperatura de entrada do ar de secagem na torre de aspersão (150 e 180 ºC), e a velocidade de rotação do disco aspersor (9.500 e 11.000 rpm). O teor de umidade residual, a morfologia, a distribuição granulométrica e o fluxo dos pós obtidos, assim como o rendimento do processo e a concentração do marcador catequina foram considerados como respostas ao desenho fatorial. O aumento da temperatura de entrada conduziu a produtos com umidade reduzida e a maior eficiência do processo. A concentração do dióxido de silício coloidal afetou principalmente as propriedades de fluxo e o teor de catequina nos pós produzidos. A maior velocidade de rotação influenciou de modo positivo somente sobre o rendimento do processo. / The present study aimed to evaluate the influence of technological parameters related to the spray drying process over the product obtained from a Maytenus ilicifolia spray dried extract. Therefore, an exploratory study was carried out using an experimental factorial design assessing four parameters: colloidal silicon dioxide concentration (10 – 30 %), dispersion time of the feed material (0.5 – 4 h), air inlet temperature in the spray dryer (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). According to an experimental factorial design four parameters were assessed: colloidal silicon dioxide concentration (10 – 30 %), mixing time (0.5 – 4 h), inlet temperature (150 – 180 ºC), and atomizer speed (9,500 – 11,000 rpm). Moisture content, morphology, particle size, flow, process yield and catechin concentration were considered as responses of the factorial design. Increasing inlet temperature led to dried products with reduced moisture content and higher process yield. Aerosil content mainly affected flow properties and catechin content in the powders. Atomizer speed at high level only enhanced process yield.

La réutilisation des eaux usées traitées pour l’irrigation est globalement acceptée et pratiquée pour faire face à la pénurie d'eau et économiser les ressources de haute qualité. Bien que cette pratique présente des avantages indéniables et contribue à un usage plus durable de l'eau douce, elle n’est pas exempt de problèmes liés à l'impact potentiel sur la qualité des sols récepteurs et sur les cultures de micropolluants contenus dans l'eau réutilisée. Parmi ces polluants, les métaux lourds (ML) en concentrations traces jouent un rôle primordial en raison de leur présence systématique dans l'eau utilisée et de leur persistance une fois libéré dans l'environnement. Le devenir des ML dans les sols peut difficilement être prédit parce que les mécanismes de mobilité à travers les sols sont extrêmement variés et liés à des phénomènes simultanés et très complexes impliquant différents équilibres chimiques. Les ML, comme beaucoup d'autres contaminants, ne sont pas seulement partagé entre la phase immobile (le sol) et les phases mobiles présentes dans l'eau. En effet, les colloïdes et les nanoparticules agissent comme une troisième phase mobile, avec leurs propres propriétés rhéologiques et des vitesses de migrations qui leur sont propres. Ce dernier aspect a été l'un des principaux objectifs d’étude de la thèse. Plusieurs essais expérimentaux ont été menés en irriguant un sol standard selon l'Organisation de coopération et de développement économiques (OCDE) avec une eau usés traités réel et / ou synthétiques, contenant des ML en concentrations traces. Pour chaque test, un sol spécifique (avec différentes teneurs en matière organique) et des eaux usées traitées de composition différente (avec différentes concentrations en métaux traces, de salinité, de la teneur en matière organique pour les eaux usées synthétiques, ou des eaux usées traitées réelles) ont été choisi afin d'évaluer les effets des conditions différentes sur le devenir global des ML. L'augmentation de la matière organique du sol de 2,5 à 10% a linéairement amélioré la mobilité des Cd, Cu et Ni avec une augmentation de la mobilité maximum de 35,6, 43,7 et 49,19% pour le Cd, Cu et Ni, respectivement. Pour la plupart des expériences, les ML ont été capturés dans la couche superficielle du sol (0,5 à 1 cm). Néanmoins, des pics de contamination ont été détectés à des profondeurs différentes dans les couches plus profondes du sol. L’étude de la composition des lixiviats montre des variations de concentrations fonction du métal étudié et des caractéristiques du sol et des eaux usées. Des pics de métaux dans le lixiviat sont apparus en même temps que la libération de la matière et / ou la libération de silicates organiques, ce qui démontre l'implication significative des colloïdes dans le transport des métaux. La concentration en sodium (20 mM) a été démontrée un impact fort sur la réduction de la mobilisation colloïdale et que plus de 95% du métal apporté a été détecté dans la couche superficielle du sol en dépit de sa teneur en matière organique. La salinité affiche donc des effets significatifs. L'irrigation avec des eaux usées traitées présentant une très haute teneur en Ca et Mg (111 et 134 mg / L, respectivement) a abouti à la libération moyenne plus élevée de silicium à partir de la matrice inorganique du sol (8,2 mg / L) par rapport à la faible salinité des eaux usées artificielle (1,9 mg / L). Par conséquent, la mobilisation ultérieure de Cd, Cu, Ni et Zn a été observée lorsque le sol a été irrigué avec des eaux usées traitées réelles. Une caractérisation spectroscopique avancée des lixiviats a été réalisée pour identifier les agrégats colloïdaux libérés par le sol dans le but d’en déterminer leur nature, leurs propriétés chimiques et leur état d'agrégation / Reuse of treated wastewater for agricultural purposes is worldwide accepted and practiced to face water scarcity and save high quality resources. Although such practice has undoubtable advantages and is certainly more sustainable respect to the use of fresh water, it is not exempt from severe concerns related to the potential impact on the receiving soil and on the crops of potentially harmful pollutants contained in the reused water at trace levels. Among these pollutants, trace heavy metals (HMs) play a primary role due to their spread presence in the used water and to their persistence once released in the environment. The fate of HMs in the soils can be hardly predicted as mechanisms of mobility through soils are extremely diverse and related to highly complex simultaneous phenomena and chemical equilibria. HMs, in fact, as many other contaminants, are not only partitioned between the solid immobile and the water mobile phases. Indeed, colloids and nanoparticles act as a third mobile phase, with their own rheological properties and velocity. This latter aspect has been one of the main focus of the thesis. In details the thesis describes the results of several experiments conducted irrigating the OECD standard soil with real and/or synthetic wastewater, containing HMs in trace. For each test a specific soil (e.g. varying the organic matter content) and wastewater composition (e.g. varying the metals concentration, the salinity, the organic matter content, or testing real treated wastewaters) has been chosen in order to evaluate the effects of different conditions on the overall HMs fate. The increase of soil organic matter from 2,5 to 10% linearly enhanced the mobility of Cd, Cu and Ni up to a maximum mobility increase of 35.6, 43.7 and 49.19 % for Cd, Cu and Ni, respectively. In most experiments metals accumulated in the top soil layer (0.5 - 1 cm). Nevertheless peaks of contamination were detected at different depths in the soil deeper layers and at different leaching time in the leachates depending on the metal and on the soil and wastewater characteristics. Peaks of metals in the leachate appeared simultaneously with release of organic matter and/or release of silicates, demonstrating outstanding involvement of colloids in metals transport. Sodium concentration (20mM) decidedly reduced colloidal mobilization whereas more than 95 % of the influent metal was detected in the top layer despite the soil organic matter content. Salinity displayed different effects. The irrigation with real treated wastewater with quite high content of Ca and Mg (111 and 134 mg/L, respectively) resulted in higher average release of silicon from the soil inorganic matrix (8.2 mg/L) compared to the low salinity artificial wastewater (1.9 mg/L). Consequently higher mobilization of Cd, Cu, Ni and Zn was observed when the soil was irrigated with real treated wastewater. An advanced spectroscopical characterization of the leachates was performed to identify such colloidal aggregates. The observation of 3D excitation-emission matrix demonstrated in all the leachates samples the presence of fulvic (230-450 nm ex-em fluorescence area) and humic (330-445 nm ex-em) substances. In this context, a novel analytical method was developed to quantify phenolic substances in soil matrices allowing the monitoring of humic matter migration in soil profiles. The novel method was more accurate and more precise respect to the traditional one, allowing to obtain higher recovery of total phenols in peat soil (15.5 % increase) with a decrease of the coefficient of variation (30.1% decrease). Organic water soluble colloids were extracted from the peat used to prepare the OECD standard soil and characterized. Results of size exclusion chromatography highlighted the supramolecular structure of the extracted organic matter. Such structure was further confirmed through fluorescence and 1H-NMR spectroscopy

Planetary ball milling (PBM) is a well-known technique for efficient size reduction and homogenization of materials that has been used for many decades in various engineering and industrial processes. More recently, it has emerged as a unique top-down nanofabrication approach for nanomaterials based on nanoscale grinding. However, its potential application in nanostructured thin film fabrication has not been fully explored, as only a limited number of studies have been carried out. In this work, the effects of different grinding parameters (speed, time and solvents) were used to create previously unstudied nanoscale grinding conditions for nanostructured thin film materials via PBM with distinct and novel properties: Nanoparticles of silicon, titanium disilicide (TiSi2) and zinc oxide (ZnO) ground in different solvents (deionized (DI) water/ ethylene glycol (EG)/isopropyl alcohol) resulted in colloidal suspensions (or nanoinks) that could be used to coat various substrates (wafers, glass, flexible substrates, etc.) via drop casting, doctor blading or dip coating. Thin film properties such as wettability, electrical conductivity and gas sensing behavior are studied. The fabricated thin film coating properties could be tuned depending on the combination of starting powder materials, grinding parameters and resulting nanoparticle size/geometry: The influence of surface chemistry, solvent type, particle geometry, surface roughness and defects was shown to alter the conductivity and surface wettability of the resultant films. Thus, thin films formed using PBM nanoinks allow varied and tunable properties for advanced multi-functional coatings and devices. To demonstrate the feasibility of PBM nanoinks for thin film device applications, ZnO nanoinks were used to create chemiresistive gas sensors that operate at room temperature. By varying grinding parameters (speed, time and solvent) thin film sensors with differing particle sizes and porosity were produced and tested with air/oxygen against hydrogen, argon and methane target gas species, in addition to relative humidity. Grinding speeds of up to 1000 rpm produced particle sizes and RMS thin film roughness below 100 nm, as measured by atomic force microscopy and scanning electron microscopy. Raman spectroscopy, photoluminescence and x-ray analysis confirmed the purity and structure of resulting films. The peak gas sensor response was found for grinding parameters of 400 rpm (average particle size 275 nm) and 30 minutes (average particle size 225 nm) in EG and DI water, respectively, which could be correlated to an increased film porosity and an enhanced electron concentration resulting from adsorption/desorption of oxygen ions on the surface of ZnO nanoparticles. Similarly, gas response and dynamic behavior were found to improve as the operating temperature was increased between 100 and 150 °C. These results demonstrate the use of low-cost PBM nanoinks to optimize the active materials for solution-processed thin film gas/humidity sensors that can operate at room temperature for use in environmental, medical, food packaging, laboratory, and industrial applications. Overall, the nanogrinding technique can produce large amounts of nanoparticle suspension with variable particle sizes for creating thin films with tunable properties. By adjusting grinding parameters, the nanoparticle shape/size and properties can be varied resulting in nanoparticle inks for inexpensive coatings on various substrates and for use in different applications. / Graduate

Les assemblages colloïdaux représentent une nouvelle piste très prometteuse dans le domaine de l'ingénierie tissulaire. Idéalement, ce type d'assemblage permet l'obtention de matériaux injectables et gélifiants sur le site lésionnel, favorisant par la suite le développement de néo-tissus viables. Ce travail porte sur la formation de tels assemblages à base de chitosane et de poly(acide lactique) (PLA). Deux types d'assemblages ont été conçus et étudiés dans ce travail. Dans une première approche, le mélange de particules anioniques de poly (acide lactique) (PLA) avec du chitosane en solution faiblement acide conduit à la formation de « gels composites », résultant des interactions colloïde-polymère. Des analyses rhéologiques et de diffusion des rayons X aux petits angles ont permit de mettre en évidence le mode de formation et l'influence de plusieurs paramètres sur les propriétés finales de ces gels. Notamment, ils présentent des propriétés rhéofluidifiantes et un caractère réversible, c'est-à-dire que le gel peut se reformer après déstructuration mécanique. Le second type d'assemblage résulte du mélange de particules anioniques de PLA et de nanogels cationiques de chitosane, conduisant à la formation de « gels colloïdaux », par interactions colloïde-colloïde. L'influence de plusieurs facteurs sur la formation et les propriétés de ces gels a également été étudiée par mesures rhéologiques. Notre étude s'est notamment orientée sur la caractérisation et la stabilité des hydrogels physiques de chitosane sous forme colloïdale, ainsi que sur l'optimisation de leur cohésion / Colloidal assemblies may be a promising pathway to obtain injectable scaffolds favoring the development of neo-tissue in regenerative medicine. This work investigates the formation of such assemblies composed of chitosan, soluble or in suspension (nano-hydrogel), and poly(lactic acid) (PLA) nanoparticles. Two types of assemblies are studied. As a first approach, mixing negatively charged PLA particles and chitosan solution leads to the formation of “composite gels”, based on colloidpolymer interactions. Rheological and Small Angle X-Ray Scattering measurements highlighted the formation process and the influence of various parameters on final properties of these gels, which features shear-thinning and reversibility behavior, that is, the capacity to gel again after yielding. PLA nanoparticles could also be mixed with cationic chitosan nanoparticles, which are crosslinker free nano-hydrogels, leading to the formation of “colloidal gels”, based on colloid-colloid interactions. Influence of various parameters on gel synthesis and properties are investigated through rheological measurements. The study also focuses on the characterization and control of the morphological and cohesion properties of chitosan nanogel

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