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La microscopie électronique à balayage est une technique essentielle pour la caractérisation des matériaux. La nouvelle génération de MEB connue sous le nom de MEB à pression variable (aussi appelée MEB environnemental) permet de travailler dans des conditions moins drastiques de pression et de tension. Cependant, l’imagerie et la micro-analyse chimique rencontrent un défi majeur en ce qui concerne la diffusion du faisceau d'électrons primaires par les atomes/molécules du milieu gazeux. Ce phénomène de diffusion (skirt) conduit à l'apparition de plusieurs artéfacts au-delà de ceux qui sont familiers dans un MEB conventionnel. Le principal artéfact reconnu est la dégradation de la résolution spatiale qui est délimitée par le volume d'interaction en mode high-vacuum. Les objectifs de la recherche rapportés ici sont les suivants: (i) étudier l'ampleur et l'étendue de la fraction du faisceau d'électrons diffusée. (ii) le développement d'une méthodologie originale et nouvelle, afin de faire face à l'effet du skirt sur la résolution spatiale. L'efficacité de cette étude est démontrée par sa capacité à quantifier les effets de certains paramètres expérimentaux sur la dégradation de la résolution spatiale. En outre, la nouvelle méthodologie proposée est un atout précieux pour garder la résolution spatiale ultime obtenue en mode high-vacuum. Cela dépend fortement du nouveau volume d'interaction (appelé le volume d'interaction en mode low-vacuum) créé à la fois par la fraction du faisceau d'électrons diffusée et la fraction non-diffusée. / Scanning electron microscope (SEM) is an essential technique to characterize materials. The new generation of SEMs known as a variable pressure SEM (also named environmental SEM) allows to work under less drastic conditions of pressure and voltage. However, the imaging and chemical microanalysis face a major challenge with regard to the scattering of the primary electron beam by the atoms/molecules of the gas medium. This phenomenon of beam skirting leads to the appearance of several artifacts beyond those familiar in conventional SEM. The main recognized artifact is the degradation of the spatial resolution which is delineated by the high-vacuum interaction volume. The objectives of the research reported herein were: (i) to study the magnitude and the extent of the electron beam skirt. (ii) and the development of an original and new methodology in order to deal with the effect of the electron beam skirt on the spatial resolution. The effectiveness of this study is demonstrated by its ability to quantify the effects of some experimental parameters on the degradation of the spatial resolution. Further, the new methodology proposed is a valuable asset to keep the ultimate spatial resolution obtained at high vacuum mode. This depend strongly on the new interaction volume (called the low-vacuum interaction volume) created by both scattered and unscattered fraction of the electron beam.

There is great interest in miniaturized analytical systems for life science research, the clinical environment, drug discovery, biotechnology, quality control, and environmental monitoring and numerous articles have been written which predict the success of microfluidic based systems. It was demonstrated in this work that a microfluidic flow system could be quickly and easily manufactured in a research lab environment without the need for clean room facilities. The microfluidic device was created using polymethylmethacrylate, a CO2 laser and a standard oven. The device was designed, manufactured and ready for use within three hours. This work also investigated a chemiluminescent system which was intended for use in protease assays in the microfluidic device. This work also focused on the use of photoinitiated polymer monoliths, with immobilized tannic acid, as protein preconcentrators. The function of the monolithic devices was demonstrated by pumping low concentration solutions of BSA BODIPY® FL through the monolith. Both loading and elution were done using pressure. It was shown that BSA could be concentrated on and successfully eluted from the monolith. The elution volume for a 125 nl monolith was found to be 4 μl. Therefore an injection of a 60 μl sample of 1 x 10⁻⁹M BSA BODIPY ® FL gave rise to a concentration factor of 15. The pH optimum for the binding of BSA BODIPY ® FL was found to be pH 8.0 and the loading capacity of the tannic acid monolith was found to be 0.6 mg.ml⁻¹.