"Previous studies carried out in our laboratory resulted in the development of noncovalently assembled multilayered thin films incorporating metal ions such as Cu(II) and organic ligands including dicarboxypyridine. In one study, a SAM consisting of 4-[(10- mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid was deposited on gold. The pyridine group was then used to complex a layer of Cu(II) ions which in turn were capped by cis- 2,2’-dipyridylethylene. This stilbene analog undergoes photoinduced cis-trans isomerization on the surface resulting in a substantial increase in the hydrophilicity of the surface leading to the possibility of creating virtual microfluidic valves and pumps. However, the photoswitchable wettability was irreversible. Stilbene-4,4-dicarboxylic acid was the ligand selected for generating a reversible system. The decision to use this stilbene moiety was based on molecular modeling and the commercial availability of both cis and trans forms. When 4-[(10-mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid was used as SAM, the stilbene-4,4’-dicarboxylic acid did not undergo photoisomerization. Prolonged irradiation leads to photodegradation of film. A mixed SAM of dodecanethiol and mercaptoundecanoic acid was used to create space on the surface and facilitate isomerization. But cis-trans isomerization of the stilbene moiety was not achieved by this system. When a mixed SAM of 4-[(10-mercaptodecyl)oxy]pyridine-2,6-dicarboxylic acid and 4-tert butylbenzenethiol was used, stilbene-4,4-dicarboxylic acid showed reversible photoinduced cis-trans isomerization for one complete cycle leading to a reversible change in wettability. After one cycle of isomerization the film photodegrades."

Bacterial adhesion is the first step of biofilm formation and in the focus of research interest since several decades. Biofilms cause many problems, sometimes dramatic, for example in health, food packing or waste water purification. Despite of high interest, bacterial adhesion process is only poorly understood yet. In this work, bacterial adhesion was investigated on well-organized and structured model surfaces with various chemistries at molecular scale. For that purpose a characterization methodology was developed to sufficiently analyze monolayers on silicon wafers, and controlled mixed monolayers surfaces with different densities of NH 2 backfilled with CH3 were developed and optimized. These controlled surfaces with different densities of 0 % NH2 up to 100% NH2 were eventually used as tool to study bacterial adhesion in batch and real time conditions. The results demonstrate a significant impact on bacterial adhesion of weak difference in the surface chemistry at molecular scale. In the batch experiments, two so-called "plateaus" zones were determined, in which bacterial adhesion is not significantly different despite the change of the amine concentration on the surface. On the contrary, one transition zone exists between the "plateaus" in which a slight chunge.in the amine concentration leads to a significant increase / decrease of the bacterial adhesion. The same trend of bacteria behavior was observed for different bacterial strains.

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L'adhésion bactérienne est la première étape du processus de formation d'un biofilm et est un enjeu majeur de la recherche depuis plusieurs dizaines d'années. Les biofilms ont des conséquences parfois dramatiques dans des domaines comme la santé, l'agroalimentaire ou la purification des eaux usées. Toutefois, l'adhésion bactérienne reste un phénomène mal compris. Dans cette thèse, l'adhésion bactérienne est étudiée sur des surfaces modèles très bien organisées et structurées, de chimie de surface variable à l'échelle moléculaire. Une méthodologie de caractérisation adaptée aux monocouches déposées sur wafers de silicium est proposée. Des surfaces modèles composées de monocouches mixtes auto-assemblées de densités variables de NH2 dans un continuum de CH, sont développées et optimisées. Ces surfaces contrôlées, de densités de 0% NH2 à 100% NH2 dans CH3, sont utilisées comme outil pour étudier l'adhésion bactérienne en conditions de culture « batch »et « temps réel ». Les résultats montrent un impact significatif sur l'adhésion bactérienne de faibles différences chimiques à l'échelle moléculaire. Les résultats des expériences menées en conditions « batch » permettent de déterminer deux zones « plateau » dans lesquelles l'adhésion bactérienne ne varie pas significativement malgré des variations importantes de la concentration en groupements amine sur la surface. Une zone de transition entre les zones « plateau » est mise en évidence, dans laquelle une faible modification de la concentration en groupement amine mène à l'augmentation / diminution significative du nombre de bactéries adhérées. Cette tendance est montrée pour deux souches différentes de bactérie. / Bacterial adhesion is the first step of biofilm formation and in the focus of research interest since several decades. Biofilms cause many problems, sometimes dramatic, for example in health, food packing or waste water purification. Despite of high interest, bacterial adhesion process is only poorly understood yet. In this work, bacterial adhesion was investigated on well-organized and structured model surfaces with various chemistries at molecular scale. For that purpose a characterization methodology was developed to sufficiently analyze monolayers on silicon wafers, and controlled mixed monolayers surfaces with different densities of NH 2 backfilled with CH3 were developed and optimized. These controlled surfaces with different densities of 0 % NH2 up to 100% NH2 were eventually used as tool to study bacterial adhesion in batch and real time conditions. The results demonstrate a significant impact on bacterial adhesion of weak difference in the surface chemistry at molecular scale. In the batch experiments, two so-called "plateaus" zones were determined, in which bacterial adhesion is not significantly different despite the change of the amine concentration on the surface. On the contrary, one transition zone exists between the "plateaus" in which a slight chunge.in the amine concentration leads to a significant increase / decrease of the bacterial adhesion. The same trend of bacteria behavior was observed for different bacterial strains.