Les microscopes en champ proche sont très largement utilisés pour caractériser des propriétés physiques à l’échelle du nanomètre. Afin d’assurer la cohérence et l’exactitude des mesures dimensionnelles qu’ils retournent, ces microscopes ont besoin d’être étalonnés périodiquement. Le raccordement à la définition du mètre SI est assuré par le biais d’étalons de transfert dont les caractéristiques dimensionnelles sont étalonnées à l’aide d’un Microscope à Force Atomique métrologique (mAFM).Les travaux de thèse portent sur la contribution à la mise en place du Microscope à Force Atomique métrologique du LNE dans le but de caractériser et réduire l’incertitude de mesure. Une tête AFM passive thermiquement et spécifiquement conçue pour des applications de nanométrologie dimensionnelle a été développée et intégrée au mAFM. Elle comporte un système original pour mesurer les déflexions du levier nécessaire à la détection des forces s’exerçant à l’extrémité de la pointe. Il utilise une évolution de la méthode du levier optique qui permet de déporter les sources de chaleurs à l’extérieur de l’instrument. Pour cela, un nouveau capteur a été développé. Il est basé sur l’utilisation d’un bundle composé de 40 000 microfibres optiques structurées en quatre quadrants. Il remplace avantageusement une photodiode quatre quadrants et permet de transporter le signal lumineux jusqu’à des photodiodes placées à l’extérieur de l’instrument. Ce système a été modélisé, caractérisé et validé expérimentalement. La tête AFM ainsi développée est passive thermiquement. Sa conception repose sur la dissociation complète de la chaine métrologique, constituée en Zerodur, afin de lui conférer une excellente stabilité thermique et mécanique. Pour les mêmes raisons, le châssis de la tête qui supporte l’ensemble des composants et notamment le système de mesure des déflexions du levier est entièrement conçu en Invar. Cette tête repose sur une structure motorisée constituée de trois moteurs à reptation permettant l’approche de pointe mais également le réglage des interféromètres. Après intégration de la tête dans le mAFM, l’ensemble de l’instrument a été caractérisé afin d’établir son bilan d’incertitude. Plusieurs composantes ont ainsi été évaluées expérimentalement comme la non-linéarité et la stabilité de la mesure de position par interférométrie, les rotations parasites du scanner, les erreurs d’Abbe, les défauts de rugosité et de planéité des miroirs ainsi que les erreurs de bras mort. L’impact de chaque composante a été quantifié et listé dans le bilan d’incertitude. Ces travaux ont permis d’avoir une première estimation de l’incertitude de mesure du mAFM. / Scanning probe microscopes are very well used for characterization at the manometer scale. To ensure the measurement coherency and the accuracy of the results, those microscopes need to be periodically calibrated. It’s done thanks to reference standards whose dimensional characteristics are measured by a metrological atomic force microscope (mAFM) for example.The aim of this thesis work is the improvement of the metrological AFM of the LNE in order to reduce the measurement uncertainty. To reach this goal, a thermally passive AFM head has been developed and integrated on the instrument. It contains an original system to measure the cantilever deflexion and thus detect the force acting between the sample and the tip. This system is based on the optical beam deflection method but allow deporting the heat sources outside the instrument. To reach this goal, a new specific sensor has been developed. It is based on a four quadrant optic fibre bundle that contains 40 000 micro-fibre and which is ideal to replace the existing four quadrant photodiode and its conditioning electronic circuit with the bundle and its conditioning electronic circuit placed outside the instrument. This sensor has been modelled, and experimentally validated.The Developed AFM head which integrates the deflection measurement system is then thermally passive. Its design is based on the complete dissociation of the metrological loop and the structural loop. The metrological loop is made of Zerodur® in other to acquire an excellent mechanical and thermal stability and thus reduce the thermal dilatation. For the same reason, the AFM head support frame is fully made of Invar. The AFM head is placed on a motorized frame based on three piezo-leg motors (tripod) to make the tip/sample approach but also to set the interferometer signal quality. The interferometer signal is improved by combining the linear displacements of the three motors to generate small rotations. This allows setting the parallelism of the mirrors linked to the head with those linked to the translation stage.Once the AFM head integrated on the instrument, the assembly is characterized in order to establish the uncertainty budget. Different uncertainty components have been experimentally evaluated as for example: the interferometer non linearity, the drift of the XYZ position, the parasitic rotations of the translation stage, the Abbe error, the roughness and the flatness of the mirrors and the dead path errors. The impact of the each component has been quantified and listed in the uncertainty budget. This allowed getting a first estimation of the combined uncertainty of the instrument.

The recent breakthroughs of Additive Manufacturing (AM) have shed light on the ever more versatile technologies this term encompasses. AM, popularly known as 3D printing, offers distinct benefits compared to traditional manufacturing, such as reduced design constraints, “complexity for free” and waste reduction. This “bottom-up” strategy differs from the more constraining “top-down” approach used in traditional manufacturing. Among the many AM processes developed for metals, Electron Beam Melting (EBM) and Selective Laser Melting (SLM) are powder-bed fusion processes allowing complex three-dimensional geometries to be produced from the selective melting of successive layers of metal powder. EBM and SLM are the two most widely used AM processes for the production of critical Ti-6Al-4V parts, particularly for the biomedical and aeronautic industries. Despite their many advantages, these technologies present severe limitations that remain to be addressed. These include the presence of build defects in the material and a high surface roughness, which is inherent to powder-bed fusion processes.Moreover, the microstructure of as-built EBM or SLM Ti-6Al-4V is far from being optimized. In order to improve the material properties of additively manufactured Ti-6Al-4V parts, postprocess treatments can be considered. This thesis aims at investigating the impact of such treatments on the microstructure and mechanical properties of Ti-6Al-4V produced by EBM. After characterizing the microstructure, texture, and tensile properties of as-built Ti-6Al-4V, the effect of standard post-treatments, such as Hot Isostatic Pressing (HIP) and surface machining, are quantified on simple geometries. The interest of HIP is clearly demonstrated, especially when combined to improvement of the surface finish via machining. The removal of critical defects from both the bulk and the surface results in a substantial increase in ductility. Removal of the rough surface via machining also increases the mechanical efficiency of the parts. Regarding microstructural optimization, considering the impossibility of applying hot working on near-net shape parts as a major limitation, innovative heat treatments have to be specifically developed for additively manufactured Ti-6Al-4V. In this thesis, dual-phase alpha+alpha’ microstructures are generated, by performing subtransus annealing followed by water quenching. Depending on the annealing temperature, a broad range of mechanical properties are obtained. For annealing temperatures of 900 to 920°C, a simultaneous increase in ultimate tensile strength and ductility is achieved. The existence of a mechanical contrast between the soft alpha’ martensite and the harder alpha phase is clearly demonstrated and partly explains the remarkable work-hardening behaviour of this heterogeneous material. Further annealing of this out-of equilibrium alpha+alpha’ microstructure generates various microstructures. In the continuous process of martensite decomposition, precipitation hardening strengthens the alpha’ phase. Eventually, bimodal microstructures consisting in coarse primary alpha and fine secondary alpha+alpha' can be engineered, without involving any hot working in the process. Post-processing is also performed on more complex structures, namely additively manufactured lattices. Since machining cannot be performed on such intricate geometries, a chemical etching procedure inducing a substantial and homogeneous decrease in surface roughness is developed. Dissolution of surface defects results in an improvement of the mechanical efficiency of the structure. As a result, when chemical etching is performed, the relative stiffness approaches that of an ideal structure. Performing subtransus annealing and water quenching in order to induce a dual-phase alpha+alpha’ microstructure substantially increases the ability of these structures to absorb energy during compression. This thesis demonstrates the interest of developing post-process treatments specifically for near-net shape additively manufactured parts. Such treatments partially address critical issues of powder bed AM, expanding the range of possible applications of additively manufactured Ti-6Al-4V. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Le développement des capteurs de déplacement à hautes performances du point de vue de la limite de résolution et de l’étendue de mesure, est devenu une demande croissante pour les systèmes mécaniques et mécatroniques. Ce mémoire présente la modélisation, la conception et la fabrication d’un capteur innovant permettant la mesure in-situ et en temps réel du déplacement linéaire d’un axe en mouvement de rotation. Ce capteur est caractérisé par une grande étendue de mesure d’une dizaine de millimètres et par une résolution micrométrique. Après une étude bibliographique portant sur les applications industrielles de ce capteur, une modélisation géométrique de la réflexion de lumière par une surface convexe a été développée. Ce modèle calcule l’intensité lumineuse détectée par le capteur en fonction du rayon de courbure de la surface. Il a montré que la sensibilité augmente en fonction du rayon de courbure (Rc) et que la résolution est optimale pour (Rc=20 mm). Ce modèle géométrique a été validé par des essais expérimentaux dont les résultats ont montré une chute de la sensibilité pour des rayons inférieurs à (Rc= 15 mm). Pour cette raison, et afin de garantir le meilleur fonctionnement du capteur, le rayon de courbure choisi pour la fabrication du réseau de cônes imbriqués a été de 25 mm. Une fois le rayon de courbure optimal choisi, une modélisation géométrique de la mesure de déplacements linéaires sur une grande étendue de mesure par l’utilisation de deux sondes et d’un réseau à cônes imbriqués a été réalisée. La technique d’usinage de haute précision (UHP) a été présentée. Un premier prototype de ce réseau en alliage d’aluminium a été obtenu. Puis, le modèle géométrique a été optimisé pour mieux prendre en compte certaines contraintes de fabrication, ce qui a conduit à l’usinage d’un deuxième prototype ayant des paramètres géométriques légèrement modifiés et un meilleur état de surface pour mieux réfléchir la lumière. Enfin, la validation expérimentale du principe de mesure du capteur à fibres optiques (CFO) a été faite pour ces deux prototypes du réseau de cônes imbriqués, à l’aide d’un montage mécanique, ce qui a permis d’orienter au mieux les sondes du CFO en face du réseau. Cette validation a permis d’évaluer les performances du CFO. Pour le premier prototype, un recouvrement de 30 µm a été vérifié entre les deux signaux. Différentes vitesses de translation et de rotation on été appliquées ; où on a remarqué l’apparition des pics périodiques. Ces pics sont dus à un problème de balourd de l’axe de rotation de la broche ; en augmentant les valeurs de la vitesse de rotation, les pics s’atténuent, car l’inertie de la broche est supérieure. Pour cette raison, on a privilégié de travailler avec des vitesses de rotation élevées et une gamme de vitesse de translation tout en tenant compte de la fréquence d’acquisition. Pour le deuxième prototype, on a validé le principe de mesure avec deux sondes à fibres optiques. Un recouvrement suffisant a été mesuré entre les deux signaux. On a constaté qu’en acceptant davantage de non-linéarité, on augmente la largeur de la zone de recouvrement, ce qui facilite le basculement d’une sonde à l’autre et ainsi assure la continuité de la mesure sur une étendue millimétrique qui est fonction du nombre de cônes, mais l’exactitude de la mesure s’en trouve diminuée. En augmentant la vitesse de translation, on diminue le nombre des points acquis dans la zone de recouvrement, ce qui exige une fréquence d’acquisition plus élevée. / The development of displacement sensors with high performances regarding the limit of resolution and the measurement range has become essential for different mechanical systems This Ph.D. presents the modeling, the design and the fabrication of an original fiber-optic sensor. lt is able to measure the linear displacement of a rotating axis. This sensor is characterized by a micrometric resolution on a measurement range of several millimeters. After a bibliography study related to the industrial applications of the sensor, a geometric model of the light reflection by a convex surface has been developed. This model calculates the light intensity detected by the sensor as a function of the radius of curvature (Re); the model shows that the sensitivity increases as a function of the radius of curvature of the reflector (Re) and the limit of resolution is optimal for (Re=20 mm). This geometric model had been experimentally validated; where it was found out that the sensitivity decreases for the radii of curvature less than 15 mm (Re= 15 mm). For that reason, and in order to ensure the best functionality of the sensor, the radius of curvature chosen for the fabrication of the canes assembled grating was 25 mm. Once the optimal radius of curvature fixed a geometric model for the linear displacement measurement on a long measurement range using two fiber-optic probes and one cones assembled grating has been developed. The first prototype of the cones assembled grating was obtained with a high precision turning machine on an aluminum alloy. Afterwards, a second prototype of the cones grating was fabricated; where several parameters have been optimized, such as: the non-inclusion of the fabrication constraints in the geometric model and a better surface roughness of the cones assembled grating. The high precision fabrication technique of the two prototypes was presented. Finally, the experimental validation of the sensor measurement principle with two fiber-optic probes with the help of a mechanical set-up was realized. The mechanical set-up is used to a better orientation of the probes in front of the grating. The experimental validation helped to evaluate the overall sensor performances. For the two prototypes, an overlap of 30 um was verified between two successive signals. Different translation and rotation speeds were applied; where periodical peaks were observed in the output signals. These peaks are due to an unbalanced rotation of the spindle axis of rotation; with high speed values, the peaks are attenuated due to the high inertia of the spindle. For this reason, it is preferred to work at high rotational speeds (20 tr./s) with a consideration of the sampling frequency. This sensor is characterized by a micrometric resolution, on a measurement range of about 10 mm.

The outstanding electrical and material properties of Graphene have made it a promising material for several fields of analog applications, though its zero bandgap precludes its application in digital and logic devices. With its remarkably high electron mobility at room temperature, Graphene also has strong potential for terahertz (THz) plasmonic devices. However there still are challenges to be solved to realize Graphene’s full potential for practical applications. In this dissertation, we investigate solutions for some of these challenges. First, to reduce the access resistances which significantly reduces the radio frequency (RF) performance of Graphene field effect transistors (GFETs), a novel device structure consisting of two additional contacts at the access region has been successfully modeled, designed, microfabicated/integrated, and characterized. The additional contacts of the proposed device are capacitively coupled to the device channel and independently biased, that induce more carriers and effectively reduce access resistance. In addition to that, in this dissertation, bandgap has been experimentally introduced to semi-metallic Graphene, by decorating with randomly distributed gold nano-particles and zinc oxide (ZnO) nano-seeds, where their interaction breaks its sublattice symmetry and opens up bandgap. The engineered bandgap was extracted from its temperature dependent conductivity characteristics and compared with reported theoretical estimation. The proposed method of device engineering combined with material bandgap engineering, on a single device, introduces a gateway towards high speed Graphene logic devices. Finally, THz plasmon generation and propagation in Graphene grating gate field effect transistors and Graphene plasmonic ring resonators have been investigated analytically and numerically to explore their potential use for compact, solid state tunable THz detectors.

This dissertation describes the development of a label-free, electrochemical immunosensing platform integrated into a low-cost microfluidic system for the sensitive, selective and accurate detection of cortisol, a steroid hormone co-related with many physiological disorders. Abnormal levels of cortisol is indicative of conditions such as Cushing’s syndrome, Addison’s disease, adrenal insufficiencies and more recently post-traumatic stress disorder (PTSD). Electrochemical detection of immuno-complex formation is utilized for the sensitive detection of Cortisol using Anti-Cortisol antibodies immobilized on sensing electrodes. Electrochemical detection techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been utilized for the characterization and sensing of the label-free detection of Cortisol. The utilization of nanomaterial’s as the immobilizing matrix for Anti-cortisol antibodies that leads to improved sensor response has been explored. A hybrid nano-composite of Polyanaline-Ag/AgO film has been fabricated onto Au substrate using electrophoretic deposition for the preparation of electrochemical immunosening of cortisol. Using a conventional 3-electrode electrochemical cell, a linear sensing range of 1pM to 1µM at a sensitivity of 66µA/M and detection limit of 0.64pg/mL has been demonstrated for detection of cortisol. Alternately, a self-assembled monolayer (SAM) of dithiobis(succinimidylpropionte) (DTSP) has been fabricated for the modification of sensing electrode to immobilize with Anti-Cortisol antibodies. To increase the sensitivity at lower detection limit and to develop a point-of-care sensing platform, the DTSP-SAM has been fabricated on micromachined interdigitated microelectrodes (µIDE). Detection of cortisol is demonstrated at a sensitivity of 20.7µA/M and detection limit of 10pg/mL for a linear sensing range of 10pM to 200nM using the µIDE’s. A simple, low-cost microfluidic system is designed using low-temperature co-fired ceramics (LTCC) technology for the integration of the electrochemical cortisol immunosensor and automation of the immunoassay. For the first time, the non-specific adsorption of analyte on LTCC has been characterized for microfluidic applications. The design, fabrication technique and fluidic characterization of the immunoassay are presented. The DTSP-SAM based electrochemical immunosensor on µIDE is integrated into the LTCC microfluidic system and cortisol detection is achieved in the microfluidic system in a fully automated assay. The fully automated microfluidic immunosensor hold great promise for accurate, sensitive detection of cortisol in point-of-care applications.

The Terahertz (1012 Hz) region of the electromagnetic spectrum covers the frequency range from roughly 300 GHz to 10 THz, which is in between the microwave and infrared regimes. The increasing interest in the development of ultra-compact, tunable room temperature Terahertz (THz) emitters with wide-range tunability has stimulated in-depth studies of different mechanisms of THz generation in the past decade due to its various potential applications such as biomedical diagnosis, security screening, chemical identification, life sciences and very high speed wireless communication. Despite the tremendous research and development efforts, all the available state-of-the-art THz emitters suffer from either being large, complex and costly, or operating at low temperatures, lacking tunability, having a very short spectral range and a low output power. Hence, the major objective of this research was to develop simple, inexpensive, compact, room temperature THz sources with wide-range tunability. We investigated THz radiation in a hybrid optical and THz micro-ring resonators system. For the first time, we were able to satisfy the DFG phase matching condition for the above-mentioned THz range in one single device geometry by employing a modal phase matching technique and using two separately designed resonators capable of oscillating at input optical waves and generated THz waves. In chapter 6, we proposed a novel plasmonic antenna geometry – the dimer rod-tapered antenna (DRTA), where we created a hot-spot in the nanogap between the dimer arms with a very large intensity enhancement of 4.1×105 at optical resonant wavelength. Then, we investigated DFG operation in the antenna geometry by incorporating a nonlinear nanodot in the hot-spot of the antenna and achieved continuously tunable enhanced THz radiation across 0.5-10 THz range. In chapter 8, we designed a multi-metallic resonators providing an ultrasharp toroidal response at THz frequency, then fabricated and experimentally demonstrated an efficient polarization dependent plasmonic toroid switch operating at THz frequency. In summary, we have successfully designed, analytically and numerically investigated novel THz emitters with the advantages of wide range tunability, compactness, room temperature operation, fast modulation and the possibility for monolithic integration, which are the most sought after properties in the new generation THz sources.

La prise en compte de machines à traitement par batch dans les problèmes d’ordonnancement d’ateliers complexes de type job-shop est particulièrement difficile. La fabrication de semiconducteurs est probablement l’une des applications pratiques les plus importantes pour ce types de problèmes. Nous considérons un problème d’ordonnancement de type job-shop flexible avec « p-batching », des flux rentrants, des temps de préparation dépendant de la séquence et des dates de début au plus tôt. Le but c’est d’optimiser différentes fonctions objectives régulières.Les approches existantes par graphe disjonctif pour ce problème utilise des nœuds dédiés pour représenter explicitement les batches. Afin de faciliter la modification du graphe conjonctif, notre nouvelle modélisation réduit cette complexité en modélisant les décisions de batching à travers les poids des arcs. Une importante contribution de cette thèse est un algorithme original qui prend les décisions de batching lors du parcours du graphe. Cet algorithme est complété par un déplacement (« move ») intégré qui permet de reséquencer ou réaffecter les opérations. Cette combinaison donne un voisinage riche que nous appliquons dans une approche méta-heuristique de type GRASP.Nous étendons cette approche en prenant en compte de nouvelles contraintes qui ont un rôle important dans l’application industrielle considérée. En particulier, nous modélisons de manière explicite les ressources internes des machines, et nous considérons un temps maximum d’attente entre deux opérations quelconques d’une gamme de fabrication. Les résultats numériques sur des instances de la littérature pour des problèmes plus simples ainsi que sur de nouvelles instances montrent la généricité et l’applicabilité de notre approche. Notre nouvelle modélisation permet de faciliter les extensions à d’autres contraintes complexes rencontrées dans les applications industrielles. / The integration of batching machines within a job-shop environment leads to a complex job-shop scheduling problem. Semiconductor manufacturing presumably represents one of the most prominent practical applications for such problems. We consider a flexible job-shop scheduling problem with p-batching, reentrant flows, sequence dependent setup times and release dates while considering different regular objective functions. The scheduling of parallel batching machines and variants of the job-shop scheduling problem are well-studied problems whereas their combination is rarely considered.Existing disjunctive graph approaches for this combined problem rely on dedicated nodes to explicitly represent batches. To facilitate modifications of the graph, our new modeling reduces this complexity by encoding batching decisions into edge weights. An important contribution is an original algorithm that takes batching decisions “on the fly” during graph traversals. This algorithm is complemented by an integrated move to resequence and reassign operations. This combination yields a rich neighborhood that we apply within a GRASP based metaheuristic approach.We extend this approach by taking further constraints into account that are important in the considered industrial application. In particular, we model internal resources of machines in detail and take maximum time lag constraints into account. Numerical results for benchmark instances of different problem types show the generality and applicability of our approach. The conciseness of our idea facilitates extensions towards further complex constraints needed in real-world applications.

Composites have been developed with great success by the use of fiber reinforcements in metallic materials. Fiber reinforced metal matrices possess great potential to be the next generation of advanced composites offering many advantages compared to fiber reinforced polymers. Specific advantages include high temperature capability, superior environmental stability, better transverse modulus, shear and fatigue properties. Although many Metal Matrix Composites (MMCs) are attractive for use in different industrial applications, Aluminium Matrix Composites (AMCs) are the most used in advanced applications because they combine acceptable strength, low density, durability, machinability, availability, effectiveness and cost. The present study focuses on the fabrication of aluminium matrix composite plates by squeeze casting using plain weave carbon fiber preform (AS4 Hexcel) as reinforcement and a matrix of wrought aluminium alloy 1235-H19. The objective is to investigate the process feasibility and resulting materials properties such as hardness at macro- and micro-scale, impact and bend strength. The properties obtained are compared with those of 6061/1235-H19 aluminium plates that were manufactured under the same fabrication conditions. The effect of fiber volume fraction on the properties is also investigated. Furthermore, the characterization of the microstructure is done using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and mechanical properties of the composites. In conclusion, aluminium matrix composite laminate plates were successfully produced. The composites show a good chemical bond between the fiber and the aluminium matrix. This bond resulted from heterogeneous precipitation of aluminium carbides (Al4C3) at the interface between aluminium matrix and carbon fiber. The hardness at macro- and micro-scale of the composites increases by over 50% and the flexural modulus increases by about 55%. The toughness of the composite decreases due to the presence of brittle phases which can be improved by better oxidation prevention. Also, an optimal carbon volume fraction was observed that provides optimal properties including peak hardness, peak stiffness and peak toughness.

The 21st century marks the defining point of human history in terms of technological advancement. In 2014, we were at the edge of acquiring a complete understanding of the fundamental construct to all life forms. The capability to manipulate and recreate lives as desired will soon be at our hands and will eventually lead to the redefinition of life and humanity. This brave new world, for better or worse, will be stitched together by scientific breakthroughs in many disciplines. Nanopore fluidic system – and microfluidic in general – might be one of the key puzzles towards the future. It is seen as a likely candidate for the next generation of rapid and low-cost genetic sequencing technology, which will allow us to gain thorough insight into the genetic code of every living organism on earth. It can also have the capability to individually detect and manipulate virtually any biological molecules, possibly allowing it to be a universal diagnostic tool or a bio-molecule synthesiser. The future of nanopore fluidic system is prosperous, but the difficulties are equally challenging. Currently, both biological and solid-state nanopores are non-trivial to create. For instance, a small solid-state nanopore can only be fabricated with expansive machinery in a low-yield, low-throughput manner. To overcome this challenge, a new set of methods involving high electric field to fabricate and enlarge a solid-state nanopore has been developed. It was found that a nanopore, when subjected to a high electric field, can be enlarged in angstrom increments and cleared of unidentified obstructions that cause low-frequency ionic current fluctuations. It was also found that an intact solid-state membrane, when subjected to a high electric field for a period of time, can leave a single nanopore imprinted onto it. The process of creation is best describe as a dielectric breakdown event and can be modeled by the percolation theory for dielectric breakdown. The resulting nanopores are cylindrical in shape and are shown to be equally capable of single molecule sensing compare to pores created by other methods. To accommodate future nanopore designs and applications and to examine the scope of applicability of the new fabrication approach, more advanced nanopore devices were created on some dual-layer solid-state membranes comprising of a metallic and a dielectric layer. Experiments indicated that the method could indeed create nanopore on such advanced membranes. It was further shown that the metallic layer receded further than the dielectric layer, forming a hollow conical shape at the opening of the dielectric nanopore. Such metalized bi-layer nanopore system was found to interact strongly with short single stranded DNA molecules, resulting in prolonged DNA translocation time. A simple picture of the mechanism was proposed to explain the observation. Lastly, to extend the limit of the new fabrication approach, I attempted to fabricate nanopore on complex multi-layer membranes involving a graphene film sandwiched in several dielectric materials. It was found that the quality of the graphene film and the transfer method were vital to the success of this project. Nevertheless, preliminary results indicated that the new method could create a nanopore through this complex multi-layer membrane. The new method to fabricate and tune both simple and complex nanopores is amongst the simplest, the least costly and the most efficient one that one can imagine. The research work has already sparked a dramatic increase in scientific throughput in our laboratory and other laboratories we had collaboration with. It fueled more than a dozen projects and involved close to a thousand nanopores in total. Such projects are far from possible if they were to rely on conventional fabrication methods. However, these are insignificant if we consider the new method is simple enough that, for the very first time, general public can easily access nanofabrication and single-molecule manipulation technology. The liberation of nanotechnology to the general public symbolically marks the beginning of a brave new world.

Initial research in the field of organic electronics focused primarily on the improvements in material performance. Significant progress has been achieved in the case of organic field effect transistors, where reported mobility values are now over 5 orders of magnitude higher than those of early devices. As a consequence, the use of organic transistors is now being considered for real-world applications in the form of integrated logic circuits. This in turn presents many new challenges, as the logic circuit requirements are more demanding on the transistor characteristics and corresponding fabrication processes. This thesis investigates the feasibility of organic technology for its potential use in future low-cost, high-volume electronic applications. The research objectives were accomplished by practical evaluation of an organic logic circuit fabrication process. First, recent advances in the fabrication of organic circuits in terms of transistor structure, material usage and fabrication techniques are reviewed. Next, a lithographic logic circuit fabrication process using PVP gate dielectric and TIPS-pentacene organic semiconductor adapted from state of the art fabrication process is presented. The logic circuit design decisions and the methodology for the fabrication process are thoroughly documented. Using this process, zero-Vgs and diode-load inverter circuits were successfully fabricated. However, the process is in need of further refinement for more complex circuit designs, as the fabrication of a comparator circuit consisting of 11 transistors was unsuccessful. Two optimisation techniques that are compatible with the logic circuit fabrication process were also explored in this work. To improve the capacitive coupling of the dielectric layer, the use of a polymer nanocomposite dielectric was investigated. The nanocomposite is prepared by blending PVP solution with a high-k inorganic nanoparticle filler, barium strontium titanate. Using the nanocomposite dielectric, both single transistors and integrated logic circuits were successfully fabricated. This is the first report on the use of PVP and barium strontium titanate nanocomposite dielectric with a lithographic based logic circuit fabrication process. The use of PFBT modified Au contacts for the fabrication process was investigated to improve theperformance of the contact electrode layer. Using PFBT, mobility increased by one order of magnitude over untreated Au electrodes for the PVP and TIPS-pentacene transistors.