Immobilization of proteins by covalent coupling to polymeric materials offers numerous excellent advantages for various applications, however, it is usually limited by coupling strategies, which are often too expensive or complex. In this study, an electron-beambased process for covalent coupling of the model protein bovine serum albumin (BSA) onto polyvinylidene fluoride (PVDF) flat sheet membranes was investigated. Immobilization can be performed in a clean, fast, and continuous mode of operation without any additional chemicals involved. Using the Design of Experiments (DoE) approach, nine process factors were investigated for their influence on graft yield and homogeneity. The parameters could be reduced to only four highly significant factors: BSA concentration, impregnation method, impregnation time, and electron beam irradiation dose. Subsequently, optimization of the process was performed using the Response Surface Methodology (RSM). A one-step method was developed, resulting in a high BSA grafting yield of 955 mgm−2 and a relative standard deviation of 3.6%. High efficiency was demonstrated by reusing the impregnation solution five times consecutively without reducing the final BSA grafting yield. Comprehensive characterization was conducted by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and measurements of zeta potential, contact angle and surface free energy, as well as filtration performance. In addition, mechanical properties and morphology were examined using mercury porosimetry, tensile testing, and scanning electron microscopy (SEM).

Additive tillverkning (AM) är en tillverkningsteknik som har använts i stor utsträckning i industrier de senaste åren. Electron beam melting (EBM) är en innovativ teknik för tillverkning inom ortopediska implantat- och flygindustrin för att EBM erbjuder hög produktivitet och lägre kostnad per del. Jämfört med traditionella tillverkningsmetoder kan EBM tillverka delar med betydande mekaniska egenskaper, men det finns några vanliga brister som hindrar EBMs förmåga att bli en vanligare bearbetningsmetod vid tillverkning. I detta arbete, som tar an formen av en State of the Art Rapport, introduceras EBM-metoden på teknisk nivå och jämförs med andra AM-metoder och konventionella tillverkningsmetoder. / Additive manufacturing (AM) is a manufacturing technology that has been widely used in industries in recent years. Electron beam melting (EBM) is an innovative technology for manufacturing of the orthopedic implant and aerospace industry because EBM offers high productivity and lower cost per part. Compared to traditional manufacturing methods, EBM can produce parts with significant mechanical properties, but there is some common shortcoming that prevent EBM's ability to become a more common processing method in manufacturing. This work, which takes the form of a State of the Art Report, introduces the EBM method at the technical level and compares with other AM methods and conventional manufacturing methods.

Electron beam melting (EBM), a metal additive manufacturing (AM) process, has received considerable industrial attention for near net shape manufacture of complex geometries with traditionally difficult-to-machine materials. This has fuelled considerable academic interest in investigating EBM of Alloy 718, a nickel ironbased superalloy possessing an exciting combination of good mechanical behaviour and cost effectiveness. EBM production of Alloy 718 is particularly promising for aerospace and other sectors which value rapid production of components with large scope for design flexibility. The EBM builds are characterized by presence of inevitable defects and, anisotropy within a build is also a concern. Consequently, as-built Alloy 718 has to be subjected to post-build thermal-treatments (post-treatments) to ensure that the parts eventually meet the critical service requirements. Not withstanding the above, limited knowledge is available about optimal post-treatments for EBM-built Alloy 718. Therefore, the main focus of the work presented in this thesis was to systematically investigate the response of EBM-built material to post-treatments, which include hotisostatic pressing (HIPing), solution treatment (ST), and aging. HIPing of EBM-built Alloy 718 led to more than an order of magnitude reduction in defect content, which was reduced from as high as 17% to &lt; 0.2% in samples built with intentionally introduced porosity to investigate limits of defect closure achievable through HIPing. In addition, HIPing also caused complete dissolution of δ and γ" phases present in the as-built condition, with the latter causing dropin hardness of the material. HIPing had no effect on the carbides and inclusions such as TiN, Al2O3 present in the built material. The evolution of microstructure during ST and aging was systematically investigated. Growth of potentially beneficial grain boundary δ phase precipitates was found to cease after a certain duration of ST, with samples subjected to prior-HIPing exhibiting lesser precipitation of the δ phase during ST. While the specimen hardness increased onaging, it was observed to plateau after a duration significantly shorted than the specified ASTM 'standard' aging cycle. Therefore, prima facie there are promising prospects for shortening the overall heat treatment duration. A combination of HIPing, ST, and aging treatments in a single uninterrupted cycle was also explored. Future work involving incorporation of a shortened heat treatment schedule in a combined cycle can have significant industrial implications. / <p>Articles submitted to journals and unpublished manuscripts are not included in this registration</p>

Bottom-up nanofabrication, although still in its early stages with formidable challenges, is considered a potential alternative method to address the limitations of traditional top-down techniques by offering benefits including process simplification, cost reduction, and environmental friendliness. DNA-templated nanofabrication, one of the most powerful bottom-up methods, presents an innovative way to create advanced nanoelectronics. In this approach, nanomaterials with specific electronic, photonic, or other functions are precisely and programmably positioned on DNA nanostructures from a disordered collection of smaller parts. These self-assembled structures offer significant potential for improving many fields such as biosensing, drug delivery and electronic device manufacturing. This dissertation reports the successful fabrication of semiconductor-metal Schottky contacts using a DNA origami scaffold. The scaffold, consisting of DNA strands organized into a specific bar-shaped architecture, facilitates the competitive arrangement of gold and cadmium sulfide nanorods, forming heterojunctions, and addressing previous limitations in semiconductor nanomaterial availability. Electrical characterization reveals nonlinear Schottky barrier properties, with electrical conductivity ranging from 1.1 to 3.7 — 104 S/m, marking a several million-fold increase over prior work. This research establishes the feasibility of using cadmium sulfide prepared as a n-type semiconductor material and an innovative self-assembly approach for making nanoscale Schottky contacts, paving the way for the future development of DNA-based nanoscale logic gate circuits.

科学研究費補助金 研究種目:基盤研究(C)(2) 課題番号:07680528 研究代表者:青山 隆彦 研究期間:1995-1996年度

Spin-polarized electron beam has not yet been produced from an unpolarized electron beam using Stern-Gerlach type spin filter, because of the Lorentz force and Heisenberg uncertainty principle. At present, electron spin detectors and filters work on the basis of spin-dependent scattering of an electron beam from crystal surfaces. Single channel efficiencies of all the spin detectors for electrons are orders of magnitudes lower than the ideal one. Specular reflection type spin-polarized low energy electron diffraction (SPLEED)-spin detectors are having higher single channel efficiencies compared to the conventional Mott detectors. Moreover, multichannel detection can be realized from specular reflection type SPLEED-spin detectors. They have higher effective efficiency than the ideal spin detector. In order to develop specular reflection type spin filter, it is important to develop a spin-polarized low energy electron diffraction system. In addition, SPLEED system allows us to study the spin-orbit and exchange scattering at crystal surfaces. The general direction of the thesis has been the development of spin-polarized low energy electron diffraction (SPLEED) system. This system has been used to investigate the spin-orbit interactions on Ir(100) surface and exchange interactions of Fe grown on Ir(100). The thesis is organized into chapters as follows. Chapter 1 introduce the reader to some of the basic concepts of polarized electrons and the evolution of spin-polarized electron sources and detectors. Sources of polarized electrons are discussed with emphasis on photocathodes such as GaAs and strained GaAs. Widely used spin detector is the Mott detector which works in the higher energy range. The working principle of the Mott detector is discussed. Commonly used spin detector in the lower energy range is the LEED detector. The concept of the LEED detector is also discussed. Working principle and recent developments of specular reflection type SPLEED spin filters are introduced. Evolution of electron spin detector is discussed towards the end of the chapter. Chapter 2 discusses about the two instruments designed and developed during the course of the thesis. The first one is a spin-polarized low energy electron diffraction system working in the reflected electron pulse counting mode in UHV. This system is capable of measuring spin asymmetries due to spin-orbit interaction and exchange interaction. This instrument is useful in understanding structure and magnetism at surfaces as well as helps to develop new spin polarimeter based on SPLEED by evaluating spin asymmetries from different surfaces. All instruments connected to SPLEED system, measurement protocol and controlling software are discussed with some details. Along with this, standard characterization tools such as X-ray diffraction and magneto-optic Kerr effect measurements are discussed. The second instrument is a novel quadratic magneto-optic Kerr effect measurement system using permanent magnets, which is simple, compact and cost-effective. We have used rotating field method to extract QMOKE component in saturation. So there is no need for precise real-time measurement of magnitude and direction of the magnetic field as in the case of vector magnet. This instrument can easily quantify QMOKE coefficients for ferrimagnetic and ferromagnetic thin films and single crystals. Chapter 3 discusses SPLEED experiments carried out on Ir(100)-(1×5)-Hex and Ir(100)-(1×2+2×1)-O surfaces. The surface structure and surface preparation techniques are discussed. The stability of the Ir(100)-(1×5)-Hex surface is evaluated by monitoring the spin asymmetry as the function of time. Within 25 hours after the surface preparation, the profile of the spin asymmetry and the reflected electron count for Ir(100)-(1×5)-Hex surface resembles that of hydrogen adsorbed Ir(100)-(1×5)-H surface. The electron energy-angle of incidence landscape of reflectivity, spin asymmetry and figure of merit are recorded for Ir(100)-(1×2+2×1)-O surface. Many wide regions with a large figure of merit are identified in the E- landscape. Chapter 4 reports SPLEED experiments carried out on Ir(100)-(1×5)-H surface. The comparison between asymmetries evaluated for the Ir(100)-(1×5)-Hex surface after 25 hours and Ir(100)-(1×5)-H surface suggests that Ir(100)-(1×5)-Hex surface is transforming to Ir(100)-(1×5)-H surface, in 25 hours. This can be due to the adsorption of more than four Langmuir of residual hydrogen during this time. The energy-angle landscape of reflectivity, asymmetry and figure of merit are recorded for Ir(100)-(1×5)-H surface in an energy range 20 eV to 100 eV and angle range 10 to 60 . Many regions are identified as the working point for specular reflection type spin filter based on SPLEED. The surface structure and surface preparation techniques are discussed. The stability of the surface is also evaluated. Chapter 5 investigates the growth and magnetic properties of Fe(100) film on Ir(100)-(1×1), Ir(100)-(1×5)-Hex and Ir(100)-(1×2+2×1)-O surfaces. LEED, MEED, LMOKE and QMOKE studies were presented. The growth is found to be layer-by-layer at least up to 20 monolayers (ML) at room temperature. At higher deposition temperature, the MEED oscillations disappear around 3-5 ML. Magnetic anisotropy of the Fe(100) film grown on Ir(100)-(1×2+2×1)-O surfaces is evaluated using LMOKE measurement using Kerr microscope. Simultaneous in-situ LMOKE and MEED measurements were carried out during the deposition. Ferromagnetic ordering with an in-plane easy axis starts above 4.5 ML at room temperature. The Kerr rotation normalized by thickness is evaluated in the pseudomorphic regime and strain relaxed regime. The probing depth of the MOKE is found to be around 14 nm in Fe(100)/Ir(100). An antisymmetric component is observed in the re-magnetization loop measured using MOKE. This antisymmetric loop arises due to the quadratic magneto-optic coupling which is separated by symmetrization and antisymmetrization procedure. The observed quadratic magneto-optic coupling suggests that the analysis based on the assumption that the magneto-optic coupling is linear in magnetization has to be modified. In order to quantify the quadratic magneto-optic coupling parameters, a QMOKE measurement system is developed and measurements were carried out. Chapter 6 discusses SPLEED experiments carried out on various thicknesses of Fe(100) film. Fe(100) films grown on Ir(100) substrate with the thickness less than or equal to 4 ML is not ferromagnetic with in-plane easy axis at room temperature. The non-zero exchange asymmetry observed for 5 ML and above indicates the presence of ferromagnetic ordering. A difference in the profile of exchange asymmetry is observed between pseudomorphic and strain relaxed regime. Large spin-orbit asymmetry is observed for 1 ML and 2 ML Fe(100) which is unexpected from a low atomic number (Z) material. The reason for large spin-orbit asymmetry is still unknown. The energy-angle landscape of reflectivity, exchange asymmetry, spin-orbit asymmetry and figure of merit were evaluated for 21 ML of Fe(100). Many working points were identified for different types multichannel spin filter based on exchange interaction Finally, the various results are summarized and a broad outlook is given.

The aim of this project was to produce an integrate-able free space optical transceiver for Specks. Specks are tiny computing units that together can form a powerful network called a SpeckNet. The SpeckNet platform is developed by the SpeckNet consortium, which consists of five Scottish Universities and combines computer science, electrical engineering and digital signal processing groups. The principal goal of creating an optical transceiver was achieved by integrating in-house fabricated VCSELs (with lasing thresholds below 400 uA) and custom designed detectors on the SpeckNet platform. The transceiver has a very low power consumption (approximately 100 uW), which removes the need for synchronous communication through the SpeckNet thus making the network more efficient. I describe both static and dynamic beam control techniques. For static control, I used micro-lenses. I fabricated the lenses by greyscale electron beam lithography and integrated them directly on VCSEL arrays. I achieved a steering angle of 10 degrees with this design. I also looked at integrated gratings etched straight into a VCSEL and observed beam steering with an efficiency of 60% For dynamic control, I implemented a liquid crystal (LC) design. I built a LC cell with 30 individually controlled pixels, but I only achieved a steering angle of 1 degree. Furthermore, I investigated two different techniques for achieving beam steering by interference, using coupled VCSELs (a phased array approach). Firstly, using photonic crystals etched into the surface of the VCSEL, I built coupled laser cavities. Secondly, I designed and built bow-tie type VCSELs that were optically coupled but electrically isolated. These designs work by differential current injection causing an interference effect in the VCSELs far field. This technique is the first stepping stone towards realising a phased optical array. Finally, I considered signal detection. Using the same VCSEL material, I built a resonant-cavity detector. This detector had a better background rejection ratio than commercially available silicon devices.

Über die additive Fertigung, oftmals bezeichnet als 3D-Druck, lassen sich Bauteile nahezu beliebiger geometrischer Komplexität herstellen. Gleichzeitig lassen die Prozessrandbedingungen die direkte Einstellung der Mikrostruktur in den verwendeten metallischen Werkstoffen zu. Hieraus ergeben sich weitreichende Möglichkeiten bezüglich der Eigenschaftsoptimierung aktueller Hochleistungswerkstoffe.

Les travaux de cette thèse concernent l'étude de l'influence des conditions de dépôt sur la microstructure et les propriétés optiques de monocouches dans le but de réaliser des filtres optiques particuliers commercialisables. La méthode de dépôt utilisée est l'évaporation par canon à électrons avec assistance ionique. L'un des deux projets a été de vérifier la faisabilité de filtres optiques infrarouges dans la gamme [2-15] µm avec des matériaux non toxiques. Les monocouches des trois fluorures étudiées ont montré des comportements différents suivant les conditions de dépôt, notamment suivant la température du substrat qui influe fortement sur leur microstructure. L'association du BaF₂ au germanium, avec des réglages optimisés, montre pour différents filtres réalisés des résultats proches de la théorie. Ces filtres sont donc commercialisables. Le second projet a été de développer une machine de dépôt dans le but de pouvoir réaliser des filtres complexes d'une centaine de couches d'épaisseur variable (de 15 à 300 nm) associant des monocouches de TiO₂ à des monocouches de SiO₂. L'étude de l'influence des paramètres de dépôts (pression, assistance ionique, préchauffage du matériau) au travers différentes caractérisations (MEB, AFM, ellipsométrie)  a permis une optimisation des réglages de l'enceinte de dépôt plus efficace et adaptée en fonction des spécifications des filtres optiques à réaliser. Puis, une étude ellipsométrique poussée de l'indice de réfraction des monocouches de TiO₂ en fonction de leur épaisseur a conduit à une nette évolution des résultats pour la réalisation du filtre complexe. / This thesis deals the study of deposition conditions 'effect on the microstructure and optical properties of monolayers in order to achieve marketable optical filters, with particular specifications. All filters and monolayers were deposited by ion-assisted electron-beam evaporation technique. One of the two projects was to test the feasibility of infrared optical filters in the range [2-15] µm with non-toxic materials. The study of monolayers of three fluorides showed different behaviors depending on the deposition conditions especially as a function of the substrate temperature that affects their microstructure. For different filters realized, the association of BaF₂ with germanium, settings of deposition optimized, shows results close to the theory and these filters are marketable. The second project was to develop a deposition chamber in order to realize complex filters built with one hundred layers of variable thickness (15 to 300 nm) associating monolayers of TiO₂ with monolayers of SiO₂. The study of the influence of deposition parameters (pressure, ionic assistance, preheating of material) through different characterizations (SEM, AFM, ellipsometry) allowed the optimization of deposition's parameter settings more effective, and adapted according to the specifications of the optical filters to realize. Then, an ellipsometric advanced study of the refractive index of TiO₂ monolayers depending on their thickness led to a significant change in results for the realization of complex filter.

Les faisceaux d’électrons et d’ions sont au cœur de nombreuses techniques instrumentales servant à explorer, analyser et agir sur des matériaux à l’échelle du micromètre au nanomètre (Microscopie électronique, spectrométrie d’électrons, techniques de « FIB »). Les limites de résolution spatiale et énergétique de ces techniques dépendent en grande partie des propriétés des sources qu’elles utilisent et en particulier de leur température de fonctionnement. De fait, depuis plus de 10 ans, le potentiel des atomes froids ionisés comme nouveau type de source d’électrons ou d’ions est intensivement exploré.Le projet expérimental réalisé au LAC et décrit dans cette thèse utilise un jet d’atomes de césium issu d’un piège magnéto-optique à deux dimensions. La température transverse du jet est de l’ordre de 100 µK. Malgré cela, le jet est encore trop divergent après la sortie de la zone de refroidissement pour notre expérience. Afin guider le jet d’atomes jusqu’à la zone d’ionisation, nous avons étudié une méthode particulière de guidage dipolaire. L’utilisation d’un seul laser convenablement réglé nous a permis de guider et pousser les atomes du jet en même temps tout en limitant le chauffage. Nous avons ainsi pu compresser avec ce laser pousseur-guideur le jet d’atomes sur un diamètre de 400 µm à 60 cm de la zone de refroidissement du PMO-2D.Le jet est ensuite ionisé par la méthode d’ionisation en champ électrique statique d’atomes de Rydberg. Les atomes sont tout d’abord excités par laser sur un état de Rydberg (n~30) en présence d’un champ électrique uniforme et homogène. Les atomes du jet ainsi excités voyagent vers une zone présentant un fort gradient de champ où ils vont alors s’ioniser autour de la même valeur de potentiel, réduisant ainsi la taille de la zone d’ionisation et donc de la dispersion en énergie potentielle initiale du faisceau d’électron. La probabilité d’ionisation des atomes dans le champ dépend grandement de l’état de Rydberg préalablement excité. Le choix de l’état de Rydberg optimal, i.e. qui a une probabilité d’ionisation la plus grande possible, nécessite une étude de l’ionisation des états de Rydberg du césium. Un modèle à deux niveaux est présenté dans cette thèse qui permet de retrouver le comportement d’ionisation d’état de Rydberg observé expérimentalement. Ce modèle simple nous a permis de comprendre quel type d’état nous devions exciter. Enfin une étude expérimentale est également présentée. / Electron and Ion beams are at the base of many instrumental techniques used to explore, to analyse and to modify materials from the micrometer to the manometer scale (Electronic Microscopy, Electron Spectrometry, Focused Ion beams techniques…). Spatial and Energetic resolutions of these techniques are strongly dependent on its source‘s properties and particularly their working temperature. In fact, for more than ten years, the potential of ionised cold atoms have been intensively studied. Our experiment at LAC, described in this thesis, uses a 2 dimensional magneto-optical trap (2D-MOT) to create a caesium atomic beam. The transverse temperature of the beam is around 100 µK. Despite this, the beam is still too divergent after exiting the cooling area. To guide the atomic beam up to the ionisation area, we have studied and implemented a particular method of dipolar guiding. The use of a unique laser properly set allowed us to push and guide altogether the atoms of the beam while limiting the heating effect. Thus, we have managed to compress the atomic beam’s size to 400 µm at 60 cm from the output of the MOT.Afterward, the atomic beam is ionised by the method of Rydberg (static) field ionisation. The atoms are firstly excited by laser on a Rydberg state (n~30) as a static homogeneous and uniform electric field is applied. The excited atoms of beam travel therefore to a high-gradient field area where they ionise around the same electric potential value, therefore reducing the ionisation area’s size and the initial potential energy spread of the electron beam. The ionisation probability of the atoms in the field depends greatly on the excited Rydberg state. The choice of an optimal Rydberg state , i.e. with the highest probability of ionisation, needs better knowledge of the ionisation of cesium Rydberg states. A two levels model us to describe the ionisation behaviour of some Ryberg. This simple models helps to understand what kind of states we want to excite in order to optimise the ionisation area‘s size. An experimental study of cesium Rydberg states is also presented.