Orientador: Carlos Kenichi Suzuki / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-14T07:35:33Z (GMT). No. of bitstreams: 1 Santos_JulianaSantiagodos_D.pdf: 5083498 bytes, checksum: a60b455d6e9c947ecbd7491e564b8f10 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho estudou-se o efeito da variação dos parâmetros do processo VAD (Vaporphase Axial Deposition) sobre as propriedades estruturais e ópticas da sílica vítrea visando o desenvolvimento de um material de alto desempenho óptico empregado no sistema óptico de equipamentos litográficos. As propriedades estruturais das preformas foram caracterizadas por microscopia eletrônica de varredura (MEV), espalhamento de raios-X a baixo ângulo (SAXS) e espectroscopia de absorção de estrutura fina de raios-X (XAFS). Absorção de raios-X (ARX) e tratamento de imagem digital foram utilizados para a obtenção da distribuição radial da densidade e da densidade média da sílica porosa, respectivamente. As propriedades ópticas foram determinadas por interferometria, espectroscopia óptica, espectrometria de polarização, espectroscopia Raman, espectroscopia no infravermelho e espectrofotometria de absorção óptica. Como principal resultado, obteve-se sílica vítrea com homogeneidade radial da estrutura, ?n = 3 ppm, birrefringência = 2 nm/cm e transmitância de 87 % em ? = 400 nm quando consolidada em atmosfera de He podendo superar 90 % quando consolidadas em vácuo. Este desempenho óptico foi obtido em até 95 % do diâmetro da preforma sem a necessidade de etapas adicionais, como o recozimento e a extração da região do diâmetro externo da preforma (geralmente a parte heterogênea) através de corte, reduzindo significativamente o tempo e custo de fabricação da sílica. / Abstract: This research reports the study of the effect of processing parameters of VAD (Vapor-phase Axial Deposition) method on structural and optical properties of silica glass aiming the development of an optically homogeneous material for use on lithographic equipments. The structural properties were characterized by the scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and X-ray absorption fine structure (XAFS). X-ray absorption (XRA) and digital image processing were used to obtain the density radial distribution and average density of silica soot, respectively. The optical properties were determined by interferometry, optical spectroscopy, polarization spectrometry, Raman spectroscopy, infrared spectroscopy, and optical absorption spectrophotometry. As a main result, silica glass was produced with structural radial homogeneity, ?n = 3 ppm, birefringence = 2 nm/cm, and transmittance of 87 % at ? = 400 nm when it was consolidated with He atmosphere and higher than 90 % in vacuum. This optical performance was obtained in 95 % of preform diameter without additional steps, such as annealing and cutting of preform outer diameter region (usually the heterogeneous part) which significantly reduces the time and cost of silica fabrication. / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

This master’s thesis deals with design and fabrication of MEMS microhotplate platform for chemical gas sensors. The theoretical part describes MEMS, sensors and processes and technologies needed for fabrication of micro hotplate. The practical part includes simulations, masks and step by step microhotplate fabrication. Fabricated heating membrane was characterized and compared to theoretical values from simulations and to similar devices presented in literature.

Photon avalanching (PA), one of the more unique nonlinear optical processes due to its combination of efficiency and extreme response, first attracted attention from the optics community more than four decades ago. But interest waned as researchers found that it did not provide immediately useful features observed in other nonlinear optical systems, such as amplified coherent light generation from lasing or optoelectronic amplification and transduction afforded by light-stimulated electron avalanching. The material systems supporting PA were also found to be rather limited, with reports concentrating on fragile, bulk lanthanide-doped crystals. However, the inter-ionic energy transfer mechanisms responsible for PA and its extreme nonlinearity are, in principle, realizable in objects with dimensions at the nanoscale. Further, new applications for PA in nanomaterials including simple super-resolution microscopy have recently been proposed. These factors motivated my research on the development of the first-ever lanthanide-doped nanoparticles capable of supporting PA behavior. In this thesis, the optical properties of Tm³⁺-doped NaYF₄ nanocrystals are investigated with photoluminescence microscopy, spectroscopy and differential rate equation model simulations. First, the photon avalanching behavior of Tm³⁺-doped NaYF₄ nanocrystals is studied. Specifically, the excitation-power-dependent luminescence of 1%, 4%, 8%, 20%, and 100% Tm³⁺-doped NaYF₄ is measured. The slopes of log-log excitation intensity versus emission intensity plots show that photon avalanche is realized in the nanocrystals when Tm³⁺ content is 8% and above. Time-resolved luminescence and rate equation model fitting to the experimental data validate the existence of photon avalanche, showing luminescence rise times > 600 ms, and the ratio of the ³F₄-to-³F₃ excited state absorption to the ³H₆-to-³F₄ ground state absorption is > 10⁴, which are signatures of photon avalanche. The design-dependent shift of the photon avalanching threshold also shows that photon avalanche is the main excitation scheme for the nanocrystals and implies potential applications for ultra-sensitive nano-sensing with the help of extreme nonlinearity. Additionally, the steep nonlinearity leads to super-resolution microscopy of single 8% Tm³⁺-doped nanocrystals with resolution down to <70 nm using conventional confocal microscopy without sophisticated techniques. In the second part of the thesis, the photodarkening effect of Tm³⁺-doped NaYF₄ nanocrystals is studied. We have found that photodarkening behavior is observed in Tm³⁺-doped nanocrystals that exhibit the photon avalanche effect. Power-dependent luminescence of a single 8% Tm3+-doped nanocrystal reveals that photodarkened nanocrystals still support photon avalanche behavior, but the avalanching threshold is shifted to a higher value. A photodarkening mechanism is proposed based on the concentration-dependent and power-dependent luminescence properties, and optical spectroscopic data. Notably, photodarkened nanocrystals are found to recover their original brightness and behavior under Vis-NIR optical illumination. This so-called “photobrightening” allows novel photoswitching of the inorganic nanocrystals, which has never before been achieved. We observe robust single nanocrystal photoswitching over 1000 cycles without permanent photodegradation. In addition, rewritable photolithography of multiple patterns using NIR lasers at 700 nm and 1064 nm is demonstrated.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21106号 / 工博第4470号 / 新制||工||1695(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 杉村 博之, 教授 邑瀬 邦明, 教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Advances in microfabrication and surface chemistry techniques have provided a new paradigm for the creation of in vitro systems for studying problems in biology and medicine in ways that were previously not practical. The ability to create devices with micro- to nano-scale dimensions provides the opportunity to non-invasively interrogate and monitor biological cells and tissue in large arrays and in a high-throughput manner. These systems hold the potential to, in time, revolutionize the way problems in biology and medicine are studied in the form of point-of-care devices, lab-on-chip devices, and biological microelectromechanical systems (BioMEMS). With new in vitro models, it will be possible to reduce the overall cost of medical and biological research by performing high-throughput experiments while maintaining control over a wide variety of experimental variables. A critical aspect of developing these sorts of systems, however, is controlling the device/tissue interface. The surface chemistry of cell-biomaterial and protein-biomaterial interactions is critical for long-term efficacy and function of such devices. The work presented here is focused on the application of surface and analytical chemistry techniques for better understanding the interface of biological elements with silica substrates and the development a novel Bio-MEMS device for studying muscle and neuromuscular biology. A novel surface patterning technique based on the use of a polyethylene glycol (PEG) silane self-assembled monolayer (SAM) as a cytophobic surface and the amine-terminated silane diethyeletriamine (DETA) as a cytophilic surface was developed for patterning a variety of cell types (e.g. skeletal muscle, and neural cells) over long periods of time (over 40 days) with high fidelity to the patterns. This method was then used to pattern embryonic rat skeletal muscle and motor neurons onto microfabricated silicon cantilevers creating a novel biological microelectromechanical system (BioMEMS) for studying muscle and the neuromuscular junction. This device was then used to study the effect of exogenously applied substances such as growth factors and toxins. Furthermore, a whispering-gallery mode (WGM) biosensor was developed for measuring the adsorption of various proteins onto glass microspheres coated with selected silane SAMS commonly used in BioMEMS system. With this biosensor it was possible to measure the kinetics of protein adsorption onto alkylsilane SAMS, in a real-time and label-free manner.

<p>An essential stage of repair for a healing wound is the proliferation of cells in the damaged space. Cells such as fibroblasts, grow and migrate to aid in construction of new tissue and to close the wound. Current methods of studying fibroblast proliferation in wound healing include a 2D wound healing assay in which a cell monolayer is scratched, and the cells migrate into the pseudo-wound. However, this lacks the 3D architecture of a physiological wound. Current 3D models of wound healing often rely on the use of a preexisting matrix for structural assistance, however an isolated system of cell growth without requirement of structural aid may gather new insights on intercellular behavior and mechanical properties. Additionally, we to desire to fabricate a high through-put and easy to use 3D wound healing model than currently offered. Our engineering objective is to create a novel 3D model of wound healing.</p> <p><br></p> <p>This project aims to optimize fibroblast adhesion and proliferation for 3D microtissue fabrication by altering surface and extracellular matrix (ECM) properties to SU-8 scaffolding. Additionally, we consider the effect of different geometries on cell proliferation and cellular stresses/strains, fibronectin production as pseudo-wounds close, and make comparisons to intercellular cancer behavior. Our results show around a 66% decrease in overall culture time required for the microtissues to reach full confluency. Varying geometries in the tessellated design have revealed structural changes in the actin cytoskeleton formation of fibroblasts, and increased fibronectin production along edges of tensioned cells preparing to “close” the wound. When compared to human breast cancer cells, the cancer cells lack the ability to make critical cell to cell junctions that we observe in fibroblasts, noting the characteristic that cancer is like a wound that never heals.</p>

Doctor of Philosophy / Department of Chemistry / Takashi Ito / This dissertation describes the fabrication and characterization of nanoscale structures in commercially available polymers via multiphoton ablation and bottom-up self assembly techniques. High-resolution surface imaging techniques, such as atomic force microscopy (AFM) and chemical force microscopy (CFM) were used to characterize the physical features and chemical properties, respectively, of these nanoscale structures. Fabrication using both top-down and bottom-up methods affords flexibility in that top-down allows random, user-defined patterning whereas bottom-up self assembly produces truly nanoscale (1-100nm) uniform features. Multiphoton induced laser ablation, a top-down method, was used to produce random sub-micron scale features in films of poly(methylmethacrylate) (PMMA), polystyrene (PS), poly(butylmethacrylate) (PBMA) and poly[2-(3-thienyl)ethyloxy-4-butylsulfonate] (PTEBS). Features with 120-nm lateral resolution were obtained in a PMMA film which was concluded to be the best polymer for use with this method. It was also found that etching resolution was highest for polymers having high glass transition temperatures, low molecular weights and no visible absorption. Bottom-up self assembly of polystyrene-poly (methylmethacrylate) (PS-b-PMMA) diblock copolymer and UV/acetic acid treatment produced nanoscale cylindrical domains supported by a substrate. AFM imaging at the free surface showed metastable vertical PMMA domain orientation on gold substrates. In contrast, horizontal orientation was obtained on oxide-coated silicon regardless of surface roughness and annealing conditions. The horizontal domain orientation on silicon substrates was ideal to probe simultaneously the difference in surface charge and hydrophilicity of the two distinct nanoscale domains of UV/AcOH treated PS-b-PMMA films. CFM on UV/acetic acid etched PS-b-PMMA revealed the presence of –COO- groups which were found to be more abundant inside the etched trenches than on the unetched PS matrix as shown by ferritin adsorption onto etched PS-b-PMMA. Lastly, the PS-b-PMMA was cast as a free-standing monolith at the end of a quartz micropipette. AFM revealed circular PMMA dots at the free surface, indicating alignment parallel to the long axis of capillary. Ion conductance within nanochannels indicated surface –charge governed ion transport at low KCl concentrations and flux of negatively-charged sulphorhodamine dye demonstrated the permselective nature of nanochannels.

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / As the field of separation science evolves so do the techniques, tools and capabilities of the discipline. The introduction of microfluidics stemmed from a desire to perform traditional analyses faster and on a much smaller scale. The small device sizes exploited in microfluidics permits the investigation of very small volumes of very dilute samples yielding information inaccessible by traditional macroscale techniques. All of the chapters presented in this dissertation illustrate attempts to supplement current microscale techniques with new tools, techniques and analysis schemes for looking at biologically relevant analyses. In chapter two I present the development and characterization of an amphiphilic polymer that has potential as a material for the fabrication of microfluidic devices. This material is composed of a poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer and is dramatically more hydrophilic than the other polymeric materials currently used for the fabrication of microfluidic templates, mainly poly(dimethylsiloxane). Biomolecules such as proteins are notoriously hydrophobic and will tend to adsorb to other hydrophobic surfaces thus the use of a hydrophilic material may serve to reduce or eliminate this problem. The amphiphilic material is of a suitable durability for micromolding and molded channel architectures can be sealed between two layers of the material by simple conformal contact permitting the execution of high speed electrophoretic separations. Chapter three contains initial results obtained while investigating the fluorescent labeling and electrophoretic separation of ecdysteroids. Ecdysteroids are hormones found in insects that are responsible for controlling the process of molting. Here we attempted to analyze these molecules by employing a reactive fluorescent probe, BODIPY FL® hydrazide, that would target the α,β-unsaturated ketone group on the steroid, permitting its analysis by capillary electrophoresis with laser induced fluorescence detection. While optimistic initial results were obtained with the labeling and analysis of similar functional groups on model compounds such as progesterone, labeling of the ecdysteroid molecules was never achieved to a degree that would permit reliable analysis. In chapter four I report the development and use of a microimmunoaffinity column for the analysis of insect serine protease inhibitors, or serpins. These proteins play a very important role in the regulation of insect immune responses and their activity may play an integral role in the effective transmission of the malaria parasite by the mosquito Anopheles gambiae. A microimmunoaffinity column was constructed from magnets, poly(dimethylsiloxane), fused silica capillary and Protein A coated magnetic microspheres. In these initial studies, purified antibodies to serpin protein, as well as purified serpin protein, were used to prepare and investigate the ability to isolate, preconcentrate, and elute serpin proteins for subsequent analysis. By implementing this miniaturized system which incorporates very small fluid volumes we hoped to extend this technique to the analysis of very small samples, and eventually to the analysis of individual small insects. Our work indicates that it is possible to isolate, elute, and detect serpin protein on a traditional western blot membrane. Chapter five presents the development of a novel polymer blend for the fabrication of paper-based microfluidic devices and use of these devices in the performance of diagnostically relevant clinical assays. We took the concept of paper-based microfluidic devices and improved upon the current photoactive polymers used for their fabrication by developing a polymer blend using an acryloxy modified siloxane polymer as well as a commercially available photoactive adhesive, Norland Optical Adhesive 74. This blended polymer resulted in a dramatic reduction in fabrication time as well as improved resolution permitting the reliable patterning of small feature sizes. We also report for the first time a demonstration of these devices performing a two-step spatially separated online chemical derivatization facilitating the analysis of urinary ketones. These devices are predominantly used for the analysis of urine, and their application was extended to the quantitation of nitrite in saliva for the purposes of hemodialysis monitoring. While varied in application, all of the data presented in this dissertation exploits the power of miniaturization to improve current methods of analysis and to extend macroscale techniques to trace biological analytes.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / A major challenge in the design and operation of High Temperature Superconducting (HTS) devices is the fabrication of reproducible Josephson junctions with good IcRn products. One objective of this thesis was to fabricate successfully HTS step-edge junctions. This objective necessitated a critical evaluation of the available facilities to provide much needed improvements. These improvements included a newly optimised photolithography process, the incorporation of a three-gridded extraction system into the in-house argon ion mill as well as alterations to the Pulsed Laser Deposition (PLD) system to improve thin film quality. These process modifications finally allowed for the fabrication of novel PrBa2Cu3O7−δ buffered step-edge junctions. These junctions were tested for dc and ac Josephson effects and displayed IcRn products of 1.5 mV at 55 K as well as well-defined Shapiro steps. A second objective was to introduce a high quality thin film deposition system that could produce smooth superconducting films for use in filters and multilayer technology. An Inverted Cylindrical Magnetron system was built and optimised to grow YBa2Cu3O7−δ thin films on MgO (001) substrates. A complete optimisation process of these films are presented by utilising several growth and electrical characterisation methods such as XRD, RBS and AFM.

Double-exposure lithography has shown promise as potential resolu- tion enhancement technique that is attractive because it is much cheaper than double-patterning lithography and it can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. Several materials have been proposed to implement a nonlinear response to exposure including re- versible contrast enhancement layers (rCELs), two-photon materials, interme- diate state two-photon (ISTP) materials, and optical threshold layers (OTLs). The performance of these materials in double-exposure applications was inves- tigated through computer simulation using a custom simulator. The results from the feasibility studies revealed that the ISTP and OTL types of materials showed much more promise than the rCEL and two-photon types of materi- als. Calculations show that two-photon materials will not be feasible unless achievable laser peak power in exposure tools can be signi¯cantly increased. Although rCEL materials demonstrated nonlinear behavior in double-exposure mode, only marginal image quality and process window improvements were ob- served. Using the results from the simulation work described herein, materials development work is currently ongoing to enable potential ISTP and OTL materials for manufacturing. A new biochip platform named \Mesoscale Unaddressed Functional- ized Features INdexed by Shape" (MUFFINS) was developed in the Willson Research Group at the University of Texas at Austin as a potential method to achieve a new low-cost biosensor system. The platform uses poly(ethylene glycol) hydrogels with bioprobes covalently cross-linked into the matrix for detection. Each sensor is shape-encoded with a unique pattern such that the information of the sensor is associated with the pattern and not its position. Large quantities of individual sensors can be produced separately and then self- assembled to form random arrays. Detection occurs through hybridization of the probes with °uorescently labeled targets. The key designs of the system include parallel batch fabrication using photolithography and self-assembly, in- creased information density using multiplexing, and enhanced shape-encoding with automated pattern recognition. The development of two aspects of the platform { self-assembly mechanics and pattern recognition algorithm, and a demonstration of all the key design elements using a single array are described herein. / text