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1
Feng, Chunhua. "Microfabrication-compatible synthesis strategies for nanoscale electrocatalysts in microfabricated fuel cell applications /". View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CENG%202007%20FENG.
Testo completo
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Grebille, Bénédicte. "Photopolymérisation radicalaire contrôlée par ATRP : études mécanistiques, applications en sciences des matériaux et perspectives en microfabrication". Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0017.
Testo completoAbstract (sommario):
Au début du XXème siècle, Giacomo Luigi Ciamician, physico-chimiste, a mis en évidence l'intérêt de recourir à la lumière comme source d'énergie renouvelable pour des réactions chimiques. À la fin du siècle, la découverte de la polymérisation radicalaire contrôlée, notamment l'ATRP (« Atom Transfer Radical Polymerization »), a marqué une avancée majeure dans la chimie des polymères. Cette technique a été largement développée et utilisée dans divers domaines, notamment pour la fonctionnalisation de surfaces à travers l'ATRP amorcée sur surface (« Surface Initiated ATRP », SI-ATRP), offrant ainsi des applications variées allant de la biologie à l'ingénierie des matériaux. La présente thèse vise principalement à explorer l'utilisation de l'ATRP photoinduite dans le domaine de la microfabrication. Pour ce faire, un nouveau système multicomposants pour l'ATRP photoinduite a été développé et étudié en détail du point de vue physico-chimique. La compréhension en profondeur de l’impact de chaque constituant du système a permis d’atteindre de la polymérisation de manière hautement contrôlée dans de nombreuses conditions, entre autres à l’air libre. De plus, ce système, comprenant un photosensibilisateur capable d'effectuer une absorption à deux photons, a pu être appliqué à diverses fins. Il a permis de réaliser de l'ATRP amorcée sur surface sous atmosphère inerte mais également en présence de dioxygène. L'optimisation de cette technique de fonctionnalisation de surface a été effectuée en vue de son utilisation pour la microfabrication. De plus, ce système multicomposants a facilité la synthèse, par ATRP photoinduite, de photosensibilisateurs hydrosolubles, dotés de propriétés d'absorption à deux photons, à partir d'un nouveau macrophotoamorceur. Cette famille de macromolécules s'est avérée efficace pour le photoamorçage de polymérisation en émulsion, ouvrant ainsi la voie à des polymérisations en émulsion photoinduites à deux photons et possiblement à la microfabrication d’hydrogelsIn the early 20th century, the physico-chemist Giacomo Luigi Ciamician, highlighted the benefits of using light as a suitable energy source for chemical reactions. At the end of this same century, the discovery of controlled radical polymerization, in particular ATRP (Atom Transfer Radical Polymerization), marked a major advance in polymer chemistry. This technique has been widely developed and used in a variety of fields, including surface functionalization through Surface Initiated ATRP (SI-ATRP), with applications ranging from biology to materials engineering. The main aim of this thesis is to explore the use of photoinduced ATRP in microprinting. For this purpose, a new multicomponent system for photoinduced ATRP has been developed and studied in detail from a physicochemical point of view. The thorough understanding of each component impact of the system has enabled to reach highly controlled polymerization under a wide variety of conditions, including in the open air. Moreover, this system, which includes a photosensitizer capable of two-photon absorption, has been used for a variety of purposes. It has been used to perform surface-initiated ATRP both in an inert atmosphere and in the presence of dioxygen. The optimization of the surface functionalization technique was used for microprinting. Furthermore, this multicomponent system facilitated the synthesis, by photoinduced ATRP from a new macrophotoinitiator, of water-soluble photosensitizers with interesting biphotonic absorption properties. This family of macromolecules has proved to be effective in photoinitiating emulsion polymerization, paving the way for two-photon photoinduced emulsion polymerization and potentially also to hydrogels microprinting
3
Altay, Gizem. "Towards the development of biomimetic in vitro models of intestinal epithelium derived from intestinal organoids". Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/664864.
Testo completoAbstract (sommario):
Intestinal epithelium is highly specialized tissue organized into crypt-villus units relevant for their effective barrier function and nutrient absorption. In the crypt units reside the proliferative intestinal stem cells (ISCs) that divide and differentiate while migrating along the villi to generate the epithelium. The proliferation, migration and differentiation of ISCs is governed by the tightly controlled spatio-chemical gradients of ISC niche factors; bone morphogenic protein (BMP), wingless/Int (Wnt) and epidermal growth factor (EGF) pathway modulators. In vitro models of the intestinal epithelium, for the most part, based on culturing of intestinal stem cells/crypts in 3D cultures forming structures called organoids. These structures faithfully recapture diverse cell populations and their multicellular organization of native intestinal epithelium. However, 3D closed geometry of intestinal organoids prevents access to the apical region of the epithelium, making them unsuitable for conventional functionality assays. Experimental modeling of intestinal epithelial biology and physiology are limited due to the lack in vitro platforms that recapitulate these key aspects of the small intestinal epithelium: its distinct cell populations, 3D architecture and the gradients of ISC niche biochemical factors along the crypt-villus axis.
Here, we describe development of in vitro models of intestinal epithelium obtained from intestinal organoid-derived crypts. First, we present a method that takes the advantage of substrate stiffness to dictate the formation of monolayers with accessible lumen rather than 3D organoids with a closed geometry. The 2D intestinal epithelium model has in vivo-like crypt-villus cellular organization with all major epithelial cell types and show physiologically relevant tissue barrier function. Then, we describe the development of a more complex model of intestinal epithelium by incorporating a 3D villus-like basement membrane substitute fabricated on hydrogels. For that, poly(ethylene glycol) diacrylate (PEGDA) hydrogels are chosen due to their highly tunable chemical, and mechanical properties, porosity and photocrosslinkable nature allowing easy microstructuring. The formation of 3D bullet-like complex shapes was achieved by photolithography-based crosslinking of PEGDA, a simple, cost-effective approach. The bioactive functionalization of otherwise inert PEGDA for cell adhesion, was achieved by copolymerizing it with acrylic acid and a variety of cell adhesion proteins can be covalently anchored to the 3D villus-like hydrogels. We establish the optimal conditions for the growth of intestinal organoid-derived epithelial monolayers and demonstrated that organoid-derived intestinal epithelial cells successfully formed epithelial monolayers on collagen type I functionalized 3D villus-like PEGDA-acrylic acid hydrogels. Finally, we describe methods to create spatiotemporal gradients of biochemical ISC niche factors on 3D villus-like hydrogels and demonstrate that these gradients can be used to compartmentalize the differentiated epithelial cells. The spatio-chemical gradients of ISC niche biochemical factors on PEGDA hydrogels with proper porosity were successfully generated based on the free diffusion of the factors from a source to a sink chamber in a custom-made microfluidic device allocating the hydrogel and visualized with light-sheet fluorescence microscopy. In silico models were developed to simulate the spatio-chemical gradients formed within the hydrogels. The 3D villus-like PEGDA hydrogels were fabricated on porous membranes and successfully adapted to Transwell® inserts that permitted access to both sides of the hydrogel and the generation of spatio-chemical gradients. The gradients generated in this fashion can be used to compartmentalize the differentiated epithelial cells more towards the tips of the villus-like microstructures.
The 3D villus-like platform improves the current models in providing cells with physiologically representative topographical and mechanical cues and biochemical gradients. Due to its utility, this platform might find uncountable applications. It can be used for the understanding of the basic biology of the intestinal epithelium. In addition, it can be used to culture human intestinal stem cells allowing for the screening of novel therapies and disease modeling.El epitelio intestinal es un tejido altamente especializado, organizado en unidades de criptas y vellosidades que son relevantes para sus eficaces funciones de barrera y absorción de nutrientes. En las unidades de criptas residen las células madre intestinales (ISC) proliferativas que se dividen y diferencian mientras migran a lo largo de las vellosidades, las cuales generan el epitelio maduro. En el epitelio maduro, las ISC y las células proliferativas se localizan en las criptas y las células absorbentes y secretoras diferenciadas en las vellosidades. La proliferación, migración y diferenciación de las ISC se rigen por los gradientes químicos espaciales altamente controlados de los factores de nicho de la ISC; Moduladores de la vía de bone morphogenic protein (BMP), wingless/Int (Wnt) y epidermal growth factor (EGF). El modelado experimental de la biología y la fisiología del epitelio intestinal está limitado debido a la falta de plataformas in vitro que recapitulan estos aspectos clave del epitelio del intestino delgado: sus distintas poblaciones celulares, la arquitectura 3D y los gradientes de factores bioquímicos de nicho ISC a lo largo del eje cripta-vellosidad. Aquí, describimos el desarrollo de modelos in vitro de epitelio intestinal obtenidos de criptas derivadas de organoides intestinales. En primer lugar, presentamos un método para obtener monocapas epiteliales intestinales 2D con lumen accesible y función de barrera fisiológica. A continuación, describimos el desarrollo de andamios biomiméticos 3D similares a vellosidades en hidrogeles de diacrilato de polietilenglicol (PEGDA) utilizando un enfoque fotolitográfico simple y rentable. Demostramos que nuestra plataforma de vellosidades sintéticas apoya la formación de monocapas epiteliales de células epiteliales intestinales derivadas de organoides. Finalmente, describimos métodos para crear gradientes espaciotemporales de factores nicho bioquímicos ISC en hidrogeles 3D similares a vellosidades y demostramos que estos gradientes se pueden usar para compartimentar las células epiteliales diferenciadas. La plataforma 3D que recrea las vellosidades intestinalesmejora los modelos actuales al proporcionar a las células las señales topográficas y mecánicas y los gradientes bioquímicos fisiológicamente representativos. Debido a su utilidad, esta plataforma puede encontrar innumerables aplicaciones. Puede ser utilizada para la comprensión de la biología básica del epitelio intestinal. Además, se puede utilizar para cultivar células madre intestinales humanas que permitan la detección de nuevas terapias y el modelado de enfermedades.
4
Caballero, Lucas Francesc. "Z-scan methods for ultrashort pulsed laser microprocessing of transparent materials". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668185.
Testo completoAbstract (sommario):
The use of femtosecond lasers has recently gained attention as a result of the recognition to Gérard Mourou and Donna Strickland with the award of the Nobel Prize in Physics 2018 "for their method of generating high-intensity, ultra-short optical pulses". The innumerable areas of application of ultrashort laser pulses have not yet been completely explored, but their possibilities for accessing the microworld are considered highly valuable.
Following this spirit, the objective of this thesis consisted in proposing and implementing feasible solutions to the challenges involved in the microfabrication of materials with ultrashort laser pulses for diverse advanced applications. To that end, attention was put in laser ablation of transparent polymers with spatial resolutions that transcend sharpness limitations due to light diffraction.
The results presented here were obtained during the development of the doctorate studies of the PhD program in Nanosciences at the Departament de Física Aplicada of the Universitat de Barcelona. It is structured as follows:
INTRODUCTION AND OBJECTIVES: This introductory chapter contains a description of the most significant microfabrication techniques, centered on laser-based methods. Having a key role in this thesis, the interaction between laser radiation and matter is shortly reviewed. The physical phenomena motivate the use of femtosecond lasers for the precise processing of transparent materials, where focus is put on their superficial laser ablation, the entailing challenges and its applications. The objectives pursued in this work close this first chapter.
EXPERIMENTAL: A description of the experimental setups implementing femtosecond laser systems, methods and materials applied during the trials constituting the developed research is presented in this chapter. The features of the laser sources together with the corresponding laser direct-write setups form the sections of this chapter, followed by some comments on Gaussian beams and their focusing. These found the presentation of the z-scan focusing technique. To close this chapter, some remarks and background about the employed materials are delivered.
Z-SCAN FOCUSING METHOD: The results obtained by putting to work the z-scan focusing technique introduced in the previous chapter are presented here. The theme is the development and characterization of the z-scan focusing technique as a method to address the issue of securing surface ablation of transparent material with femtosecond laser pulses. Its successful implementation in surface ablation of the transparent polymer polymethyl methacrylate (PMMA) with high spatial resolution is given as proof of the viability of the proposed strategy for a precise focusing of laser beams onto transparent materials.
The contents of this chapter include studies on transmittance and reflectance measurements at different focusing distances between the laser beam waist and the processed material surface through single laser pulse surface ablation and laser surface scanning for channel microfabrication (comparing their results), the beam waist position determination thanks to the transmittance measurements and analysis of the produced surface ablation.
APPLICATIONS IN LASER MICROFABRICATION OF MATERIALS: the implementation of the developed z- scan focusing technique was put to use in laser microfabrication of materials with diverse applications.
The applications include the irradiation with femtosecond laser pulses of biodegradable polymers for profound hole ablation in polylactic acid (PLA) and study of the its influence in biodegradability of polylactic-co-glycolic acid, the laser perforation for leakage studies on
medical use polypropylene bags, and the laser fabrication of microfluidic guides for conductive line printing.
Owing to their diversity the chapter is divided in four sections, one for each topic. The various processed materials are briefly introduced, with some background supporting their study.
CONCLUSIONS: The last chapter sums up the most relevant results and main achievements that have been obtained during the development of this thesis in the form of closing remarks.L’ús de làsers d’impulsos ultracurts ha rebut atenció recentment degut al reconeixement amb el Premi Nobel de Física de l’any 2018 a la tècnica que en permet la seva generació. Les seves àrees d’aplicació encara no han estat completament explorades, però les seves possibilitats per accedir al món microscòpic són considerades prometedores. Seguint aquest esperit, l’objectiu d’aquesta tesi és proposar i implementar solucions viables als reptes relacionats amb la microfabricació de materials amb impulsos làser ultracurts, específicament l’ablació làser de polímers transparents amb resolucions espacials que transcendeixin les limitacions de definició associades a la difracció de la llum. INTRODUCCIÓ I OBJECTIUS: Aquest capítol descriu les tècniques de microfabricació més significatives, centrant-se en els mètodes làser. Degut al paper clau del làser en aquesta tesi, es fa una descripció breu de la interacció entre la radiació làser i la matèria. Els objectius plantejats completen aquest primer capítol. EXPERIMENTAL: En aquest apartat es presenta una descripció dels muntatges experimentals amb sistemes làser de duració ultracurta, els mètodes i els materials emprats durant les proves que constitueixen la recerca i que serveixen de base per a la presentació del mètode d’enfocament z-scan. MÈTODE D’ENFOCAMENT Z-SCAN: Els resultats obtinguts amb la tècnica proposada d’enfocament per z-scan són presentats aquí. El tema central és el desenvolupament i caracterització d’aquesta tècnica com a mètode per l’ablació superficial de materials transparents amb impulsos làser ultracurts. La implementació exitosa de l’ablació superficial del polimetilmetacrilat (PMMA) amb elevada resolució espacial demostra la viabilitat de l’estratègia proposada per enfocar amb precisió un feix làser a la superfície de materials transparents. APLICACIONS PER AL MICROPROCESSAMENT LÀSER DE MATERIALS: La implementació de la tècnica desenvolupada d’enfocament per z-scan s’ha pogut traslladar al microprocessament de materials amb làser en diverses aplicacions com la irradiació de polímers biodegradables per a la producció de forats profunds en àcid polílàctic (PLA), la seva influència en la biodegradabilitat de l’àcid polílàctic-co-glicòlic (PLGA), la perforació de fuites en bosses de polipropilè d’ús mèdic, i la fabricació de guies microfluídiques per la impressió de línies conductores. Conclusions: L’últim capítol resumeix els resultats més rellevants i els principals assoliments.
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Cannon, Andrew Hampton. "Unconventional Microfabrication Using Polymers". Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/19845.
Testo completoAbstract (sommario):
Current microfabrication materials include silicon, a wide variety of metals, dielectrics, and some polymers. Because of the low cost and high processing flexibility that polymers generally have, expanding the use of polymers in microfabrication would benefit the microfabrication community, enabling new routes towards goals such as low-cost 3D microfabrication.
This work describes two main unconventional uses of polymers in microfabrication. The first unconventional use is as a carrier material in the self-assembly (SA) of millimeter-scale parts in which functional electronic components and electrical interconnects were cast into 5 mm cubes of Polymethylmethacrylate (PMMA). The second unconventional use is as a non-flat micromold for an alumina ceramic and as transfer material for multiple layers of micropatterned carbon nanotubes (CNTs). Both of these uses demonstrate 3D low-cost microfabrication routes.
In the SA chapter, surface forces induced both gross and fine alignment of the PMMA cubes. The cubes were bonded using low-melting temperature solder, resulting in a self-assembled 3D circuit of LEDs and capacitors. The PMMA-encasulated parts were immersed in methyl methacrylate (MMA) to dissolve the PMMA, showing the possibility of using MEMS devices with moving parts such as mechanical actuators or resonators. This technique could be expanded for assembly of systems having more than 104 components. The ultimate goal is to combine a large number of diverse active components to allow the manufacture of systems having dense integrated functionality.
The ceramic micromolding chapter explores micromolding fabrication of alumina ceramic microstructures on flat and curved surfaces, transfer of carbon nanotube (CNT) micropatterns into the ceramic, and oxidation inhibition of these CNTs through ceramic encapsulation. Microstructured master mold templates were fabricated from etched silicon, embossed thermally sacrificial polymer, and flexible polydimethylsiloxane (PDMS). The polymer templates were themselves made from silicon masters. Thus, once the master is produced, no further access to a microfabrication facility is required. Using the flexible PDMS molds, ceramic structures with mm-scale curvature were fabricated having microstructures on either the inside or outside of the curved macrostructure. It was possible to embed CNTs into the ceramic microstructures. To do this, micropatterned CNTs on silicon were transferred to ceramic via vacuum molding. Multilayered micropatterned CNT-ceramic devices were fabricated, and CNT electrical traces were encapsulated with ceramic to inhibit oxidation. During oxidation trials, encapsulated CNT traces showed an increase in resistance that was 62% less than those that were not encapsulated.
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Florian, Baron Camilo. "Laser direct-writing for microfabrication". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400403.
Testo completoAbstract (sommario):
Digital manufacturing constitutes a real industrial revolution that is transforming the production processes from the early stages of research and development to mass production and marketing. The biggest difference in comparison with old fabrication methods is the possibility to perform changes in the pattern design just by using mouse clicks instead of modifying an already fabricated prototype, which results in faster, cheaper and more efficient fabrication processes. For example, new technologies enabling the production of printed electronic devices on flexible substrates and compatible with roll-to-roll processing methods would result in cheaper fabrication costs than the traditional batch processing of silicon wafers. Such fabrication methods comprise a series of processing steps which are applied to the substrates while they are moving on rolls in the fabrication line. Therefore, it is desired that the new technologies can work at high speeds allowing at the same time the production of miniaturized features.
Lasers are a versatile tool that can meet the demands of flexibility, speed, resolution and compatibility with roll-to-roll processing of digital manufacturing. The main advantages of laser radiation rely in its unique properties: high directionality, coherence and monochromaticity. The combination of such properties allows generating high intensities that can be focused into extremely small volumes, which makes lasers an ideal tool for the processing of materials at the micro- and nano-scale, not only as a subtractive but also as an additive technique.
Laser ablation is the best known subtractive technique and it consists in the irradiation of a material with a focused laser beam. In the case of working with transparent materials, surface ablation constitutes a serious challenge since it is necessary to develop new strategies that allow controlling the position where the energy is delivered to ensure that ablation really occurs in the surface without modifying the bulk material. On the other hand, lasers can also be used as additive tools. For example, laser-induced forward transfer (LIFT) allows the transfer of materials in both solid and liquid state with high spatial resolution. In spite of the extensive amount of research on LIFT, some challenges still remain. For instance, the understanding of the particular printing dynamics encountered during the high speed printing of liquids, or the problem of printing uniform, continuous and stable lines with high spatial resolution.
The objective of this thesis is to propose and implement feasible solutions to some of the challenges that are associated with both the subtractive and additive laser based techniques presented above. On one side, we study the laser ablation of transparent polymers using femtosecond laser pulses with the aim of achieving spatial resolutions that overcome the diffraction limit, and at the same time solving the problem of the required precise focusing of the laser beam on the materials surface. On the other side, we study the LIFT transfer dynamics during the high speed printing of liquids, and we propose alternative printing strategies to solve the inherent quality defects usually encountered during the formation of printed lines. Finally, two different approaches that are a combination of both subtractive and additive techniques are presented; we implement LIFT for the fabrication of liquid microlenses used for the surface nanopatterning of materials, and on the other side, we create fluidic guides by laser ablation for the printing of high quality continuous lines.La fabricació digital de dispositius tecnològics requereix el desenvolupament de noves i millors tècniques per al microprocessament de materials que al mateix temps siguin compatibles amb mètodes de producció en sèrie a gran escala com el roll-to-roll processing. Aquestes tècniques han de complir certs requisits relacionats amb la possibilitat de realitzar canvis de disseny ràpids durant el procés de fabricació, alta velocitat de processament, i al mateix temps permetre la producció de motius de forma controlada amb altes resolucions espacials. En la present tesi es proposen i implementen solucions viables a alguns dels reptes presents a la microfabricació amb làser tant substractiva com additiva. D'una banda, es presenta un nou mètode d'enfocament del feix làser sobre la mostra per l'ablació superficial de materials transparents que permet obtenir resolucions espacials que superen el límit de difracció del dispositiu òptic. D'altra banda, es duu a terme un estudi de la dinàmica de la impressió de líquids mitjançant làser a alta velocitat, de gran interès de cara a la implementació industrial de la tècnica. A més, es presenten estratègies d'impressió de tintes conductores amb l'objectiu de produir línies contínues amb alta qualitat d'impressió. Finalment s'inclouen dues propostes que són producte de la combinació d’ambues tècniques, la impressió de líquids i l'ablació amb làser.
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Wang, Weihua. "Tools for flexible electrochemical microfabrication /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/9854.
Testo completo
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Barham, Oliver M. "Microfabricated Bulk Piezoelectric Transformers". Thesis, University of Maryland, College Park, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10615552.
Testo completoAbstract (sommario):
Piezoelectric voltage transformers (PTs) can be used to transform an input voltage into a different, required output voltage needed in electronic and electro- mechanical systems, among other varied uses. On the macro scale, they have been commercialized in electronics powering consumer laptop liquid crystal displays, and compete with an older, more prevalent technology, inductive electromagnetic volt- age transformers (EMTs). The present work investigates PTs on smaller size scales that are currently in the academic research sphere, with an eye towards applications including micro-robotics and other small-scale electronic and electromechanical sys- tems. PTs and EMTs are compared on the basis of power and energy density, with PTs trending towards higher values of power and energy density, comparatively, indicating their suitability for small-scale systems. Among PT topologies, bulk disc-type PTs, operating in their fundamental radial extension mode, and free-free beam PTs, operating in their fundamental length extensional mode, are good can- didates for microfabrication and are considered here. Analytical modeling based on the Extended Hamilton Method is used to predict device performance and integrate mechanical tethering as a boundary condition. This model differs from previous PT models in that the electric enthalpy is used to derive constituent equations of motion with Hamilton’s Method, and therefore this approach is also more generally applica- ble to other piezoelectric systems outside of the present work. Prototype devices are microfabricated using a two mask process consisting of traditional photolithography combined with micropowder blasting, and are tested with various output electri- cal loads. 4mm diameter tethered disc PTs on the order of .002cm
3 , two orders smaller than the bulk PT literature, had the followingperformance: a prototype with electrode area ratio (input area / output area) = 1 had peak gain of 2.3 (± 0.1), efficiency of 33 (± 0.1)% and output power density of 51.3 (± 4.0)W cm
-3 (for output power of80 (± 6)mW) at 1M? load, for an input voltage range of 3V-6V (± one standard deviation). The gain results are similar to those of several much larger bulk devices in the literature, but the efficiencies of the present devices are lower. Rectangular topology, free-free beam devices were also microfabricated across 3 or- ders of scale by volume, with the smallest device on the order of .00002cm
3 . These devices exhibited higher quality factorsand efficiencies, in some cases, compared to circular devices, but lower peak gain (by roughly 1/2 ). Limitations of the microfab- rication process are determined, and future work is proposed. Overall, the devices fabricated in the present work show promise for integration into small-scale engi- neered systems, but improvements can be made in efficiency, and potentially voltage gain, depending on the application
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Mehregany, Mehran. "Microfabricated silicon electric mechanisms". Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14042.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.Includes bibliographical references (leaves 151-156).
by Mehran Mehregany.
Ph.D.
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Griffith, Alun Wyn. "Applications of microfabrication in biosensor technology". Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361768.
Testo completo
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Jeffery, Nicholas Toby. "PET radiochemistry on microfabricated devices". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420892.
Testo completo
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Velásquez, García Luis Fernando 1976. "A microfabricated colloid thruster array". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/82201.
Testo completo
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Lubratt, Mark Paul. "A voltage-tunable microfabricated accelerometer". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/37497.
Testo completo
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Harris, Robert Michael. "Geometric simulation of microfabricated structures". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11842.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 295-302).
Robert Michael Harris.
Ph.D.
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Duan, Xuefeng 1981. "Microfabrication : using bulk wet etching with TMAH". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97942.
Testo completoAbstract (sommario):
In November 2002 a Microfabrication Lab was established in the physics department of McGill University to support research in nanoscience and technology. At the same time, I arrived at McGill to begin my graduate study. So I was assigned to do research on microfabrication, especially bulk wet etching of silicon using TetraMethyl Ammonium Hydroxide (TMAH).The content of microfabrication is quite broad, and also very useful in both industry and academic. Since our fab is a newly built one and I had no experience in this area before, this thesis mainly included some basic processes in microfabrication, such as the photolithography, wet etching, reactive ion etching, and soon. Also it compared the wet etching with dry etching. Some results of TMAH wet etching were showed in the thesis, which agreed well with that of the other groups. A simulation program was developed to predict the etching result of TMAH and it appeared to work well. Finally, based on the knowledge and experience acquired, processes in making cantilever and tip structures, which are critical in the scanning probe microscopes, were developed. Silicon oxide cantilevers with length of 100-200 mum, width of 30-50 mum, and thickness of 1 mum were obtained. Pyramid like silicon tips were also fabricated using the wet etching.
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DiBartolomeo, Franklin. "HIGH SPEED CONTINUOUS THERMAL CURING MICROFABRICATION SYSTEM". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/105.
Testo completoAbstract (sommario):
Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 1.9 in2/sec (~1200 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.
17
Charlton, Martin David Brian. "Computational design and microfabrication of photonic crystals". Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287304.
Testo completo
18
Zoorob, Majd Elias. "Computational design and microfabrication of photonic quasicrystals". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342813.
Testo completo
19
Shur, Maiya 1980. "Microfabrication methods for the study of chemotaxis". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27130.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 59-60).
We have developed a system for studying chemotaxis in a microfabricated system. The goal was to develop a system capable of generating spatially and temporally stable concentration gradients of a chemotactic molecule while providing a viable environment for the cell. Numerical models were generated to investigate fluid flow in microchannels for given geometries. Through computational modeling and experimentally-driven iteration of the design, features of the chamber were determined and geometry was established. Prototypes of the system were fabricated using soft lithography and multi-layer soft lithography techniques. Three fluid delivery methods for establishing gradients in the system have been studied: gravity feed system, dual-syringe pump feed system, and integrated individually-controlled peristaltic pump feed system. We were able to create spatially and temporally stable gradients using the dual-syringe feed setup. Two syringes were used to pump a chemokine and a buffer in parallel channels that are connected by a cross-channel and terminated to a single output. Microbeads in the flow were used to confirm the lack of movement in the cross-channel. Human neutrophil viability over the course of several hours and directed cell movement was demonstrated in microchannels.
by Maiya Shur.
S.M.
20
Tu, Yudi. "Photo Processing and Microfabrication of Graphene Oxide". Kyoto University, 2018. http://hdl.handle.net/2433/232039.
Testo completo
21
Lund, Jason Matthew. "Advanced Techniques for Carbon Nanotube Templated Microfabrication". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7769.
Testo completoAbstract (sommario):
Carbon nanotube templated microfabrication (CNT-M) is a term describing a grouping of processes where carbon nanotubes (CNTs) serve a structural role in the fabrication of a material or device. In its basic form, CNT-M is comprised of two steps: produce a template made from carbon nanotubes and infiltrate the porous template with an additional material. Vertically aligned carbon nanotube (VACNT) templates can be grown to heights ranging from microns to millimeters and lithographically patterned to a desired form. Deposition of an existing thin film material onto a CNT template will coat all template surfaces and can produce a near solid material with dimensions on the millimeter scale with resulting material properties coming primarily from the thin film. Progress within CNT-M falls broadly within one of two categories: control of the CNT template's properties and form, or control of infiltration and new materials.Three-dimensional CNT templates were developed to allow patterned multilayer VACNT structures. In one embodiment, VACNTs were grown below an existing, patterned and capillary-formed VACNT structure by reusing the original catalyst in combination with newly deposited catalyst to create a CNT-based microneedle array on a VACNT support. In another embodiment, VACNTs were mechanically coupled from the initial stages of growth to create a smooth, low porosity surface on which a secondary, patterned CNT forest was grown using standard film deposition and lithographic techniques.A microfabrication compatible thermal barrier was produced using CNTs as a sacrificial template for silicon oxide. The resulting thermal barrier exhibited a thermal conductivity that could be tuned across 2 orders of magnitude based on the degree to which the sacrificial template was removed. Carbon infiltrated carbon nanotubes (CI-CNTs) were produced that exhibited a Young's modulus ranging from 5GPa to 26GPa based on controlled process parameters. Porosity, centroid position, and the second moment of area was calculated from SEM images of CI-CNT structures using an automatic pore identification technique. The porosity results suprisingly show little to no porosity gradient across the width of the structure and a nearly linear increase in porosity from the top to bottom. This work advances the understanding of existing CNT-M processes and demonstrates novel techniques for producing future CNT templates.
22
Guan, Jingjiao. "Microfabricated particulate devices for drug delivery". Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1118247862.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxiii, 163 p.; also includes graphics. Includes bibliographical references (p. 118-123). Available online via OhioLINK's ETD Center
23
McAllister, Devin Vincent. "Microfabricated needles for transdermal drug delivery". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/11031.
Testo completo
24
Henry, Sʹebastien. "Microfabricated device for transdermal drug delivery". Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/20707.
Testo completo
25
Steyn, J. Lodewyk (Jasper Lodewyk) 1976. "A microfabricated ElectroQuasiStatic induction turbine-generator". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32463.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.Includes bibliographical references (p. [263]-268).
An ElectroQuasiStatic (EQS) induction machine has been fabricated and has generated net electric power. A maximum power output of 192 [mu]W at 235 krpm has been measured under driven excitation of the six phases. Self excited operation was also demonstrated. Under self-excitation, no external drive electronics are required and sufficient power was produced to dimly light four LED's on two of the six phases. This is believed to be the first demonstration of both power generation and self-excited operation of an EQS induction machine of any scale reported in the open literature. The generator comprises 5 silicon layers, fusion bonded together, and annealed at 700⁰C. The turbine rotor, 4 mm in diameter, is supported on gas bearings. The thrust bearings are formed by a shallow etch of 1.5 [mu]m to define the thrust bearing gap. Thrust bearing pressurization is through 10 [mu]m diameter nozzles, etched 100 [mu]m deep. The journal bearing is a precision, ... wide, 300 [mu]m deep annular trench around the periphery of the turbine disk. The generator airgap is 3 [mu]m. The inner radius of the generator is 1.011 mm, and the outer radius 1.87mm. The machine has ].31 poles for each of the 6 phases, for a total of 786 stator electrodes. Precise microfabrication and aligned, full-wafer fusion bonding enabled turbine generator devices to be operated at rotational speeds as high as 850 krpm. A detailed state-space model of the EQS machine and its external parasitics is presented. The external stray capacitances, and their unbalance, play a critical role in the performance of the device. A method for estimating the strays experimentally is discussed.
(cont.) This estimated, updated model made it possible to use computer optimization techniques to find the optimal drive conditions for the device to generate maximum power. Carrier depletion in the moderately doped polysilicon rotor conductor film prevented the generator from producing power at higher voltages, and limited the maximum machine terminal voltage under self-excitation to approximately 30 Vp-p.
by Jasper Lodewyk Steyn.
Ph.D.
26
Muller, Rikky 1980. "A microfabricated dielectrophoretic micro-organism concentrator". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28393.
Testo completoAbstract (sommario):
Thesis (M. Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, June 2004."May 2004."
Includes bibliographical references (leaves 83-85).
This project focuses on the development of a micro-organism concentrator. Pathogen detection, particularly MEMS based detection, is often limited by sample concentration. The proposed concentrator will interface with a pathogen detector. This type of pathogen concentrator can be useful for many kinds of applications including water purification systems, medical applications and biological warfare agent detection. Due to the nature of these applications, the concentrator must be able to operate under real-world conditions, and be robust to particulates and variations in solution conductivity. The concentrator is an active filter, which concentrate bacteria in solution using negative dielectrophoresis, which pushes objects away from the electrodes toward field minima. An electric field barrier is set up to guide cells toward a concentrated outlet flow path while the bulk of the fluid, which permeates the electric field barrier, is sent to a waste outlet. The cells are collected at the outlet and selectively released by turning off the applied voltage. I have fully designed and modeled the characteristics of the proposed concentrator and successfully fabricated the design. I have characterized the system throughput using polystyrene beads and I have characterized the system electrically using lumped circuit element models.
by Rikky Muller.
M.Eng.and S.B.
27
Srinivasan, Ravi 1971. "Microfabricated reactors for partial oxidation reactions". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9865.
Testo completo
28
Mehta, Ankur 1983. "A microfabricated solid oxide fuel cell". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/27050.
Testo completoAbstract (sommario):
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 83-85).
With the ever-increasing ubiquity of mobile consumer electronic devices comes the rising demand for portable electric power. Current battery technology gives a very modest energy return per weight or volume. Hydrocarbons have a significantly higher energy density, and so fuel conversion systems only need to have several percent efficiency to match and surpass the specific energy of conventional batteries. Thus, there is a strong market for successful portable fuel powered electric generators. The goal of this thesis is to investigate the design of one such device, a two-chamber microfabricated solid oxide fuel cell (SOFC). This device produces electric current through the electrochemical oxidation of fuel through an ionic conductor. Oxide ions permeate across a ceramic electrolyte membrane to react with the fuel, driving electrons back around through the load. The focus of this work is to analyze the behavior of these membranes to prevent failure as the device is heated to its operating temperature near 800K. Experiments and analysis of free-standing electrolyte membranes indicate that failure is unavoidable over the required temperature range, and so supported structures are investigated. The results of experiments with a perforated nitride supported membrane presented herein indicate the need for a more thorough understanding of the thin film stresses responsible for membrane failure, as well as careful support structures to accommodate these. Designs for future devices are presented to improve stability and move closer to a final complete portable power system.
by Ankur Mehta.
S.B.
M.Eng.
29
Hsing, I.-Ming 1968. "Simulation strategies for microfabricated chemical systems". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10061.
Testo completo
30
Lin, Chia-Hua. "A Microfabricated Deep Brain Stimulation Electrode". Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1244061398.
Testo completo
31
Gao, Yuanfang. "Microfabricated devices for single cell analysis". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4429.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 1, 2009) Vita. Includes bibliographical references.
32
Stillman, Janet Allyn. "Three-dimensional microfabrication with laser-patterned photostructurable glass". Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1779690371&sid=28&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Testo completo
33
Cantarella, Giuseppe. "Design, microfabrication and characterisation of Photonic Integrated Circuits". Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28500.
Testo completoAbstract (sommario):
This doctoral dissertation deals with the design, fabrication and characterization of state-of-the-art Photonic Integrated Circuits (PICs) for non-linear applications. Silicon PICs is a technology mainly used for application in telecommunications and quantum optics. The strong third order non-linearity of silicon makes it also attractive for non-linear PIC design. In FWM applications, SOI technology can be used not only for non-linear generation but also to fabricate photonic filters to remove the residual pump. This thesis deals with three requirements for the realisation of on-chip FWM optical devices, the dual polarisation rejection of the pump on-chip and the integration and stabilisation of the FWM source and optical filter. In this work two of the most used SOI photonic integrated filters, ring resonators and Bragg gratings, are presented. These devices present two different solutions for high extinction(≈ 60 dB) dual polarisation filtering. An integrated structure of non-linear source and filter is presented. The device used for non-linear generation is then monolithically integrated with a novel ring resonators cascade filter technology. FWM experiments were carried out obtaining an on chip pump high dual polarisation extinction of 62 dB with a low insertion loss for the propagating signal and idler of only 1.8 dB.The realisation of a microprocessor feedback loop stabilisation system integrated with SOI non-linear structures is also demonstrated. The system is based on a local thermal heater element on-chip used to stabilise the PICs against thermal refractive index variations. Using this method, a silicon π-phase shifted grating with a cavity Q-factor of 40k is demonstrated to operate over an ambient temperature detuning range of 40 oC and injection wavelength range of 1.5 nm, nearly 3 orders of magnitude greater than the resonant cavity line width. The last part of this work is dedicated to the description of a custom made laser photolitography system for rapid prototyping of PIC designs, a tool designed to overcome the costs of the typical lithography systems and drastically decrease the time required for multiple micro-fabrications. The hardware and the software created for this tool are presented together with the first results on the fabrication of SU-8 Photoresist (SU − 8) on Silicon Dioxide (SiO2) waveguides, bends, Mach Zehnder interferometers and ring resonators.
34
Song, Mi Yeon. "Microfabrication of silicon tips for scanning probe microscopy". Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/482/.
Testo completoAbstract (sommario):
This thesis investigates the microfabrication of silicon tips for Scanning Probe Microscopy. First, a microfabrication process was developed to produce silicon tips over 100 um height with a sharp apex of ~10–20 nm. To prevent inadvertent contact between the substrate bearing the tip and the sample being probed, the tip is elevated on a mesa structure. Atomic resolution STM images of graphite are successfully obtained using silicon tips. Subsequently, a co-axial tip was developed for SPELS. SPELS uses an STM tip in field emission mode and then analyses the energy of electrons backscattered. However, the electric field distorts the trajectories of the backscattered electrons. A screened co-axial tip was thus designed; the tip consists of a multilayer Si/Au/HfO\(-2\)/Au structure. The outermost Au layer is grounded. SPELS spectra of graphite were successfully obtained for the first time. Third, a multilayered tip was fabricated for the Scanning Probe Electron AnalyseR.. This approach is a combination of STM with an ultraviolet light source. The designed structure is a multilayered silicon tip consisting of Si/SiO\(_2\)/Au/SiO\(_2\)/Au; the three conducting layers act as an electron collector, retarding field analyser, and grounded shield layer, respectively.
35
Hastings, Abel Z. 1973. "Assessing the viability of various metallic microfabrication techniques". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8460.
Testo completoAbstract (sommario):
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.Includes bibliographical references (p. 85-89).
An investigation was completed to assess the viability of a group of metallic microfabrication techniques aimed at the production of microelectromechanical systems (MEMS) This undertaking was done to show which methods hold the most promise for the near future. The methods investigated include LIGA, micromilling, jet molding, three dimensional printing, microcasting, micro-injection molding, metal injection molding, Microforming, and microextrusion. This study presents a technique overview, assembly issues, an applications survey, basic cost modeling and a survey of the relevant intellectual property.
by Abel Z. Hastings.
M.Eng.
36
Britton, Joe. "Microfabrication techniques for trapped ion quantum information processing". Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337078.
Testo completo
37
Boyer, Nathan Edward. "Microfabrication with Smooth, Thin CNT/Polymer Composite Sheets". BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/5923.
Testo completoAbstract (sommario):
Carbon nanotube (CNT)/polymer composite sheets can be extremely high strength and lightweight, which makes them attractive for fabrication of mechanical structures. This thesis demonstrates a method whereby smooth, thin CNT/polymer composite sheets can be fabricated and patterned on the microscale using a process of photolithography and plasma etching. CNT/polymer composites were made from CNTs grown using chemical vapor deposition using supported catalyst growth and floating catalyst growth. The composite sheets had a roughness of approximately 30nm and were about 61¼m or 261¼m depending on whether they were made from supported catalyst grown or floating catalyst grown CNTs. The composites were patterned using an oxygen plasma as the etchant and a hard mask of silicon nitride.
38
Ghio, Simone. "Design and microfabrication of multifunctional bio-inspired surfaces". Doctoral thesis, Università degli studi di Trento, 2018. https://hdl.handle.net/11572/367604.
Testo completoAbstract (sommario):
In this thesis, we used CMOS-like technologies to produce improved, hierarchical multifunctional bioinspired surfaces. Different natural surfaces have been surveyed including well-known lotus leaf, sharkskin, back of the Namib Desert beetle, butterfly wings, and legs of water-walking insects. The lotus leaf features superhydrophobicity, which leads to low adhesion and self-cleaning. Sharkskin is composed of ripples that manage to reduce skin-friction and thus drag resistance. The Namib Desert beetle, harvests water from the heterogeneous pattern having hydrophilic/hydrophobic bumps on his back. Butterfly wings have re-entrant structures that manage to reach superhydrophobicity from a hydrophilic substrate. Hairy legs of water-walking insects are superhydrophobic with low adhesion that allows them to fight and jump on water.
In chapter 1, we have undertaken a review of bioinspired surfaces that emulate the abilities of such natural surfaces.
Then, in chapter 2 we have described the innovative CMOS-like techniques used for generating several hierarchical and re-entrant microstructures.
Chapter 3 depicts the analysis of surfaces with hierarchical structures generated with a fast and easy process; this latter forms a second hierarchical level composed of random pyramidal elements using wet etching. Surfaces realized with this process manage to reach remarkably high contact angle and low contact angle hysteresis. Additionally, in this chapter we have introduced an analytical model to study the stability of Cassie-Baxter state over Wenzel state for these hierarchical surfaces.
In chapter 4 the fabrication and analysis of surfaces composed of controlled hierarchical levels, which combine sharkskin with single-level lotus leaf-inspired pillared structures are reported. These particular hierarchical surfaces are demonstrated to hold high superhydrophobic properties along with low skin-friction. The superhydrophobicity of these surfaces has been characterized in a series of tests on an inclined plane. The data extrapolated from this measurement was used to evaluate the total dissipated energy of the sliding drop. Combining the data collected during this experiment with contact angle and contact angle hysteresis measurements we propose a global parameter that evaluates the superhydrophobic “level†of a surface.
Furthermore, in chapter 5 similar hierarchical surfaces have also been tested for water harvesting together with single-level pillared surfaces that feature heterogeneous chemistry with hydrophilic/hydrophobic spot on every single pillar.
In chapter 6 a series of tests have also been performed on butterfly-inspired surfaces. Although the substrate of such surfaces is hydrophilic, thanks to the re-entrant structures the surfaces reach high level of hydrophobicity. An implemented mathematical model and experimental test confirm the stability of this hydrophobic state.
In chapter 7, we describe two sets of surfaces inspired by the hairy legs of water walking insect the first is composed of stretchable pyramidal-pillars and the second of truncated-conical silicon pillars. The ability of sharp structures to easily detach from water surfaces is exploited to change the contact angle value of a water drop deposed on this fast type of stretchable micropatterned surface. A mathematical model has been implemented and experimental tests have been carried out to evaluate the stability of the water-air composite interface on both types of microstructured surfaces. In particular, in the polymeric surfaces elasto-capillarity seams to influence the metastability of the Cassie-Baxter state.
39
Ghio, Simone. "Design and microfabrication of multifunctional bio-inspired surfaces". Doctoral thesis, University of Trento, 2018. http://eprints-phd.biblio.unitn.it/2854/1/Thesis_GHIO_S..pdf.
Testo completoAbstract (sommario):
In this thesis, we used CMOS-like technologies to produce improved, hierarchical multifunctional bioinspired surfaces. Different natural surfaces have been surveyed including well-known lotus leaf, sharkskin, back of the Namib Desert beetle, butterfly wings, and legs of water-walking insects. The lotus leaf features superhydrophobicity, which leads to low adhesion and self-cleaning. Sharkskin is composed of ripples that manage to reduce skin-friction and thus drag resistance. The Namib Desert beetle, harvests water from the heterogeneous pattern having hydrophilic/hydrophobic bumps on his back. Butterfly wings have re-entrant structures that manage to reach superhydrophobicity from a hydrophilic substrate. Hairy legs of water-walking insects are superhydrophobic with low adhesion that allows them to fight and jump on water.
In chapter 1, we have undertaken a review of bioinspired surfaces that emulate the abilities of such natural surfaces.
Then, in chapter 2 we have described the innovative CMOS-like techniques used for generating several hierarchical and re-entrant microstructures.
Chapter 3 depicts the analysis of surfaces with hierarchical structures generated with a fast and easy process; this latter forms a second hierarchical level composed of random pyramidal elements using wet etching. Surfaces realized with this process manage to reach remarkably high contact angle and low contact angle hysteresis. Additionally, in this chapter we have introduced an analytical model to study the stability of Cassie-Baxter state over Wenzel state for these hierarchical surfaces.
In chapter 4 the fabrication and analysis of surfaces composed of controlled hierarchical levels, which combine sharkskin with single-level lotus leaf-inspired pillared structures are reported. These particular hierarchical surfaces are demonstrated to hold high superhydrophobic properties along with low skin-friction. The superhydrophobicity of these surfaces has been characterized in a series of tests on an inclined plane. The data extrapolated from this measurement was used to evaluate the total dissipated energy of the sliding drop. Combining the data collected during this experiment with contact angle and contact angle hysteresis measurements we propose a global parameter that evaluates the superhydrophobic “level” of a surface.
Furthermore, in chapter 5 similar hierarchical surfaces have also been tested for water harvesting together with single-level pillared surfaces that feature heterogeneous chemistry with hydrophilic/hydrophobic spot on every single pillar.
In chapter 6 a series of tests have also been performed on butterfly-inspired surfaces. Although the substrate of such surfaces is hydrophilic, thanks to the re-entrant structures the surfaces reach high level of hydrophobicity. An implemented mathematical model and experimental test confirm the stability of this hydrophobic state.
In chapter 7, we describe two sets of surfaces inspired by the hairy legs of water walking insect the first is composed of stretchable pyramidal-pillars and the second of truncated-conical silicon pillars. The ability of sharp structures to easily detach from water surfaces is exploited to change the contact angle value of a water drop deposed on this fast type of stretchable micropatterned surface. A mathematical model has been implemented and experimental tests have been carried out to evaluate the stability of the water-air composite interface on both types of microstructured surfaces. In particular, in the polymeric surfaces elasto-capillarity seams to influence the metastability of the Cassie-Baxter state.
40
Yang, Yanyin. "Synthesis, characterization, microfabrication and biological applications of conducting polymers". Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127316668.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 192 p.; also includes graphics (some col.). Includes bibliographical references (p. 183-192). Available online via OhioLINK's ETD Center
41
Chien, Hsin-I. "Microfabrication of barium strontium titanate BaxSr(1-x)TiO3". Thesis, London South Bank University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618692.
Testo completo
42
Forsberg, Pontus. "Diamond Microfabrication for Applications in Optics and Chemical Sensing". Doctoral thesis, Uppsala universitet, Mikrosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192567.
Testo completoAbstract (sommario):
Diamond is a material with many exceptional properties. In this thesis methods for fabrication of microstructures as well as several applications of such structures in optics, microfluidics and electrochemistry are presented. A method for etching deep and highly precise gratings is described. This method was used to fabricate circularly symmetric half wave plates for use in vector vortex coronagraphs. Such coronagraphs are a very promising approach to the direct imaging of extrasolar planets. By varying the lateral etch rate of the aluminum mask during diamond etching in an inductively coupled plasma, the sidewall angle of the etched structures could be controlled. This method was used to make smooth sloped sides on a waveguide for coupling light into it. Antireflective structures that drastically reduced the surface reflection in a wavelength band between 10 and 50 µm were also fabricated. An array of boron doped diamond microelectrodes for electrochemical measurements in a microchannel was fabricated and tested, showing very good stability and reusability. Several hundred hours of use did not adversely affect their performance and no damage to them could be detected by atomic force microscopy or scanning electron microscopy. Superhydrophobic surfaces in diamond were demonstrated, using both hydrogen and fluorine termination. Hydrogen termination on a flat surface gives contact angles below 90°. To achieve a superhydrophobic surface with this low intrinsic hydrophobicity, structures looking like microscopic nail heads were fabricated. The effect of water pressure on immersed superhydrophobic surfaces was also studied and it was found that the collapse of the superhydrophobic state due to pressure was sometimes reversible as the pressure was lowered. Finally, a method was tested for functionalizing diamond surfaces using block copolymers of polyethylene oxide and polypropylene oxide to both passivate the surface and to attach synthetic binder molecules. This method was found to give very high signal to noise ratios when detecting C-reactive protein.
43
Sterling, Robin C. "Ytterbium ion trapping and microfabrication of ion trap arrays". Thesis, University of Sussex, 2012. http://sro.sussex.ac.uk/id/eprint/39684/.
Testo completoAbstract (sommario):
Over the past 15 years ion traps have demonstrated all the building blocks required of a quantum computer. Despite this success, trapping ions remains a challenging task, with the requirement for extensive laser systems and vacuum systems to perform operations on only a handful of qubits. To scale these proof of principle experiments into something that can outperform a classical computer requires an advancement in the trap technologies that will allow multiple trapping zones, junctions and utilize scalable fabrication technologies. I will discuss the construction of an ion trapping experiment, focussing on my work towards the laser stabilization and ion trap design but also covering the experimental setup as a whole. The vacuum system that I designed allows the mounting and testing of a variety of ion trap chips, with versatile optical access and a fast turn around time. I will also present the design and fabrication of a microfabricated Y junction and a 2- dimensional ion trap lattice. I achieve a suppression of barrier height and small variation of secular frequency through the Y junction, aiding to the junctions applicability to adiabatic shuttling operations. I also report the design and fabrication of a 2-D ion trap lattice. Such structures have been proposed as a means to implement quantum simulators and to my knowledge is the first microfabricated lattice trap. Electrical testing of the trap structures was undertaken to investigate the breakdown voltage of microfabricated structures with both static and radio frequency voltages. The results from these tests negate the concern over reduced rf voltage breakdown and in fact demonstrates breakdown voltages significantly above that typically required for ion trapping. This may allow ion traps to be designed to operate with higher voltages and greater ion-electrode separations, reducing anomalous heating. Lastly I present my work towards the implementation of magnetic fields gradients and microwaves on chip. This may allow coupling of the ions internal state to its motion using microwaves, thus reducing the requirements for the use of laser systems.
44
Losey, Matthew W. "Novel multiphase chemical reaction systems enabled by microfabrication technology". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8634.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2001.Includes bibliographical references (p. 237-251).
Advances in MEMS (micro-electromechanical systems) have enabled some of the "Lab-on-a-Chip" technologies and microfluidics that are pervasive in many of the current developments in analytical chemistry and molecular biology. Coinciding with this effort in micro-analytics has been research in chemical process miniaturization -- reducing the characteristic length scale of the unit operation to improve heat and mass transfer, and ultimately process performance. My research has involved the design and fabrication of novel chemical reaction systems using MEMS and microfabrication methods (photolithography, deep-reactive-ion etching, thin-film growth and deposition, and multiple wafer bonding). Miniature chemical systems provide the opportunity for distributed, on-demand manufacturing, which would eliminate the hazards of transportation and storage of toxic or hazardous chemical intermediates. Reactions that are particularly suitable for miniaturized chemical systems are those that are fast and involve toxic intermediates: the controlled synthesis of phosgene is such a reaction and has been demonstrated in a microfabricated packed bed reactor. Owing to the high surface-to-volume ratios, micro chemical systems also have the potential to make improvements in process performance through enhanced heat and mass transfer.
(cont.) Heterogeneously catalyzed gas-liquid reactions have been performed in the microfabricated reactors and have been shown to have mass transfer coefficients several orders of magnitude larger than their industrial-scale counterparts. Multiphase reactions are often hindered by mass-transfer limitations owing to the difficulty in transporting the gaseous reactant through the liquid to the catalytic surface. The microchemical device has been designed to increase the interfacial gas-liquid contacting area by promoting dispersion and preventing coalescence. Microfabrication allows the design of reactors with complicated fluidic distribution networks, staggered arrays of microstructural features to promote mixing, and the integration of sensing and temperature control. Other uses of microfabrication include the incorporation of porous silicon as a high surface area catalyst support. In all, performing multiphase chemistry on a chip has been demonstrated to have inherent advantages, particularly for those fast reactions that can benefit from improved mixing and mass transfer.
by Matthew W. Losey.
Ph.D.
45
Ge, Yufei S. M. Massachusetts Institute of Technology. "Microfabrication of surface electrode ion traps for quantum manipulation". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99280.
Testo completoAbstract (sommario):
Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-132).
Trapped ions are a promising approach to quantum computation. This approach uses a qubit state which is the atomic state and quantum motional state of a trapped ion to encode information, and uses laser-ion interactions to manipulate the qubit state. A major obstacle to the realization of a practical ion trap quantum computer is decoherence. In trapped ion quantum computation experiments, decoherence is dominated by the uncontrolled heating of ion motional states. In this thesis, we present the detailed microfabrication of several series of surface electrode linear Paul traps made from different electrode materials, followed by the ion motional heating experiment results for these traps. We demonstrate that the ion motional heating strongly depends on fabrication process. In particular, we explore how grain size and grain orientation affect the ion motional heating rate. This thesis is divided into two parts. In the first part, we describe the fabrication of gold, silver, aluminum and niobium traps from different processes, which results in various surface morphologies and grain structures. Ion motional heating rate measurements are then conducted both at cryogenic temperatures and at room temperature. We employ a physical model based on the fluctuating patch potential theory to explain the ion heating behavior. We use gold traps to study the temperature and frequency dependence of the ion heating. We use aluminum traps to study the ion heating dependence on the amorphous dielectric layer. And we use silver traps to study the ion heating dependence on the grain structure. These results suggest that excess ion heating could possibly be suppressed by suitable fabrication selection. In the second part, we present the process of using SU8 to fabricate a multilayer surface electrode point Paul trap, which has the advantage of allowing ion height variation within the same trap and enables testing of the distance dependence of ion heating.
by Yufei Ge.
S.M.
46
Wasley, Thomas J. "Digitally driven microfabrication of 3D multilayer embedded electronic systems". Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/23237.
Testo completoAbstract (sommario):
The integration of multiple digitally driven processes is seen as the solution to many of the current limitations arising from standalone Additive Manufacturing (AM) techniques. A technique has been developed to digitally fabricate fully functioning electronics using a unique combination of AM technologies. This has been achieved by interleaving bottom-up Stereolithography (SL) with Direct Writing (DW) of conductor materials alongside mid-process development (optimising the substrate surface quality), dispensing of interconnects, component placement and thermal curing stages. The resulting process enables the low-temperature production of bespoke three-dimensional, fully packaged and assembled multi-layer embedded electronic circuitry. Two different Digital Light Processing (DLP) Stereolithography systems were developed applying different projection orientations to fabricate electronic substrates by selective photopolymerisation. The bottom up projection orientation produced higher quality more planar surfaces and demonstrated both a theoretical and practical feature resolution of 110 μm. A top down projection method was also developed however a uniform exposure of UV light and planar substrate surface of high quality could not be achieved. The most advantageous combination of three post processing techniques to optimise the substrate surface quality for subsequent conductor deposition was determined and defined as a mid-processing procedure. These techniques included ultrasonic agitation in solvent, thermal baking and additional ultraviolet exposure. SEM and surface analysis showed that a sequence including ultrasonic agitation in D-Limonene with additional UV exposure was optimal. DW of a silver conductive epoxy was used to print conductors on the photopolymer surface using a Musashi dispensing system that applies a pneumatic pressure to a loaded syringe mounted on a 3-axis print head and is controlled through CAD generated machine code. The dispensing behaviour of two isotropic conductive adhesives was characterised through three different nozzle sizes for the production of conductor traces as small as 170 μm wide and 40 μm high. Additionally, the high resolution dispensing of a viscous isotropic conductive adhesive (ICA) also led to a novel deposition approach for producing three dimensional, z-axis connections in the form of high freestanding pillars with an aspect ratio of 3.68 (height of 2mm and diameter of 550μm). Three conductive adhesive curing regimes were applied to printed samples to determine the effect of curing temperature and time on the resulting material resistivity. A temperature of 80 °C for 3 hours resulted in the lowest resistivity while displaying no substrate degradation. ii Compatibility with surface mount technology enabled components including resistors, capacitors and chip packages to be placed directly onto the silver adhesive contact pads before low-temperature thermal curing and embedding within additional layers of photopolymer. Packaging of components as small as 0603 surface mount devices (SMDs) was demonstrated via this process. After embedding of the circuitry in a thick layer of photopolymer using the bottom up Stereolithography apparatus, analysis of the adhesive strength at the boundary between the base substrate and embedding layer was conducted showing that loads up to 1500 N could be applied perpendicular to the embedding plane. A high degree of planarization was also found during evaluation of the embedding stage that resulted in an excellent surface finish on which to deposit subsequent layers. This complete procedure could be repeated numerous times to fabricate multilayer electronic devices. This hybrid process was also adapted to conduct flip-chip packaging of bare die with 195 μm wide bond pads. The SL/DW process combination was used to create conductive trenches in the substrate surface that were filled with isotropic conductive adhesive (ICA) to create conductive pathways. Additional experimentation with the dispensing parameters led to consistent 150 μm ICA bumps at a 457 μm pitch. A flip-chip bonding force of 0.08 N resulted in a contact resistance of 2.3 Ω at a standoff height of ~80 μm. Flip-chips with greater standoff heights of 160 μm were also successfully underfilled with liquid photopolymer using the SL embedding technique, while the same process on chips with 80 μm standoff height was unsuccessful. Finally the approaches were combined to fabricate single, double and triple layer circuit demonstrators; pyramid shaped electronic packages with internal multilayer electronics; fully packaged and underfilled flip-chip bare die and; a microfluidic device facilitating UV catalysis. This new paradigm in manufacturing supports rapid iterative product development and mass customisation of electronics for a specific application and, allows the generation of more dimensionally complex products with increased functionality.
47
Le, Van Suu Thierry. "Etude analytique, conception et microfabrication de microphones capacitifs miniatures". Le Mans, 2008. http://cyberdoc.univ-lemans.fr/theses/2008/2008LEMA1016.pdf.
Testo completoAbstract (sommario):
Au cours de la dernière décennie, les capteurs capacitifs de pression acoustique fabriqués sur puce silicium, ont fait l'objet d'études théoriques, expérimentales et technologiques, de manière à réaliser des microphones miniatures qui présentent de l'intérêt dans de nombreuses applications. Ces études ont été menées plus particulièrement sur les systèmes d'architectures conventionnelles, c'est à dire sur la modélisation et la microfabrication de dispositifs qui comportent un diaphragme (considéré comme une membrane), une électrode arrière plane (perforée ou non), et une couche de fluide visqueux et thermoconducteur située dans cet entrefer, prolongé par un réservoir périphérique. Le travail présenté dans ce mémoire de thèse constitue dans l'ensemble une extension de ceux menés depuis plusieurs années dans plusieurs laboratoires de par le monde dont le Laboratoire d'Acoustique de l'Université du Maine. Une nouvelle architecture dans laquelle l'électrode arrière n'est plus plane a été proposée récemment dans la littérature. Les méthodes analytiques classiques utilisées ont conduit à des expressions simples pour la sensibilité du microphone, mais elles se trouvent limitées lorsque l'étude requiert des résultats très précis. C'est ainsi qu'une solution générale est proposée ici, qui prend en compte le couplage fluidemembrane d'une manière plus réaliste. Par ailleurs, le diaphragme est habituellement considéré comme circulaire et/ou comme ayant un comportement de membrane. C'est ainsi que, dans la seconde partie de cette étude analytique, des solutions sont proposées pour des plaques carrées, chargées par le fluide, incluant une extension au cas du ruban précontraint qui doivent répondent aux attentes de la communauté. La seconde partie de la thèse est double: -i) un microphone miniature, réalisé à l'aide des procédés de micro fabrication disponibles dans la centrale de micro technologies localisée à l'ENSIM, a été conçu et les principales étapes de sa réalisation ont été validées, ii) Une méthode expérimentale de mesure simultanée du module d'Young et des contraintes résiduelles est présentée et validée, qui se substitue avantageusement à notre sens aux méthodes en usage qui ne permettent l'accès qu'à un seul des deux paramètres, l'autre étant supposé connuDuring the last decade, capacitive acoustic pressure sensors fabricated on silicon chips was the subject of theoretical, experimental and technological studies, in order to design miniaturized microphones whose interest in many applications would be of importance. These studies concentrate on the devices classically designed, namely on the modelling and on the micro machining of devices comprising a diaphragm (considered as a membrane), a planar perforated (or not) backing electrode, and a viscous and thermalconducting fiuid trapped between both and/or enclosed by a peripheral reservoir. Ln many respects, the work presented in this PhD thesis is an extension of those carried out for several years in laboratories around the world, including the Laboratoire d'Acoustique de l'Université du Maine. A new design in which the backing electrode is non-planar has been proposed recently in the literature. A standard analytic procedure yielded simple expression for the sensitivity of the microphone, whose the limitations can be pointed out when a precise solution is needed. Therefore herein, a general solution is proposed, which accounts for the coupling between the membrane and the fiuid layer in a more realistic way. On the other hand, the diaphragm is usually assumed to be circular and/or to behave as a membrane. The aim of the second chapter of the analytical studies presented here is to propose solutions for square loaded plates, including extensions for stretched ribbon, leading to awaited results. The second part of the thesis is twofold : -i) a miniaturised microphone, made using the micro machining pro cesses available in the clean room facility at ENSIM, has been designed and the main process steps have been validated, -ii) an experimental method for measuring simultaneously the Young's modulus and the residual stress is suggested and validated, supplanting in our opinion other known methods which usually provide only one of these two parameters (assuming that the other one is known)
48
Hou, Linlin. "Advanced 3D Microfabrication and Demonstration of Arrayed Electrowetting Microprisms". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1328546291.
Testo completo
49
Peeni, Bridget A. "Microfabrication and evaluation of planar thin-film microfluidic devices /". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1564.pdf.
Testo completo
50
Le, Van Suu Thierry Bruneau Michel Durand Stéphane. "Etude analytique, conception et microfabrication de microphones capacitifs miniatures". [S.l.] : [s.n.], 2008. http://cyberdoc.univ-lemans.fr/theses/2008/2008LEMA1016.pdf.
Testo completo