Dissertations / Theses on the topic 'Micromachining'
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Mian, Aamer Jalil. "Size effect in micromachining." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/size-effect-in-micromachining(91bf7280-a937-4509-9c40-4ff2e36d26c6).html.
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The world is experiencing a growing demand for miniaturised products. Micro-milling, using carbide micro tools has the potential for direct, economical manufacture of micro parts from a wide range of workpiece materials. However, in previous studies several critical issues have been identified that preclude the direct application of macro machining knowledge in the micro domain through simple dimensional analysis. The research presented in this thesis focused on some of the areas that require development of the scientific knowledge base to enable determining improved microscale cutting performance. In the mechanical micro machining of coarse grained materials, the programmed undeformed chip thickness can be lower than the length scale of the workpiece grains. Moreover, when the microstructure of such materials is composed of more than one phase, the micro cutting process can be undertaken at a length scale where this heterogeneity has to be considered. Driven by this challenge, the material microstructure 'size effect' on micro-machinability of coarse grain steel materials was investigated in this PhD. In this regard, a predominantly single phase ferritic workpiece steel material and another workpiece material with near balanced ferrite/pearlite volume fractions was studied over a range of feedrates. The results suggested that for micro machined parts, differential elastic recovery between phases leads to higher surface roughness when the surface quality of micro machined multiphase phase material is compared to that of single phase material. On the other hand, for single phase predominantly ferritic materials, reducing burr size and tool wear are major challenges. In micro machining the so called 'size effect' has been identified as critical in defining the process performance. However, an extensive literature search had indicated that there was no clear reported evidence on the effect of process variables on driving this size effect phenomenon. It is often assumed in literature that the un-deformed chip thickness was the main factor driving the size effect. This limit manufactures to only altering the feedrate to try and influence size effect. To explore the significance of a range of inputs variables and specifically, cutting variables on the size effect, micro cutting tests were conducted on Inconel 718 nickel alloy. Taguchi methodology along with signal processing techniques were applied to micro milling acoustic emission signals to identify frequency/energy bands and hence size effect specific process mechanism. The dominant cutting parameters for size effect characteristics were determined by analysis of variance. These findings show that despite most literature focussing on chip thickness as the dominant parameter on size effect, the cutting velocity is a dominant factor on size effect related process performance. This suggests that manipulating the cutting speed can also be a very effective strategy in optimising surface finish in micro machining and in breaking the lower limit of micro machining.In micro machining the lower limit of the process window is set by the minimum chip thickness. Identifying this limit is thus important for establishing the process window. Process windows are valuable guidelines for industrial selection of cutting conditions. Additionally, understanding factors that influence the value of minimum chip thickness is even more important for progressing micro machining capability to the nano-scale machining regime. For this reason, in this PhD study, acoustic emission signatures emanating from microscale milling of six different workpiece materials were characterised to identify the rubbing mode and this enabled the identification of the threshold conditions for occurrence of minimum chip thickness. The minimum chip thickness predicted by this novel approach compares reasonably well to the values that exist in published literature. Additionally, the decomposition of raw acoustic signal allowed the determination of energy levels corresponding to deformation mechanisms. The PhD work provides significant and new knowledge on the utility and importance of acoustic emission signals in characterising chip formation in micro machining. A novel method for determining the minimum chip thickness was developed, micro machining chip formation mechanisms were identified and the machinability of coarse grained multiphase material is presented.
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Hobbs, Neil Townsend. "Anisotropic etching for silicon micromachining." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/40632.
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Silicon micromachining is the collective name for several processes by which three dimensional
structures may be constructed from or on silicon wafers. One of these
processes is anisotropic etching, which utilizes etchants such as KOH and ethylene
diamine pyrocatechol (EDP) to fabricate structures from the wafer bulk. This project is a
study of the use of KOH to anisotropically etch (lOO)-oriented silicon wafers. The thesis
provides a thorough review of the theory and principles of anisotropic etching as applied
to (100) wafers, followed by a few examples which serve to illustrate the theory. Next,
the thesis describes the development and experimental verification of a standardized
procedure by which anisotropic etching may be reliably performed in a typical research
laboratory environment. After the development of this procedure, several more etching
experiments were performed to compare the effects of various modifications of the etching
process. Multi-step etching processes were demonstrated, as well as simultaneous doublesided
etching using two different masks. The advantages and limitations of both methods
are addressed in this thesis. A comparison of experiments performed at different etchant
temperatures indicates that high temperatures (800 C) produces reasonably good results at
a very high etch rate, while lower temperatures (500 C) are more suited to high-precision
structures since they produce smoother, higher-quality surfaces.
Master of Science
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Ozkeskin, Fatih Mert. "Feedback Controlled High Frequency Electrochemical Micromachining." Texas A&M University, 2008. http://hdl.handle.net/1969.1/86041.
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Microsystem and integrated circuitry components are mostly manufactured using
semiconductor technologies. Fabrication using high strength metals, for demanding
aerospace, mechanical, or biomedical applications, requires novel technologies which
are different from those for silicon. A promising mass production method for
micro/meso scale components is electrochemical micromachining.
The complex system, however, requires high precision mechanical fixtures and
sophisticated instrumentation for proper process control. This study presents an
electrochemical micromachining system with a closed-loop feedback control
programmed using a conditional binary logic approach.
The closed-loop control is realized using electrical current as the dynamic
feedback signal. The control system improves material removal rate by 250% through
optimizing inter electrode gap and provides robust automation reducing machining
variation by 88%. The new system evokes production of higher quality
microcomponents. Workpiece damage is reduced by 97% and increased feature
sharpness is observed.
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Greuters, Jako. "UV laser micromachining of photonics materials." Thesis, University of Hull, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431044.
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Key, Philip Henry. "Excimer laser micromachining of inorganic materials." Thesis, University of Hull, 1989. http://hydra.hull.ac.uk/resources/hull:11090.
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Bian, Qiumei. "Femtosecond laser micromachining of advanced materials." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/15140.
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Doctor of PhilosophyDepartment of Industrial and Manufacturing Systems Engineering
Shuting Lei
Shuting Lei
Femtosecond (fs) laser ablation possesses unique characteristics for micromachining, notably non-thermal interaction with materials, high peak intensity, precision and flexibility. In this dissertation, the potential of fs laser ablation for machining polyurea aerogel and scribing thin film solar cell interconnection grooves is studied. In a preliminary background discussion, some key literature regarding the basic physics and mechanisms that govern ultrafast laser pulse interaction with materials and laser micromachining are summarized. First, the fs laser pulses are used to micromachine polyurea aerogel. The experimental results demonstrate that high quality machining surface can be obtained by tuning the laser fluence and beam scanning speed, which provides insights for micromachining polymers with porous structures. Second, a new fs laser micro-drilling technique is developed to drill micro-holes in stainless steel, in which a hollow core fiber is employed to transmit laser pulses to the target position. The coupling efficiency between the laser and the fiber is investigated and found to be strongly related to pulse energy and pulse duration. Third, the fs laser with various energy, pulse durations, and scanning speeds has been utilized to pattern Indium Tin Oxide (ITO) glass for thin film solar cells. The groove width decreases with increasing pulse duration due to the shorter the pulse duration the more effective of the energy used to material removal. In order to fully remove ITO without damaging the glass, the beam scanning speed need to precisely be controlled. Fourth, fs laser has been utilized to scribe Molybdenum thin film on Polyimide (PI) flexible substrate for Copper Indium Gallium Selenide (CIGS) thin film solar cells. The experimental parameters and results including ablation threshold, single- and multiple-pulse ablation shapes and ablation efficiency were discussed in details. In order to utilize the advantages of the fs lasers, the fabrication process has to be optimized for thin film patterning and structuring applications concerning both efficiency and quality. A predictive 3D Two Temperature Model (TTM) was proposed to predict ablation characteristics and help to understand the fs laser metal ablation mechanisms. 3D temperature field evolution for both electrons and lattice were demonstrated. The ablation model provides an insight to the physical processes occurring during fs laser excitation of metals. Desired processing fluence and process speed regime can be predicted by calculating the ablation threshold, ablation rate and ablation crater geometry using the developed model.
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Singh, Ramesh K. "Laser Assisted Mechanical Micromachining of Hard-to-Machine Materials." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19803.
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There is growing demand for micro and meso scale devices with applications in the field of optics, semiconductor and bio-medical fields. In response to this demand, mechanical micro-cutting (e.g. micro-milling) is emerging as a viable alternative to lithography based micromachining techniques. Mechanical micromachining methods are capable of generating three-dimensional free-form surfaces to sub-micron level precision and micron level accuracies in a wide range of materials including common engineering alloys. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials such as tool and die steels, limited machine-tool system stiffness and low tool flexural strength are major impediments to the use of mechanical micromachining methods.
This thesis presents the design, fabrication and analysis of a novel Laser-assisted Mechanical Micromachining (LAMM) process that has the potential to overcome these limitations. The basic concept involves creating localized thermal softening of the hard material by focusing a solid-state continuous wave laser beam of diameter ranging from 70-120 microns directly in front of a miniature (300 microns-1 mm wide) cutting tool. By suitably controlling the laser power, spot size and speed, it is possible to produce a sufficiently large decrease in flow stress of the work material and, consequently, the cutting forces. This in turn will reduce machine/tool deflection and chances of catastrophic tool failure. The reduced machine/tool deflection yields improved accuracy in the machined feature. In order to use this process effectively, adequate thermal softening needs to be produced while keeping the heat affected zone in the machined surface to a minimum. This has been accomplished in the thesis via a detailed process characterization, modeling of process mechanics and optimization of process variables.
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Albri, Frank. "High precision laser micromachining for sensing applications." Thesis, Heriot-Watt University, 2014. http://hdl.handle.net/10399/2951.
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In this PhD thesis the development of laser-based processes for sensing applications is investigated. The manufacture of optical fibre sensors is of particular interest because fibre optics offers advantages in space constraint environments or in environments where electronic sensors fail. Laser micromilling of the transparent and mechanically challenging to machine materials sapphire and fused silica is investigated. An industrial picosecond laser providing 6 ps pulses with the ability to emit at 1030 nm (IR), 515 nm (green) and 343 nm (UV) is used for processing of these materials; providing a maximum laser pulse energy of 25 μJ at UV, 75 μJ at green and 125 μJ in IR. The UV wavelength is identified as the most reliable machining wavelength for these materials with the least amount of cracking and achieving a surface roughness Rq of just 300 nm compared to 1220 nm (green) and 1500 nm (IR) in fused silica. In sapphire the surface roughness is 420 nm using UV , with green it is 500 nm and using IR it is 800 nm. The material removal rates using this laser milling process are larger than with other micromachining techniques, hence it was applied to manufacture cantilever sensors on the end of an optical fibre. The monolithic fibre top sensor is carved out of conventional telecommunications optical fibre. The cantilever is a structure of less than 10 μm thickness, 20 μm width and 125 μm length. Using the Fabry-Perot interferometer method the sensor detects small movements with a resolution better than 15 nm. A technique is developed to correct for laser machining angles and hence generate parallel interferometer faces. An electric arc cleaning process of the laser manufactured cantilever sensors is investigated that reduces the surface roughness to 30 nm. The manufacturing process reduces manufacturing times by a factor of 100. A working sensor is demonstrated in a deflection experiment. Such short pulses are not always required to manufacture the highest resolution sensors. The manufacture of high precision optical encoder scales (pitch 8 μm, depth 200 nm) with two processes (i) ablative removal of a polyimide layer and (ii) a melt reflow process on nickel coated scales is demonstrated. Both processes are using 33 ns laser pulses at 355 nm generating a pulse energy of up to 1 mJ.
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Haneveld, Jeroen. "Nanochannel fabrication and characterization using bond micromachining." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/51105.
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Bostock, R. M. "Silicon micromachining for micro-optical device manufacture." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596797.
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All current laser pig-tailing methods employ either glue or a weld to secure the fibre in place. This leads to difficulty in attaining initial alignment; to movement during bonding and to instability throughout the service life. Precautions are also required to avoid device damage due to glue wicking. The approach taken in the present research is to adopt a mechanical solution, eliminating the use of either glue or a weld. In addition, this must be integrated in one part with rest of the optical system to form a compatible solution. A novel solution is developed using silicon nitride clips which hold the fibre, and are fabricated as part of the substrate. This requires the selection of a process compatible material for the clips and a method to manufacture features to allow insertion of the fibre and ensure precision alignment. The manufacture of these devices is described, both where the core of the optical fibre is below the level of the silicon substrate surface, and through the use of an extension to the process, where the fibre core is above the substrate surface. The first instance is ideal for fibre-fibre and fibre-detector connection, and the second case is required for fibre to device connection. The fabrication of these components uses innovative process steps developed through research in this work. Results of the mechanical characteristics of these devices, and of the performance under environmental testing are presented. These demonstrate that this fibre interconnection technique offers significant benefits over the current methods and that the technique meets the required environmental specifications for telecommunications components. In summary, this thesis is a description of the development of the fibre attach technique and the integration of a complete process. The research is brought to the stage where all of the steps of the complete process have been tested in practice. The results of these tests, and the results of testing working devices based on the process are presented.
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Ozdemir, C. Hakan. "Electrochemical behaviour of silicon for micromachining applications." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315540.
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Wu, Kenneth Chu-Chao. "Novel etch-stop materials for silicon micromachining." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9868.
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Spieser, Alexandre Frederic Jean. "Development of an electrochemical micromachining (μECM) machine." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/10659.
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Electrochemical machining (ECM) and especially electrochemical micromachining (μECM) became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro applications such as microfluidics systems and stressfree drilled holes in the automotive and aerospace sectors. Electrochemical machining is considered as a non-conventional machining process based on the phenomenon of electrolysis. This process requires maintaining a small gap - the interelectrode gap (IEG) - between the anode (workpiece) and the cathode (tool-electrode) in order to achieve acceptable machining results (i.e. accuracy, high aspect ratio with appropriate material removal rate and efficiency). This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has 3 axes of motion (X, Y and Z) and a spindle allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2nmresolution encoders for ultra-precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the machine and allows the electrolyte to be changed quickly. A pulse power supply unit (PSU) and a special control algorithm have been implemented. The pulse power supply provides not only ultra-short pulses (50ns), but also plus and minus biases as well as a polarity switching functionality. It fulfils the requirements of tool preparation with reversed ECM on the machine. Moreover, the PSU is equipped with an ultrafast over current protection which prevents the tool-electrode from being damaged in case of short-circuits. Two different process control algorithms were made: one is fuzzy logic based and the other is adapting the feed rate according to the position and time at which short-circuits were detected. The developed machine is capable of drilling micro holes in hard-to-machine materials but also machine micro-styli and micro-needles for the metrology (micro CMM) and medical sectors. This work also presents drilling trials performed with the machine with an orbiting tool. Machining experiments were also carried out using electrolytes made of a combination of HCl and NaNO₃ aqueous solutions. The developed machine was used to fabricate micro tools out of 170μm WC-Co alloy shafts via micro electrochemical turning and drill deep holes via μECM in disks made of 18NiCr6 alloy. Results suggest that this process can be used for industrial applications for hard-to-machine materials. The author also suggests that the developed machine can be used to manufacture micro-probes and micro-tools for metrology and micro-manufacturing purposes.
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Cheng, Jian. "Ultrafast Picosecond Laser Micromachining of Metallic Materials." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526772.
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Zdebski, Daniel. "The impact of tool performance on micromachining capability." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7789.
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Micro-milling represents a versatile and fast manufacturing process suitable for production of fully 3D micro-components. Such components are demanded for a vast number of industrial applications including safety systems, environmental sensors, personalized medical devices or micro-lenses and mirrors. The ability of micro-milling to process a wide range of materials makes it one of the best candidates to take a leading position in micromanufacturing. However, so far it does not seem to happen. By discussion with various industrialists, low predictability of micro-milling process was identified as the major limiting factor. This is mainly because of strong effects of the tool tolerances and process uncertainties on machining performance. Although, these issues are well known, they are not reflected by the current modelling methods used in micro-milling. Therefore, the research presented in this thesis mainly concentrates on development of a method allowing a prediction of the tool life in manner of tool breakage probability. Another important criterion which must be fulfilled is the method applicability to industrial applications. This means that the method must give sufficiently accurate prediction in reasonable time with minimum effort and interactions with day-to-day manufacturing process. The criteria listed above led to development of a new method based on analytically/numerical modelling techniques combined with an analysis of real tool variations and process uncertainty. Although, the method is presented in a relatively basic form, without considering some of the important factors, it shows high potential for industrial applications. Possibility of further implementation of additional factors is also discussed in this thesis. Additionally, some of the modelling techniques presented in this thesis are assumed to be suitable for application during designing of micro end-mills. Therefore, in the last part of this thesis is presented a systematic methodology for designing of micro end-mills. This method is based on knowledge and experience gained during this research.
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Ismail, Alyani. "Design of microwave waveguides and filters for micromachining." Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433532.
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Zhang, Hao. "INVESTIGATION TO A COST-EFFECTIVE 3D MICROMACHINING METHOD." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372250848.
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Ali, Arham. "Chemo-Thermal Micromachining of Glass: An Explorative Study." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin154392221273875.
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Muhammad, Noorhafiza Binti. "Laser micromachining of coronary stents for medical applications." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/laser-micromachining-of-coronary-stents-for-medical-applications(96e969b4-3fda-474c-ab3a-1eda44f9d968).html.
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This PhD thesis reports an investigation into medical coronary stent cutting using three different types of lasers and associated physical phenomena. This study is motivated by a gap in the current knowledge in stent cutting identified in an extensive literature review. Although lasers are widely used for stent cutting, in general the laser technology employed is still traditionally based on millisecond pulsed Nd:YAG lasers. Although recent studies have demonstrated the use of fibre lasers, picosecond and femtosecond lasers for stent cutting, it has been preliminary studies.To further understand the role of new types of lasers such as pulsed fibre lasers, picosecond and femtosecond pulsed lasers in stent cutting, these three lasers based stent cutting were investigated in this project. The first investigation was on a new cutting method using water assisted pulsed (millisecond) fibre laser cutting of stainless steel 316L tubes to explore the advantages of the presence of water compared to the dry cutting condition. Significant improvements were observed with the presence of water; narrower kerf width, lower surface roughness, less dross attachment, absence of backwall damage and smaller heat affected zone (HAZ). This technique is now fully commercialised by Swisstec, an industrial project partner that manufactures stent cutting machines.The second investigation used the picosecond laser (with 6 ps pulse duration in the UV wavelength range) for cutting nickel titanium alloy (nitinol) and platinum iridium alloy. The main achievement in this study was obtaining dross-free cut as well as clean backwall, which may eliminate the need for extensive post-processing. Picosecond laser cutting of stents is investigated and reported for the first time. The third area of investigation was on the use of a femtosecond laser at 100 fs pulse duration for cutting nickel titanium alloy tubes. It was found that dry cutting degraded the cut quality due to debris and recast formation. For improvement, a water assisted cutting technique was undertaken, for the first time, by submerging the workpiece in a thin layer of water for comparison with the dry cutting condition. The final part of the thesis presents a three dimensional numerical model of the laser micromachining process using smoothed particle hydrodynamics (SPH). The model was used to provide better understanding of the laser beam and material interaction (with static beam) including the penetration depth achieved, phase changes, melt ejection velocity, also recast and spatter formation. Importantly, the model also simulated the wet machining condition by understanding the role of water removing the melt ejected during the process which avoided backwall damages. Results with the fibre laser in millisecond pulse duration were used for the validation purposes. The conclusions reached in this project and recommendations for future work are enclosed.The work has resulted in the publication of 3 journal papers and 2 additional journal paper submissions.
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Mathai, George K. "Abrasive assisted brush deburring of micromilled features with application to a novel surgical device." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47735.
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Burrs severely inhibit the performance and aesthetics in machined parts besides posing a safety risk to the user and manufacturer. Abrasive assisted brushing presents a fast and effective method for deburring these parts but is difficult to control. The dependence of deburring rate on the workpiece material, abrasive grit size, type and rotational speed of the brush is studied. It is found that deburring rate is proportional to initial burr height indicating fracture of the burr at the root. Deburring rate increases with spindle speed and is higher for diamond than SiC. The formation of burrs in micromilling of a thin nickel-titanium alloy (nitinol or NiTi) foil used in implantable biomedical device applications is analyzed as a function of micromilling process parameters such as spindle speed, feed, tool wear, backing material and adhesive used to attach the foil to the backing material. All factors except spindle speed are found to affect burr size. If initial penetration is sufficient to cause the foil to fail in tension, the foil tears with the crack starting closer to the upmilling side and thereby resulting in larger downmilling burrs. If penetration is insufficient, the foil plastically deforms until it tears typically in the middle of the cutter tooth path. A kinematic model that captures this behavior is used to predict burr widths and is verified through experiments. The thesis also presents an investigation of the abrasive impregnated brush deburring process for thin NiTi foils. Models based on Hertzian indentation and fracture mechanics are proposed to predict the rates of indentation and deburring during brushing and are validated using experiments. The predictions of the models are within the experimental variation. Burrs can be removed with this process within 12 minutes for a 6 mm long groove with no more than a micron change in foil thickness. Knowledge of burr formation and deburring is applied to a novel micromilled thin shape memory based NiTi foil device used for the surgical correction of Age-related Macular Degeneration (AMD), a leading cause of blindness in the western world in those over age 50. Burrs on the surface of the structure are used successfully to mechanically constrain and translocate an autograft to replace the diseased RPE-Bruch's membrane under the macula. The shape memory device is analyzed using experiments and simulations.
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Borowiec, Andrzej Haugen Harold Kristen. "Ablation and micromachining of INP with femtosecond laser pulses /." *McMaster only, 2004.
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Marinescu, Cristina. "A surface micromachining fabrication process for aluminium MEMS micromirrors /." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98996.
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This thesis focuses on the implementation of a surface micromachining fabrication process for electrostatically actuated MEMS micromirrors in the McGill University's Nanotools microfabrication laboratory. The process consists in fabricating the devices out of aluminum using photoresist as a sacrificial material. To this effect simple cantilever micromirror structures were designed. They were then modeled and simulated using finite-element analyses from the commercially-available software ANSYS. Finally, in order to validate the results of the new process, the same structures were fabricated out of polysilicon using the Multi-User MEMS Processes (PolyMUMPS) technology available through the Canadian Microelectronics Corporation (CMC). The theoretical and experimental results from the PolyMUMPS micromirrors were compared. The results at low voltages were similar, but they diverged for larger voltages and deflections, with the simulations usually predicting stiffer structures. The characterization of the structures fabricated with the Nanotools process indicated that they remained stuck to the substrate after the release process. Manipulation during testing caused some of them to be partially released, at which point they could be electrostatically actuated. With a better understanding of the aluminum properties and modifications to the original designs, one can fabricate viable aluminum structures using this process. Different areas of improvement as well as future directions for MEMS fabrication in this laboratory were also identified.
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Kota, Nithyanand. "Mechanical Micromachining-Effect of Crystallographic Anisotropy on Machining Forces." Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/70.
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With increased application of mechanical micromachining for creating small features with complex geometries on a broad range of materials, the need for understanding the mechanics of machining at the micro-scale has been recognized. During mechanical micromachining of metals, the tool-workpiece interaction occurs entirely within either a single crystal or a few crystals of the workpiece material. Consequently, the crystallographic properties (e.g., anisotropy) of individual crystals strongly affect the machining response, including micromachining forces and resulting surface finish. Hence, the crystallographic effects that are generally neglected (due to the perceived isotropic nature of the workpiece) in macro-scale machining need to be studied both experimentally and theoretically for gaining a better understanding of the micromachining process.
This thesis aims to understand the effects of crystallographic anisotropy on machining response of face centered cubic metals through physics-based modeling and experimental analysis. The thesis begins with an introduction to micromachining and the associated crystallographic effects on the micromachining response. Subsequently, a literature review is presented and the shortcomings of the available research are identified. In particular, (a) the lack of physically realistic machining force models incorporating the effects of anisotropy, and (b) a necessity for experimental data analyzing the effect of anisotropy over a broad range of machining conditions, are addressed. The work is performed in three stages, with the first two addressing the former, and the last one addressing the latter shortcoming.
First, a simplified machining force model incorporating the effects of anisotropy is developed by combining a plasticity theory and the Merchant's machining model. Since the deformation geometry is unknown a-priori in machining operations, a shear angle determination scheme is necessary before predicting the forces. For a given crystallographic orientation, the model considers the minimization of the total power, including the shearing (plastic) and rake-face friction power, to determine the shear angle and predict the machining forces. The calculation of shearing power is performed using the Bishop and Hill's plasticity theory, thus incorporating the effects of anisotropy. The model is calibrated and validated using the available (but limited) machining force data from the literature. An analysis of the model is also performed to observe the effects of orientation, friction angle and rake angle. The simplified model neglected the effects of hardening and lattice rotation observed during large strain deformation (such as that experienced in machining).
Second, a more physically realistic rate sensitive plasticity-based machining (RSPM) force model is developed to enhance the simplified model by incorporating the hardening and lattice rotation effects. Similar to the simplified model, minimization of the total power (sum of plastic and friction power) is used to determine the shear angle. When calculating the required plastic power, rate-sensitive constitutive equations with hardening and kinematics of single crystal deformation (including lattice rotation) are used. The obtained shear angle is then used to predict the machining forces. The RSPM model is calibrated using the Kriging-algorithm-based SuperEGO (efficient global optimization) code to obtain the five material parameters required. Both the calibration and the subsequent validation are performed using the machining force data available in the literature. Use of the RSPM model improved the match with the experiments over the use of the simplified model. The RSPM model is then used to analyze the effects of orientation, rake angle, coefficient of friction and material properties on machining forces.
Third, to address the need for comprehensive experimental data and analysis, a precision turning and a precision planing apparatus are designed and constructed. Initial machining experiments performed on single crystal and coarse-grained polycrystal aluminum showed that the machining force and surface finish values vary strongly with crystallographic orientations. A measurement of deformation below the cut surface also indicated the importance of measuring the subsurface deformation in future studies. Subsequently, a comprehensive study on the effect of anisotropy over a range of cutting parameters is performed for coarse-grained polycrystal aluminum. In these experiments, in addition to the machining parameters, the effect of subsurface deformation is studied by comparing experimental results from cases with and without cleanup cut. The results from these experiments quantified the effects of crystallographic anisotropy, its interaction with machining parameters and the effect of sub surface deformation on machining forces and surface finish.
The thesis concludes with a discussion of future work covering both modeling and experimental aspects of the research. The future work is divided into near term and long term future work, where the near term work includes planing and plunge turning experiments on single crystals and the extension of the RSPM model to oblique machining. In the longer term, modifications to the machining force model to include the non-homogeneity of the shear zone, and extension of the model to three dimensional machining operations like milling are proposed.
The fundamental contributions of this thesis research are focused on modeling and experimental investigations on single-crystal and coarse-grained materials. Specific contributions include; (1) A simplified machining model that includes the crystallographic anisotropy; (2) A comprehensive rate-sensitive plasticity-based machining force model including hardening and crystal rotation effects and large deformations; (3) An experimental infrastructure, including precision planing and plunge-turning testbeds, to facilitate experimental investigations and model validations in the presence of crystallographic effects; and (4) An experimental understanding on the effects of crystallography when micro-machining single-crystal and coarse-grained materials.
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Prochaska, A. "Silicon micromachining technology for drop-on-demand liquid dispensers." Thesis, Queen's University Belfast, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368466.
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Cho, Seong-Ho 1966. "Laser micromachining of active and passive photonic integrated circuits." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30086.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2004.Includes bibliographical references (leaves 149-158).
This thesis describes the development of advanced laser resonators and applications of laser-induced micromachining for photonic circuit fabrication. Two major advantages of laser-induced micromachining are direct patterning and writing on large areas of substrates at high speed following the exposure of laser light, without using complicated photomask steps. For passive photonic devices fabrication, a novel femtosecond laser with unprecedented low repetition rates of 4 MHz is demonstrated to generate high intensity pulses, as high as 1.25 MW with 100 nJ pulse energies and 80 fs pulse durations directly from this laser resonator, without using any active devices or amplifiers. These high intensity pulses are applied to transparent glass materials to demonstrate micromachining of waveguides, gratings, couplers, and three dimensional waveguides and their beam couplings. Active and passive semiconductor devices can be monolithically integrated by employing high energy laser pulses to locally disorder quantum well regions. The 45 nm bandgap shifts at 1.55 ptm with a standard Q-switched Nd:YAG laser at 535 nm are realized. Finally, unidirectional semiconductor ring lasers for high-density integration are developed as a potential application to photonic integrated circuits. Hybrid semiconductor S-crossover and retro-reflected ring lasers, as prototypes for unidirectional operation, are built and result in up to 21.5 dB and 24.5 dB of counter-mode suppression ratio, respectively, which is in good agreement with theoretical predictions.
by Seong-Ho Cho.
Ph.D.
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Mlcak, Richard. "Electrochemical and photoelectrochemical micromachining of silicon in HF electroytes." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37526.
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Williams, Eleri. "Experimental and theoretical investigations of nanosecond fibre laser micromachining." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/72916/.
Full textAbstract:
Pulsed ytterbium-doped fibre lasers based on a master oscillator power amplifier (MOPA) architecture possess attractive characteristics over their Q-switched diode-pumped solid-state counterparts. These include a relatively low cost of ownership and a flexible operating window with respect to the pulse duration, shape and repetition rate. For micro machining applications, given this inherent large processing window available with respect to the pulse characteristics, the effect of process parameters on particular machining outcomes needs to be investigated. The literature review conducted identified four important gaps in the knowledge surrounding the nanosecond fibre laser machining of materials. These gaps included the optimisation of the nanosecond fibre laser machining during milling operations, with the aim of obtaining both high surface quality and material removal rates, as well as the need for complimentary theoretical and experimental studies on the basic nanosecond laser material interaction for a wide range of engineering materials. In addition, the characterisation of the nanosecond laser machining of bulk metallic glasses, and the investigation of processing conditions leading to crystallisation of their amorphous structure, were identified as knowledge gaps that need to be addressed. The first knowledge gap was the focus of Chapter 3. The particular parameters under investigation in this study were the pulse duration and repetition frequency, the pulse overlap, the scanning strategy and the distance between linear machined tracks when processing aluminium. The results showed that, for each of the pulse durations studied, the specific frequency at which both the highest energy and average power are delivered leads to the maximum material removal rate (MRR) achievable, and to high values of surface roughness. It was also observed that the lowest surface roughness obtained corresponds to a specific frequency range which is common for all pulse durations. Following this, a design of experiments was conducted for a given pulse duration with the aim of identifying an optimum combination of parameters with respect to the attained surface roughness while operating at the frequency resulting in the highest MRR. This optimisation study resulted in a 60% decrease in the achieved surface roughness and also showed that the distance between machined tracks had the highest influence on the surface finish among the parameters considered. In the following chapter, a theoretical model was developed to predict the topographical evolution of the single pulse craters as a result of the time-dependent temperature rise in the processed materials when the laser beam is incident on its surface. In addition to this theoretical study, in an to attempt to understand the laser material interaction on a more fundamental level, single pulse experiments were conducted at varying laser fluence values and pulse durations leading to the formation of single craters on the surface of a number of materials namely, titanium, silicon and silicon carbide. In particular, different pulse lengths were investigated at decreasing values of fluence until no visible effect on the material surface could be observed. Based on this investigation, the fluence corresponding to the ablation threshold for each material at different pulse durations could be found whilst identifying the relationship between the laser processing parameters and the dimensions of the single craters. Scanning Electron Microscopy (SEM) micrographs of the craters were also used to observe phenomena such as melt ejection as a result of varying the process parameters. The experimental results were compared with the theoretical predictions and a good agreement between both set of data was found with respect to the achieved depths and diameters of the craters. The additional knowledge gaps were the focus of Chapter 5. In particular, the characterisation of nanosecond laser machining of a zirconium-based bulk metallic glass (BMG) was conducted using the approach employed in Chapter 4. Similar conclusions were reached with regard to the single pulse material removal behaviour when varying the fluence and pulse duration. In addition, milling of the material with different parametric combinations was implemented to investigate the crystallisation behaviour of the BMG. To complement these experimental tests, the theoretical model reported in Chapter 4 was further developed to predict the heating and cooling rates of the milling process. From this study, it was found that varying the process parameters of the machining of BMG results in a variation in the critical cooling rate (from the melt temperature to the glass transition temperature) which may result in crystallisation of the material.
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Shah, Umer. "Novel RF MEMS Devices Enabled by Three-Dimensional Micromachining." Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-143757.
Full textAbstract:
This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved.QC 20140328
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Chen, Ta-Tung. "Electrochemical micromachining of microdevices from NiTi shape memory alloys." Thesis, Cranfield University, 1999. http://dspace.lib.cranfield.ac.uk/handle/1826/10697.
Full textAbstract:
This thesis aimed to develop a reproducible process for batch-fabricating microdevices
required for MEMS and medical applications, such as micro actuators and stents, from
heat-sensitive NiTi shape memory materials. Electrochemical micromachining was
chosen to carry out this work. This is a non-traditional machining process involving
photoresist processing and electrolytic etching which has received much attention
recently for the processing of thin films. The electrolyte used was a non-aqueous solution
of 5% sulphuric acid in methanol.
The optimum parameters for the photoresist processing were obtained by evaluation of
the thickness and exposure time of the KTFR photoresist coating. A quantitative
investigation of the electrolytic etching of NiTi was carried out to study the influence of
applied voltage, etch time and line width of the test pattern on the etching behaviour, e.g.
etch rate, undercut, depth of etch and etch factor. The anodic polarisation behaviour of
NiTi in 5% sulphuric acid in methanol was investigated under a potentiostatic control
system to establish the optimum etching parameters.
The materials used for the fabrication of micro actuators (required by Forschungszentrum
Karlsruhe, Germany to make a prototype microvalve) were NiTi alloy thin film materials
(sputtered or cold-rolled) with thicknesses ranging from 5 to 46J...lm displaying a one-way
or two-way shape m:emory effect. A variety of optimised designs of micro actuator were
successfully etched electrolytically at 8V. The etch rate was found to depend directly on
the anodic current density. The addition of a third alloying element such as Pd or eu
reduced the anodic current density and maintained a similar etch rate. However it
resulted in the breaking of the films during etching due to the reduction in the ductility of
the material.
The materials for the micro fabrication of stents were 100J...lm thick NiTi sheets. The
problem of non-uniform metal dissolution was observed. However, by adding a
sacrificial etch band as a current 'robber', periodic rotation of the anode and properly
adjusting the electrochemical and geometric parameters, the stents were etched
successfully with improved yield and dimensional accuracy.
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Голобородько, Любов Вікторівна, Любовь Викторовна Голобородько, Liubov Viktorivna Holoborodko, Сергій Сергійович Некрасов, Сергей Сергеевич Некрасов, and Serhii Serhiiovych Nekrasov. "Особенности лезвийной микрообработки." Thesis, Издательство СумГУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26847.
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Fazal, Imran. "Development of a gas microvalve based on fine- and micromachining." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/58024.
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Campbell, Stuart. "Advances in femtosecond pulse laser micromachining and index waveguide inscription." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/67.
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Fanger, David J. (David James). "Variation reduction of a closed-loop precision ceramic micromachining process." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41429.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.Includes bibliographical references (p. 125-132).
by David J. Fanger.
S.M.
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Balsamy, Kamaraj Abishek. "Study of Pulse Electrochemical Micromachining using Cryogenically Treated Tungsten Microtools." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352484381.
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Kleine, Klaus. "Micromachining with single mode fibre lasers for medical device production." Thesis, University of Liverpool, 2009. http://livrepository.liverpool.ac.uk/1295/.
Full textAbstract:
This Thesis is based on several research and development programs to implement the use of fibre lasers in the manufacturing of medical devices like stents and pacemakers. In general, the medical device manufacturing industry has a high demand for laser micromachining applications. The content of the thesis describes laser micromachining of metallic components with single mode fibre lasers. At the started of the research work for this thesis, most laser machining processes used flash-lamp pumped solid-state lasers for those applications. Reliable laser operation and low maintenance are required to meet the yields and up-time requirements for medical devices, such as stent cutting and pacemaker welding. Many lasers for micromachining applications are configured to operate near the diffraction limited beam performance to achieve very small feature sizes. It is challenging to maintain such a laser system performance in a production environment. The fibre laser provides a number of attractive features that could address the needs to maintain high up-time and high yields: • A single mode fibre laser does not require mirror alignment. • Diode pumped fibre lasers reduce maintenance due to eliminating the lamp change. • The compact air-cooled design helps to save expensive clean room space on the production floor. By 2000 the increases in average laser power extended the use of the fibre lasers into industrial applications such as cutting and welding.. The lasers investigated in this thesis generated 50 W to 200 W of laser power, representing the highest power levels commercially available at that time. For the microcutting of medical implants such as stents and guide wires, kerf width and sidewall surface quality are of special interest. Developing processes capable of achieving these criteria was the primary objective of the research described in this thesis. A secondary concern is the heat affected zone created by the laser machining process. Operation conditions to minimize this effect are also discussed in this thesis. Many microwelding applications in the electronics, telecom and medical device industry require smaller and smaller laser joining areas. The quality of a laser welded joint is very dependant on the temporal and spatial parameters of the laser beam. These parameters must be adjusted to match to the processing speed and the materials being welded. Switching continuous wave fibre lasers can achieve the parameters for processes requiring low average power. However the pulse-to-pulse stability can effect the process and has been investigated. Some welding applications require focus spot diameters in the order of 50 μm and pulse energy levels as low as 10 mJ. The fibre laser’s excellent single mode beam quality provides the desired spot size and laser power density. The research summarized in this thesis was performed to prove that fibre lasers are viable tools for micromachining. This thesis compares fibre laser machining results with those using legacy laser processes and describes ways to improve the quality of the fibre laser machining process.
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Jia, Chenping. "Mikromechanische Ultraschallwandler aus Silizium." Doctoral thesis, kostenfrei, 2005. http://archiv.tu-chemnitz.de/pub/2005/0175.
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Suzuki, Norikazu, Akihiro Nakamura, Eiji Shamoto, Kazuhiro Harada, Makoto Matsuo, and Michio Osada. "Ultraprecision Micromachining of Hardened Steel by Applying Ultrasonic Elliptical Vibration Cutting." IEEE, 2003. http://hdl.handle.net/2237/7305.
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Ksouri, Sarah Isabelle [Verfasser], Andreas [Gutachter] Ostendorf, and Martin [Gutachter] Koch. "Optical micromachining tool / Sarah Isabelle Ksouri ; Gutachter: Andreas Ostendorf, Martin Koch." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1129452395/34.
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Lam, Eric W. (Eric Wing-Jing). "Fabrication and material characterization of silver cantilevers via direct surface micromachining." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45613.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
Microelectromechanical Systems (MEMS) rely heavily on the semiconductor industry's manufacturing paradigm. While the standardized process model allows semiconductor chips to benefit from economy of scale and be sold at low prices, MEMS devices use specialized processes and subsequently have to be sold at higher prices. This severely hinders MEMS development because it is not economically feasible to research and develop specialized devices where only small volumes are needed. As such, tools and processes which divorce MEMS fabrication from this paradigm are needed. Using Hewlett-Packard thermal inkjet technology mounted to an X-Y microcontroller stage, we present a mask-less, or direct, surface micromachining process flow with a 250°C thermal budget. The process uses Cabot Corp.'s silver-based conductive ink for the structural layer and PMMA for the sacrificial layer. Several other materials were tested for use as sacrificial inks in addition to PMMA. Silver cantilevers with dimensions of 200x50[mu]m and 200x100[mu]m were fabricated as a demonstration of the process. The silver cantilevers were mechanically characterized by using force-deflection measurements made by a P-10 contact profilometer or a Hysitron nanoindentor. We present findings of 21.9±1.50GPa or 22±1.5GPa for the silver ink's Young's modulus of elasticity, depending on the characterization method. These measurements were consistent with results measured by nanoindentating Cabot silver films. We hypothesize that the film's porosity is the cause of the silver's reduced material properties. Some preliminary data supporting this hypothesis is provided, and potential methods of improving the material properties and the surface micromachining process are discussed.
by Eric W. Lam.
S.M.
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Dvorson, Leonard 1974. "Micromachining and modeling of focused field emitters for flat panel displays." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8215.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001."September 2001."
Includes bibliographical references (p. 120-126).
We present a comprehensive study of field emitter arrays with or without an integrated focus electrode. The former configuration is referred to as field emitter with integrated focus (IFE-FEA) or double-gate FEA (DG-FEA). The main application of IFE-FEA is to improve the resolution of field emission displays (FEDs). We developed the first analytical model of conical field emitters that captures all details of device geometry and produces quantitatively accurate closed-form expressions for the FN coefficients. A novel CMP-based process for making IFE-FEA is presented. We obtained devices with gate and focus apertures of 0.8 and 1.2 gm diameter, respectively, which is 1.5 times smaller than in any previously reported IFE-FEA. Single-gate FEAs whose gate was identical to the lower gate of the IFE-FEA were also fabricated. Their emission current was 100 nA/tip at 45 V; for IFE-FEAs with the gate and focus biased at the same potential (VG=VF) this figure was 100 nA/tip at 42 V, in agreement with the analytical model. It was deduced that the tip radius of curvature (ROC) is 2.4-3.6 nm. Analytical model, numerical simulation, and TEM micrographs all gave tip ROC values in this range. We generalized the FN equation to IFE-FEA and used 4-terminal measurements to determine gate and focus field factors, [3G and 13F. Their ratio was found to vary from 0.15 (emission current independent of focus voltage) to 2.7. We demonstrated via numerical simulation that this ratio is probably determined by the degree of gate shielding of the tip.
(cont.) We studied electron beam collimation with lowering VF at different values of VG. It was observed that the optimal VF is about 0.25VG. Beam collimation was also studied as a function of cathode-anode separation - a novel experiment. From these measurements we deduced horizontal velocity of electrons and determined that it is practically equal to zero when the beam is optimally collimated. Under optimal collimation, diameter of the spot size produced by a 5x5 array with a 40x40 ptm2 footprint on the phosphor screen biased at 5kV and located 15 mm away was at most 50 tm.
by Leonard Dvorson.
Ph.D.
41
Wlodarczyk, Krystian Lukasz. "Surface deformation mechanisms in laser smoothing and micromachining of optical glasses." Thesis, Heriot-Watt University, 2011. http://hdl.handle.net/10399/2430.
Full textAbstract:
The thesis addresses important issues in laser processing of optical glasses, such as fused silica (HPFS®7980 Corning), Borofloat®33, and some selected lead-silicate glasses, when treated by a CO2 laser beam at a 10.6 μm wavelength, using beam diameters of either 1 mm or 50 μm. The investigations were carried out in the melting and vaporization regimes to study laser-induced surface deformations and stresses, and laser smoothing of fused silica etched structures. Novel applications for CO2 laser polishing have been found and some preliminary results are presented. With regard to the surface deformations and stresses, it has been discovered that fused silica behaves differently than other glasses. Deformations in fused silica are observed to be in the form of shallow depressions, as a result of glass densification driven by a fictive temperature increase. These deformations are completely removed by annealing. In raster scanning, the depressions merge to generate surface stress in the range of 10 - 30 MPa, which is largely reduced by annealing. In contrast, CO2 laser radiation of Borofloat®33 produces surface bumps, now driven by both the fictive temperature and an irreversible Marangoni effect. In this case, the bumps are only partially removed by annealing. However, laser machining and polishing conditions for non-cracking treatment of Borofloat®33 have been successfully established, now opening the possibility of using the CO2 laser-based processes for manufacturing micro-optical components. Lead-silicate glasses were found to have strong bumping and complex Marangoni shaping, limiting the prospects for CO2 laser machining of micro-optics. Application of CO2 laser smoothing for surface relaxation of binary gratings and multi-level etched structures has shown that sharp step edges can be relaxed over a distance from submicron to about 30 μm. An optical method based on analysis of light scatter from binary gratings provides an excellent calibration method for CO2 laser polishing. The submicron resolution in smoothing may be applied for fine relaxation of diffractive optics and nanostructures fabricated in fused silica. On the other hand, large scale relaxation of the etched steps provides a promising result to be used for the fabrication of micro-optics, as a viable alternative to the thermal reflow process. A pioneering approach for the rapid prototyping of silica toroidal mirrors has given a high ratio of principle radii of curvature, successfully applied in mode-selective resonator configurations to improve the laser beam quality of planar waveguide lasers.
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Argyrakis, Petros. "Application of micromachining technology for bio-inspired and pressure sensing microsystems." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/11331.
Full textAbstract:
The main body of this thesis focuses on the fabrication of micro-electro-mechanical (MEM) fluidic flow sensor for integration with large scale integration (LSI) neuron circuit and robot. The proposed MEM sensor consists of a) piezoresistive wheatstone bridge circuits consisting of p-type boron doped regions in n-type single crystalline silicon, integrated with patterned metallization, b) silicon cantilever beams that are integrated with the aforementioned piezoresistive wheatstone bridge/metallization circuits, c) out of plane flaps that are integrated at the free end of the silicon cantilever beams. The p-type piezoresistive wheatstone bridge microfeatures are fabricated by boron implantation in n-type single crystalline silicon, forming p-n junction. Patterned metallizations have been integrated with boron doped microfeatures and the circuits have been characterised by electrical probing. The electrical circuits and microcantilever beams have been fabricated on the device layer of silicon on insulator (SOI) wafers, followed by release of the microstructures by bulk micromachining step, where the silicon handle wafer and buried silicon oxide of the SOI wafer beneath the pre-defined cantilever beams has been removed. However, devices fabricated in the first design iteration did not meet the specifications and therefore could not be integrated with the LSI neuron circuit. In an attempt to address this issue, the MEM device has been redesigned to meet the specifications. For the fabrication of out of plane flaps, the plastic deformation magnetic assembly (PDMA) method has been developed. The final part of this thesis focuses on amorphous silicon carbide thin films and investigation of their suitability for application in SiC membrane based pressure sensors. As amorphous SiC films have been found to not be robust, circular membranes of thermally grown polycrystalline 3C-SiC films for application in absolute pressure sensing devices have been fabricated. Boron doped polycrystalline silicon strain gauges in half active wheatstone bridge arrangement have been integrated with SiC released membranes to transduce pressure induced mechanical deformation of the membranes into electrical signal.
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Heath, Daniel. "Digital micromirror devices and femtosecond laser pulses for rapid laser micromachining." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/417275/.
Full textAbstract:
Laser machining techniques are almost ubiquitous in industry for micro- to nanoscale fabrication. It is essential for the advancement of the field that faster, cheaper processes be developed. Enhancements in speed and fidelity of production can be made to both additive and subtractive writing techniques by using Digital Micromirror Devices (DMD), particularly when coupled with femtosecond laser pulses. The objective of this thesis is the demonstration of DMDs used in conjunction with ultrafast laser pulses for both novel and rapid machining applications; primarily image-projection based techniques, using DMDs as dynamic intensity masks, will be used for subtractive patterning, laserinduced transfer, multi-photon polymerisation and centimetre-scale micro-machining. The dynamic nature of the DMD enables its application to the field of multiple exposures, and the centimetre-scale machining is applied to functional biological assays. Adaptive mask techniques are used to enhance the image reproduction achieved, correct for positional errors introduced by translation stages, as well as to attain greyscale intensity control with a DMD in single ultrashort pulses. A new technique for producing digital holograms is developed, and will form the basis of future work. Image projection-based patterning using DMDs as dynamic intensity masks is shown via ablation, multiphoton polymerisation and Laser-Induced Transfer (LIT). Ablation was achieved in a range of materials (including, but not limited to: gold, graphite, diamond, bismuth telluride and antimony telluride, glass, nickel, glucose, and gelatin), with 2 micron resolutions in samples and overall sizes of 1cm2. A multiple exposure technique reduced final structure resolution by 2.7 compared to the diffraction limit possible in a single exposure – from 1m to 370nm on one experimental setup, and from 727nm to 270nm on a second setup. The first demonstration of shaped, solid-phase LIT deposits has been made, both in forward and backward directions of transfer. Adaptive optics techniques have been developed for DMD mask corrections, and have reduced the positional error of samples introduced by translation stages. Greyscale intensity patterns have been projected at samples using the strictly binary-style DMD display technology, and the loss of intensity in high spatial frequencies at the sample has been addressed. A novel method for the generation of binary holograms is introduced, which allows for several additional degrees of control over spatial intensity patterns when using DMDs, such as the effective mask position relative to imaging optics, greyscale control, the formation of images at multiple planes, phase control, and overall lateral shifts of the intensity distribution below a single DMD pixel width.
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Kumsa, Doe Wondwossen. "Theoretical Aspects of Selected Electrochemical Processes: Micromachining, Ohmic Microscopy and Electrocatalysis." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1342191081.
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Lim, Yong Chae. "Development and Demonstration of Femtosecond Laser Micromachining Processes for Biomedical Applications." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313505193.
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Jang, Shyh-Cherng, and 張世誠. "Development of Multifunctional Micromachining Center and Research of Micromachining." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/15371399825742512095.
Full textAbstract:
碩士國立雲林科技大學
機械工程技術研究所
83
If a microhole with diameter less than 50μm is fabricatedby traditional tooling system , the tiny tools are worn out or broken very often , and professional technicians are necessary. Especially ,it is extremel difficult to perform micromachining in some materials , e.g. SUS304 or Tungusten Carbide . The technique of electrodischarge machining E.D.M provides more advantages than traditional machining in this application area. By the heat produced by electrodischarge arc ,localized melting occurs on the surface of working parts.and the andesired mater- ials are removed . E.D.M , has been one of the most important manufaturing techniques for certain materials which are diffi- cult to fabricated . This research has an important contribu- tion in the field of precision micromachining , at the current sytage of progress in Taiwan manufacturing industry . In this research, a multifunctional micromachining center is established , by integrating E.D.M and servo control system , which can operate continuously from the preparation of microtools to the fabrication of micro f elements.The measuring microscope and SEM are used to investigate the parts made in the machine,in order to optimize the the machining conditions . In the machine developed in the laboratory microholes with diameter as 30SYMBOL 109 \f "Symbol"m and depth as 30μm have successfully fabricated . Besides promoting the technological level in the field , this research can extend vanious applications .
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Hsu, Kuo-Yi, and 徐國益. "Fabrication of Si-based Suspending Antenna by Bulk-micromachining and Surface-micromachining Technologies." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39492731827125651042.
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碩士國立中山大學
電機工程學系研究所
98
For the application of 802.11a wireless communication system, this thesis aims to develop a novel suspending antenna with periodic structures to reduce electromagnetic wave from substrate using electrochemical deposition, surface micromachining and bulk micromachining technologies. This research presents two particular structures to increase the bandwidth and the radiation efficient and to reduce the return loss of the antenna, including: (i) the optimum design of periodic structures to restrain electromagnetic wave from substrate and to reduce the return loss of the antenna. To reduce the effective dielectric constant of the silicon substrate and to increase the bandwidth of the antenna, anisotropic etching the backside of the silicon substrate formed regular cavities using bulk-micromachining technology, (ii) to utilize a suspending structure to reduce the power loss through the substrate and to confirm the result using high frequency simulator. The implemented Si-based suspending antenna with periodic structures were characterized by a commercial network analyzer under 1~8 GHz testing frequency range. All the bandwidth and the return loss of the antenna proposed in this thesis are extracted by the commercial simulation software. Based on the measurement results, the center frequency is equal to 4.85 GHz, the return loss is around -35.5 dB and the bandwidth is equal to 42.9% (3.75~5.8 GHz). Eventually, this thesis successfully develops a low-loss and broadband antenna with novel structures using high frequency simulator and MEMS technologies for 802.11a wireless communication system.
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Mayyas, Mohammad A. "Methodologies for automated microassembly /." 2007. http://hdl.handle.net/10106/900.
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翁炳國. "Silicon micromachining technique and applications." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/05055598641774567988.
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Liu, Chia-Hung, and 劉嘉洪. "Surface Micromachining Capacitive Ultrasonic Transducers." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/35783394327397040079.
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博士國立臺灣海洋大學
系統工程暨造船學系
96
This thesis presents the primary design, fabrication and measurement of the Capacitive Micromachined Ultrasonic Transducer (cMUT). Previous studies have investigated the bias effect, vibration behavior of the cMUT and optimum size of the top electrode; however, these studies did not analyze combining the resonant frequency drop of the cMUT with the effects of bias and added mass. In this thesis, reasonable boundary conditions for solving the modified Mason model, acoustic radiation impedance of medium, bias effect and added mass effect of the top electrode are all utilized to derive an accurate equivalent circuit for cMUT design. Computer simulations of the cMUT are performed and several numerical examples are computed. The modified cMUT model predicts behaviors of the cMUT’s membrane with increased accuracy, especially on the resonant frequency. The cMUT fabrication uses the full surface micromachining techniques of the Micro Electro Mechanical System (MEMS), which are compatible with integrated circuit fabrication processes, have been further developed over the recent decade. These techniques include Low Pressure Chemical Vapor Deposition (LPCVD), photolithography, Reactive Ion Etching System (RIE) dry etching, sacrificial layer wet etching, metal thermal evaporation coating and Plasma-Enhanced Chemical Vapor Deposition (PECVD). Several important issues regarding fabrication process that the bottom electrode, insulating layer, sacrificial layer, etching hole, etching channel, membrane particular, and metal electrode are discussed for optimizing the performance of the cMUT. Finally, the input impedance of the cMUT is measured and the measured result agrees with the theoretical prediction having simply supported membrane boundary conditions. The received signal has a 35 dB signal-to-noise ratio indicating that practical applications of the immersion cMUT are feasible and that the radiation pattern measurement of the cMUT array has good beamforming characteristics for underwater imaging.