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1
Fisher, Brian. "Surface Acoustic Wave (SAW) Cryogenic Liquid and Hydrogen Gas Sensors". Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5208.
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This research was born from NASA Kennedy Space Center's (KSC) need for passive, wireless and individually distinguishable cryogenic liquid and H2 gas sensors in various facilities. The risks of catastrophic accidents, associated with the storage and use of cryogenic fluids may be minimized by constant monitoring. Accidents involving the release of H2 gas or LH2 were responsible for 81% of total accidents in the aerospace industry. These problems may be mitigated by the implementation of a passive (or low-power), wireless, gas detection system, which continuously monitors multiple nodes and reports temperature and H2 gas presence. Passive, wireless, cryogenic liquid level and hydrogen (H2) gas sensors were developed on a platform technology called Orthogonal Frequency Coded (OFC) surface acoustic wave (SAW) radio frequency identification (RFID) tag sensors. The OFC-SAW was shown to be mechanically resistant to failure due to thermal shock from repeated cycles between room to liquid nitrogen temperature. This suggests that these tags are ideal for integration into cryogenic Dewar environments for the purposes of cryogenic liquid level detection. Three OFC-SAW H2 gas sensors were simultaneously wirelessly interrogated while being exposed to various flow rates of H2 gas. Rapid H2 detection was achieved for flow rates as low as 1ccm of a 2% H2, 98% N2 mixture. A novel method and theory to extract the electrical and mechanical properties of a semiconducting and high conductivity thin-film using SAW amplitude and velocity dispersion measurements were also developed. The SAW device was shown to be a useful tool in analysis and characterization of ultrathin and thin films and physical phenomena such as gas adsorption and desorption mechanisms.?Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
2
Wilson, William. "Multifunctional Orthogonally-Frequency-Coded Saw Strain Sensor". VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3157.
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A multifunctional strain sensor based on Surface Acoustic Wave (SAW) Orthogonal Frequency Coding (OFC) technology on a Langasite substrate has been investigated. Second order transmission matrix models have been developed and verified. A new parameterizable library of SAW components was created to automate the layout process. Using these new tools, a SAW strain sensor with OFC reflectors was designed, fabricated and tested. The Langasite coefficients of velocity for strain (γS = 1.699) and Temperature (γT = 2.562) were experimentally determined. The strain and temperature characterization of this strain sensor, along with the coefficients of velocity, have been used to demonstrate both the ability to sense strain and the capability for temperature compensation. The temperature-compensated SAW OFC strain sensor has been used to detect anomalous strain conditions that are indicators of fastener failures during structural health monitoring of aircraft panels with and without noise on a NASA fastener failure test stand. The changes in strain that are associated with single fastener failures were measured up to a distance of 80 cm between the sensor and the removed fastener. The SAW OFC strain sensor was demonstrated to act as an impact sensor with and without noise on the fastener failure test stand. The average measured signal to noise ratio (SNR) of 50, is comparable to the 29.1 SNR of an acoustic emission sensor. The simultaneous use of a high pass filter for impact detection, while a low pass filter is used for strain or fastener failure, demonstrates the multifunctional capabilities of the SAW OFC sensor to act as both as a fastener failure detector and as an impact detector.
3
Friedlander, Jeffrey B. "Wireless Strain Measurement with Surface Acoustic Wave Sensors". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306874020.
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Parmar, Biren Jagadish. "Development Of Point-Contact Surface Acoustic Wave Based Sensor System". Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/279.
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Surface Acoustic Waves (SAW) fall under a special category of elastic waves that need a material medium to propagate. The energy of these waves is confined to a limited depth below the surface over which they propagate, and their amplitudes decay with increasing depth. As a consequence of their being a surface phenomenon, they are easily accessible for transduction. Due to this reason, a lot of research has been carried out in the area, which has resulted in two very popular applications of SAW - SAW devices and in Non-Destructive Testing and Evaluation.
A major restriction of SAW devices is that the SAW need a piezoelectric medium for generation, propagation and reception. This thesis reports the attempt made to overcome this restriction and utilize the SAW on non-piezoelectric substrates for sensing capabilities. The velocity of the SAW is known to be dependent purely on the material properties, specifically the elastic constants and material density. This dependence is the motivation for the sensor system developed in the present work.
Information on the survey of the methods suitable for the generation and reception of SAW on non-piezoelectric substrates has been included in the thesis. This is followed by the theoretical and practical details of the method chosen for the present work - the point source/point receiver method. Advantages of this method include a simple and inexpensive fabrication procedure, easy customizability and the absence of restrictions due to directivity of the SAW generated. The transducers consist of a conically shaped PZT element attached to a backing material. When the piezoelectric material on the transmitter side is electrically excited, they undergo mechanical oscillations. When coupled to the surface of a solid, the oscillations are transferred onto the solid, which then acts as a point source for SAW. At the receiver, placed at a distance from the source on the same side, the received mechanical oscillations are converted into an electrical signal as a consequence of the direct piezoelectric effect. The details of the fabrication and preliminary trials conducted on metallic as well as non-metallic samples are given.
Various applications have been envisaged for this relatively simple sensor system. One of them is in the field of pressure sensing. Experiments have been carried out to employ the acoustoelastic property of a flexible diaphragm made of silicone rubber sheet to measure pressure. The diaphragm, when exposed to a pressure on one side, experiences a varying strain field on the surface. The velocity of SAW generated on the stressed surface varies in accordance with the applied stress, and the consequent strain field generated. To verify the acoustoelastic phenomenon in silicone rubber, SAW velocities have been measured in longitudinal and transverse directions with respect to that of the applied tensile strain. Similar measurements are carried out with a pressure variant inducing the strain. The non-invasive nature of this setup lends it to be used for in situ measurement of pressure.
The second application is in the field of elastography. Traditional methods of diagnosis to detect the presence of sub-epidermal lesions, some tumors of the breast, liver and prostate, intensity of skin irritation etc have been mainly by palpation. The sensor system developed in this work enables to overcome the restrictive usage and occasional failure to detect minute abnormal symptoms. In vitro trials have been conducted on tissue phantoms made out of poly (vinyl alcohol) (PVA-C) samples of varying stiffnesses. The results obtained and a discussion on the same are presented.
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Ippolito, Samuel James y sipp@ieee org. "Investigation of Multilayered Surface Acoustic Wave Devices for Gas Sensing Applications: Employing piezoelectric intermediate and nanocrystalline metal oxide sensitive layers". RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070227.123029.
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In this thesis, the author proposes and develops novel multilayered Surface Acoustic Wave (SAW) devices with unique attributes for gas sensing applications. The design, simulation, fabrication and gas sensing performance of three multilayered SAW structures has been undertaken. The investigated structures are based on two substrates having high electromechanical coupling coefficient: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), with a piezoelectric zinc oxide (ZnO) intermediate layer. Sensitivity towards target gas analytes is provided by thin film indium oxide (InOx) or tungsten trioxide (WO3). The high performance of the gas sensors is achieved by adjusting the intermediate ZnO layer thickness. Sensitivity calculations, undertaken with perturbation theory illustrate how the intermediate ZnO layer can be employed to modify the velocity-permittivity product of the supported SAW modes, resulting in highly sensitive conductometric SAW gas sensors. The work contained within this thesis addresses a broad spectrum of issues relating to multilayered SAW gas sensors. Topics include finite-element modelling, perturbation theory, micro-fabrication, metal oxide deposition, material characterisation and experiential evaluation of the layered SAW sensors towards nitrogen dioxide (NO2), hydrogen (H2) and ethanol gas phase analytes. The development of two-dimensional (2D) and three dimensional (3D) finite-element models provides a deep insight and understanding of acoustic wave propagation in layered anisotropic media, whilst also illustrating that the entire surface of the device can and should be used as the active sensing area. Additionally, the unique and distinctive surface morphology of the layered structures are examined by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The crystalline structure and orientation of the ZnO and WO3 layers are also examined by X-ray Diffraction Spectroscopy (XRD). The novel multilayered SAW structures a re shown to be highly sensitive, capable of sensing NO2 and ethanol concentration levels in the parts-per-billion and parts-per-million range, respectively, and H2 concentrations below 1.00% in air. The addition of platinum or gold catalyst activator layers on the WO3 sensitive layer is shown to improve sensitivity and dynamic performance, with response magnitudes up to 50 times larger than bare WO3. The gas sensing performance of the investigated structures provide strong evidence that high sensitivity can be achieved utilising multilayered SAW structures for conductometric gas sensing applications.
6
Srinivasan, Krishnan. "Nanomaterial Sensing Layer Based Surface Acoustic Wave Hydrogen Sensors". Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/873.
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This thesis addresses the design and use of suitable nanomaterials and surface acoustic wave sensors for hydrogen detection and sensing.
Nanotechnology is aimed at design and synthesis of novel nanoscale materials. These materials could find uses in the design of optical, biomedical and electronic devices. One such example of a nanoscale biological system is a virus. Viruses have been given a lot of attention for assembly of nanoelectronic materials. The tobacco mosaic virus (TMV) used in this research represents an inexpensive and renewable biotemplate that can be easily functionalized for the synthesis of nanomaterials. Strains of this virus have been previously coated with metals, silica or semiconductor materials with potential applications in the assembly of nanostructures and nanoelectronic circuits. Carbon nanotubes are another set of well-characterized nanoscale materials which have been widely investigated to put their physical and chemical properties to use in design of transistors, gas sensors, hydrogen storage cells, etc. Palladium is a well-known material for detection of hydrogen. The processes of absorption and desorption are known to be reversible and are known to produce changes in density, elastic properties and conductivity of the film. Despite these advantages, palladium films are known to suffer from problems of peeling and cracking in hydrogen sensor applications. They are also required to be cycled for a few times with hydrogen before they give reproducible responses.
The work presented in this thesis, takes concepts from previous hydrogen sensing techniques and applies them to two nanoengineered particles (Pd coated TMV and Pd coated SWNTs) as SAW resonator sensing materials. Possible sensing enhancements to be gained by using these nanomaterial sensing layers are investigated. SAW resonators were coated with these two different nano-structured sensing layers (Pd-TMV and Pd-SWNT) which produced differently useful hydrogen sensor responses. The Pd-TMV coated resonator responded to hydrogen with nearly constant increases in frequency as compared to the Pd-SWNT coated device, which responded with concentration-dependent decreases in frequency of greater magnitude upon hydrogen exposure. The former behavior is more associated with acousto-electric phenomena in SAW devices and the later with mass loading. The 99% response times were 30-40 seconds for the Pd-TMV sensing layer and approximately 150 seconds for the Pd-SWNT layer. Both the films showed high robustness and reversibility at room temperature. When the Pd film was exposed to hydrogen it was observed that it produced decreases in frequency to hydrogen challenges, conforming to mass loading effect. It was also observed that the Pd film started degrading with repeated exposure to hydrogen, with shifts after each exposure going smaller and smaller.
7
Manoosingh, Lane Leslie. "Design of a chemical agent detector based on polymer coated surface acoustic wave (SAW) resonator technology". [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000412.
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Fechete, Alexandru Constantin y e54372@ems rmit edu au. "Layered Surface Acoustic Wave Based Gas Sensors Utilising Nanostructured Indium Oxide Thin Layer". RMIT University. Electrical and Computer Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091105.141111.
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Planar two-dimensional (2-D) nanostructured indium oxide (InOx) and one-dimensional (1-D) tin oxide (SnO2) semiconductor metal-oxide layers have been utilised for gas sensing applications. Novel layered Surface Acoustic Wave (SAW) based sensors were developed consisting of InOx/SiOxNy/36°YXLiTaO3, InOx/SiNx/SiO2/36°YXLiTaO3 and InOx/SiNx/36°YXLiTaO3 The 1 µm intermediate layers of silicon oxynitride (SiOxNy), silicon nitride (SiNx) and SiO2/SiNx matrix were deposited on lithium tantalate (36°YXLiTaO3) substrates by r.f. magnetron sputtering, electron-beam evaporation and plasma enhanced chemical vapour deposition (PECVD) techniques, respectively. As a gas sensitive layer, a 100 nm thin layer of InOx was deposited on the intermediate layers by r.f. magnetron sputtering. The targeted gases were ozone (O3) and hydrogen (H2). An intermediate layer has multiple functions: protective role for the interdigital transducers' electrodes as well as an isolating effect from InOx sensing layer, thereby improving the sensor performance. The developed SAW sensors' exhibited high response magnitudes with repeatable, reversible and stable responses towards O3 and H2. They are capable of sensing concentrations as low as 20 parts-per-billion for O3 and 600 parts-per-million for H2. Additionally a conductometric type novel sensing structure of SnO2/36°YX LiTaO3 was also developed by depositing a thin layer of SnO2 nanorods by PECVD. The gas sensing performance exhibited repeatable, reversible, stable responses towards NO2 and CO. The surface morphology, crystalline structure and preferred orientation of the deposited layers were investigated by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A polycrystalline, oxygen deficient non-stoichiometric InOx with grain sizes of 20-40 nm was revealed. The 1-D nanostructures were characterised by Transmission Electron Microscopy (TEM) showing nanorods with needle-like shape , diameters of 10-20 nm a t the top and 30-40 nm at the base as well as a preferential growth orientation of [ ] on the LiTaO3 substrate. The developed sensors are promising for O3, H2 and CO sensing.
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Onen, Onursal. "Analytical Modeling, Perturbation Analysis and Experimental Characterization of Guided Surface Acoustic Wave Sensors". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4555.
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In this dissertation, guided surface acoustic wave sensors were investigated theoretically and experimentally in detail for immunosensing applications. Shear horizontal polarized guided surface acoustic wave propagation for mass loading sensing applications was modeled using analytical modeling and characterized by perturbation analysis. The model verification was performed experimentally and a surface acoustic wave immunosensor case study was presented. The results of the immunosensing were also investigated using the perturbation analysis.
Guided surface acoustic wave propagation problem was investigated in detail for gravimetric (or mass loading) guided wave sensors, more specifically for immunosensors. The analytical model was developed for multilayer systems taking viscoelasticity into account. The closed form algebraic solutions were obtained by applying appropriate boundary conditions. A numerical approach was used to solve dispersion equation. Detailed parametric investigation of dispersion curves was conducted using typical substrate materials and guiding layers. Substrate types of ST-cut quartz, 41° YX lithium Niobate and 36° YX lithium tantalate with guiding layers of silicon dioxide, metals (chromium and gold), and polymers (Parylene-C and SU-8) were investigated. The effects of frequency and degree of viscoelasticity were also studied. The results showed that frequency only has effect on thickness with same shaped dispersion curves. Dispersion curves were found to be unaffected by the degree of viscoelasticity. It was also observed that when there was a large shear velocity difference between substrate and guiding layer, a transition region with a gradual decrease in phase velocity was obtained. However, when shear velocities were close, a smooth transition was observed. Furthermore, it was observed that, large density differences between substrate and guiding layer resulted in sharp and with nearly constant slope transition. Smooth transition was observed for the cases of minimal density differences. Experimental verification of the model was done using multi-layer photoresists. It was shown that with modifications, the model was able to represent the cases studied.
Perturbation equations were developed with first order approximations by relating the slope of the dispersion curves with sensitivity. The equations were used to investigate the sensitivity for material selection (substrate, guiding layer, and mass perturbing layer) and degree of viscoelasticity. The investigations showed that the sensitivity was increased by using guiding layers with lower shear velocities and densities. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold and chrome. The perturbation investigations were also extended to viscoelasticity and to protein layers for immunosensing applications. It was observed that, viscous behavior resulted in slightly higher sensitivity; and sensitivity to protein layers was very close to sensitivity for polymers. The optimum case is found to be ST-cut quartz with Parylene-C guiding layer for protein layer sensing.
Finally, an immunosensing case study was presented for selective capture of protein B-cell lymphoma 2 (Bcl-2), which is elevated in many cancer types including ovarian cancer. The immunosensor was designed, fabricated, and experimentally characterized. An application-specific surface functionalization scheme with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 was developed and applied. Characterization was done using the oscillation frequency shift of with sensor used as the feedback element of an oscillator circuit. Detection of Bcl-2 with target sensitivity of 0.5 ng/ml from buffer solutions was presented. A linear relation between frequency shift and Bcl-2 concentration was observed. The selectivity was shown with experiments by introducing another protein, in addition to Bcl-2, to the buffer. It was seen that similar detection performance of Bcl-2 was obtained even with presence of control protein in very high concentrations. The results were also analyzed with perturbation equations.
10
Westafer, Ryan S. "Investigation of phononic crystals for dispersive surface acoustic wave ozone sensors". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41165.
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The object of this research was to investigate dispersion in surface phononic crystals (PnCs) for application to a newly developed passive surface acoustic wave (SAW) ozone sensor. Frequency band gaps and slow sound already have been reported for PnC lattice structures. Such engineered structures are often advertised to reduce loss, increase sensitivity, and reduce device size. However, these advances have not yet been realized in the context of surface acoustic wave sensors. In early work, we computed SAW dispersion in patterned surface structures and we confirmed that our finite element computations of SAW dispersion in thin films and in one dimensional surface PnC structures agree with experimental results obtained by laser probe techniques. We analyzed the computations to guide device design in terms of sensitivity and joint spectral operating point. Next we conducted simulations and experiments to determine sensitivity and limit of detection for more conventional dispersive SAW devices and PnC sensors. Finally, we conducted extensive ozone detection trials on passive reflection mode SAW devices, using distinct components of the time dispersed response to compensate for the effect of temperature. The experimental work revealed that the devices may be used for dosimetry applications over periods of several days.
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Cular, Stefan. "Designs and applications of surface acoustic wave sensors for biological and chemical sensing and sample handling". [Tampa, Fla.] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002335.
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Rocha, Gaso María Isabel. "Analysis, implementation and validation of a Love mode surface acoustic wave device for its application as sensor of biological processes in liquid media". Doctoral thesis, Editorial Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/32492.
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En las últimas dos décadas, han surgido diferentes tecnologías acústicas
para aplicaciones biosensoras como alternativas a tecnologías de detección
bien establecidas ¿acústicas o ópticas¿ como son la Microbalanza de Cuarzo
(QCM, por sus siglas en inglés) y la Resonancia de Plasmón de Superficie
(SPR, de sus siglas en inglés). En la primera parte de este documento se
revisan dichas tecnologías alternativas para aplicaciones en medio líquido.
Como resultado de esta revisión, se determina que los dispositivos de onda
acústica superficial Love (LW, de sus siglas en inglés) son los más
prometedores y viables para conseguir el principal objetivo de esta Tesis,
que es establecer una comparativa en las mismas condiciones entre
inmnosensores desarrollados con la tecnología seleccionada en esta tesis y
los inmunosensores desarrollados con QCMs de Alta Frecuencia
Fundamental (HFF-QCM, por sus siglas en inglés). Después de esta revisión
se presenta el estado del arte de los dispositivos LW en su aplicación como
biosensores, así como una discusión de las tendencias y retos actuales de
este tipo de sensores. Posteriormente se reúne la información más
actualizada sobre aspectos de diseño, principios de operación y modelado de
estos sensores. Algunos aspectos de diseño son estudiados y probados para
establecer el diseño final de los dispositivos LW. Previamente a su
fabricación, también se realizan simulaciones para modelar el
comportamiento del dispositivo elegido previamente a su fabricación.
Posteriormente, se describe la fabricación del dispositivo así como la celda
de flujo diseñada para trabajar con el dispositivo en medios líquidos.
Adicionalmente, un sistema electrónico de caracterización, previamente
validado para sensores QCM, se adapta para sensores LW. Como resultados,
se valida el sistema electrónico para caracterizar los sensores LW fabricados
y montados en la celda de flujo y, finalmente, se desarrolla un inmunosensor
para la detección del pesticida carbaril que se compara con otras tecnologías
inmunosensoras.In the last two decades, different acoustic technologies for biosensors applications have emerged as promising alternatives to other better established detection technologies ¿ acoustic or optic ones- such as traditional Quartz Crystal Microbalance (QCM) and Surface Plasmon Resonance (SPR). The alternative acoustic technologies for in liquid measurements are reviewed in this manuscript. Surface Acoustic Wave (SAW) Love Mode or Love Wave (LW) sensors are determined to be the most promising and viable option to work with for achieving the main aim of this Thesis. Such aim is the development of a LW immunosensor for its comparison with the same application based on High Fundamental Frequency-QCM (HFF-QCM) sensors and under the same conditions. Consequently, the state-of-the-art of LW devices for biosensing is provided and a discussion about the current trends and future challenges of these sensors is presented. In order to start working with suitable LW devices, upto- date information regarding the design aspects, operation principles and modeling of such devices is gathered. Some design aspects are explored and tested to establish the design of the final LW device. Different simulations for modeling the chosen device behavior are carried out before its fabrication. Later, the device fabrication is described. Next, to start working with the fabricated device in liquid media, a flow cell is designed and implemented. In addition, an electronic characterization system, previously validated for QCM sensors, is adapted and tested for the fabricated LW device. As results, the adapted electronic characterization system is validated for LW devices mounted in the fabricated flow cell and, finally, a LW-based immunosensor for the determination of carbaryl pesticide was developed and compared with other immunosensor technologies.
Rocha Gaso, MI. (2013). Analysis, implementation and validation of a Love mode surface acoustic wave device for its application as sensor of biological processes in liquid media [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32492
Alfresco
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Puccio, Derek. "DESIGN, ANALYSIS AND IMPLEMENTATION OF ORTHOGONAL FREQUENCY CODING IN SAW DEVICES USED FOR SPREAD SPECTRUM TAGS AND SENSORS". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2836.
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SAW based sensors can offer wireless, passive operation in numerous environments and various device embodiments are employed for retrieval of the sensed data information. Single sensor systems can typically use a single carrier frequency and a simple device embodiment, since tagging is not required. In a multi-sensor environment, it is necessary to both identify the sensor and retrieve the sensed information. This dissertation presents the concept of orthogonal frequency coding (OFC) for applications to SAW sensor technology. OFC offers all advantages inherent to spread spectrum communications including enhanced processing gain and lower interrogation power spectral density (PSD). It is shown that the time ambiguity in the OFC compressed pulse is significantly reduced as compared with a single frequency tag having the same code length and additional coding can be added using a pseudo-noise (PN) sequence. The OFC approach is general and should be applicable to many differing SAW sensors for temperature, pressure, liquid, gases, etc. Device embodiments are shown and a potential transceiver is described. Measured device results are presented and compared with COM model predictions to demonstrate performance. Devices are then used in computer simulations of the proposed transceiver design and the results of an OFC sensor system are discussed.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
14
Hotel, Olivier. "Algorithmes, méthodes et modèles pour l'application des capteurs à ondes acoustiques de surface à la reconnaissance de signatures de composés chimiques". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066565/document.
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Récemment, les systèmes multicapteurs ont trouvé de nombreuses applications dans des domaines tels que l’industrie agroalimentaire, l’environnement, la médecine et la défense. Parmi les technologies existantes, les capteurs à ondes acoustiques de surface sont l’une des plusprometteuses et fait l’objet de nombreuses recherches. Les travaux décrits dans ce manuscrit concernent le développement d’algorithmes permettant la reconnaissance de composés chimiques et l’estimation de leur concentration. Cette étude décrit une méthode permettant d’estimer les paramètres des phénomènes de transduction. L’intérêt de ces derniers est mis en évidence expérimentalement dans des applications consistant à identifier des toxiques chimiques, des capsules de café contrefaites et à détecter la présence de DMMP et de 4-NT en présence d’interférentsRecently, gas sensor arrays have found numerous applications in areas such as the food, the environment, the medicine and the defenseindustries. Among the existing technologies, the surface acoustic wave technology is one of the most promising and has been the subject of abundant research. The work described in this manuscript concerns the development of algorithms allowing the recognition of chemical compounds and the estimation of their concentration. This study describes a method for estimating the parameters of transduction phenomena. Their interest is demonstrated experimentally in applications consisting in identifying toxic chemical compounds, counterfeit coffee capsules and in detecting the presence of DMMP and 4-NT in the presence of interfering compounds
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Maxwell, Andrew Douglas. "A CO2 measurement system for low-cost applications using chemical transduction". University of Southern Queensland, Faculty of Engineering and Surveying, 2002. http://eprints.usq.edu.au/archive/00001468/.
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It is demonstrated that by using a miniature chemical reaction vessel under adaptive mechatronic control, it is possible to design and construct a low-cost carbon dioxide measurement system. With further development such a system would be potentially suitable for low-cost commercial application, in particular as sacrificial, single-mission instrumentation packages in horticultural cargo monitoring. Current instrumentation systems for carbon dioxide (CO2) gas measurement are reviewed and their limitations with respect to low cost commercial applications determined. These utilise technology intended for laboratory measurements. In particular the optical energy absorbance of CO2 in the infra-red electromagnetic spectrum. These systems require large optical paths (typically 10cm) in order to measure small CO2 concentrations. This in turn has a large impact on the physical size of the sensing system. Of the many applications requiring online CO2 sensing packages (such as medical, petroleum, environmental and water treatment)the horticultural industry is the primary focus for this research. CO2 sensing systems are primarily used in horticulture to monitor the produce environment and help extend storage time. For these applications CO2 concentrations are typically low (in the range 0 to 1%) and the paramount need is for low-cost (and possibly disposable) sensing packages. The basis of the measurement technique is the use of bulk (but small volume) aqueous chemical reaction under mechatronic control. Unlike thin film technologies where very thin membranes are passively exposed to the gaseous sample, here a small volume (approximately 2mL) of simple and very cheap liquid chemical indicator (calcium hydroxide solution) is used to produce an opaque precipitate. CO2 concentration is then assessed by low-cost optical attenuation measurements of the developing opacity of the solution. The instrumentation package comprises pumps, flowmeter, reaction cell and infra-red optics for the turbidity measurement, plus reagent and waste vessels, pipelines and electronics. During each measurement cycle, the reaction cell is flushed, with fresh chemical indicator and a sample of gas admitted. The indicator and the sample gas are then vigorously mixed and the change in the indicators optical properties measured at regular intervals. An embedded 8-bit microcontroller performs the necessary analysis to deduce the CO2 concentration (as percentage by volume) for the sample gas by reference to one or more of five ``Time-To-Threshold'' calibration models. These models evaluate the trend in turbidity development as precipitate is formed. First and second prototypes of the measurement system have been constructed and their (low-cost) components and overall performance evaluated, the first a `proof-of-concept' and the second to investigate methodology shortcomings. As a result the design of a third prototype is outlined. The measurement systems have been shown to work adequately well within expected limitations, resulting in a usable low-cost measurement technique. The current prototypes have a useful range of at least 5% to 100% CO2 with a discrimination of typically +-6%. Deficiencies, particularly performance at low concentrations, are identified and potential enhancements for future prototypes proposed.
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Kozlovski, Nikolai. "Passive wireless SAW sensors with new and novel reflector structures design and applications". Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4954.
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Surface acoustic wave (SAW) devices are a solution for today's ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like refector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi-transducer approaches yield devices with adjustable input impedances and enhanced collision properties for OFC TDM SAW sensor devices. Each track-transducer is designed for optimum performance for loss, coding, and chip reflectivity. Experimental results and theoretical predictions confirm a constant Q for SAW transducers for a given operational bandwidth, independent of device and transducer embodiment. Results on these new NLR SAW structures and devices along with a new novel 915 MHz transceiver based on a software radio approach was designed, built, and analyzed. Passive wireless SAW temperature sensors were interrogated and demodulated in a spread spectrum correlator system using a new adaptive filter. The first-ever SAW OFC four-sensor operation was demonstrated at a distance of 1 meter and a single sensor was shown to operate up to 3 meters. Comments on future work and directions are also presented.ID: 029809964; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 161-166).
Ph.D.
Doctorate
Electrical and Computer Engineering
Engineering and Computer Science
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Saldanha, Nancy. "Modeling, design and fabrication of orthogonal and psuedo-orthogonal frequency coded SAW wireless spread spectrum RFID sensor tags". Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5025.
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Surface acoustic wave (SAW) sensors offer a wireless, passive sensor solution for use in numerous environments where wired sensing can be expensive and infeasible. Single carrier frequency SAW sensor embodiments such as delay lines, and resonators have been used in single sensor environments where sensor identification is not a necessity. The orthogonal frequency coded (OFC) SAW sensor tag embodiment developed at UCF uses a spread spectrum approach that allows interrogation in a multi-sensor environment and provides simultaneous sensing and sensor identification. The SAW device is encoded via proper design of multiple Bragg reflectors at differing frequencies. To enable accurate device design, a model to predict reflectivity over a wide range of electrode metallization ratios and metal thicknesses has been developed and implemented in a coupling of modes (COM) model. The high coupling coefficient, reflectivity and temperature coefficient of delay (TCD) of YZ LiNbO[sub3] makes it an ideal substrate material for a temperature sensor, and the reflectivity model has been developed and verified for this substrate. A new concept of pseudo-orthogonal frequency coded (POFC) SAW sensor tags has been investigated, and with proper design, the POFC SAW reduces device insertion loss and fractional bandwidth compared to OFC. OFC and POFC sensor devices have been fabricated at 250 MHz and 915 MHz using fundamental operation, and 500 MHz and 1.6 GHz using second harmonic operation. Measured device results are shown and compared with the COM simulations using the enhanced reflectivity model. Additionally, the first OFC devices at 1.05 GHz were fabricated on 128[superscript o] YX LiNbO[sub3] to explore feasibility of the material for future use in OFC sensor applications. Devices at 915 MHz have been fabricated on YZ LiNbO[sub3] and integrated with an antenna, and have then been used in a transceiver system built by Mnemonics, Inc. to wirelessly sense temperature.; The first experimental wireless POFC SAW sensor device results and predictions will be presented.ID: 029809657; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 148-152).
Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
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Tortissier, Grégory. "Étude et développement d’une plateforme de détection chimique à ondes acoustiques de surface pour environnement sévère haute température". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13859/document.
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Ces travaux ont donc visé le développement d’une plateforme complète de détection de gaz pour environnement sévère haute température. Cette plateforme intègre un dispositif à ondes acoustiques de surface sur substrat Langasite, une résistance chauffante, une couche sensible inorganique nanostructurée et est placée dans une enceinte hermétique. Des températures de l’ordre de 450°C ont été atteintes et des tests de cyclages ont démontré un fonctionnement en accord avec les modèles théoriques et une reproductibilité des mesures. Des tests de détection de composés organiques volatils (éthanol et toluène) ont mis en avant des seuils de détection de l'ordre de quelques ppmMeasuring pollutants concentrations in gas and vapors emissions are important environmental issues. This work presents a stand-alone portable device for high temperature assessment. The system includes a Langasite (LGS) acoustic sensor, a ceramic heater and a platform with RF connections for remote in-situ measurements. The packaging consists in a hermetic stainless steel cell which enables safe gas detection. In situ temperature measurements have been achieved and the thermal behavior was successfully investigated in the temperature range 25-450°C. The designed cell highlights good agreement with theoretical models and reproducibility of the measures. Volatile organic compounds exposures have been investigated and promising ppm level detections have been obtained
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Tuncay, Orbay. "Wireless Strain Gauge System in a Multipath Environment". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1222089977.
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Sagnard, Marianne. "Conception et développement de composants à ondes élastiques de surface, dédiés à la détection passive et sans fil de grandeurs physiques et au filtrage radiofréquences à bandes multiples". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD051.
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Les travaux décrits dans ce mémoire ont pour but de conduire à la réalisation de capteurs et de filtres à ondes élastiques de surface (SAW) innovants, passifs et sans fil, dédiés à une utilisation en environnement sévère. Différentes structures de composants SAW sont alors étudiées. Les caractéristiques générales, telles que les pertes d’insertion ou les bandes passantes relatives atteignables, des structures usuelles (résonateurs, lignes à retard, LCRF, filtres en échelle…) sont connues de l’homme de l’art. Cependant, pour concevoir un dispositif SAW qui respecte les critères d’un cahier des charges donné, il est impératif de définir le comportement spécifique de chaque dispositif avant son envoi en production.Pour ce faire, des modèles numériques sont développés, qui incluent à la fois la possibilité d’analyser le comportement de systèmes à la géométrie complexe (filtres en échelles, transducteurs apodisés) et qui prennent en compte la présence de phénomènes perturbateurs (modes transverses, pertes liées à la nature des matériaux). La comparaison entre les calculs numériques et les mesures a mis en avant l’adéquation des résultats expérimentaux et de calculs.La mise en place de ces outils permet le développement de capteurs et filtres SAW innovants grâce à une analyse numérique rapide et fiable de leur comportement.Ainsi, l’étude de résonateurs et capteurs dédiés à une utilisation à des températures excédant les 700°C est menée. Il est démontré qu’en dépit de son inhomogénéité, le Ba2TiSi2O8 est un matériau adapté à la réalisation de SAW soumis à des températures élevées pour des fréquences de l’ordre de 300 MHz jusqu’au GHz.Par ailleurs, une structure disposant d’un transducteur à trois doigts par longueur d’ondes est utilisée dans le but de réaliser des résonateurs insensibles aux effets de la directivité lorsque la température évolue. Cette même configuration a mis en exergue la possibilité de réaliser des capteurs n’utilisant qu’un seul résonateur (contre au moins deux jusqu’à présent). Ce dernier point permet de limiter l’encombrement des composants et résout la problématique du vieillissement différentiel des structures.Un second type de capteurs, passifs et sans fil, fondés sur l’utilisation d’un seul SAW et dédiés à la mesure d’hygrométrie, a été étudié. Dans cette nouvelle configuration, un SAW de type LCRF est utilisé comme transpondeur et la zone sensible est externalisée. La sensibilité des modes (de plus d’un MHz) à la variation d’un élément capacitif ou d’une antenne dipôle a été mise en avant numériquement. En pratique, la fabrication des dispositifs a montré une variation différentielle de plusieurs centaines de kHz des résonances selon la condition électrique appliquée à l’un des ports.Finalement, des filtres, dédiés aux applications stratégiques, agiles en fréquence sont réalisés. L’objectif de faire varier la fréquence centrale des dispositifs au cours de leur fonctionnement est atteinte en modifiant les conditions électriques appliquées aux réflecteurs. Deux types de tirage en fréquence sont observés : un glissement fin, de quelques ‰ de la fréquence centrale, cyclique, et un saut de fréquences lié au glissement et à l’ouverture de la bande de Bragg des miroirs aux hautes fréquences. La fabrication des structures et leur connexion à des interrupteurs MEMS validé la faisabilité de la structure.Ces travaux mettent en lumière les capacités de prédiction du comportement des structures SAW grâce au développement de logiciels dédiés. De plus, l’étude et la réalisation de filtres et capteurs innovants ouvre la voie à de nouvelles fonctionnalitésThis thesis aims at designing innovative, passive and wireless surface acoustic waves (SAW) sensors and filters, dedicated to harsh environments. Several types of SAW components are consequently studied. The main characteristics, such as insertion losses or relative bandwidth, of usual structures (resonators, delay lines, LCRF, ladder filters…) are known by men of the art. However, to design a SAW device that respects specific requirements, the definition of the proper behavior of each device must be established before the manufacturing.For this purpose, numerical models are developed. Not only they include the possibility to analyse he beha-vior of systems with complex geometry (ladder filters, apodised transducers) but they take into account disturbing phenomena (transverse modes, losses due to the intrinsic nature of the materials). The comparison between computations and measures points out the match between experimental results and calculations.The implementation of these tools allows the development of innovative SAW sensors and filters thanks to a fast and reliable numerical analysis of their behavior.Thus, the design of resonators and sensors dedicated to a use at temperatures exceeding 700°C is studied. It is demonstrated that despite its inhomogeneity, Ba2TiSi2O8 is suitable for the manufacturing of SAW devices subject to high temperatures and in a frequency range from 300 MHz to the GHz.Furthermore, a structure composed of a three electrodes per wavelength transducer is used to produce re-sonators that are not subject to directivity effects when the temperature changes. This configuration offers the possibility to design sensors that use a single resonator (versus at least two until now). This last point makes smaller components possible and solves the question of a differential aging of the structures.A second type of sensors, also passive and wireless, dedicated to humidity measurements, based on the use of a single SAW, is studied. In this new configuration, a LCRF is used as a transponder and the sensitive area is outsourced. The mode sensitivity (of more than a MHz) to the variation of a capacitance or a dipole antenna is numerically brought to light. In practice, the device manufacturing showed a differential variation of the resonances of about 600 kHz depending on the electric condition applied to one of the ports.Finally, filters, dedicated to strategic applications, with frequency agility are designed. The purpose is to make the frequency vary depending on the electrical conditions applied to the mirrors. Two kinds of agility are identified : a slight sliding, of a few ‰ of the initial central frequency, periodic, and a frequency jump due to the shift of the Bragg band to the high frequencies. The manufacturing of some structures and their connection to MEMS switches attest the feasibility of such a structure.This work highlights the ability to predict the behavior of SAW structures thanks to the development of dedicated software. Moreover, the analysis and the manufacturing of innovative sensors and filters pave the way to new functionalities
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Dubosc, Fabrice. "Etude et réalisation d'un capteur acoustique à ondes de surface : vers l'utilisation du silicium poreux comme surface sensible". Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4027.
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Les capteurs à ondes de surface (SAW) présentent plusieurs intérêts, tels que leur robustesse, leur adaptabilité et leur faible coût de fabrication. Un des facteurs de performance de ce type de capteur est sa sensibilité. Généralement pour l’améliorer les efforts se concentrent sur la couche sensible. Une alternative innovante est l’augmentation de la surface active en porosifiant le substrat. L’ouverture du matériau piézoélectrique le long du chemin de propagation permettra, ainsi, la captation des espères dans les pores du substrat. L’objectif de cette thèse est de proposer une nouvelle architecture de capteur permettant l’usage du silicium poreux en tant que couche guidante et sensibleSurface wave sensors (SAW) have several advantages, such as robustness, adaptability and low manufacturing costs. One of the key performance factors of this type of sensor is its sensitivity. Generally to improve it, the efforts focus on the sensitive layer. An innovative alternative is the increase of the active surface by porosifying the substrate. The opening of the piezoelectric material along the path of propagation and its replacement by porous silicon will thus enable the capture of the species to be detected in the pores. The objective of this thesis is to propose a new sensor architecture allowing the use of porous silicon as a guiding and sensing layer
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Gell, Jennifer Rachel. "Surface-acoustic-wave (SAW) driven light sources". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599350.
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This thesis concentrates on the interaction between SAWs (surface acoustic wave) and low-dimensional systems studied using optical techniques. In particular SAW-driven luminescence from a lateral p-n junction is demonstrated. The lateral p-n junction is formed by molecular beam epitaxy regrowth on a patterned GaAs substrate. Silicon is used as an amphoteric dopant to create a high mobility two-dimensional electron gas on flat (100) planes and a two-dimensional hole gas on angled (311)A facets. A lateral p-n junction is formed at the interface between these planes. SAWs with a frequency of ~1 GHz are generated using an interdigitated transducer. When a continuous radio frequency (RF) signal is used to excite the transducer, SAW-driven light emission from the p-n junction is demonstrated by peaks in the current/light emission at the resonant frequency of the transducer. To investigate the nature of the luminescence further, short RF pulses are used to drive the transducer. The short pulses temporally isolate the SAW-driven light emission from any emission due unwanted pick-up of the free space electromagnetic wave. In the final section the modulation of the emission energies of a single self-assembled quantum dot by a SAW is investigated. The compression and expansion of the crystal due to the strain wave causes the energy of the dot lines to oscillate around their equilibrium values. The shape of the SAW broadened emission lines was seen to depend on the nature of the transition in the dot offering an alternative way of identifying charged and neutral species in this sample. The modulation of the dot energy levels by the SAW is used to control the time of photon emission from the system.
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Morrill, Samuel. "Combined Metal-Enhanced Fluorescence-Surface Acoustic Wave (MEF-SAW) Biosensor". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5081.
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Immunofluorescence assays are capable of both detecting the amount of a protein and the location of the protein within a cell or tissue section. Unfortunately, the traditional technique is not capable of detecting concentrations on the nanoscale. Also, the technique suffers from non-specific attachment, which can cause false-positives, as well as photobleaching when detecting lower concentrations is attempted. There is also a time constraint problem since the technique can take from many hours to a few days in some cases.
In this work, metal-enhanced fluorescence (MEF) is used to lower the detection limit and reduce photobleaching. Unfortunately, MEF also increases the intensity of non-specifically bound proteins (NSBPs). Therefore, a surface acoustic wave (SAW) device is used to remove the more weakly bound NSBPs. Previously, this has been shown on lithium niobate, but it is used with a quartz substrate in this work. The SAW device is also used to cause micro-mixing which speeds the process up significantly.
In this research, it was found that silver nanocubes can lower the detection limit down to below 1 ng/mL. Quartz SAW devices are shown to remove NSBPs at a power of 10 mW applied for five minutes. Micro-mixing is shown to be improved by a factor of six at 10 mW for 10 minutes by saturating the antibody used in this research, which takes 1 hour without micro-mixing. Finally, all three components are combined. In this work, the whole device is used to detect 50 ng/mL. After micro-mixing, the intensity is the same as with MEF, and, after removal, it has been lowered by 7 a.u.
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Gizeli, Electra. "New acoustic wave sensor geometries". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282004.
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Haskell, Reichl B. "A Surface Acoustic Wave Mercury Vapor Sensor". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/HaskellRB2003.pdf.
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Sehra, Gurmukh S. "Surface acoustic wave based flavour sensor system". Thesis, University of Warwick, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416148.
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Meng, Qingbin. "Surface acoustic wave controlled semiconductor optical source". Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518122.
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A semiconductor optical source monolithically integrated with a surface acoustic wave (SAW) Bragg-cell to operate as a functional device is proposed in this thesis. The practical structure of such an integrated device is demonstrated and design guidelines are presented. Compared with conventional optical beam processed devices, this functional integrated semiconductor optical source (FISOS) is revised to be compact in size, flexible in function and potentially robust in performance. The FISOS is analyzed as two sub-divisions, optical source and acoustic processor, which have the common substrate structure. The optical beams excited from the optical source part of the device undergoes a scattering in the Bragg grating formed by SAWs that are generated by an IDT positioned on top of the acoustic processing part of device. By altering the property (power, frequency, etc.) of the SAW, versatile functionalities such as modulation, filtering, beam steering and so on of the optical beams can be realized in this optical source device.
A multilayer structure based on GaN/InGaN MQWs grown on sapphire is designed for the FISOS to be blue light emitting and efficiently launching SAWs. An etch-down technique employed in the SAW processing part is taken to improve the overlap between the optical and acoustic waves and then the interaction efficiency. Optimizations to the geometrical dimensions of the FISOS, such the width of the ridge waveguide, the position of the IDT and the etching depth, etc., are discussed in the given structure.
Numerical models are investigated to access the operational characteristics and then to provide design guidelines for the proposed integrated device. The Bragg diffraction of optical waves occurring within the acoustic waves in the proposed structure are simulated as a two-dimensional interaction between two guided optical modes and an acoustic surface wave.
The modal distributions and propagation velocities of SAWs in a multilayer system are calculated using Adler’s matrix method. The electrical characteristics of an IDT, such as impedance, insertion loss, electromechanical constant and so on are also discussed.
Transverse and lateral optical modes in the given multilayer structure are analyzed by the transfer matrix method. The interaction of optical waves and acoustic waves are modeled using the rigorous grating diffraction theory. Starting from Floquet’s theory, the well-known coupled-wave method and modal method can both be derived from the rigorous grating diffraction theory. Discussions of some useful approximate methods are also presented. In this thesis, the simulations of the acoustooptic interaction are performed using the coupled-wave method.
From the simulation results, the angular distribution profile and spatial profile of the output of the FISOS are evaluated. An improvement to the expression of the diffraction efficiency in such an integrated device is proposed. The so-called beam diffraction efficiency gives a more complete measure to the acoustooptic diffraction and is used to investigate the features of FISOS different from conventional acoustooptic devices. Contour plots of the beam efficiency varying with acoustic frequency and power in a FISOS is demonstrated to be a convenient and powerful approach in the device design.
The operational performances of an integrated deflector and a modulator in FISOS are analyzed to investigate the feasibility of FISOS. The trade-off of the efficiency-resolution in an integrated deflector design is discussed. Short interaction length, high acoustic frequency and narrow ridge are proved to be helpful for a larger number of resolvable spots with a fairly high efficiency. In the case of the integrated modulator, given that the figure of merit Q is fixed, it is demonstrated that the smaller the Q, the longer the interaction length, larger ridge width and lower acoustic frequency will give rise to a larger bandwidth, though the highest efficiency might appear at a higher frequency.
Some practical issues such as the misalignment of planar elements on the device and the incoherence of the integrated optical source are also discussed. A modified working frequency can be used to compensate the efficiency loss in the former case; in the latter case, it is demonstrated that a distortion of beam diffraction efficiency versus acoustic power with an incoherent optical source arises due to the wide spectrum of the incident optical waves.
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Wang, Tao. "Optimization and Characterization of Integrated Microfluidic Surface Acoustic Wave Sensors and Transducers". Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6153.
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Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the mechanical pump and biosensor areas.
Manipulation of liquids in microfluidic channels is important for many mechanical, chemical and biomedical applications. In this dissertation, we first introduced a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employed a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrated long distance media delivery (up to 8mm) and a high pumping velocity, which increased the device’s application space and mass production potential. Additionally, the device design didn’t need precise layers of water and glass between substrate and channel, which simplified the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, and input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicated that the pumping velocity for a constant liquid volume with the same applied input power could be increased by over 130% (2.31 mm/min vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 µm vs 500 µm) design. This device could be used in circulation, dosing, metering and drug delivery applications which necessitated small-scale precise liquid control and delivery.
This dissertation also introduced a novel SAW-based sensor designed and employed for detecting changes in cell concentration. Before conducting cell concentration experiments, preliminary experiments were conducted on weight concentration differentiation of microfluidic particles based on a polydimethylsiloxane (PDMS) channel and surface acoustic wave resonator design. The results confirmed that our device exerted an ultra-stable status to detect liquid properties by monitoring continuous fluids. An improved design was carried out by depositing a 200 nm ZnO layer on top of the lithium tantalate substrate surface increased the sensitivity and enabled cell concentration detection in a microfluidic system.
Comprehensive studies on cell viability were carried out to investigate the effect of shear horizontal (SH) SAWs on both a cancerous (A549 lung adenocarcinoma) and a non-cancerous (RAW264.7 macrophage) cell line. Two pairs of resonators consisting of interdigital transducers (IDTs) and reflecting fingers were used to quantify mass loading by the cells in suspension media as well as within a 3-dimensional cell culture model. In order to predict the characteristics and optimize the design of the SH-SAW biosensor, a 3D COMSOL model was built to simulate the mass loading response of the cell suspensions. These results were compared to experimental data generated by pipetting cell concentrations of 3.125K, 6.25K 12.5K, 25K and 50K cells per 100µL into the PDMS well and measuring to obtain the relative frequency shift from the two oscillatory circuit systems (one of which functioned as a control). Frequency shift measurements were also collected from A549 cells cultured on a 3D nanofiber scaffold produced by electrospinning to evaluate the device’s ability to detect changes in cell density as the cells proliferated in culture over the course of eight days. The device’s ability to detect changes in cell density over time in a 3D model along with its biocompatibility reveal great potential for this device to be incorporated into 3D in vitro cancer research applications.
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Cameron, Thomas P. (Thomas Philip) Carleton University Dissertation Engineering Electrical. "Circuit factor compensation for saw filters using modal analysis". Ottawa, 1988.
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Achour, Bilel. "Capteurs à ondes acoustiques de surface fonctionnant à 104 et 208 MHz. : modélisation, développement et application à la détection d’ions lourds métalliques". Thesis, Le Mans, 2020. http://www.theses.fr/2020LEMA1017.
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Les capteurs à ondes acoustiques de surfaces (SAW : Surface Acoustic Waves) présentent de nombreux avantages, dont une grande sensibilité, un paramètre clé dans diverses applications. Dans cette thèse, deux voies sont explorées pour améliorer la sensibilité des dispositifs SAWs : le passage en mode de Love, avec une couche guide d’onde en résine époxyde SU-8, et la montée en fréquence de 104 à 208 MHz. Avant de réaliser de tels dispositifs en salle blanche puis de les utiliser en tant que capteurs chimiques, des simulations numériques ont été entreprises, en utilisant tout d’abord le logiciel MATLAB, puis par la méthode des éléments finis, via le logiciel COMSOL Multiphysics. L’épaisseur optimale de la couche guide d’onde, permettant un gain important en sensibilité, a été estimée. Un écart entre l’expérience et la simulation a été trouvé soulignant la nécessité de poursuivre les phases d’optimisation dans cette voie. Une confrontation calculs/expériences a été menée avec succès pour les structures SH-SAW. Ces dispositifs ont été fonctionnalisés avec un dérivé d’anthracène pour détecter les ions zinc en milieu aqueux. Les résultats gravimétriques ont montré un gain en sensibilité d’un facteur 2.3, en augmentant la fréquence de travail de 104 MHz à 208 MHzSurface Acoustic Wave (SAW) sensors have many advantages mainly a high sensitivity, which is a key parameter in various applications. Two strategies were explored, in this thesis, to enhance the sensitivity of SAW devices: switching to Love mode, with a waveguide layer in SU-8 epoxy resin, and frequency increase from 104 to 208 MHz. Prior to the realization of such devices in a clean room and their further use as chemical sensors, numerical simulations were done, first with MATLAB software, and then with the finite element method, via COMSOL Multiphysics software. The optimum thickness of the waveguide layer, allowing a significant gain in sensitivity, was estimated. A disagreement between experience and simulation was found highlighting the need to continue optimization steps. A confrontation between calculations / experiments was carried out for the SH-SAW structures. These devices were functionalized with an anthracene derivate for zinc ions detection in aqueous media. Gravimetric results indicate that increasing the operating frequency from 104 MHz to 208 MHz permits a gain in sensitivity by a factor of 2.3
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Banerjee, Markus K. "Acoustic wave interactions with viscous liquids spreading in the acoustic path of a surface acoustic wave sensor". Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302521.
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Li, Chunhui. "Quantitative assessment of elasticity properties of skin using surface acoustic wave (SAW) method". Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/22096156-38ee-4824-be9d-b6537d02cd43.
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Mechanical properties are important tissue parameters of skin that are useful for understanding skin patho-physiology, and aiding disease diagnosis and treatment. They are indicators of functional changes and pathological variations in the micro-structure. This research thesis studies the intersection of acoustics, optics and biomechanics for skin mechanical properties measurement. Surface acoustic wave (SAW) is induced and applied to a range of different tissue mimicking phantom models, Thiel cadavers and in vivo human skin. Different optical systems, i.e. low coherence interferometer and phase sensitive optical coherence tomography (PhS-OCT), are employed to detect the SAW. The Young’s moduli and thicknesses of model layers are assessed by the analysis of the wave phase velocity curves. The PhS-OCT detection system can also provide the real time high resolution depth-resolved cross-sectional microstructure imaging of the interrogated sample to assist the elasticity evaluation of the heterogeneous tissue. Results prove that the novel combination of optical imaging technology with SAW method is able to assess the elasticity change in both axial and transverse directions in soft material. It can be used to evaluate the mechanical properties of single, double-layer soft tissue mimicking phantoms and different sites of human skin ex vivo and in vivo non-invasively. This study also demonstrates that the SAW method can be successfully utilized to map the elasticity of soft heterogeneous tissues quantitatively. The results represent an important step towards the development of SAW method as a clinical diagnosis tool in dermatology, and may offer potential in diagnostic and therapeutic clinical applications.
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Richardson, Mandek. "Theoretical and Experimental Investigations to Improve the Performance of Surface Acoustic Wave (SAW) Biosensors". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5566.
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The objective of this dissertation is to improve the performance of surface acoustic wave (SAW) biosensors for use in point-of-care-testing (POCT) applications. SAW biosensors have the ability to perform fast, accurate detection of an analyte in real time without the use of labels. However, the technology suffers from the inability to differentiate between specific and non-specific binding. Due to this limitation, direct testing of bodily fluids using SAW sensors to accurately determine an analyte's concentration is difficult. In addition, these sensors are challenged by the need to detect small concentrations of a biomarker that are typically required to give a clinical diagnosis. Sensitivity, selectivity and reliability are three critical aspects for any sensing platform. To improve sensitivity the delay path of a SAW sensor has been modified with microcavities filled with various materials. These filled cavities increased sensitivity by confining wave energy to the surface by way of constructive interference and waveguiding. Thus, the improved sensitivity will result in a lower limit of detection. In addition, insertion loss is decreased as a consequence of increased wave confinement to the surface. Sensor selectivity and reliability are adversely affected by non-specific binding of unwanted species present in a sample. To address this issue a multifunctional SAW sensor is presented. The sensor consists of two SAW delay lines oriented orthogonal to each on ST-quartz in order to generate two distinct wave modes. One wave mode is used for sensing while the other is used to remove loosely bound material. By using the same transduction mechanism for both removal and sensing, the sensor chip is simplified and complex electronics are avoided. The findings of this research involve the technological advances for SAW biosensors that make their use in POCT possible.
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Pavlina, John. "DESIGN AND SIMULATION FOR ENCODED PN-OFC SAW SENSOR SYSTEMS". Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2827.
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Surface acoustic wave (SAW) sensors provide versatility in that they can offer wireless, passive operation in numerous environments. Various SAW device embodiments may also be employed for retrieval of the sensed data. Single sensor systems typically use a single carrier frequency and a simple device embodiment since tagging is not required. However, it is necessary in a multi-sensor environment to both identify the sensor and retrieve the information. Overlapping sensor data signals in time and frequency present problems when attempting to collect the sensed data at the receiver. This dissertation defines a system simulation environment exclusive to SAW sensors. The major parameters associated with a multi-device system include the transmitter, the channel, and the receiver characteristics. These characteristics are studied for implementation into the simulation environment. A coupling of modes (COM) model for SAW devices is utilized as an accurate software representation of the various SAW devices. Measured device results are presented and compared with COM model predictions to verify performance of devices and system. Several coding techniques to alleviate code collisions and detection errors were investigated and evaluated. These specialized techniques apply the use of time, frequency, and spatial diversity to the devices. Utilizing these multiple-access techniques a multi-device system is realized. An optimal system based on coding technique, frequency of operation, range, and related parameters is presented. Funding for much of this work was provided through STTR contracts from NASA Kennedy Space Center.Ph.D.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering PhD
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Gruetzmann, Anna [Verfasser]. "Wireless ECG Sensor in Surface Acoustic Wave Transponder Technology / Anna Gruetzmann". München : Verlag Dr. Hut, 2010. http://d-nb.info/1009484524/34.
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Hamidon, Mohd Nizar. "Fabrication of high temperature surface acoustic wave devices for sensor applications". Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420236.
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Wang, Zhuochen. "Study of High-Throughput Particle Separation Device Based on Standing Surface Acoustic Wave (SSAW) Technology". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1341606856.
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Humphries, James R. "A novel approach for extending delay time in surface acoustic wave devices". Honors in the Major Thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1423.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering and Computer Science
Engineering
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Manohar, Greeshma. "Investigation of Various Surface Acoustic Wave Design Configurations for Improved Sensitivity". Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4365.
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Surface acoustic wave sensors have been a focus of active research for many years. Its ability to respond for surface perturbation is a basic principle for its sensing capability. Sensitivity to surface perturbation changes with every inter-digital transducer (IDT) design parameters, substrate selection, metallization choice and technique, delay line length and working environment.
In this thesis, surface acoustic wave (SAW) sensors are designed and characterized to improve sensitivity and reduce loss. To quantify the improvements with a specific design configuration, the sensors are employed to measure temperature. Four SAW sensors design configurations, namely bi-directional, split electrode, single phase unidirectional transducer (SPUDT) and metal grating on delay line (shear transvers wave sensors) are designed and then fabricated in Nanotechnology Research and Education Center (NREC) facility using traditional MEMS fabrication processes Additionally, sensors are then coated with guiding layer SU8-2035 of 40 m using spin coating and SiO2 of 6 m using plasma enhanced chemical vapor deposition (PECVD) process. Sensors are later diced and tested for every 5oC increment using network analyzer for temperature ranging from 30oC–0.5oC to 80oC–0.5oC. Data acquired from network analyzer is analyzed using plot of logarithmic magnitude, phase and frequency shift.
Furthermore, to investigate the effect of metallization technique on the sensor performance, sensors are also fabricated on substrates that were metallized at a commercial MEMS foundry. All in-house and outside sputtered sensor configurations are compared to investigate quality of sputtered metal on wafer. One with better quality sputtered metal is chosen for further study. Later sensors coated with SU8 and SiO2 as guiding layer are compared to investigate effect of each waveguide on sensors and determine which waveguide offers better performance.
The results showed that company sputtered sensors have higher sensitivity compared to in-house sputtered wafers. Furthermore after comparing SU8 and SiO2 coated sensors in the same instrumental and environmental condition, it was observed that SU8 coated di-directional and single phase unidirectional transducer (SPUDT) sensors showed best response.
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Singh, Reetu. "Development of Three Dimensional Fluid-Structure Interaction Models for the Design of Surface Acoustic Wave Devices: Application to Biosensing and Microfluidic Actuation". Scholar Commons, 2009. http://scholarcommons.usf.edu/etd/3677.
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Surface acoustic wave (SAW) devices find uses in a plethora of applications including
but not limited to chemical, biological sensing, and microfluidic actuation. The primary aim of
this dissertation is to develop a SAW biosensor, capable of simultaneous detection of target
biomarkers in fluid media at concentrations of picogram/ml to nanogram/ml levels and removal
of non-specific proteins from sensor surface using the process of acoustic streaming, for potential
chemical sensing, medical, and clinical diagnostic applications. The focus is on the development
of three dimensional finite element structural and fluid-structure interaction models to study wave
propagation and acoustic actuation of fluids in a SAW biosensor. This work represents a
significant improvement in understanding fluid flow over SAW devices, over the currently
available continuum model of Nyborg. The developed methodology includes use of a novel
substrate, namely, Langasite coupled with various combinations of novel multidirectional
interdigital transducer (IDT) configurations such as orthogonal, focused IDTs as well as sensor
surface modifications, such as micro-cavities. The current approach exploits the capability of the
anisotropic piezoelectric crystal to launch waves of different characteristics in different
directions, which can be put to the multiple uses including but not limited to sensing via
shear
horizontal waves and biofouling elimination via
Rayleigh wave induced acoustic streaming.
Orthogonal IDTs gives rise to constructive interference, thereby enhancing the magnitudes of
device displacements and fluid velocities. The net effect is an increase in device sensitivity and
acoustic streaming intensity. The use of micro-cavities in the delay path provides a synergistic
effect, thereby further enhancing the device sensitivity and streaming intensity. Focused IDTs are
found to enhance the device displacements and fluid velocities, while focusing the device
displacements and fluid motion at the device focal point, thereby enhancing the SAW device
biosensing performance. The work presented in this dissertation has widespread and immediate
use for enhancing sensor sensitivity and analyte discrimination capabilities as well as biofouling
removal in medical diagnostic applications of SAW sensors. This work also has a broad relevance
to the sensing of multiple biomarkers in medical applications as well as other technologies
utilizing these devices such as microfluidic actuation.
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Chen, Li. "A Novel Nonlinear Mason Model and Nonlinear Distortion Characterization for Surface Acoustic Wave Duplexers". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5782.
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Surface acoustic wave (SAW) technology has been in use for well over one century. In the last few decades, due to its low cost and high performance, this technology has been widely adopted in modern wireless communication systems, to build filtering devices at radio frequency (RF). SAW filters and duplexers can be virtually found inside every mobile handset. SAW devices are traditionally recognized as passive devices with high linear signal processing behavior. However, recent deployments of third generation (3G) and fourth generation (4G) mobile networks require the handsets to handle an increasing number of frequency bands with more complex modulation /demodulation schemes and higher data rate for more subscribers. These requirements directly demand more stringent linearity specifications on the front end devices, including the SAW duplexers. In the past, SAW duplexer design was based on empirically obtained design rules to meet the linearity specifications. Lack of predictability and an understanding of the root cause of the nonlinearity have limited the potential applications of SAW duplexers. Therefore, research on the nonlinearity characterization and an accurate modeling of SAW nonlinearity for mobile device applications are very much needed. The Ph.D. work presented here primarily focuses on developing a general nonlinear model for SAW resonators/duplexers. Their nonlinear characteristics were investigated by measuring the harmonic and intermodulation distortions of resonators. A nonlinear Mason model is developed and the characterization results are integrated into SAW duplexer design flows to help to simulate the nonlinear effects accurately and improve the linearity performance of the products. In this dissertation, first, a novel nonlinear Mason equivalent circuit model including a third order nonlinear coefficient in the wave propagation is presented. Next, the nonlinear distortions of SAW resonators are analyzed by measuring large-signal harmonic and intermodulation spurious emission on resonators using a wafer probe station. The influence of the setups on the measurement reliability and reproducibility is discussed. Further, the nonlinear Mason model is validated by comparing its simulation results with harmonic and intermodulation measurements on SAW resonators and a WCDMA Band 5 duplexer. The Mason model developed and presented here is the first and only nonlinear physical model for SAW devices based on the equivalent circuit approach. By using this new model, good simulation measurement agreements are obtained on both harmonic and intermodulation distortions for SAW resonators and duplexers. These outcomes demonstrate the validity of the research on both the characterization and modeling of SAW devices. The result obtained confirms that the assumption of the representation of the 3rd order nonlinearity in the propagation by a single coefficient is valid.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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Roe, Austin R. "RESONANT ACOUSTIC WAVE ASSISTED SPIN-TRANSFER-TORQUE SWITCHING OF NANOMAGNETS". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6029.
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We studied the possibility of achieving an order of magnitude reduction in the energy dissipation needed to write bits in perpendicular magnetic tunnel junctions (p-MTJs) by simulating the magnetization dynamics under a combination of resonant surface acoustic waves (r-SAW) and spin-transfer-torque (STT). The magnetization dynamics were simulated using the Landau-Lifshitz-Gilbert equation under macrospin assumption with the inclusion of thermal noise. We studied such r-SAW assisted STT switching of nanomagnets for both in-plane elliptical and circular perpendicular magnetic anisotropy (PMA) nanomagnets and show that while thermal noise affects switching probability in in-plane nanomagnets, the PMA nanomagnets are relatively robust to the effect of thermal noise. In PMA nanomagnets, the resonant magnetization dynamics builds over few 10s of cycles of SAW application that drives the magnetization to precess in a cone with a deflection of ~45⁰ from the perpendicular direction. This reduces the STT current density required to switch the magnetization direction without increasing the STT application time or degrading the switching probability in the presence of room temperature thermal noise. This could lead to a pathway to achieve energy efficient switching of spin-transfer-torque random access memory (STT-RAM) based on p-MTJs whose lateral dimensions can be scaled aggressively despite using materials with low magnetostriction by employing resonant excitation to drive the magnetization away from the easy axis before applying spin torque to achieve a complete reversal.
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Arsat, Rashidah y rashidah arsat@student rmit edu au. "Investigation of Nanostructured Thin Films on Surface Acoustic Wave and Conductometric Transducers for Gas Sensing Applications". RMIT University. Electrical and Computer Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091002.094407.
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In this thesis, the author proposed and developed nanostructured materials based Surface Acoustic Wave (SAW) and conductometric transducers for gas sensing applications. The device fabrication, nanostructured materials synthesis and characterization, as well as their gas sensing performance have been undertaken. The investigated structures are based on two structures: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). These two substrates were chosen for their high electromechanical coupling coefficient. The conductometric structure is based on langasite (LGS) substrate. LGS was selected because it does not exhibit any phase transition up to its melting point (1470°C). Four types of nanostructured materials were investigated as gas sensing layers, they are: polyaniline, polyvinylpyrrolidone (PVP), graphene and antimony oxide (Sb2O3). The developed nanostructured materials based sensors have high surface to volume ratio, resulting in high sensitivity towards di¤erent gas species. Several synthesis methods were conducted to deposit nanostructured materials on the whole area of SAW based and conductometric transducers. Electropolymerization method was used to synthesize and deposit polyaniline nanofibers on 36° YX LiTaO3 and 64° YX LiNbO3 SAW substrates. By varying several parameters during electropolymerization, the effect on gas sensing properties were investigated. The author also extended her research to successfully develop polyaniline/inorganic nanocomposites based SAW structures for room temperature gas sensing applications. Via electrospinning method, PVP fibres and its composites were successfully deposited on 36° YX LiTaO3 SAW transducers. Again in this method, the author varied several parameters of electrospinning such as distance and concentration, and investigated the effect on gas sensing performance. Graphene-like nano-sheets were synthesized on 36° YX LiTaO3 SAW devices. This material was synthesized by spin-coating graphite oxide (GO) on the substrate and then exposin g the GO to hydrazine to reduce it to graphene. X-ray photoelectron spectroscopy (XPS) and Raman characterizations showed that the reduced GO was not an ideal graphene. This information was required to understand the properties of the deposited graphene and link its properties to the gas sensing properties. Thermal evaporation method was used to grow Sb2O3 nanostructures on LGS conductometric transducers. Using this method, different nanoscale structures such as nanorods and lobe-like shapes were found on the gold interdigitated transducers (IDTs) and LGS substrate. The gas sensing performance of the deposited nanostructured Sb2O3 based LGS conductometric sensors was investigated at elevated temperatures. The gas sensing performance of the investigated nanostructured materials/SAW and conductometric structures provide a way for further investigation to future commerciallization of these types of sensors.
44
Winkler, Andreas. "SAW-basierte, modulare Mikrofluidiksysteme hoher Flexibilität". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-84978.
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Diese Dissertation beschäftigt sich mit der Entwicklung eines neuartigen Konzepts für Herstellung und Handhabung von Mikrofluidiksystemen auf der Basis akustischer Oberflächenwellen (SAW) sowie der Nutzung dieses Konzepts zur Fertigung anwendungsrelevanter Teststrukturen. Schwerpunkte sind dabei unter anderem eine hohe Leistungsbeständigkeit und Lebensdauer der Chipbauelemente und eine hohe technologische Flexibilität bezüglich Herstellung und Einsatz. Ausgehend von einer modularen Betrachtungsweise der Bauelemente wurden vielseitig einsetzbare, elektrisch-optimierte Interdigitalwandler entworfen, verschiedene Herstellungsvarianten für vergrabene Interdigitalwandler hoher Leistungsbeständigkeit auf piezoelektrischen Lithiumniobat-Substraten entwickelt und experimentell verifiziert, ein Sputterverfahren für amorphe SiO2-Dünnschichten hoher Qualität optimiert und eine Federstiftkontakt-Halterung entworfen. Durch Kombination dieser Technologien wurden SAW-Bauelemente für die mikrofluidische Aktorik mit hoher Performance und Reproduzierbarkeit entworfen, charakterisiert und beispielhaft für das elektroakustische Zerstäuben von Fluiden und das Mischen in Mikrokanälen eingesetzt.
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WANG, YU-HSIEN y 汪祐賢. "Characteristics of metal oxide sensing layers on the surface acoustic wave (SAW) for ammonia sensors". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/jgckrr.
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碩士國立臺南大學
綠色能源科技學系碩士班
106
The thesis presents a high sensitivity ammonia sensor based on the principle of Surface acoustic wave (SAW). To improve the sensitivity of the proposed sensor, SAW sensor has combined with Zinc Oxide (ZnO) film, which is grown with the hydrothermal method. The goal is to achieve the characteristics of miniaturization and high sensitivity of the SAW sensor. In the thesis, we use ZnO nanosheet which is nanohole polymer featured with high chemical activity, to increase the selectivity and sensitivity of the sensor. The research adopts four different electrode distance splitter, matching with four different thicknesses of 50 nm, 75 nm, 100 nm, 125 nm of ZnO thin films to check the efficiency of detecting component and conclude the best process condition. In the research, we found that the proposed sensor has highest sensitivity under the temperature of 45℃and the distance of 5 mm from the finger and the fork electrode, and the optimal thickness of the sensing film is 75 nm under the concentration range of 0.01 PPM to 20 PPM. The Ammonia gas sensor has the characteristics of recovery and selectivity, especially applied in measuring low concentration.
46
Young, Ming-Sheng y 楊明昇. "Characteristics of Surface Acoustic Wave Sensor". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/81672173386487190179.
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碩士國立成功大學
電機工程學系
89
This paper is primarily divided into two sections. In section 1, the design and fabrication of IF SAW device are described. In section 2, the sensing property of SAW gas sensor for ethanol vapor is discussed. Based on sensing requirement, the first condition for SAW device design is low insertion loss that promising whole oscillation circuit can work normally. We choose LiNbO3 to be substrate and construct grating reflectors. The insertion loss of SAW device with 30 pairs grating reflections is 4 ~ 4.5dB, and that with 50 pairs grating reflectors is about 3.5dB. By using mass loading effect, SAW device may regard as ethanol vapor density sensor. The response due to changes in the medium density on the SAW transmission path causes transmission velocity change and resonant frequency shift. This is the basic principle of a SAW gas sensor. In order to increase sensitivity, coating stearic acid as sensing film on the transmission path is used. For different film depth, we discuss the responses of resonant frequency shift and find out the optimum. At last, the improvements of sensor system, range and stability are given.
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Cheng, Chi Yuan y 鄭期元. "Cigarette Detection by Surface Acoustic Wave Gas Sensor". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/86802169712159978126.
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碩士國立清華大學
奈米工程與微系統研究所
103
Statistical data says that people exposed to secondhand smoke (SHS) have a higher risk of getting lung cancer and coronary heart disease. The research goal is making a cigarette sensor by surface acoustic wave (SAW) to prevent from tobacco hazards. In order to detect low concentration of cigarette marker, sensitivity and stability are two important issues. The SAW sensor is coated with oxidized hollow meso-porous carbon nano-sphere (O-HMC) to replace generally used polymer as new type sensing material, which is more sensitive than poly-acrylic acid due to the much more carboxyl group bonded by HNO3 treated, increasing the sensitivity of 3-EP from 37.8 to 51.2 Hz/ppm and also preventing the drawbacks of polymer based sensing material, such as lack of thermal stability and swelling effect. An 800μL micro-chamber is designed for enhancing stability by blocking environmental interferences, and the HMC coated chip is used as control due to the higher similarity of surface state between experiment and reference would increase stability, finally the noise can down to 5 Hz. The small volume of chamber and the large surface area of sensing material, caused by porous structure is leading to rapid detection at the low flow rate of 20 mL/min. The SAW sensor successfully detects cigarette smoke with high sensitivity and good repeatability by filtering above 1μm particles and tar to solve the adhesion problem; as compared to four interfered gas, ammonia, methane, carbon monoxide and carbon dioxide, the SAW sensor has 5 times more selective to cigarette smoke. This SAW sensor also detects water vapor to remove the influence of humidity and uses the resulting trend line to calibrate the frequency shift by detecting cigarette. In addition to detect SHS, this research takes the same SAW detector to sense the thirdhand smoke (THS) on different clothing fabrics, such as wool, cotton and polyester, finally knows that wool will absorb the maximum amount of THS and get the longest residual time.
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Chen, Yu-Ju y 陳右儒. "The Fabrication of Surface Acoustic Wave Alcohol Sensor". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/52682878487266706559.
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碩士國立成功大學
電機工程學系碩博士班
91
This thesis gives a historical account of the development, and the theory of piezoelectric phenomenon, Rayleigh wave, interdigital transducer (IDT), surface acoustic wave (SAW), performance criteria and device for application in sensor. The alcohol gas sensing properties of stearic acid film, deposited onto 1280YX-LiNbO3 substrate, have been monitored shift in frequency by SAW delay lines and analysis the properties of the alcohol gas sensor. The effect of humidity on SAW alcohol gas response is negligible for the typical conditions at room ambient temperature. And studied with respect to the remnant gas in tubes, the comparison of the stability between electrical and flop flow controllers, temperature effect of the flowed alcohol gas, the film aging, spray coating uniform, optimum spin parameter, optimum the concentration of stearic acid solution, and so on. The devices are based on the dual two ports resonator structure adds to appropriate control of the environment effect, and appropriate coating method. It is shown that the devices have good sensitivity, reversible, stability, repeatability, fast response time. And the ratio of signal to noise is greater than two.
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LAI, JUN-CHEN y 賴俊辰. "Applied of surface-active agent on Surface Acoustic Wave liquid sensor". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/63731844845883368321.
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碩士國立勤益科技大學
機械工程系
101
The energyof propagationof surface acoustic wave (SAW) is concentrated within the surface of substrates and the energy lossof SAW is less than the bulk wave.The properties of propagation depend on the material of substrates and boundary condi-tion.In this study, we detect the surfactants by SAW devices. The composition of the SAW devices were piezoelectric substrates sputtered with interdigital transducers and then surface acoustic waves were excited. In the propagation path, we designed metal and free surface, the loading liquid with various effect of acoustic-electricwould lead to affect the properties of SAW, we can identifythe loading liquid by detect the change of SAW. First, we choice the material of 41°YX LiNbO3 as substrate, which can be ex-cited SH SAW and have the characters of higher Electromechanical coupling factor, faster phase velocity and stable temperature coefficient. Using the technology of MEMS, we design resonators with split IDT and the central frequency is 59.9M Hz. The split IDT have lower insertion loss than normal IDT. One group of resonators deposit Al thin film on sensing region to exclude electrical characteristics of liquid to achieve accurately detect the types of surfactants. In this study, we measure the prop-erties of surfactants (SNDS, SDBS, SLS,TritonX-100, ..etc.) using immersion mea-surements, the sensor immersed in the liquid under test can effectively rule out the liquid quality and environmental impact of interfering factors on the velocity, and real-time monitoring of changes. Experimental results show split type SAW sensor refers to a center frequency of 60.4947MHz, compare to the theoretical calculation approximately 1% error. In the free surface propagation path, the order of attenuation of energy is wa-ter&;lt;SLS&;lt;TritonX-100&;lt;DN-60. In terms of the metal-film surface propagation path, the order of attenuation of energy is water&;lt; TritonX-100&;lt; SLS&;lt; DN-60. Therefore, we can identify the surfactants by detect the attenuation of energy.
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Huang, Wang-Tsung y 黃望宗. "Gas Detecting Properties of Surface Acoustic Wave Ammonia Sensor". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/39712216187187276867.
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碩士義守大學
電機工程學系
91
This work investigates the advanced properties of an improved surface acoustic wave (SAW) ammonia gas sensor. The sensor was based upon a dual delay line SAW configuration. The chemical interface was L-Glutamic acid hydrochloride deposited on the surface of SAW sensor. The frequency shift of SAW devices took in real-time measurement to analyze the detection for low ammonia concentration. The perturbation mechanism is proved in this work, and the optimal sensing conditions and properties are studied. The SAW sensor based on L-Glutamic acid hydrochloride presented excellent sensitivity, reversibility, repeatability and selectivity to ammonia. Rising the operating temperature could improve the performance of sensors. The curve of frequency shift versus ammonia concentration showed the linearity and sensitivity at high temperature, especially at 50oC. The sensitivity was 0.05 ppm/ppm at 50oC, and it could estimate the limitation of detection (LOD) to be 0.08 ppm (=80 ppb). The water vapor in air significantly influenced the detection of ammonia. Therefore, SAW sensors based on L-Glutamic acid hydrochloride are suitable for operating at 50oC in dry air.