Dissertations / Theses on the topic 'Love wave acoustic sensor'

Avec les progrès du développement des appareils connectés et de l’Internet des objets (IoT), la surveillance continue des paramètres physiques et chimiques est devenue un défi actuel pour notre société.De plus, les dispositifs à ondes acoustiques de surface (SAW), largement utilisés comme filtres dans les télécommunications, remplissent désormais la fonction de capteurs.C’est dans ces deux contextes que se situent les travaux de cette thèse.L'objectif est de développer un système de lecture sans fil utilisant l'un de ces capteurs, notamment le capteur à ondes de Love (Love Wave ou LW) à sensibilité reconnue en milieu liquide. Peu de travaux impliquent ce dispositif en effectuant une lecture à distance, et exclusivement en utilisant sa réponse acoustique. Dans cette thèse, nous employons une approche plus générale considérant sa réponse électromagnétique et un protocole spécifique de mesure et d'acquisition de données pour détecter des solutions salines à sa surface. Compte tenu de sa nature passive, un système de lecture sans fil est présenté, ainsi qu'une discussion sur ses principales caractéristiques, avantages, inconvénients et limites<br>With the advancement in the development of connected devices and the Internet of Things (IoT), continuous monitoring of physical and chemical parameters has become a current challenge for our society. Additionally, surface acoustic wave (SAW) devices, widely used as filters in telecommunications, now serve the function of sensors.It is within these two contexts that the work of this thesis is situated. The goal is to develop a wireless reading system using one of these sensors, particularly the Love Wave (LW) sensor with recognized sensitivity in liquid media. Few studies involve this device by performing a remote reading, and exclusively using its acoustic response.In this thesis, we employ a more general approach considering its electromagnetic response and a specific measurement and data acquisition protocol for detecting saline solutions on its surface. Given its passive nature, a wireless reading system is demonstrated, as well as discussion on its key characteristics, advantages, disadvantages, and limitations

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.

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.

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.<br>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.<br>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<br>Alfresco

The fields of health care and environment control have an increasing demand for sensors able to detect low concentrations of specific molecules in gaseous or liquid samples. The recent introduction of microfabricated devices in these fields gave rise to sensors with attractive properties. A cutting edge technology is based on guided acoustic waves, which are perturbed by events occurring at the nanometer scale. A first part of the thesis investigates the Love mode waveguide, a versatile structure in which a thin film is guiding the acoustic wave generated in a piezoelectric substrate. A systematic analysis of its sensitivity was obtained using a transmission line model generalized to discriminate the rigid or viscous nature of the probed layers. We developed a novel integrated combination of the Love mode device with a Surface Plasmon Resonance optical sensor to quantify the thickness and the composition of soft layers. The electromagnetic interferences in the recorded signal were modeled to determine the phase velocity in the sensing area and to provide new mechanisms for an enhanced sensitivity. The experimental aspects of this work deal with the fabrication, the important issue of the packaging and the sensitivity calibration of the Love mode biosensor. A second part of the thesis investigates nanocrystalline diamond under the form of a thin film membrane suspended to a rigid silicon frame. The high mechanical and chemical resistance of nanocrystalline diamond, close to single-crystal diamond, open ways to membrane based acoustic sensors such as Flexural Plate Wave and thin Film Bulk Acoustic Resonators (FBAR). A novel dynamic characterization of the thin film is reported and the properties of composite FBAR devices including a diamond thin film membrane and a piezoelectric aluminum nitride layer are assessed using the perturbation theory. This study is applied to evaluate the high sensing potential of the first prototype of an actual diamond-based composite FBAR.

[EN] Different electronic interfaces have been proposed to measure major parameters for the characterization of quartz crystal microbalance (QCM) during the last two decades. The measurement of the adequate parameters of the sensor for a specific application is very important, since an error in this measure can lead to an error in the interpretation of the results. The requirements of the system of characterization depend on the application. In this thesis we propose two characterization systems for two types of applications that involve the majority of sensor applications: 1) Characterization of materials under variable damping conditions and 2) Detection of substances with high measurement resolution. The proposed systems seek to solve the problems detected in the systems currently in use. For applications in which the sensor damping varies during the experiment, we propose a system based on a new configuration of the technique of automatic capacitance compensation (ACC). This new configuration provides the measure of the series resonance frequency, the motional resistance and the parallel capacitance of the sensor. Moreover, it allows an easy calibration of the system that improves the precision in the measurement. We show the experimental results for 9 and 10 MHz crystals in fluid media, with different capacitances in parallel, showing the effectiveness in the capacitance compensation. The system presents some deviation in frequency with respect to the series resonance frequency, as measured with an impedance analyser. These deviations are due to the non-ideal, specific behaviour of some of the components of the circuit. A new circuit is proposed as a possible solution to this problem. For high-resolution applications we propose an integrated platform to characterize high-frequency acoustic sensors. The proposed system is based on a new concept in which the sensor is interrogated by means of a very stable, low-noise external source at a constant frequency, while the changes provoked by the charge in the phase of the sensor are monitored. The use of high-frequency sensors enhances the sensitivity of the measure, whereas the design characterization system reduces the noise in the measurement. The result is an improvement in the limit of detection (LOD). This way, we achieve one of the challenges in the acoustic high-frequency devices. The validation of the platform is performed by means of an immunosensor based in high fundamental frequency QCM crystals (HFF-QCM) for the detection of two pesticides: carbaryl and thiabendazole. The results obtained for carbaryl are compared to the results obtained by another high-frequency acoustic technology based in Love sensors, with the optical technique based in surface plasmonic resonance and with the gold standard technique Enzyme Linked Immunoassay (ELISA). The LOD obtained with the acoustic sensors HFF-QCM and Love is similar to the one obtained with ELISA and improves by one order of magnitude the LOD obtained with SPR. The conceptual ease of the proposed system, its low cost and the possibility of miniaturization of the quartz resonator, allows the characterization of multiple sensors integrated in an array configuration, which will allow in the future to achieve the challenge of multianalyte detection for applications of High-Throughput Screening (HTS).<br>[ES] Durante las dos últimas décadas se han propuesto diferentes interfaces electrónicos para medir los parámetros más importantes de caracterización de los cristales de microbalanza de cuarzo (QCM). La medida de los parámetros adecuados del sensor para una aplicación específica es muy importante, ya que un error en la medida de dichos parámetros puede resultar en un error en la interpretación de los resultados. Los requerimientos del sistema de caracterización dependen de la aplicación. En esta tesis se proponen dos sistemas de caracterización para dos ámbitos de aplicación que comprenden la mayoría de las aplicaciones con sensores QCM: 1) Caracterización de materiales bajo condiciones de amortiguamiento variable y 2) detección de sustancias con alta resolución de medida. Los sistemas propuestos tratan de resolver la problemática detectada en los ya existentes. Para aplicaciones en las que el amortiguamiento del sensor varía durante el experimento, se propone un sistema basado en una nueva configuración de la técnica de compensación automática de capacidad (ACC). La nueva configuración proporciona la medida de la frecuencia de resonancia serie, la resistencia dinámica y la capacidad paralelo del sensor. Además, permite una fácil calibración del sistema que mejora la precisión en la medida. Se presentan resultados experimentales para cristales de 9 y 10MHz en medios fluidos, con diferentes capacidades en paralelo, demostrando la efectividad de la compensación de capacidad. El sistema presenta alguna desviación en frecuencia con respecto a la frecuencia resonancia serie, medida con un analizador de impedancias. Estas desviaciones son explicadas convenientemente, debidas al comportamiento no ideal específico de algunoscomponentes del circuito. Una nueva propuesta de circuito se presenta como posible solución a este problema. Para aplicaciones de alta resolución se propone una plataforma integrada para caracterizar sensores acústicos de alta frecuencia. El sistema propuesto se basa en un nuevo concepto en el que el sensor es interrogado, mediante una fuente externa muy estable y de muy bajo ruido, a una frecuencia constante mientras se monitorizan los cambios producidos por la carga en la fase del sensor. El uso de sensores de alta frecuencia aumenta la sensibilidad de la medida, por otro lado, el sistema de caracterización diseñado reduce el ruido en la misma. El resultado es una mejora del límite de detección (LOD). Se consigue con ello uno de los retos pendientes en los dispositivos acústicos de alta frecuencia. La validación de la plataforma desarrollada se realiza con una aplicación de un inmunosensor basado en cristales QCM de alta frecuencia fundamental (HFF-QCM) para la detección de dos pesticidas: carbaryl y tiabendazol. Los resultados obtenidos para el Carbaryl se comparan con los obtenidos con otra tecnología acústica de alta frecuencia basada en sensores Love, con la técnica óptica basada resonancia superficial de plasmones (SPR) y con la técnica de referencia Enzyme Linked Immuno Assay (ELISA). El LOD obtenido con los sensores acústicos HFFQCM y Love es similar al obtenido con las técnicas ELISA y mejora en un orden de magnitud al obtenido con SPR. La sencillez conceptual del sistema propuesto junto con su bajo coste, así como la capacidad de miniaturización del resonador de cuarzo hace posible la caracterización de múltiples sensores integrados en una configuración en array, esto permitirá en un futuro alcanzar el reto de la detección multianalito para aplicaciones High-Throughput Screening (HTS).<br>[CAT] Durant les dues últimes dècades s'han proposat diferents interfases electrònics per a mesurar els paràmetres més importants de caracterització dels cristalls de microbalança de quars (QCM). La mesura dels paràmetres adequats del sensor per a una aplicació específica és molt important, perquè un error en la interpretació dels resultats pot resultar en un error en la interpretació dels resultats. Els requeriments del sistema de caracterització depenen de l'aplicació. En aquesta tesi, es proposen dos sistemes de caracterització per a dos àmbits d'aplicació que comprenen la majoria de les aplicacions amb sensors QCM: 1) Caracterització de materials sota condicions d'amortiment variable i 2) detecció de substàncies amb alta resolució de mesura. Els sistemes proposats tracten de resoldre la problemàtica detectada en els ja existents. Per a aplicacions en les quals l'amortiment del sensor varia durant l'experiment, es proposa un sistema basat en una nova configuració de la tècnica de compensació automàtica de capacitat (ACC). La nova configuració proporciona la mesura de la freqüència de ressonància sèrie, la resistència dinàmica i la capacitat paral¿lel del sensor. A més, permet un calibratge fàcil del sistema que millora la precisió de la mesura. Es presenten els resultats experimentals per a cristalls de 9 i 10 MHz en mitjans fluids, amb diferents capacitats en paral¿lel, demostrant l'efectivitat de la compensació de capacitat. El sistema presenta alguna desviació en freqüència respecte a la freqüència ressonància sèrie, mesurada amb un analitzador d'impedàncies. Aquestes desviacions són explicades convenientment, degudes al comportament no ideal específic d'alguns components del circuit. Una nova proposta de circuit es presenta com a possible solució a aquest problema. Per a aplicacions d'alta resolució es proposa una plataforma integrada per a caracteritzar sensors acústics d'alta freqüència. El sistema proposat es basa en un nou concepte en el qual el sensor és interrogat mitjançant una font externa molt estable i de molt baix soroll, a una freqüència constant mentre es monitoritzen els canvis produïts per la càrrega en la fase del sensor. L'ús de sensors d'alta freqüència augmenta la sensibilitat de la mesura, per altra banda, el sistema de caracterització dissenyat redueix el soroll en la mateixa. El resultat és una millora en el límit de detecció (LOD). S'aconsegueix amb això un dels reptes pendents en els dispositius acústics d'alta freqüència. La validació de la plataforma desenvolupada es realitza amb una aplicació d'un immunosensor basat en cristalls QCM d'alta freqüència fonamental (HFF-QCM) per a la detecció de dos pesticides: carbaryl i tiabendazol. Els resultats obtinguts per al carbaryl es comparen amb els obtinguts amb altra tecnologia acústica d'alta freqüència basada en sensors Love, amb la tècnica òptica basada en ressonància superficial de plasmons (SPR) i amb la tècnica de referència Enzyme Linked Immuno Assay (ELISA). El LOD obtingut amb els sensors acústics HFF-QCM i Love és similar al obtingut amb les tècniques ELISA i millora en un ordre de magnitud el obtingut amb SPR. La senzillesa conceptual del sistema proposat junt amb el seu baix cost, així com la capacitat de miniaturització del ressonador de quars fa possible la caracterització de múltiples sensors integrats en una configuració en array, el que permetrà en un futur assolir el repte de la detecció multianalit per a aplicacions High-Throughput Screening (HTS).<br>García Narbón, JV. (2016). Improved characterization systems for quartz crystal microbalance sensors: parallel capacitance compensation for variable damping conditions and integrated platform for high frequency sensors in high resolution applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63249<br>TESIS

Le contrôle de la propagation des ondes élastiques repose principalement sur la conception de milieu artificiel à base de matériaux structurés pour obtenir une ingénierie avancée de la dispersion de la propagation. Au cours de la thèse, la dispersion du mode guidé de polarisation transverse horizontale (mode de Love) dans la structure bi-couche SiO2/Quartz (Coupe ST-90°) a été numériquement étudié et les applications résultantes explorées. Les propriétés des cristaux phononiques (CPns) à base de trous micro-usinés dans la couche SiO2 ont été étudié, ainsi que l’interaction de ce mode avec des plots déposés à la surface de cette couche guidante. Dans le cas des CPns à trous nous avons montré qu’il est possible d’ouvrir des bandes interdites, cette propriété a été exploitée pour le design d’un résonateur cavité. Les performances de ce résonateur sont étudiées en fonction des paramètres géométriques qui le caractérisent. Il est aussi proposé d’étudier l’interaction des modes de cavité avec les modes de résonance des plots déposés à la surface de la cavité. Ceci peut mieux confiner les modes et donc améliorer drastiquement le facteur de qualité. On s’est intéressé aussi à l’interaction du mode Love avec des métasurfaces à base de plots déposés à la surface de SiO2. Les couplages entre des plots de géométries identiques ou non ont donné lieu aux divers phénomènes comme analogue acoustique de Autler-Townes Splitting, résonance Fabry-Perot, transparence induite acoustiquement et résonance Fano. Les résultats présentés pourraient être utilisés pour des applications potentielles telles que le traitement du signal, le contrôle des ondes, les métamatériaux et les biocapteurs<br>The control of the propagation of elastic waves relies mainly on the design of artificial medium based on structured materials to obtain an advanced engineering of the dispersion of the propagation. During the thesis, the dispersion of the shear horizontal polarised guided mode (Love mode) in the bi-layer SiO2/Quartz (90ST-cut) structure was numerically investigated and the resulting applications explored. The properties of phononic crystals (PnCs) based on micro-machined holes in the SiO2 layer, and the interaction of this mode with pillars deposited on the surface of this guiding layer, have been studied. In the case of holey PnCs we have shown that it is possible to open band gaps, this property has been exploited for the design of a cavity resonator. The performances of this resonator are studied according to the geometrical parameters characterizing it. It is also proposed to study the interaction of the cavity resonator’s modes with the resonant modes of pillars deposited on the surface of the cavity. This has the effect of a better confinement of the modes and thus a drastic improvement of the quality factor. We also investigated the interaction between the Love mode and metasurfaces based on pillars deposited on the surface of SiO2. The couplings between pillars of identical or not geometries gave rise to various phenomena like acoustic analogue of Autler-Townes Splitting, Fabry-Perot resonance, acoustically induced transparency and Fano resonance. The results presented in this study could be used for potential applications such as signal processing, wave control, metamaterials and biosensors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Vita.<br>Includes bibliographical references (p. 175-188).<br>(cont.) The self consistent defect model established the defect chemistry of langasite, enabling important parameters describing reduction (Er = 5.70± -0.06eV and 6.57±-0.24eV for acceptor and donor doped langasite respectively) and oxidation (Eo = 2.18±0.08eV), intrinsic electron-hole generation (Eg [approx. equals] 4.0-4.4eV) and defect ionization (ED-ion = 52±0.06eV for Nb ionization), to be extracted. The predictive defect model was used to calculate the dependence of the partial ionic and electronic conductivities and mass change as functions of temperature, dopant level and pO₂. Given that the magnitudes of conductivity and mass change directly affect the resolution and sensitivity limits of langasite resonators, their predictions allowed for the definition of acceptable operating limits and/or the design of properties for optimum resolution and sensitivity. Two high temperature applications of resonant sensors were studied. Praseodymiumcerium oxide was selected for oxygen partial pressure monitoring and is representative of films which change mass upon absorption or desorption of gaseous species. Barium carbonate film was selected for NO₂ sensing and is representative of films which change mass upon reaction with the gas phase to form a new product phase. Both sensors showed sensitivity to their respective target chemicals and demonstrated the feasibility of high temperature sensor applications. The performance of each sensor was discussed and suggestions for improving sensor performance were presented.<br>The high temperature transport properties of langasite, La₃Ga₅SiO₁₄, were investigated with special attention focused on their potential impact on the utilization of langasite as a mass sensitive resonant platform for high temperature sensor applications. The electrical properties of acceptor and donor doped langasite were examined at temperatures ranging from 700 to 1000 ⁰C, and pO₂ of 1 to 10-25atm. Acceptor doped langasite was shown to exhibit mixed ionic-electronic conductivity behavior, with predominant ionic conduction due to mobile oxygen vacancies at high pO₂, and n-type electronic conduction due to electrons at low pO₂. Increasing acceptor level resulted in the appearance of p-type hole conduction at high pO₂ and increased ionic conductivity, while the n-type electron conduction was depressed. Donor doped langasite was shown to be electronic at all temperatures and pO₂. The electron mobility of langasite was found to be activated (polaron hopping) with an activation energy of 0.15(±0.01)eV, whereas the holes were assumed to be quasi free carriers. The activation energy for oxygen vacancy migration was estimated to be 0.91(±0.01)eV under dilute solution conditions and 1.27(±0.02)eV for 1% Sr level under concentrated solution conditions. Both values of activation energy of ionic conductivity-temperature product are consistent with activation energy of oxygen self-diffusivity in the respective materials. The electrical properties were related to the underlying defect and transport processes using defect modeling.<br>by Huankiat Seh.<br>Ph.D.

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.

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.

Sensing in harsh environments is always in great need. Although many sensors and sensing systems are reported, such as optical fiber sensors and acoustic sensors, they all have drawbacks. In this dissertation, fused quartz and sapphire acoustic waveguides and sensors are developed for high temperature and heavy gamma radiation. The periodic structure, acoustic fiber Bragg grating (AFBG), is the core sensor structure in this dissertation. To better analyze the propagation of acoustic waves, the acoustic coupled more analysis is proposed. It could solve for the reflection spectrum of the AFBG with at most 2.1% error. For the waveguide, the fused quartz "suspended core" waveguide is designed. It achieved strong acoustic energy confinement so surface perturbations no longer affected the wave propagation. Single crystal sapphire fiber features low acoustic loss, and survivability under high temperature. It is also chosen as an acoustic waveguide. AFBGs are fabricated in both waveguides. The fused quartz suspended core AFBG is shown to sense temperature up to 1000 C and to have stable reading at 700 C for 14 days. The sapphire AFBG as a temperature sensor works up to 1500 C and also provides continuous stable reading at 1100 C for 12 days. Both waveguides with AFBGs are then tested under long-term gamma radiation. Despite some fluctuations from radiation-related causes, the readings of both sensors generally remain stable. Given the experimental observations, the fused quartz AFBG waveguide and the sapphire AFBG waveguide are shown to work well in high temperature and gamma radiations.<br>Doctor of Philosophy<br>Sensing in harsh environments, like high temperature, high pressure, and corrosive environment, is always in great need. Efficient and safe operation of instruments like nuclear reactors could be better secured. Although many sensors and sensing systems are reported, such as optical fiber sensors and acoustic sensors, they all have drawbacks so new designs are constantly in need.newline In this dissertation, silica (a glass commonly acquired by melting sand) and sapphire (used in iphone screens due to its transparency and hardness) acoustic waveguides and sensors are developed. A periodic structure known as acoustic fiber Bragg grating (AFBG) is the core sensor structure in this dissertation. A calculation method is proposed first. Acoustic wave needs a waveguide to propagate somewhere further, and a new waveguide structure is made to keep the acoustic energy within the very center of the waveguide, so any change on the outer surface does not affect the wave inside. Also, sapphire has good acoustic property and is used. The AFBGs are fabricated in both waveguides. These sensing waveguides are shown to work at >1000 C temperature and provide stable reading for more than 10 days. Long term exposure to gamma radiation for weeks or months resulted in stable performances. Therefore, it is concluded that silica and sapphire waveguide sensors are successfully developed for high temperature and nuclear radiation applications.

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.?<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering

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.

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.

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.

El gran impacto de la tecnología FBAR tanto en sistemas de radio frecuencia como más recientemente en sensores han motivado el desarrollo de aplicaciones integradas. Esto implica que los procesos de fabricación deberían lograr producir dispositivos resonadores con un alto factor de calidad, al tiempo que permitir la integración de los FBAR con tecnologías CMOS estándar. De tal manera, esta tesis doctoral aborda dichos requerimientos, contribuyendo con el diseño, fabricación y caracterización de resonadores FBAR; su integración con tecnologías CMOS estándar; y su aplicación a sistemas de sensores. <br/>El desarrollo de la tecnología de fabricación de los FBAR ha involucrado la puesta a punto de las técnicas de depósito y micro-mecanización de la estructura en capas del resonador, la cual está comprendida por una película de material acústico hecha de nitruro de aluminio (AlN). Se realizaron diversas pruebas para analizar la calidad del AlN depositado. También se probaron y pusieron a punto diferentes tecnologías de micro¬mecanización para liberar la estructura del FBAR, destacando entre ellas la técnica de ataque en seco por la cara de componentes, dados los altos factores de calidad obtenidos (superiores a 2.000 a 2,4 GHz). Sobre los dispositivos fabricados se realizaron caracterizaciones estructurales, modelos utilizando análisis de elementos finitos y la extracción de parámetros de circuito equivalente. Una variación del proceso que involucraba el diseño, modelado y fabricación de un dispositivo FBAR con compensación de temperatura fue igualmente desarrollada. En este ámbito vale la pena resaltar la concepción y realización de una novedosa técnica post-fabricación para el ajuste fino de la frecuencia de resonancia de los FBAR por medio de un haz de iones focalizados (FIB). <br/>Basado en la tecnología arriba mencionada, se desarrolló un método de integración heterogénea a nivel de oblea de los dispositivos FBAR en sustratos CMOS estándar. De acuerdo con este método, se logró fabricar por primera vez dispositivos FBAR flotando sobre sustratos CMOS estándar. Este método ha sido exitosamente demostrado por medio de la integración de los FBAR tanto con la tecnología comercial AMS035 como con la CNM25, desarrollada en el CNM-IMB (CSIC). <br/>En el terreno de las aplicaciones, se diseñaron y realizaron diferentes aplicaciones de sensores basadas en FBAR, siendo el detector de masas localizadas la más relevante de entre ellas. Es de anotar que esta aplicación fue demostrada por primera vez utilizando FBARs de alta frecuencia como elemento sensor. De tal forma, se contrastaron los resultados experimentales y de modelado del sensor. Por otra parte, se presenta también el concepto de sensores mecánicos basados en FBAR. Para ello se han desarrollado dos ejemplos: el acelerómetro basado en FBAR y el sensor de fuerza para aplicaciones de puntas de AFM. Se reporta también en esta tesis la fabricación y caracterización de un nuevo tipo de resonadores acústicos de AlN sin contacto entre electrodos.<br>The high impact of FBAR on radio-frequency and, most recently, on sensing systems has motivated the development of integrated applications. This means that the fabrication process should succeed in producing high-quality-factor resonators and, at the same time, in integrating FBARs with standard CMOS technologies. Hence, this Ph.D. thesis addresses these requirements by contributing with the design, fabrication and characterization of thin-film bulk acoustic wave resonators (FBAR); their integration with standard complementary-metal-oxide-semiconductor (CMOS) technologies; and their application to sensing systems. <br/>The development of the FBAR's fabrication technology has involved the set up of the deposition and micromachining techniques of the layered structure of the resonator, which comprises an acoustic layer made of aluminum nitride (AlN). Several tests on the deposition and characterization of the AlN quality were carried out. Also, different micro-machining technologies for FBAR releasing were tested, the front-side micro-machining technique having obtained the best quality-factor results (over 2,000 at 2.4 GHz). Structural and device experimental characterization; and equivalent-circuit parameter and finite-element modeling of the FBAR were carried out. A process variation involving the design, modeling and fabrication of a temperature-compensated (TC) FBAR device was also implemented. Another remarkable result is the implementation of a post-fabrication, focused-ion-beam assisted technique for tuning of the resonance frequency of the FBAR. <br/>Based on the foregoing-mentioned FBAR technology, a method for performing wafer-level heterogeneous integration of the FBAR with a CMOS substrate was developed. According to this method, the fabrication of a floating FBAR above standard CMOS substrates has been achieved for the first time. The method was demonstrated by integrating FBARs on the commercial AMS035 and the in-house CNM25 CMOS technologies. <br/>On the application side, different FBAR-based sensor applications were implemented, the localized-mass detector being the most relevant, which has been demonstrated for the first time for high-frequency bulk-acoustic resonators. Experimental and modeling results have been contrasted. Also, the concept of FBAR-based mechanical sensor has been introduced. Two examples are the embedded-FBAR accelerometer and the force sensor for AFM-cantilever applications. The fabrication and characterization results of an AlN-based contactless acoustic resonator are also reported in this thesis.

Une technologie novatrice de fabrication des FBAR a tout d'abord été développée : en particulier des techniques de dépôt et de micro-mécanisation de la structure en couches du résonateur ont été mises au point. La modélisation électrique sous la forme d'un circuit équivalent, la modélisation mécanique par la méthode des éléments finis (FEM), ainsi que les caractérisations structurale et électrique des FBARs, ont été réalisées. Par ailleurs, une variation du procédé de fabrication aboutissant à des dispositifs FBAR avec compensation de température (TC) a aussi été développée. Un autre résultat marquant de cette thèse a été l'implémentation d'une nouvelle procédure d'ajustement de la fréquence résonance du FBAR basée sur l'utilisation d'un faisceau d'ions focalisé (FIB). Basée sur la technologie FBAR déjà mentionnée, une méthode permettant de réaliser l'intégration hétérogène à niveau wafer des FBARs avec substrats CMOS a été conçue et implémentée. De cette manière, et pour la première fois, des dispositifs FBAR localisés sur substrat CMOS ont été fabriqués avec succès. De plus, cette méthode de co-intégration a été démontrée pour plusieurs technologies : avec une CMOS commerciale [AMS035] mais aussi avec la CNM25, développée au CNM. Enfin, différentes applications de dispositifs FBAR en tant que capteurs ont été proposées, la plus pertinente étant une implémentation comme capteur de masse localisée, ce qui représente un première pour des FBARs. Par ailleurs, le concept de capteur mécanique basé sur un FBAR a été introduit et expérimentalement démontré à travers deux exemples : accéléromètres encastrés et capteurs de force pour des applications de microscopie à force atomique (AFM). Pour terminer, la fabrication et la caractérisation d'un résonateur acoustique sans contact entre électrodes et couche mince d'AlN ont été proposées<br>The FBAR's fabrication technology has been developed. The technology involves the set up of the deposition and micro-machining techniques of the layered structure of the resonator, which comprises an acoustic layer made of aluminum nitride (AlN). Structural and device experimental characterization; and equivalent-circuit parameter and finite-element modeling of the FBAR were carried out. A process variation involving the design, modeling and fabrication of a temperature-compensated (TC) FBAR device was also implemented. Another remarkable result is the implementation of a post-fabrication, focused-ion-beam assisted technique for tuning of the resonance frequency of the FBAR. Based on the foregoing-mentioned FBAR technology, a method for performing wafer-level heterogeneous integration of the FBAR with a CMOS substrate was developed. According to this method, the fabrication of a floating FBAR above standard CMOS substrates has been achieved for the first time. The method was demonstrated by integrating FBARs on the commercial AMS035 and the in-house CNM25 CMOS technologies. On the application side, different FBAR-based sensor applications were implemented, the localized-mass detector being the most relevant, which has been demonstrated for the first time for high-frequency bulk-acoustic resonators. Also, the concept of FBAR-based mechanical sensor has been introduced. Two examples are the embedded-FBAR accelerometer and the force sensor for AFM-cantilever applications. The fabrication and characterization results of an AlN-based contact-less acoustic resonator are also reported in this thesis

The goal of this research was to develop acoustic sensors and actuators for microfluidic applications. To this end, capacitive micromachined ultrasonic transducers (cMUTs) were developed which generate guided acoustic waves in fluid half-spaces and microchannels. An interdigital transducer structure and a phased excitation scheme were used to selectively excite guided acoustic modes which propagate in a single lateral direction. Analytical models were developed to predict the geometric dispersion of the acoustic modes and to determine the sensitivity of the modes to changes in material and geometric parameters. Coupled field finite element models were also developed to predict the effect of membrane spacing and phasing on mode generation and directionality. After designing the transducers, a surface micromachining process was developed which has a low processing temperature of 250C and has the potential for monolithically integrating cMUTs with CMOS electronics. The fabrication process makes extensive use of PECVD silicon nitride depositions for membrane formation and sealing. The fabricated interdigital cMUTs were placed in microfluidic channels and demonstrated to sense changes in fluid sound speed and flow rate using Scholte waves and other guided acoustic modes. The minimum detectable change in sound speed was 0.25m/s, and the minimum detectable change in flow rate was 1mL/min. The unique nature of the Scholte wave allowed for the measurement of fluid properties of a semi-infinite fluid using two transducers on a single substrate. Changes in water temperature, and thus sound speed, were measured and the minimum detectable change in temperature was found to be 0.1C. For fluid pumping, interdigital cMUTs were integrated into microchannels and excited with phase-shifted, continuous wave signals. Highly directional guided waves were generated which in turn generated acoustic streaming forces in the fluid. The acoustic streaming forces caused the fluid to be pumped in a single, electronically-controlled direction. For a power consumption of 43mW, a flow rate of 410nL/min was generated against a pressure of 3.4Pa; the thermodynamic efficiency was approximately 5x10-8%. Although the efficiency and pressure head are low, these transducers can be useful for precisely manipulating small amounts of fluid around microfluidic networks.

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.

<p>The aim of the work was to investigate the possibility to combine information from PPG and bio-acoustic technology to extract information that is related to the blood pressure. The measurements have been carried out with several different configurations. First the relation between arterial sounds and the PPG-signal was studied. After those measurements with both PPG and the bio- acoustic technique was concluded on people in different positions and after riding a bike. The goal was to vary the blood pressure. The conclusion that can be drawn in this report is that the bio-acoustic and the PPG-signal in peripheral arteries have the same source. That implies that arterial sounds are a product of turbulence when the pulse wave passes by. Further it can be assumed that it is the first heart sound that is represented in the arterial sounds. The time before and after the arterial sound in one heart cycle vary whit the blood pressure. There relationship seems also to vary with the bloodpressure but it vary differently under different conditions.</p>

Au cours des dernières décennies, on a assisté à une croissance considérable dans le domaine des technologies des capteurs magnétiques. Le domaine est passé de simples dispositifs micro-usinés à base de silicium à des microsystèmes intégrés plus complexes combinant des transducteurs de haute performance ainsi que des interfaces sans fil. Cependant, presque tous ces appareils fonctionnent avec un mécanisme complexe tout en étant alimentés simultanément de l'extérieur et coûteux. Il y a donc un besoin profond de développer un capteur magnétique qui surmonte ces défis. Ces travaux de recherche ont porté sur le développement de capteurs à ondes élastiques de surface (SAW) pour la détection des champs magnétiques. La configuration résonateur a été considérée dans cette étude afin de permettre une interrogation sans fil. La première partie de notre travail est consacrée à l’étude de la physique et à l'interaction entre les ondes élastiques et les couches magnétostrictives lorsqu'elles sont soumises à un champ magnétique. Nous avons donc étudié des résonateurs SAW en utilisant le niobate de lithium comme substrat et un empilement multicouches [TbCo2/FeCo] comme électrode et matériau sensible. Nous avons étudié et montré le rôle de l'effet de forme dans le magnétisme résultant de la géométrie de l'électrode. Un banc de mesure expérimental a été mis au point pour démontrer l’utilisation d’un capteur magnétique SAW pour la mesure du courant électrique le long d’une lignes hautes tension. Par la suite, nous avons développé un capteur auto-compensé en température rendant sa fréquence de résonance uniquement sensible à l’intensité du champ magnétique. Ce capteur à structure multicouche utilise la coupe ST du quartz comme substrat avec comme direction de propagation des ondes X+90°C. Cette direction de la coupe ST présente un coefficient de température positif (TCF) qui a été compensé par le les couches de ZnO et du CoFeB qui présentent un TCF négatif. Enfin, en combinant nos connaissances sur les effets de forme magnétiques et sur le comportement des structure SAW multicouche pour développer un dispositif qui non seulement annule les effets de la température sur la fréquence de résonance mais également sur l'anisotropie magnétique. De plus, cette structure présente également la possibilité de réaliser un dispositif multisensoriel puisque dans le même dispositif, plusieurs modes sont générés. En plus du mode compensé en température qui permet de mesurer l’intensité du champ magnétique, un autre peu sensible au champ magnétique, permettra de mesurer la température de l’environnement de fonctionnement<br>The last few decades have seen tremendous growth in the area of magnetic sensor technologies. The field has grown from simple micro-machined silicon based devices to more complex integrated microsystems combining high performance transducers as well as wireless interfaces. However, almost all of these devices operate with a complex mechanism while simultaneously being externally powered as well as expensive. Thus, there arises a deep need to develop a magnetic sensor that overcomes the challenges. This research work focused on the development of surface acoustic wave (SAW) sensors for the detection of magnetic field. Owing to the possibility of wireless interrogation, SAW devices of the resonator configuration have been considered in this study. The first part of our work aims to address the physics and interaction between the acoustic waves and magnetostrictive layers when subjected to a magnetic field. We investigated SAW resonators using LiNbO3 as the substrate and multi-layered [TbCo2/FeCo] as the electrode and sensitive material. We studied and showed the role of the shape effect in magnetism arising from the electrode geometry. A model experimental set-up was developed to demonstrate an application of the fabricated device as a sensor for detection of current along a cable. Subsequently, we developed a device that is self-compensated for the effects of temperature on the resonance frequency. The multi-layered sensor was based on ST-cut Quartz as the substrate whose positive temperature coefficient of frequency (TCF) was compensated for by the negative TCF of ZnO and CoFeB. Finally, we combine our understandings of the shape effects in magnetism and the multi-layered TCF compensated SAW structure to develop a device that is not only compensated for the effects of temperature on the resonance frequency but also on the magnetic anisotropy. In addition, this structure also presents the possibility of a proof-of-concept multi-sensory device because along with the temperature compensated resonance peak, there exist other resonances which are highly sensitive to any change in the temperature while at the same time immune to magnetic field

This thesis describes two separate projects. The first is a theoretical and experimental investigation of surface acoustic wave streaming in microfluidics. The second is the development of a novel acoustic glucose sensor. A separate abstract is given for each here. Optimization of acoustic streaming in microfluidic channels by SAWs Surface Acoustic Waves, (SAWs) actuated on flat piezoelectric substrates constitute a convenient and versatile tool for microfluidic manipulation due to the easy and versatile interfacing with microfluidic droplets and channels. The acoustic streaming effect can be exploited to drive fast streaming and pumping of fluids in microchannels and droplets (Shilton et al. 2014; Schmid et al. 2011), as well as size dependant sorting of particles in centrifugal flows and vortices (Franke et al. 2009; Rogers et al. 2010). Although the theory describing acoustic streaming by SAWs is well understood, very little attention has been paid to the optimisation of SAW streaming by the correct selection of frequency. In this thesis a finite element simulation of the fluid streaming in a microfluidic chamber due to a SAW beam was constructed and verified against micro-PIV measurements of the fluid flow in a fabricated device. It was found that there is an optimum frequency that generates the fastest streaming dependent on the height and width of the chamber. It is hoped this will serve as a design tool for those who want to optimally match SAW frequency with a particular microfluidic design. An acoustic glucose sensor Diabetes mellitus is a disease characterised by an inability to properly regulate blood glucose levels. In order to keep glucose levels under control some diabetics require regular injections of insulin. Continuous monitoring of glucose has been demonstrated to improve the management of diabetes (Zick et al. 2007; Heinemann & DeVries 2014), however there is a low patient uptake of continuous glucose monitoring systems due to the invasive nature of the current technology (Ramchandani et al. 2011). In this thesis a novel way of monitoring glucose levels is proposed which would use ultrasonic waves to ‘read’ a subcutaneous glucose sensitive-implant, which is only minimally invasive. The implant is an acoustic analogy of a Bragg stack with a ‘defect’ layer that acts as the sensing layer. A numerical study was performed on how the physical changes in the sensing layer can be deduced by monitoring the reflection amplitude spectrum of ultrasonic waves reflected from the implant. Coupled modes between the skin and the sensing layer were found to be a potential source of error and drift in the measurement. It was found that by increasing the number of layers in the stack that this could be minimized. A laboratory proof of concept system was developed using a glucose sensitive hydrogel as the sensing layer. It was possible to monitor the changing thickness and speed of sound of the hydrogel due to physiological relevant changes in glucose concentration.

Cette thèse porte sur la conception et la caractérisation de micro-dispositifs à ondes acoustiques multicouches. La cinquième génération de communication (5G) nécessite des résonateurs acoustiques plus performants (fréquences &gt; 3GHz, bande passante plus large). Dans ce contexte, nous avons conçu et optimisé par simulation FEM la géométrie de résonateurs à ondes de Lamb à base d’AlScN. Le dispositif final, constitué d’une couche composée de 30% de Sc et déposée sur un miroir de Bragg W/SiO2, montre d’excellentes performances (coefficient de couplage de 5% et facteur de qualité de 768) et un bon accord avec la simulation. Pour caractériser la surface de BAW et SAW sur la gamme de fréquence 5G, nous avons également conçu et développé un interféromètre hétérodyne. Ce dernier a été utilisé avec succès pour caractériser des vibrations de surface d'une amplitude comprise entre 1 et 10 pm à 5,95 GHz. Par ailleurs, grâce à leur robustesse et leur capacité à être interrogé sans-fil, les capteurs SAW sont utilisés dans des environnements difficiles et suscitent un grand intérêt pour les applications médicales et de contrôle de santé intégré. Récemment, l’introduction d’empilements multi-matériaux offre de nouvelles opportunités de développements. Nous avons ainsi étudié un capteur de pression composé de deux couches complémentaires, ainsi qu'un capteur dit package-less utilisant des couches d’impédances acoustiques différentes. Pour concevoir ces nouveaux capteurs, nous avons développé un outil de simulation reposant sur l'extraction de paramètres de couplage de modes et tenant compte des effets de la température, des contraintes et des déformations pour estimer leur sensibilité<br>This thesis deals with the design and characterization of multilayer acoustic wave micro-devices. The fifth generation of communication (5G) requires more efficient acoustic resonators (frequencies &gt; 3GHz, wider bandwidth). In this context, we have designed and optimized using FEM simulation, the geometry of Lamb wave resonator based on AlScN. The final device, consisting of a layer composed of 30% Sc and deposited on a Bragg W/SiO2 mirror, shows excellent performance (coupling coefficient of 5% and quality factor of 768) as well as a good agreement with the simulation. To characterize the surface of BAW and SAW over the 5G frequency range, we also designed and developed a heterodyne interferometer. The latter has been used successfully to characterize surface vibrations with amplitudes between 1 and 10 pm at 5.95 GHz. Furthermore, thanks to their robustness and ability to be wirelessly interrogated,SAW sensors are used in harsh environments and are of great interest for medical applications and structural health monitoring. Recently, the introduction of multi-material stacks offers new development opportunities. We thus studied a pressure sensor composed of two complementary layers, as well as a so-called package- less sensor using different acoustic impedance layers. To design these new sensors, we have developed a simulation tool based on the extraction of mode coupling parameters and taking into account the effects of temperature, stresses and strains to estimate their sensitivity

Thesis (Ph.D.)--Biomedical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: William D Hunt; Committee Member: Bruno Frazier; Committee Member: Dale Edmondson; Committee Member: Marie Csete; Committee Member: Peter Edmonson; Committee Member: Ruth O'Regan

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.<br>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).<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science

Les chiffres des statistiques du cancer colorectal en France et dans le mondemontrent la nécessité de développement de plateformes technologiques plus rapides,sensibles et spécifiques pour assurer le diagnostic du cancer. Un diagnostic rapide va ainsiaider à améliorer l’état de santé et réduire le temps d’attente des résultats qui peut être ungrand facteur de stress pour les patients. L’analyse des biomarqueurs dans le sang, lesurines et autres fluides corporels est l’une des méthodes appliquées pour la détectionprécoce de la maladie. Dans le cadre de ce projet des nucléosides urinaires ont été identifiéscomme biomarqueurs pour le cancer colorectal. Financée par l’Agence Nationale de laRecherche (ANR), à travers le projet CancerSensor (programme TECSAN), cette thèse s’estdéroulée au sein de l’équipe MDA (Microsystèmes de Détection Acoustique) du laboratoireIMS. Dans le cadre de ce projet, nous avons proposé une solution technologique dedétection et de suivi de biomarqueurs du cancer colorectal. Notre choix de la stratégie dedétection s’est porté sur les polymères à empreintes moléculaires comme élément dereconnaissance des biomarqueurs. Celui-ci sera associé à un transducteur acoustique àondes de Love mis au point lors de travaux précédents au sein de l’équipe MDA. Lebiocapteur ainsi développé va cibler les nucléosides mis en évidence pour le cancercolorectal<br>Colorectal cancer statistics in France and all over the world demonstrate theneed for fast, sensitive and specific technological platforms development for cancerdiagnosis. A rapid diagnosis will improve the patients’ health status and reduce the resultswaiting time which could be a great stress factor. Biomarkers analysis in blood, urine andother body fluids is recognized as one of the applied methods for early cancer detection. Inframe of this project, urinary nucleosides have been identified as colorectal cancerbiomarkers. Funded by the National Research Agency (ANR), through the cancer sensorproject (TECSAN program), this thesis was carried out in IMS laboratory. Hence, a colorectalcancer biomarkers detection and monitoring technological solution has been proposed. Inour detection strategy, Molecularly Imprinted Polymers (MIP) has been identified asbiomarker recognition element. The MIP layer has been associated to Love Wave acoustictransducer. This biosensor will sense the identified colorectal cancer nucleosides

Ce travail a pour objectif de développer de nouveaux microcapteurs à onde acoustique de surface (SAW) capables de détecter le dioxyde de souffre (SO₂) à l’échelle de traces par l’intermédiaire d’une couche sensible à base d’un polymère fonctionnel. Une famille originale de cinq polyuréthaneimides (PUIs) à blocs contenant un nombre contrôlé de sites amines tertiaires de structures différentes a été synthétisée et caractérisée. Ces matériaux présentent des propriétés originales, en solution et à l’état solide, qui sont dues essentiellement à la présence des sites basiques et à la structure à blocs associant des blocs souples polyéthers et des blocs rigides en partie fluorés. Leur excellent caractère filmogène a permis leur application en tant que couche sensible au SO₂ sur des microcapteurs SAW. Deux structures de microcapteurs à onde de Love, bicouche et tri-couche, ont été développées en respectant les conditions de génération de l’onde. La structure bicouche comporte le Quartz-ST 90° comme substrat et l’un des PUIs joue le double rôle de couche guidante et sensible. Cette structure génère bien l’onde de Love mais elle présente une forte sensibilité à la température, inconvénient majeur pour les capteurs de gaz. L’ajout d’une couche guidante à base de ZnO, dans une structure tri-couche, a permis de rendre le dispositif peu sensible à la température et donc compatible avec l’application visée. Les résultats des tests de détection du SO₂ montrent que tous les PUIs étudiés contribuent à une amélioration de la sensibilité comparativement au dispositif sans couche polymère. La présence des sites amines tertiaires conduit à une amélioration importante de la sensibilité qui n’est pas seulement gouvernée par leur basicité mais également par leur encombrement stérique dont le rôle apparaît déterminant<br>This work aimed at developing new surface acoustic wave (SAW) microsensors capable of detecting traces of sulfur dioxide (SO₂) through a sensitive layer based on a functional polymer. An original family of five polyurethaneimide (PUI) block copolymers containing a controlled number of tertiary amine sites with different chemical structures was synthesized and characterized. These materials exhibited original properties in solution and solid state, which were mainly due to the presence of the basic sites and the block structure combining polyether soft blocks and partially fluorinated hard blocks. Their excellent film-forming character allowed their application as SO₂ sensitive layers on SAW microsensors. Two bi-layer and three-layer structures of Love wave microsensors were developed by respecting the conditions of the Love wave generation. The bi-layer structure included the Quartz ST-90° as the piezoelectric substrate and one of the PUIs acting as both guiding and sensitive layer. This structure generated the Love wave but its high sensitivity to temperature was a major drawback for gas sensors. The addition of a ZnO guiding layer in a three-layer structure led to a microsensor almost insensitive to temperature and thus compatible with the targeted application. The experimental results for SO₂ detection showed that all the PUIs contributed to improve the sensitivity compared to the device without polymer layer. The presence of tertiary amine sites led to a significant improvement in gas sensitivity which was not only governed by their basicity but also by their steric hindrance which played a determining role

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>94<br>Poly-crystal ZnO:Mg ( MZO ) films with c-axis ( 002 ) orientation have been successfully grown on the Fused quartz and 64° YX-LiNbO3 substrate by RF magnetron sputtering technique. We try to deposit c-axis ( 002 ) orientation ZnO film on the two substrates. The deposited films were characterized as a function of argon-oxygen gas flow ratio, chamber pressure, RF power, deposited time, target component, substrate temperature, and annealing temperature. Crystalline structures, stress, surface roughness, transmittance and work function characteristics of the films were investigated by X-ray diffraction ( XRD ), scanning electron microscopy ( SEM ), atomic force microscopy ( AFM ) measurement, UV-visible spectrometer and Photo-electron spectrometer in air Modol (AC-2). Firstly, we deposited the films on the LiNbO3 substrate ( MZO / IDTs / LiNbO3 ) as a Love wave sensor. With different conditions of MZO thin film, the frequency response, the sensitivity, and the temperature coefficient of frequency are measured. As a function of layer thickness., the maximum sensitivity is obtained under the ratio of thickness to wave length t/λ of 0.041 (1.67 um film thickness with the center frequency of 108.6 MHz). Secondly, the Love wave sensor provides higher sensitivity for MZO films sputtered on unheated substrate than on heated substrate, the sensitivity is 3.86× 10-8 m2s kg-1 and the roughness 7.42nm. With the different doping ratio of Mg , the ratio of 3 mol % Mg doped ZnO films has the best sensitivity with the roughness of 7.42nm. Since the substrate and the films both have negative temperature coefficient of frequency, there are little improvements on the temperature coefficient of frequency. Thirdly, we deposit thin film on Fused Quartz substrate and investigate its optical characteristics, including the transmittance, the band gap, the work function, and the refractive index. According to the experimental result, the films depositied on the unheated substrate show better optical transmittance. Besudes, both the band gap and the work function decrease with increasing temperature, and the maximum refractive index is obtained for the substrate temperature of 250oC. It is found that the optical transmittance of the MZO films decrease with increasing the annealing temperature, However, the band gap and the work function doesn’t change obviously, and the refractive index increases with increasing the annealing temperature. Finally, the transmittance doesn’t change obviously with the different doping ratio of Mg, the band gap and the work function increases with increasing the ratio of Mg, and the refractive index decreases with increasing the ratio of Mg.

碩士<br>國立成功大學<br>電機工程學系<br>89<br>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.

碩士<br>大同大學<br>機械工程學系(所)<br>98<br>In recent years, piezoelectric acoustic wave sensors, such as quartz crystal microbalance (QCM) and lateral field excited (LFE) acoustic wave sensor, have been widely investigated in biochemical sensing applications due to their high sensitivity and simple fabrication. However, the QCM is not capable of sensing surface electrical alteration, and the LFE sensor cannot be excited in air. Therefore, a novel piezoelectric acoustic wave sensor, namely pseudo lateral field excited (Pseudo-LFE) acoustic wave sensor, is proposed in this study. Finite element method and experiments were implemented to discuss sensitivities of the sensor to the characteristic variations of liquid or gas. The LFE sensor and QCM were also analyzed and measured for comparison. Results show that the Pseudo-LFE sensor successfully senses the mechanical and electrical variations of liquid or gas. Moreover, this sensor exhibits a higher sensitivity than the QCM and LFE sensor. According to the simulation and experimental results, we conclude that the Pseudo-LFE sensor is very suitable to apply in biochemical sensing.

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>91<br>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.

碩士<br>國立清華大學<br>奈米工程與微系統研究所<br>103<br>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.

碩士<br>義守大學<br>電機工程學系碩士班<br>97<br>Recently, surface acoustic wave (SAW) devices have played an important role in the well-developed communication technology. For instance, the filters and the duplexers in the mobile phones are usually the SAW devices. Moreover, the SAW devices are often applied in the application of detection due to their small size, low cost, and sensitive responses. The goal of this thesis is to develop a SAW gas sensor that is sensitive to ppm-level NO2 at room temperature. In this work, the substrate was STX-quartz and the chemical interface was polyaniline/WO3 nanocomposite. The SAW sensor developed in this work exhibits sensitive and reversible responses in a range of 10-80 ppm NO2 at room temperature. The response time and recovery time are also discussed in the work.

碩士<br>義守大學<br>電機工程學系<br>91<br>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.

碩士<br>國立成功大學<br>機械工程學系<br>89<br>This project is to develop and to build up the fundamentals of the acoustic wave sensors for the measurements of the fluid density and viscosity. Love wave sensor with pure shear-horizontal (SH) waveguide mode, in the presence of a SiO2 guiding layer, is introduced and is shown that it is very promising for liquid sensing due to its low radiation loss into the liquid. The variation of the liquid viscosity level (1 cP＜ηf ＜50 cP) gives rise to the phase shift and the increase of the insertion loss of the transmission response (S21) in order to obtain the fractional velocity change and the attenuation of Love wave affected by a viscous fluid. Moreover, the propagation characteristics of Love wave with different sensing distance has been studied and the alternative method for measuring the phase shift by the unwrap of the phase transmission response (S21) has been recommended. The theoretical and experimental study of Love waves affected by a viscous fluid are present in this work..

碩士<br>國立中正大學<br>機械工程所<br>96<br>The purpose of this work is to develop the wireless torque sensor for the rotating shaft applications. We designed and characterized the wireless torque sensors based on the one-port surface acoustic wave resonator (SAWR). The torque sensor has two distinct SAWRs of 433.42 MHz and 433.92 MHz respectively. The two SAWRs are mounted on the shaft of +-45o respectively relative to the shaft axis. The purpose of this arrangement is to make temperature compensation of the torque sensor. From another viewpoint, this double-SAWR sensor can measure the torque and temperature simultaneously. From the frequency shift direction, we are also able to identify the direction (CW or CCW) of the applied torque. We also developed a curve-fitting method to estimate the central frequency of the SAWR under the applied load. From the experimental result, we proved this curve-fitting method has the accuracy about 1 ppm. Finally, we mounted the torque sensors on the shaft in two different methods: the direct mounting method and the in-direct cap-mounting method. We compared the sensitivity and repeatability of these two mounting methods.