Дисертації: "Surface acoustic wave sensor"

1

Haskell, Reichl B. "A Surface Acoustic Wave Mercury Vapor Sensor." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/HaskellRB2003.pdf.

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2

Gizeli, Electra. "New acoustic wave sensor geometries." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282004.

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3

Sehra, Gurmukh S. "Surface acoustic wave based flavour sensor system." Thesis, University of Warwick, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416148.

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4

Banerjee, Markus K. "Acoustic wave interactions with viscous liquids spreading in the acoustic path of a surface acoustic wave sensor." Thesis, Nottingham Trent University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302521.

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5

Parmar, Biren Jagadish. "Development Of Point-Contact Surface Acoustic Wave Based Sensor System." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/279.

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Surface Acoustic Waves (SAW) fall under a special category of elastic waves that need a material medium to propagate. The energy of these waves is confined to a limited depth below the surface over which they propagate, and their amplitudes decay with increasing depth. As a consequence of their being a surface phenomenon, they are easily accessible for transduction. Due to this reason, a lot of research has been carried out in the area, which has resulted in two very popular applications of SAW - SAW devices and in Non-Destructive Testing and Evaluation. A major restriction of SAW devices is that the SAW need a piezoelectric medium for generation, propagation and reception. This thesis reports the attempt made to overcome this restriction and utilize the SAW on non-piezoelectric substrates for sensing capabilities. The velocity of the SAW is known to be dependent purely on the material properties, specifically the elastic constants and material density. This dependence is the motivation for the sensor system developed in the present work. Information on the survey of the methods suitable for the generation and reception of SAW on non-piezoelectric substrates has been included in the thesis. This is followed by the theoretical and practical details of the method chosen for the present work - the point source/point receiver method. Advantages of this method include a simple and inexpensive fabrication procedure, easy customizability and the absence of restrictions due to directivity of the SAW generated. The transducers consist of a conically shaped PZT element attached to a backing material. When the piezoelectric material on the transmitter side is electrically excited, they undergo mechanical oscillations. When coupled to the surface of a solid, the oscillations are transferred onto the solid, which then acts as a point source for SAW. At the receiver, placed at a distance from the source on the same side, the received mechanical oscillations are converted into an electrical signal as a consequence of the direct piezoelectric effect. The details of the fabrication and preliminary trials conducted on metallic as well as non-metallic samples are given. Various applications have been envisaged for this relatively simple sensor system. One of them is in the field of pressure sensing. Experiments have been carried out to employ the acoustoelastic property of a flexible diaphragm made of silicone rubber sheet to measure pressure. The diaphragm, when exposed to a pressure on one side, experiences a varying strain field on the surface. The velocity of SAW generated on the stressed surface varies in accordance with the applied stress, and the consequent strain field generated. To verify the acoustoelastic phenomenon in silicone rubber, SAW velocities have been measured in longitudinal and transverse directions with respect to that of the applied tensile strain. Similar measurements are carried out with a pressure variant inducing the strain. The non-invasive nature of this setup lends it to be used for in situ measurement of pressure. The second application is in the field of elastography. Traditional methods of diagnosis to detect the presence of sub-epidermal lesions, some tumors of the breast, liver and prostate, intensity of skin irritation etc have been mainly by palpation. The sensor system developed in this work enables to overcome the restrictive usage and occasional failure to detect minute abnormal symptoms. In vitro trials have been conducted on tissue phantoms made out of poly (vinyl alcohol) (PVA-C) samples of varying stiffnesses. The results obtained and a discussion on the same are presented.

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6

Friedlander, Jeffrey B. "Wireless Strain Measurement with Surface Acoustic Wave Sensors." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306874020.

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7

Kaplan, Emrah. "Surface acoustic wave enhanced electroanalytical sensors." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6557/.

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In the last decade, miniaturised “lab-on-a-chip” (LOC) devices have attracted significant interest in academia and industry. LOC sensors for electrochemical analysis now commonly reach picomolar in sensitivities, using only microliter-sized samples. One of the major drawbacks of this platform is the diffusion layer that appears as a limiting factor for the sensitivity level. In this thesis, a new technique was developed to enhance the sensitivity of electroanalytical sensors by increasing the mass transfer in the medium. The final device design was to be used for early detection of cancer diseases which causes bleeding in the digestive system. The diagnostic device was proposed to give reliable and repeatable results by additional modifications on its design. The sensitivity enhanced-sensor model was achieved by combining the surface acoustic wave (SAW) technology with the electroanalytical sensing platform. The technique was practically tested on a diagnostic device model and a biosensing platform. A novel, substrate (TMB) based label-free Hb sensing method is developed and tested. Moreover, the technique was further developed by changing the sensing process. Instead of forming the sensitive layer on the electrodes it was localised on polystyrene wells by a rapid one-step process. Results showed that the use of acoustic streaming, generated by SAW, increases the current flow and improves the sensitivity of amperometric sensors by a factor of 6 while only requiring microliter scale sample volumes. The heating and streaming induced by the SAW removes the small random contributions made by the natural convection and temperature variation which complicate the measurements. Therefore, the method offers stabilised conditions for more reliable and repeatable measurements. The label-free detection technique proved to be giving relevant data, according to the hemoglobin concentration. It has fewer steps than ELISA and has only one antibody. Therefore, it is quick and the cross-reactivity of the second antibody is eliminated from the system. The additional modifications made on the technique decreased the time to prepare the sensing platform because the passivation steps (i.e., pegylation), prior to structuring a sensitive layer were ignored. This avoidance also increased the reliability and repeatability of the measurements.

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8

Fisher, Brian. "Surface Acoustic Wave (SAW) Cryogenic Liquid and Hydrogen Gas Sensors." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5208.

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This research was born from NASA Kennedy Space Center's (KSC) need for passive, wireless and individually distinguishable cryogenic liquid and H2 gas sensors in various facilities. The risks of catastrophic accidents, associated with the storage and use of cryogenic fluids may be minimized by constant monitoring. Accidents involving the release of H2 gas or LH2 were responsible for 81% of total accidents in the aerospace industry. These problems may be mitigated by the implementation of a passive (or low-power), wireless, gas detection system, which continuously monitors multiple nodes and reports temperature and H2 gas presence. Passive, wireless, cryogenic liquid level and hydrogen (H2) gas sensors were developed on a platform technology called Orthogonal Frequency Coded (OFC) surface acoustic wave (SAW) radio frequency identification (RFID) tag sensors. The OFC-SAW was shown to be mechanically resistant to failure due to thermal shock from repeated cycles between room to liquid nitrogen temperature. This suggests that these tags are ideal for integration into cryogenic Dewar environments for the purposes of cryogenic liquid level detection. Three OFC-SAW H2 gas sensors were simultaneously wirelessly interrogated while being exposed to various flow rates of H2 gas. Rapid H2 detection was achieved for flow rates as low as 1ccm of a 2% H2, 98% N2 mixture. A novel method and theory to extract the electrical and mechanical properties of a semiconducting and high conductivity thin-film using SAW amplitude and velocity dispersion measurements were also developed. The SAW device was shown to be a useful tool in analysis and characterization of ultrathin and thin films and physical phenomena such as gas adsorption and desorption mechanisms.?
Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering

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9

Gruetzmann, Anna [Verfasser]. "Wireless ECG Sensor in Surface Acoustic Wave Transponder Technology / Anna Gruetzmann." München : Verlag Dr. Hut, 2010. http://d-nb.info/1009484524/34.

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10

Hamidon, Mohd Nizar. "Fabrication of high temperature surface acoustic wave devices for sensor applications." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420236.

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11

Manohar, Greeshma. "Investigation of Various Surface Acoustic Wave Design Configurations for Improved Sensitivity." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4365.

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Surface acoustic wave sensors have been a focus of active research for many years. Its ability to respond for surface perturbation is a basic principle for its sensing capability. Sensitivity to surface perturbation changes with every inter-digital transducer (IDT) design parameters, substrate selection, metallization choice and technique, delay line length and working environment. In this thesis, surface acoustic wave (SAW) sensors are designed and characterized to improve sensitivity and reduce loss. To quantify the improvements with a specific design configuration, the sensors are employed to measure temperature. Four SAW sensors design configurations, namely bi-directional, split electrode, single phase unidirectional transducer (SPUDT) and metal grating on delay line (shear transvers wave sensors) are designed and then fabricated in Nanotechnology Research and Education Center (NREC) facility using traditional MEMS fabrication processes Additionally, sensors are then coated with guiding layer SU8-2035 of 40 m using spin coating and SiO2 of 6 m using plasma enhanced chemical vapor deposition (PECVD) process. Sensors are later diced and tested for every 5oC increment using network analyzer for temperature ranging from 30oC–0.5oC to 80oC–0.5oC. Data acquired from network analyzer is analyzed using plot of logarithmic magnitude, phase and frequency shift. Furthermore, to investigate the effect of metallization technique on the sensor performance, sensors are also fabricated on substrates that were metallized at a commercial MEMS foundry. All in-house and outside sputtered sensor configurations are compared to investigate quality of sputtered metal on wafer. One with better quality sputtered metal is chosen for further study. Later sensors coated with SU8 and SiO2 as guiding layer are compared to investigate effect of each waveguide on sensors and determine which waveguide offers better performance. The results showed that company sputtered sensors have higher sensitivity compared to in-house sputtered wafers. Furthermore after comparing SU8 and SiO2 coated sensors in the same instrumental and environmental condition, it was observed that SU8 coated di-directional and single phase unidirectional transducer (SPUDT) sensors showed best response.

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12

Srinivasan, krishnan. "Nanomaterial sensing layer based surface acoustic wave hydrogen sensors." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001325.

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13

Srinivasan, Krishnan. "Nanomaterial Sensing Layer Based Surface Acoustic Wave Hydrogen Sensors." Scholar Commons, 2005. https://scholarcommons.usf.edu/etd/873.

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This thesis addresses the design and use of suitable nanomaterials and surface acoustic wave sensors for hydrogen detection and sensing. Nanotechnology is aimed at design and synthesis of novel nanoscale materials. These materials could find uses in the design of optical, biomedical and electronic devices. One such example of a nanoscale biological system is a virus. Viruses have been given a lot of attention for assembly of nanoelectronic materials. The tobacco mosaic virus (TMV) used in this research represents an inexpensive and renewable biotemplate that can be easily functionalized for the synthesis of nanomaterials. Strains of this virus have been previously coated with metals, silica or semiconductor materials with potential applications in the assembly of nanostructures and nanoelectronic circuits. Carbon nanotubes are another set of well-characterized nanoscale materials which have been widely investigated to put their physical and chemical properties to use in design of transistors, gas sensors, hydrogen storage cells, etc. Palladium is a well-known material for detection of hydrogen. The processes of absorption and desorption are known to be reversible and are known to produce changes in density, elastic properties and conductivity of the film. Despite these advantages, palladium films are known to suffer from problems of peeling and cracking in hydrogen sensor applications. They are also required to be cycled for a few times with hydrogen before they give reproducible responses. The work presented in this thesis, takes concepts from previous hydrogen sensing techniques and applies them to two nanoengineered particles (Pd coated TMV and Pd coated SWNTs) as SAW resonator sensing materials. Possible sensing enhancements to be gained by using these nanomaterial sensing layers are investigated. SAW resonators were coated with these two different nano-structured sensing layers (Pd-TMV and Pd-SWNT) which produced differently useful hydrogen sensor responses. The Pd-TMV coated resonator responded to hydrogen with nearly constant increases in frequency as compared to the Pd-SWNT coated device, which responded with concentration-dependent decreases in frequency of greater magnitude upon hydrogen exposure. The former behavior is more associated with acousto-electric phenomena in SAW devices and the later with mass loading. The 99% response times were 30-40 seconds for the Pd-TMV sensing layer and approximately 150 seconds for the Pd-SWNT layer. Both the films showed high robustness and reversibility at room temperature. When the Pd film was exposed to hydrogen it was observed that it produced decreases in frequency to hydrogen challenges, conforming to mass loading effect. It was also observed that the Pd film started degrading with repeated exposure to hydrogen, with shifts after each exposure going smaller and smaller.

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14

Fechete, Alexandru Constantin, and e54372@ems rmit edu au. "Layered Surface Acoustic Wave Based Gas Sensors Utilising Nanostructured Indium Oxide Thin Layer." RMIT University. Electrical and Computer Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091105.141111.

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Planar two-dimensional (2-D) nanostructured indium oxide (InOx) and one-dimensional (1-D) tin oxide (SnO2) semiconductor metal-oxide layers have been utilised for gas sensing applications. Novel layered Surface Acoustic Wave (SAW) based sensors were developed consisting of InOx/SiOxNy/36°YXLiTaO3, InOx/SiNx/SiO2/36°YXLiTaO3 and InOx/SiNx/36°YXLiTaO3 The 1 µm intermediate layers of silicon oxynitride (SiOxNy), silicon nitride (SiNx) and SiO2/SiNx matrix were deposited on lithium tantalate (36°YXLiTaO3) substrates by r.f. magnetron sputtering, electron-beam evaporation and plasma enhanced chemical vapour deposition (PECVD) techniques, respectively. As a gas sensitive layer, a 100 nm thin layer of InOx was deposited on the intermediate layers by r.f. magnetron sputtering. The targeted gases were ozone (O3) and hydrogen (H2). An intermediate layer has multiple functions: protective role for the interdigital transducers' electrodes as well as an isolating effect from InOx sensing layer, thereby improving the sensor performance. The developed SAW sensors' exhibited high response magnitudes with repeatable, reversible and stable responses towards O3 and H2. They are capable of sensing concentrations as low as 20 parts-per-billion for O3 and 600 parts-per-million for H2. Additionally a conductometric type novel sensing structure of SnO2/36°YX LiTaO3 was also developed by depositing a thin layer of SnO2 nanorods by PECVD. The gas sensing performance exhibited repeatable, reversible, stable responses towards NO2 and CO. The surface morphology, crystalline structure and preferred orientation of the deposited layers were investigated by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A polycrystalline, oxygen deficient non-stoichiometric InOx with grain sizes of 20-40 nm was revealed. The 1-D nanostructures were characterised by Transmission Electron Microscopy (TEM) showing nanorods with needle-like shape , diameters of 10-20 nm a t the top and 30-40 nm at the base as well as a preferential growth orientation of [ ] on the LiTaO3 substrate. The developed sensors are promising for O3, H2 and CO sensing.

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15

Ippolito, Samuel James, and sipp@ieee org. "Investigation of Multilayered Surface Acoustic Wave Devices for Gas Sensing Applications: Employing piezoelectric intermediate and nanocrystalline metal oxide sensitive layers." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070227.123029.

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In this thesis, the author proposes and develops novel multilayered Surface Acoustic Wave (SAW) devices with unique attributes for gas sensing applications. The design, simulation, fabrication and gas sensing performance of three multilayered SAW structures has been undertaken. The investigated structures are based on two substrates having high electromechanical coupling coefficient: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), with a piezoelectric zinc oxide (ZnO) intermediate layer. Sensitivity towards target gas analytes is provided by thin film indium oxide (InOx) or tungsten trioxide (WO3). The high performance of the gas sensors is achieved by adjusting the intermediate ZnO layer thickness. Sensitivity calculations, undertaken with perturbation theory illustrate how the intermediate ZnO layer can be employed to modify the velocity-permittivity product of the supported SAW modes, resulting in highly sensitive conductometric SAW gas sensors. The work contained within this thesis addresses a broad spectrum of issues relating to multilayered SAW gas sensors. Topics include finite-element modelling, perturbation theory, micro-fabrication, metal oxide deposition, material characterisation and experiential evaluation of the layered SAW sensors towards nitrogen dioxide (NO2), hydrogen (H2) and ethanol gas phase analytes. The development of two-dimensional (2D) and three dimensional (3D) finite-element models provides a deep insight and understanding of acoustic wave propagation in layered anisotropic media, whilst also illustrating that the entire surface of the device can and should be used as the active sensing area. Additionally, the unique and distinctive surface morphology of the layered structures are examined by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The crystalline structure and orientation of the ZnO and WO3 layers are also examined by X-ray Diffraction Spectroscopy (XRD). The novel multilayered SAW structures a re shown to be highly sensitive, capable of sensing NO2 and ethanol concentration levels in the parts-per-billion and parts-per-million range, respectively, and H2 concentrations below 1.00% in air. The addition of platinum or gold catalyst activator layers on the WO3 sensitive layer is shown to improve sensitivity and dynamic performance, with response magnitudes up to 50 times larger than bare WO3. The gas sensing performance of the investigated structures provide strong evidence that high sensitivity can be achieved utilising multilayered SAW structures for conductometric gas sensing applications.

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16

Sabkha, Aimen. "Implantable Wireless Surface Acoustic Wave Sensors for Blood Pressure Measurement." Thesis, Oxford Brookes University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491086.

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17

Wilson, William. "Multifunctional Orthogonally-Frequency-Coded Saw Strain Sensor." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3157.

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A multifunctional strain sensor based on Surface Acoustic Wave (SAW) Orthogonal Frequency Coding (OFC) technology on a Langasite substrate has been investigated. Second order transmission matrix models have been developed and verified. A new parameterizable library of SAW components was created to automate the layout process. Using these new tools, a SAW strain sensor with OFC reflectors was designed, fabricated and tested. The Langasite coefficients of velocity for strain (γS = 1.699) and Temperature (γT = 2.562) were experimentally determined. The strain and temperature characterization of this strain sensor, along with the coefficients of velocity, have been used to demonstrate both the ability to sense strain and the capability for temperature compensation. The temperature-compensated SAW OFC strain sensor has been used to detect anomalous strain conditions that are indicators of fastener failures during structural health monitoring of aircraft panels with and without noise on a NASA fastener failure test stand. The changes in strain that are associated with single fastener failures were measured up to a distance of 80 cm between the sensor and the removed fastener. The SAW OFC strain sensor was demonstrated to act as an impact sensor with and without noise on the fastener failure test stand. The average measured signal to noise ratio (SNR) of 50, is comparable to the 29.1 SNR of an acoustic emission sensor. The simultaneous use of a high pass filter for impact detection, while a low pass filter is used for strain or fastener failure, demonstrates the multifunctional capabilities of the SAW OFC sensor to act as both as a fastener failure detector and as an impact detector.

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18

Mishra, Harshad. "Magnetic field sensor based on micro-structured magnetoelastic surface acoustic waves devices." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0147.

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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
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

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19

Westafer, Ryan S. "Investigation of phononic crystals for dispersive surface acoustic wave ozone sensors." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41165.

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The object of this research was to investigate dispersion in surface phononic crystals (PnCs) for application to a newly developed passive surface acoustic wave (SAW) ozone sensor. Frequency band gaps and slow sound already have been reported for PnC lattice structures. Such engineered structures are often advertised to reduce loss, increase sensitivity, and reduce device size. However, these advances have not yet been realized in the context of surface acoustic wave sensors. In early work, we computed SAW dispersion in patterned surface structures and we confirmed that our finite element computations of SAW dispersion in thin films and in one dimensional surface PnC structures agree with experimental results obtained by laser probe techniques. We analyzed the computations to guide device design in terms of sensitivity and joint spectral operating point. Next we conducted simulations and experiments to determine sensitivity and limit of detection for more conventional dispersive SAW devices and PnC sensors. Finally, we conducted extensive ozone detection trials on passive reflection mode SAW devices, using distinct components of the time dispersed response to compensate for the effect of temperature. The experimental work revealed that the devices may be used for dosimetry applications over periods of several days.

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20

Mörel, Zeynep. "Platelet adhesion to various surfaces studied by on-line acoustic wave sensor." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/MQ45517.pdf.

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21

Manoosingh, Lane Leslie. "Design of a chemical agent detector based on polymer coated surface acoustic wave (SAW) resonator technology." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000412.

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22

Thiele, Jeremy Allan. "High Temperature LGX Acoustic Wave Devices and Application for Gas Sensors." Fogler Library, University of Maine, 2005. http://www.library.umaine.edu/theses/pdf/ThieleJA2005.pdf.

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23

Arsat, Rashidah, and rashidah arsat@student rmit edu au. "Investigation of Nanostructured Thin Films on Surface Acoustic Wave and Conductometric Transducers for Gas Sensing Applications." RMIT University. Electrical and Computer Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091002.094407.

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In this thesis, the author proposed and developed nanostructured materials based Surface Acoustic Wave (SAW) and conductometric transducers for gas sensing applications. The device fabrication, nanostructured materials synthesis and characterization, as well as their gas sensing performance have been undertaken. The investigated structures are based on two structures: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). These two substrates were chosen for their high electromechanical coupling coefficient. The conductometric structure is based on langasite (LGS) substrate. LGS was selected because it does not exhibit any phase transition up to its melting point (1470°C). Four types of nanostructured materials were investigated as gas sensing layers, they are: polyaniline, polyvinylpyrrolidone (PVP), graphene and antimony oxide (Sb2O3). The developed nanostructured materials based sensors have high surface to volume ratio, resulting in high sensitivity towards di¤erent gas species. Several synthesis methods were conducted to deposit nanostructured materials on the whole area of SAW based and conductometric transducers. Electropolymerization method was used to synthesize and deposit polyaniline nanofibers on 36° YX LiTaO3 and 64° YX LiNbO3 SAW substrates. By varying several parameters during electropolymerization, the effect on gas sensing properties were investigated. The author also extended her research to successfully develop polyaniline/inorganic nanocomposites based SAW structures for room temperature gas sensing applications. Via electrospinning method, PVP fibres and its composites were successfully deposited on 36° YX LiTaO3 SAW transducers. Again in this method, the author varied several parameters of electrospinning such as distance and concentration, and investigated the effect on gas sensing performance. Graphene-like nano-sheets were synthesized on 36° YX LiTaO3 SAW devices. This material was synthesized by spin-coating graphite oxide (GO) on the substrate and then exposin g the GO to hydrazine to reduce it to graphene. X-ray photoelectron spectroscopy (XPS) and Raman characterizations showed that the reduced GO was not an ideal graphene. This information was required to understand the properties of the deposited graphene and link its properties to the gas sensing properties. Thermal evaporation method was used to grow Sb2O3 nanostructures on LGS conductometric transducers. Using this method, different nanoscale structures such as nanorods and lobe-like shapes were found on the gold interdigitated transducers (IDTs) and LGS substrate. The gas sensing performance of the deposited nanostructured Sb2O3 based LGS conductometric sensors was investigated at elevated temperatures. The gas sensing performance of the investigated nanostructured materials/SAW and conductometric structures provide a way for further investigation to future commerciallization of these types of sensors.

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24

Man, Gabriel. "Towards all-polymer surface acoustic wave chemical sensors for air quality monitoring." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17469.

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Анотація:

Volatile organic compounds (VOCs) are a precursor to the formation of ground-level ozone and airborne particulate matter, both of which are hazardous to human health. Currently in Canada, other air pollutants such as ozone and nitrous oxides are measured by an air quality monitoring network in real-time, while VOCs are collected in canisters and sent to a central laboratory for analysis. This is a time-consuming and non real-time method, and due to the spatial variability of air pollution, many points of measurement are needed. A distributed point sensor network could address the resolution and real-time challenges, but would impose an added operating expenditure burden on air quality monitoring agencies. Low-cost, yet sensitive chemical sensors could contribute to lowering operating expenditures of a network’s sensing units over the installed lifetime of the units. The objective of this work was to lay the groundwork for a sensing platform from which low-cost yet sensitive chemical sensors can be developed. The sensing platform is an all-polymer surface acoustic wave (SAW) device, and the materials selected for its fabrication are Polyvinylidene Fluoride (PVDF) for the sensor substrate and Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) for the interdigital transducer electrodes. In this work, an apparatus and a process for preparing piezoelectric PVDF film was developed. PVDF-based resonators were successfully demonstrated. In addition, repeatable processes for inkjet micropatterning highly electrically conductive PEDOT:PSS electrode tracks on PVDF were developed for three inkjet nozzle orifice sizes (20, 30, 40 µm). For tracks micropatterned using the same process, the electrical resistances have a standard deviation of 8.5% of the average. The electrical conductivity of micropatterned tracks is approximately 150 S/cm, or one-sixth of the manufacturer’s claimed bulk film conductivity. Using the 30 µm nozzle, the smallest electrode track width that can be micropatterned repeatably is 75 µm. A track width of 55 µm was achieved using the 20 µm nozzle.

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25

Chaudhari, Amol V. "Development of Surface Acoustic Wave Sensors Using Nanostructured Palladium for Hydrogen Detection." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/989.

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Анотація:

This thesis addresses the development of new gas sensor using surface acoustic wave (SAW) technology. SAW sensors detect the change in mass, modulus, and conductivity of a sensing layer material via absorption or adsorption of an analyte. The advantage of SAW sensor includes low cost, small size, high sensitivity. We investigated the use of nano-crystalline palladium film for sensing hydrogen gas. We also investigated SAW fabrication for radio frequency (RF) range operation where high signal-to-noise ratios can be achieved. A test-bed consisting of a gas dilution system, a temperature-controlled test cell, a network analyzer, and computer-based measurement system was used for evaluating the performance of SAW gas sensors at very low concentrations. Both single and dual delay line SAW devices were fabricated by means of photolithography on a lithium niobate substrate. Tests are carried to determine response speed, resolution, reproducibility, and linear characteristics, over a range of analyte concentrations.

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26

Wang, Tao. "Optimization and Characterization of Integrated Microfluidic Surface Acoustic Wave Sensors and Transducers." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6153.

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Анотація:

Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the mechanical pump and biosensor areas. Manipulation of liquids in microfluidic channels is important for many mechanical, chemical and biomedical applications. In this dissertation, we first introduced a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employed a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrated long distance media delivery (up to 8mm) and a high pumping velocity, which increased the device’s application space and mass production potential. Additionally, the device design didn’t need precise layers of water and glass between substrate and channel, which simplified the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, and input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicated that the pumping velocity for a constant liquid volume with the same applied input power could be increased by over 130% (2.31 mm/min vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 µm vs 500 µm) design. This device could be used in circulation, dosing, metering and drug delivery applications which necessitated small-scale precise liquid control and delivery. This dissertation also introduced a novel SAW-based sensor designed and employed for detecting changes in cell concentration. Before conducting cell concentration experiments, preliminary experiments were conducted on weight concentration differentiation of microfluidic particles based on a polydimethylsiloxane (PDMS) channel and surface acoustic wave resonator design. The results confirmed that our device exerted an ultra-stable status to detect liquid properties by monitoring continuous fluids. An improved design was carried out by depositing a 200 nm ZnO layer on top of the lithium tantalate substrate surface increased the sensitivity and enabled cell concentration detection in a microfluidic system. Comprehensive studies on cell viability were carried out to investigate the effect of shear horizontal (SH) SAWs on both a cancerous (A549 lung adenocarcinoma) and a non-cancerous (RAW264.7 macrophage) cell line. Two pairs of resonators consisting of interdigital transducers (IDTs) and reflecting fingers were used to quantify mass loading by the cells in suspension media as well as within a 3-dimensional cell culture model. In order to predict the characteristics and optimize the design of the SH-SAW biosensor, a 3D COMSOL model was built to simulate the mass loading response of the cell suspensions. These results were compared to experimental data generated by pipetting cell concentrations of 3.125K, 6.25K 12.5K, 25K and 50K cells per 100µL into the PDMS well and measuring to obtain the relative frequency shift from the two oscillatory circuit systems (one of which functioned as a control). Frequency shift measurements were also collected from A549 cells cultured on a 3D nanofiber scaffold produced by electrospinning to evaluate the device’s ability to detect changes in cell density as the cells proliferated in culture over the course of eight days. The device’s ability to detect changes in cell density over time in a 3D model along with its biocompatibility reveal great potential for this device to be incorporated into 3D in vitro cancer research applications.

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27

Onen, Onursal. "Analytical Modeling, Perturbation Analysis and Experimental Characterization of Guided Surface Acoustic Wave Sensors." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4555.

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In this dissertation, guided surface acoustic wave sensors were investigated theoretically and experimentally in detail for immunosensing applications. Shear horizontal polarized guided surface acoustic wave propagation for mass loading sensing applications was modeled using analytical modeling and characterized by perturbation analysis. The model verification was performed experimentally and a surface acoustic wave immunosensor case study was presented. The results of the immunosensing were also investigated using the perturbation analysis. Guided surface acoustic wave propagation problem was investigated in detail for gravimetric (or mass loading) guided wave sensors, more specifically for immunosensors. The analytical model was developed for multilayer systems taking viscoelasticity into account. The closed form algebraic solutions were obtained by applying appropriate boundary conditions. A numerical approach was used to solve dispersion equation. Detailed parametric investigation of dispersion curves was conducted using typical substrate materials and guiding layers. Substrate types of ST-cut quartz, 41° YX lithium Niobate and 36° YX lithium tantalate with guiding layers of silicon dioxide, metals (chromium and gold), and polymers (Parylene-C and SU-8) were investigated. The effects of frequency and degree of viscoelasticity were also studied. The results showed that frequency only has effect on thickness with same shaped dispersion curves. Dispersion curves were found to be unaffected by the degree of viscoelasticity. It was also observed that when there was a large shear velocity difference between substrate and guiding layer, a transition region with a gradual decrease in phase velocity was obtained. However, when shear velocities were close, a smooth transition was observed. Furthermore, it was observed that, large density differences between substrate and guiding layer resulted in sharp and with nearly constant slope transition. Smooth transition was observed for the cases of minimal density differences. Experimental verification of the model was done using multi-layer photoresists. It was shown that with modifications, the model was able to represent the cases studied. Perturbation equations were developed with first order approximations by relating the slope of the dispersion curves with sensitivity. The equations were used to investigate the sensitivity for material selection (substrate, guiding layer, and mass perturbing layer) and degree of viscoelasticity. The investigations showed that the sensitivity was increased by using guiding layers with lower shear velocities and densities. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold and chrome. The perturbation investigations were also extended to viscoelasticity and to protein layers for immunosensing applications. It was observed that, viscous behavior resulted in slightly higher sensitivity; and sensitivity to protein layers was very close to sensitivity for polymers. The optimum case is found to be ST-cut quartz with Parylene-C guiding layer for protein layer sensing. Finally, an immunosensing case study was presented for selective capture of protein B-cell lymphoma 2 (Bcl-2), which is elevated in many cancer types including ovarian cancer. The immunosensor was designed, fabricated, and experimentally characterized. An application-specific surface functionalization scheme with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 was developed and applied. Characterization was done using the oscillation frequency shift of with sensor used as the feedback element of an oscillator circuit. Detection of Bcl-2 with target sensitivity of 0.5 ng/ml from buffer solutions was presented. A linear relation between frequency shift and Bcl-2 concentration was observed. The selectivity was shown with experiments by introducing another protein, in addition to Bcl-2, to the buffer. It was seen that similar detection performance of Bcl-2 was obtained even with presence of control protein in very high concentrations. The results were also analyzed with perturbation equations.

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28

Young, Ming-Sheng, and 楊明昇. "Characteristics of Surface Acoustic Wave Sensor." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/81672173386487190179.

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Анотація:

碩士
國立成功大學
電機工程學系
89
This paper is primarily divided into two sections. In section 1, the design and fabrication of IF SAW device are described. In section 2, the sensing property of SAW gas sensor for ethanol vapor is discussed. Based on sensing requirement, the first condition for SAW device design is low insertion loss that promising whole oscillation circuit can work normally. We choose LiNbO3 to be substrate and construct grating reflectors. The insertion loss of SAW device with 30 pairs grating reflections is 4 ~ 4.5dB, and that with 50 pairs grating reflectors is about 3.5dB. By using mass loading effect, SAW device may regard as ethanol vapor density sensor. The response due to changes in the medium density on the SAW transmission path causes transmission velocity change and resonant frequency shift. This is the basic principle of a SAW gas sensor. In order to increase sensitivity, coating stearic acid as sensing film on the transmission path is used. For different film depth, we discuss the responses of resonant frequency shift and find out the optimum. At last, the improvements of sensor system, range and stability are given.

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29

Cheng, Chi Yuan, and 鄭期元. "Cigarette Detection by Surface Acoustic Wave Gas Sensor." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/86802169712159978126.

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Анотація:

碩士
國立清華大學
奈米工程與微系統研究所
103
Statistical data says that people exposed to secondhand smoke (SHS) have a higher risk of getting lung cancer and coronary heart disease. The research goal is making a cigarette sensor by surface acoustic wave (SAW) to prevent from tobacco hazards. In order to detect low concentration of cigarette marker, sensitivity and stability are two important issues. The SAW sensor is coated with oxidized hollow meso-porous carbon nano-sphere (O-HMC) to replace generally used polymer as new type sensing material, which is more sensitive than poly-acrylic acid due to the much more carboxyl group bonded by HNO3 treated, increasing the sensitivity of 3-EP from 37.8 to 51.2 Hz/ppm and also preventing the drawbacks of polymer based sensing material, such as lack of thermal stability and swelling effect. An 800μL micro-chamber is designed for enhancing stability by blocking environmental interferences, and the HMC coated chip is used as control due to the higher similarity of surface state between experiment and reference would increase stability, finally the noise can down to 5 Hz. The small volume of chamber and the large surface area of sensing material, caused by porous structure is leading to rapid detection at the low flow rate of 20 mL/min. The SAW sensor successfully detects cigarette smoke with high sensitivity and good repeatability by filtering above 1μm particles and tar to solve the adhesion problem; as compared to four interfered gas, ammonia, methane, carbon monoxide and carbon dioxide, the SAW sensor has 5 times more selective to cigarette smoke. This SAW sensor also detects water vapor to remove the influence of humidity and uses the resulting trend line to calibrate the frequency shift by detecting cigarette. In addition to detect SHS, this research takes the same SAW detector to sense the thirdhand smoke (THS) on different clothing fabrics, such as wool, cotton and polyester, finally knows that wool will absorb the maximum amount of THS and get the longest residual time.

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30

Chen, Yu-Ju, and 陳右儒. "The Fabrication of Surface Acoustic Wave Alcohol Sensor." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/52682878487266706559.

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Анотація:

碩士
國立成功大學
電機工程學系碩博士班
91
This thesis gives a historical account of the development, and the theory of piezoelectric phenomenon, Rayleigh wave, interdigital transducer (IDT), surface acoustic wave (SAW), performance criteria and device for application in sensor. The alcohol gas sensing properties of stearic acid film, deposited onto 1280YX-LiNbO3 substrate, have been monitored shift in frequency by SAW delay lines and analysis the properties of the alcohol gas sensor. The effect of humidity on SAW alcohol gas response is negligible for the typical conditions at room ambient temperature. And studied with respect to the remnant gas in tubes, the comparison of the stability between electrical and flop flow controllers, temperature effect of the flowed alcohol gas, the film aging, spray coating uniform, optimum spin parameter, optimum the concentration of stearic acid solution, and so on. The devices are based on the dual two ports resonator structure adds to appropriate control of the environment effect, and appropriate coating method. It is shown that the devices have good sensitivity, reversible, stability, repeatability, fast response time. And the ratio of signal to noise is greater than two.

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31

LAI, JUN-CHEN, and 賴俊辰. "Applied of surface-active agent on Surface Acoustic Wave liquid sensor." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/63731844845883368321.

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Анотація:

碩士
國立勤益科技大學
機械工程系
101
The energyof propagationof surface acoustic wave (SAW) is concentrated within the surface of substrates and the energy lossof SAW is less than the bulk wave.The properties of propagation depend on the material of substrates and boundary condi-tion.In this study, we detect the surfactants by SAW devices. The composition of the SAW devices were piezoelectric substrates sputtered with interdigital transducers and then surface acoustic waves were excited. In the propagation path, we designed metal and free surface, the loading liquid with various effect of acoustic-electricwould lead to affect the properties of SAW, we can identifythe loading liquid by detect the change of SAW. First, we choice the material of 41°YX LiNbO3 as substrate, which can be ex-cited SH SAW and have the characters of higher Electromechanical coupling factor, faster phase velocity and stable temperature coefficient. Using the technology of MEMS, we design resonators with split IDT and the central frequency is 59.9M Hz. The split IDT have lower insertion loss than normal IDT. One group of resonators deposit Al thin film on sensing region to exclude electrical characteristics of liquid to achieve accurately detect the types of surfactants. In this study, we measure the prop-erties of surfactants (SNDS, SDBS, SLS,TritonX-100, ..etc.) using immersion mea-surements, the sensor immersed in the liquid under test can effectively rule out the liquid quality and environmental impact of interfering factors on the velocity, and real-time monitoring of changes. Experimental results show split type SAW sensor refers to a center frequency of 60.4947MHz, compare to the theoretical calculation approximately 1% error. In the free surface propagation path, the order of attenuation of energy is wa-ter&;lt;SLS&;lt;TritonX-100&;lt;DN-60. In terms of the metal-film surface propagation path, the order of attenuation of energy is water&;lt; TritonX-100&;lt; SLS&;lt; DN-60. Therefore, we can identify the surfactants by detect the attenuation of energy.

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32

Huang, Wang-Tsung, and 黃望宗. "Gas Detecting Properties of Surface Acoustic Wave Ammonia Sensor." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/39712216187187276867.

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Анотація:

碩士
義守大學
電機工程學系
91
This work investigates the advanced properties of an improved surface acoustic wave (SAW) ammonia gas sensor. The sensor was based upon a dual delay line SAW configuration. The chemical interface was L-Glutamic acid hydrochloride deposited on the surface of SAW sensor. The frequency shift of SAW devices took in real-time measurement to analyze the detection for low ammonia concentration. The perturbation mechanism is proved in this work, and the optimal sensing conditions and properties are studied. The SAW sensor based on L-Glutamic acid hydrochloride presented excellent sensitivity, reversibility, repeatability and selectivity to ammonia. Rising the operating temperature could improve the performance of sensors. The curve of frequency shift versus ammonia concentration showed the linearity and sensitivity at high temperature, especially at 50oC. The sensitivity was 0.05 ppm/ppm at 50oC, and it could estimate the limitation of detection (LOD) to be 0.08 ppm (=80 ppb). The water vapor in air significantly influenced the detection of ammonia. Therefore, SAW sensors based on L-Glutamic acid hydrochloride are suitable for operating at 50oC in dry air.

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33

cheng, Yung-hsi, and 鄭永錫. "The Detection Properties of NO2 Surface Acoustic Wave Sensor." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/47620148594717327582.

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Анотація:

碩士
義守大學
電機工程學系碩士班
97
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.

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34

Chou, Tai-hsu, and 周代栩. "A High Precision Nanomaterial Based Surface Acoustic Wave Humidity Sensor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/31495811068753154444.

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Анотація:

碩士
臺灣大學
應用力學研究所
95
There is a growing demand for developing a sensing system to measure relative humidity not only for human comfort but also for industry applications. Up to date, various sensitive materials with good sensing characteristics are mainly polymers. Thus, development of the real-time and precise humidity sensor which utilizes easy synthesis and stable sensing materials at room temperature is highly needed. A good sensor should be characterized by high sensitivity, wide dynamic range, fast response, good reproducibility, easy interface electronics, small size, and minimum cost. Existing sensors with single sensing system are hard for matching all these criterions. However, surface acoustic wave (SAW) sensing devices are promising candidates to pursue the above goals. In this thesis, a 145 MHz based SAW resonator was fabricated and integrated with the amplifier to form an oscillator. To function as a humidity sensor, HCL-doped and CSA-doped polyaniline nanofibers were coated on the delay line of the resonator as the sensing film. Moreover, dual channel configuration was constructed for reducing environmental influences such as temperature and pressure, etc. Then, the sensing devices were exposed to various relative humidity to investigate the performances and compared the efficiency between different materials on room temperature. Good linearity and high sensitivity were acquired toward various relative humidity sensing.

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35

Chen, Yu-Cheng, and 陳又誠. "Fabrication and characterization of the surface acoustic wave torque sensor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/77427305299804678957.

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Анотація:

碩士
國立中正大學
機械工程所
96
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.

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36

Wang, Jyh-Hom, and 王智弘. "AFeasibility Study of Molecular Sensor Using Surface Acoustic Wave Device." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/77351896726529386159.

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Анотація:

碩士
國立清華大學
電子工程研究所
87
We try to design gas sensors by theory of surface acoustic waves and do some research about that. A surface acoustic waves gas sensor includes substrate, interdigital transducers and coating. The convenient generation of a surface acoustic wave requires a substrate material which is piezoelectric. An interdigital transducer is used to apply the electric field to the piezoelectric substrate. The operating frequency is determined by the spacing between the interdigital electrodes. The coating is chose by what we want this sensor to detect. In my research, I choose ST cut quartz be the substrate of gas sensor. This special material has low temperature coefficient and high electromechanical coupling coefficient.Then, I design the interdigital electrode for low frequency and high frequency measurement. About the coating, I choose three kinds of thin film as the coating of gas sensor. They are palladium, tin oxide and polyimide. Palladium is for detecting hydrogen. Tin oxide is usually used to detect carbon monoxide. Polyimide is for humidity measurement. We just need the technology of thin film deposition and photolithography process to make this gas sensor. Then we do some low frequency and high frequency measurement about the characteristic of this gas sensor. From the result of measurement, we can observe and get the relation between the change of mass of the coating and the change of operating frequency. We can prove the theory and the sensor are correct and practicable. In future I hope to keep on the research of this surface acoustic waves gas sensor. We can reach objective of gas sensor array by linking different kinds of gas sensor. We even can combine the field of biology and medical science to reach the target of completing the electronic noses.

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37

Chou, Tai-hsu. "A High Precision Nanomaterial Based Surface Acoustic Wave Humidity Sensor." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2607200720540800.

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38

Lu, Yishen. "Surface acoustic wave sensor for low concentration mercury vapor detection." Thesis, 2017. https://hdl.handle.net/2144/20833.

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Mercury (Hg) has always been a serious risk to the environment and human health. It is a very common contamination in petroleum industry, which may lower product quality, threaten operation safety and worker’s health even at a very low concentration. Consequently the detection of mercury is very necessary. Gold is widely used as sensing material of mercury because it has a specific affinity with mercury and the adsorption of mercury changes characteristics of gold such as resistivity and effective mass density. In this thesis, common methods for sensing mercury vapor concentration were summarized and a surface acoustic wave (SAW) sensor utilizing the adsorption of mercury on gold electrodes was proposed for 1 μg/m3 level low concentration mercury vapor detection. The working principle of SAW sensor was studied and finite element method models were built to optimize the sensor design. The influence of several physical structure parameters such as electrode width and pitch on the sensor sensitivity and response time were studied using the simulation model. According to the simulation results a prototype of SAW sensor was designed and fabricated. The sensor was then analyzed with network analyzer and tested with mercury vapor. Preliminary results were presented and analyzed in this work. Finally potential future work was proposed and discussed.

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39

Jun-Yi, Wu. "Study of 128 YX-LiNbO3 Based Surface Acoustic Wave Humidity Sensor." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2707200613423600.

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40

Hung, Wei Chang, and 張宏維. "Preparation and Application of Surface Acoustic Wave Gas- and Bio-Sensor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/03185375908092466914.

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Анотація:

博士
國立臺灣師範大學
化學系
96
Surface acoustic wave gas and Bio-sensors were developed to detect organic gases and biospecies, e.g. proteins and insulin. An inexpensive surface acoustic wave (SAW) sensor system was developed and used to detect trace pollutants in the air. For liquid environment, a shear-horizontal surface acoustic wave sensor system was established to apply in immunosensor system to detect various samples, e.g. hemoglobin, myoglobin, gliadin, and insulin, in aqueous solution. The homemade SAW gas sensor is composed of a low cost (< 10 $USD) SAW chip for correspondence, an inexpensive counter and RS-232 computer interface with a written computer program for frequency signal acquisition and data processing. With different adsorbent coatings, various SAW gas sensors were prepared to detect organic pollutants, e.g. carboxylic acids, aldehydes, alchohols, alkanes, alkenes, alkynes in the air. Furthermore, the multi-channel SAW gas detection system was also developed to detect various air pollutants simultaneously. Shear horizontal surface acoustic wave sensors immobilized with C60/proteins, e.g. C60/hemoglobin(C60-Hb), C60/myoglobin(C60-Mb), and C60/gliadin, and C60/anti-insulin coatings were prepared and applied to detect specific antibodies, e.g. anti-hemoglobin, anti-myoglobin, anti-gliadin, insulin, respectively, in liquid environments. The immobilizations of hemoglobin and myoglobin onto fullerene were studied through a C60-coated SH-SAW sensor system in liquid. The partially irreversible responses for these proteins were observed by the desorption study, which implied that fullerene could chemically react with these proteins. Both C60-Hb and C60-Mb coating materials were successfully prepared and identified with an FTIR spectrometer. The C60-Hb and C60-Mb coated SH-SAW immunosensors exhibited linear frequency responses to the concentration of anti-Hb and anti-Mb antibodies with sensitivities of 0.14 and 1.27 kHz/ (g/mL), respectively. Both C60-protein coated SH-SAW immunosensorms showed detection limits of 0.32 and 0.035 g/mL for anti-Hb and anti-Mb antibodies, respectively, in aqueous solution. In addition, dual channel SAW immunosensors coated with C60-Hb and C60-Mb were prepared and applied to detect anti-Hb and anti-Mb antibodies simultaneously. An immobilized fullerene C60/anti-insulin antibody was prepared and applied in shear horizontal surface acoustic wave (SH-SAW) immunosensors to detect insulin in aqueous solutions. Within the range of normal human insulin concentration, the SH-SAW immunosensors immobilized with C60/anti-insulin coating exhibited linear frequency responses to the concentration of insulin with sensitivity of 130 Hz/pM. The SH-SAW immunosensor with C60/anti-insulin coating showed detection limit of 0.58 pM for insulin in aqueous solution.

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41

Chen, Yun-Ju, and 陳韻如. "The Study of Scattering Characteristic of Surface Acoustic Wave Liquid Sensor." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/34419186254449474738.

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Анотація:

碩士
義守大學
電機工程學系
91
Propagation characteristics of surface acoustic waves (SAWs) generated by interdigital transducers (IDTs) on piezoelectric substrates exhibit different modes depending on substrate material properties and device structures. With liquid loading on the substrates the waves propagation are even more complex. Acoustoelectrical properties of the fluid medium strongly influence the propagation characteristics of SAW. In this thesis the characteristics of SAWs were studied by solving Christoffel’s equations subject to appropriate boundary conditions. The effects of different liquid loadings on phase velocity and attenuation constant were calculated. With calculated phase velocity and attenuation constant, a transmission matrix method was used to analyze the scattering characteristics of SAW devices for the purpose of using them as sensors. By cascading matrix form of equations composed as two IDTs, two delay lines and a sensing area the transmission coefficients of SAW under different liquid loading can be easily obtained. From the results under different viscosity and conductivity liquid loadings, leaky wave mode is preferred to Rayleigh wave for sensors applications.

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42

Li, Yi-Tian, and 李宜恬. "Polymer-Coated Surface Acoustic Wave Sensor for Low Concentration Gas Detection." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/45998714568024683774.

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43

Chiang, Ming-Chang, and 江明璋. "Improved Surface Acoustic Wave Sensor for Low-concentration Gas Mixture Detection." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72175671673098643148.

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Анотація:

碩士
國立清華大學
動力機械工程學系
102
The detection results for mixture gas (ammonia/methane) by polymer deposited on 128° YX-LiNbO3 surface acoustic wave (SAW) delay lines are studied in this work. The adsorption of mixture gas by sensitive coating material modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect. Thus, the targeted mixture gas can be evaluated by recording the frequency shift of the SAW device. In this research, we used the SAW sensor to detect chemical compounds such as ammonia, methane, and ammonia-methane mixture gases. To enhance the sensitivity and accuracy of the surface acoustic wave sensors, the sensing chamber and polymer films was improved. Miniature cover with fluidic channels (200 μl) has replaced 1L 4-neck bottle chamber as a sensing chamber of the system. PNVP with mesoporous carbon hollow nanosphere has replaced PNVP with platelet mesoporous carbon as a sensing film of the system. Very low concentration of ammonia (≈ 250 ppb) and methane (≈ 9 ppm) can be detected by our SAW devices. From the ammonia gas and methane gas database, we can find that the frequency shift of ammonia/methane mixtures equal to the sum of frequency shift of ammonia and methane. Besides, the signal loss of ammonia is much stronger than methane in high relative humidity conditions. By quantitative measurement results of ammonia/methane mixture gas, we can use synergistic effects of the gas mixture to predict the signal intensity of different concentrations. The SAW sensor can also be applied to other industrial and environmental detection, and hope the gas sensor can be widely used in the daily life.

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44

Lin, Hung-Bin, and 林宏斌. "Preparation and Application of C60-Cryptand Coated Surface Acoustic Wave Sensor." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/69678926488799326764.

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Анотація:

碩士
國立臺灣師範大學
化學研究所
90
Preparation and Application of C60-Cryptand Coated Surface Acoustic Wave Sensor Abstract A C60-cryptand [2,2] coated surface acoustic wave (SAW) detection system was prepared and applied as Gas Chromatographic detector for various vapors. The frequency of surface acoustic wave oscillator decrease due to the adsorption of gas molecules on C60-cryptand [2,2] . The C60-cryptand [2,2] coated surface acoustic wave sensor was used to measure various organic moleculesr and CO gas. A software was written to control the interface and data acquisition. In the stationary system, three coating materials (C60, cryptand [2,2] and C60-cryptand [2,2] ) was tested in organic molecules. The C60-cryptand [2,2] coated SAW dector exhibited more sensitive to polar molecule than Fullerene or cryptand [2,2] coated system respectively. Effect of functional groups, molecular weight, steric hindrance and polarity of organic molecules in both static and flow cell on frequency response of surface acoustic wave sensor had been investigated. The frequency shifts of the C60-cryptand [2,2] coated SAW sensor for various organic molecules and isomer in the order: Alcohols (ROH) > Aldehydes (RCHO) > Ketones (RCOR’); 1-Hexyne>1-Hexene >n-Hexane; Aromatic > cyclo-Alkane > Alkane; 10alcohol > 20alcohol > 30alcohol. The greater frequency shift of a molecule with large molecular weight, less steric hindrance and more polar molecule (especially can form hydrogen bond) was funded. The adsorption of C60-cryptand [2,2] to most organic molecules was found to be physical adsorption(a reversible type) ,which could be desorbed by introducing N2 gas. The detection system also showed the good detection limit of 0.2~3 mg/L for organic molecules. The frequency response of C60-cytptand[2,2] coated SAW for various organic molecules in the flow system showed quite accordance with that in static system. In the application of Gas Surface acoustic Wave (GC-SAW) in GC, the C60-cryptand[2,2] SAW sensor showed higher selectivity than the TCD for polar organic molecules. In CO gas study, various metal-ion/C60-cryptand[2,2] adsorbents, e.g. Ti4+/C60-cryptand [2,2]; Co2+/C60-cryptand [2,2]; Al3+/C60-cryptand, were used to adsorb and detect CO gas. The Co2+/C60-cryptand [2,2] coated SAW sensor exhibited more sensitive than another adsorbent for CO gas. It also showed no significant effect for anion group (e.g. SO42-; NO3-; Cl-). The detection limit of the SAW sensor for CO was found to be about 0.13 ppm.

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45

Wu, Jun-Yi, and 吳俊億. "Study of 128°YX-LiNbO3 Based Surface Acoustic Wave Humidity Sensor." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/70482414737865719936.

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Анотація:

碩士
國立臺灣大學
應用力學研究所
94
With the development of industries, there is a growing need for sensitive, accurate, and inexpensive sensors of measuring relative humidity. Humidity sensors are expected for a broad spectrum of applications in meteorology, chemical industry, process control, medical instrument, agriculture, and etc. A good sensor should be characterized by high sensitivity, wide dynamic range, fast response, good reproducibility, easy interface electronics, small size, and minimum cost. It is hard for single sensing system matches all these criterions. However, surface acoustic wave ( SAW) sensing devices are promising candidates to pursue the above goals. In this thesis, the 145MHz based SAW resonator is fabricated and integrated with the amplifier to form a SAW-based oscillator. To function as a humidity sensor, hygroscopic polymer polyethylenimine is coated on the delay line of the resonator as sensing film by airbrush method. Moreover, dual delay line configuration is constructed for the common mode rejection for external influences such as temperature, drift, etc. Then, the sensing devices are exposed to repeated cycles with various relative humidity to investigate the performances including sensitivity, reproducibility, and repeatability. The results reveal good linearity between frequency shifts and various relative humidity and enough short-term repeatability.

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46

Pedrick, Michael K. Tittmann Bernhard R. "Layered surface acoustic wave devices for film characterization and sensor applications." 2007. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1857/index.html.

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47

Kuo, Fang Yu, and 郭芳妤. "PM2.5 Detection by Surface Acoustic Wave Sensor with a Cyclone Separator." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/ma24h2.

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Анотація:

碩士
國立清華大學
奈米工程與微系統研究所
105
In this research, a PM2.5 monitor prototype is designed and developed, including the shear horizontal mode surface acoustic wave (SH-SAW) sensor combining with a cyclone separator. In the experiments, aerosols generated by incense smoke will be separated and sampled inside the designed cyclone separator first, and the sampled PM2.5 will be introduced into the sensing area of SH-SAW chip for the detection. Microcentrifuge tubes as the cyclone separator can reduce the device size and power consumption effectively; 122 MHz surface acoustic wave (SAW) chips are fabricated by MEMS techniques in well design and processes; gold interdigital transducers are deposited on the 36° YX-LiTaO3 and using different frequency shift to identify the concentration of sample. Therefore the research is divided into two major parts: cyclone separator design, efficiency simulation and SAW chip detection experiment. To accomplish the goal of detecting the PM concentration in normal atmosphere, the efficiency, device size of the separator and the sensitivity, stability of the SAW chip will be discussed and improved. 0.2 mL microcentrifuge tube with 0.5mm inlet and outlet diameter as the separator has the separation cutoff diameters (d50) at 2.5μm, and the required inlet volumetric flow rate is 0.125 LPM simulated by CFD software; SAW sensor exhibits sensitivity approximately 9Hz/ng; PM2.5 detection experiment conducting with integrated device, shows the strong positive linear correlation between aerosol monitor data, the concentration limit of detection is 11μg/m3 with 160 seconds sample time, total detection time is 5 minutes.

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48

Chou, Yu-Chen, and 周鈺禎. "Preparation and Application of Bi-channel Surface Acoustic Wave Gas Sensor." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/93735367348539093227.

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Анотація:

碩士
國立臺灣師範大學
化學系
93
C60-polyphenylacetylene(C60-PPA) and polyvinylpyrrolidone(PVP) coated two-channel surface acoustic wave (SAW) detection system was developed and employed to detect carbon disulfide (CS2) and methanol (CH3OH) in this study. The frequency of surface acoustic wave oscillator decreases due to the adsorption of gas molecules on the coated materials of the SAW sensor. The two-channel SAW detection system also includes a homemade computer interface for data acquisition and data processing with a computer program in BASIC. In the stationary system, six coating materials (C60-PPA, nafion, PPA, crytand [2,2], polyethene glycol and PVP ) were used to absorb and detect carbon disulfide and methanol gases. The adsorption of all the six coating materials to CS2 and CH3OH was found to be physical adsorption (a reversible type), which could be desorbed by introducing N2 gas.The C60-PPA coated SAW detector exhibited more sensitive to CS2 than the other coating materials. In contrast, the PVP coated SAW detector exhibited more sensitive to CH3OH than the other coating materials. Then , coating load effect on the response of the SAW crystal was investigated and discussed.When 500 ng C60-PPA coated SAW detection system for CS2 showed the best sensitivity. Coating load effect of polyvinylpyrrolidone coated SAW sensor for CH3OH showed the linear relationship so we chosen to coat polyvinylpyrrolidone as much as C60-PPA. In SAW mobile gas system, the SAW sensor with the homemade working cell was prepared to detect CS2 and CH3OH. Effects of concentration, flow rate and reproducibility on frequency response of surface acoustic wave sensor were studied and discussed. The SAW gas sensor obviously showed the good sensitivity and reproducibility for CS2 and CH3OH. In bi-channel SAW detection system, the C60-PPA coated SAW showed the good detection limit of 0.4 ppm and good reproducibility with RSD of 3.37﹪( n＝10) for CS2. Similarly, the PVP coated SAW also showed the good detection limit of 0.05 ppm and good reproducibility with RSD of 0.86﹪(n＝10) for CH3OH in bi-channel SAW detection system. The interference effect of organic molecules (aceton, 1-propanol and n-propylamine) on the SAW detection system was negligible except that the absorption of C60-PPA to propylamine was found to be irreversible type. The frequency signals from the two channel SAW sensor array were processed by back-propagation artificial neural network（BPN）and multiple regression analysis（MRA）.The qualitative and quantitative analyses of CS2 and CH3OH in their mixtures has been successfully realized by using the sensor array,BPN and MRA.

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49

Tsai, Hsien-Jen, and 蔡顯仁. "Preparation and Application of Surface Acoustic Wave Sensor for Inorganic Gases." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/65858618073233508584.

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Анотація:

碩士
國立臺灣師範大學
化學系
93
A multichannel surface acoustic wave (SAW) gas sensor system was prepared to detect NO2 and CO in the air. The coated Ru3+/ cryptand[2,2] and Zn2+/ cryptand[2,2] SAW crystals were applied to recognize NO2 and CO, respectively. The physical adsorption was found for the adsorption of these inorganic gases onto respective coating materials. The SAW sensor also showed good reproducibility and good enough lifetime of ≧ 30 days for detection of NO2 and CO. The detection limits of this SAW sensor with Ru3+/ cryptand[2,2] and Zn2+/ cryptand[2,2] coatings for NO2 and CO were 0.172 and 0.699 ppm respectively, which were lower than occapational exposure limits for both gases and implied that the developed SAW sensor in this study could be employed for environmental analysis for both gases. The concentration effect of NO2 and CO on the frequency responses of the SAW sensor was studied and showed good linear responses with the concentrations of NO2 and CO, respectively. Effects of temperature and humidity on the SAW sensor were also investigated and discussed. Furthermore, the interference of some organic vapors to the detection of NO2 and CO with the SAW sensor was also studied and discussed. The principal component analysis (PCA) was also applied in this study to confirm that appropriate coating materials for NO2 and CO were selected. Two dimension PCA scores plot showed good separation between NO2 and CO which implied that NO2 and CO can be distinguished clearly by the two-channel SAW sensor. In addition, an artificial neural network, using back propagation network (BPN), was also used to recognize NO2 and CO gases and it shows the distinction of these inorganic gases qualitatively by the two-channel SAW sensor with Ru3+/ crypand[2,2] and Zn2+/ crypatnd[2,2] coatings. The quantitative analysis for NO2 and CO were also studied by the multivariate multiple regression analysis.

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50

Wu, Jeng-hua, and 吳政樺. "A Study of Surface Acoustic Wave Torque Sensor for High Speed Spindle." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/15666838450614166130.

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Анотація:

碩士
國立中正大學
機械工程所
93
Abstract This research is about wireless SAW Torque Sensor , when putting SAW Sensor on 65mm spindle, the torsion is 4.2876Hz/Nm and the sensitivity effect of temperature is -2343.9Hz/1oC. Besides, this research is in the way of mechanics of materials, claiming SAW rotate in high-speed in 30000rpm would cause centrifugal force of spindle and SAW. The frequency variety of them is 43.757Hz and -1361Hz respectly. The centrifugal force would affect the measure of torque, therefore this research consider to how to increase the torque sensitivity and temperature compensation. In the design of SAW Resonators: (1) By using the equivalent circuit showing from Lumped-element to simulate the frequency of one-port SAW resonators.(2) Using Coupling-of-Modes submitted by Cross & Schmidt analyze Surface acoustic waves to simulate the response of two-Port surface sound wave .Considering lots of the design parameter ,for example: piezoelectric substrates ,the number of IDT finger-pairs ,the number of grating elements and thin-film metal strips ,how these items affect central frequency and increase the sensitivity by decade BW3 bandwidth. Finally, operating in coordination with MEMS, using 128oYX-LiNbO3 as the frame, central frequency is 40MHz two port SAW resonators, anaylizing the figure difference between the experiment and simulation.

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