Download or read book Piezoelectric Micromachined Ultrasound Transducers for Air coupled Applications written by Stefon Eric Shelton and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasound transducers are used for many applications including medical imaging, non-destructive testing, obstruction detection, flow sensing, and gesture recognition. Piezoelectric micromachined ultrasound transducers (PMUTs) offer an attractive alternative to traditional bulk piezoelectric ultrasonic sensors, due to their compact size, increased transduction efficiency, and integrated array configuration. In this work, the development of aluminum nitride PMUTs for air coupled use is presented. The transducer consists of a circular composite diaphragm actuated using an aluminum nitride piezoelectric layer. An equivalent circuit model for a single clamped plate PMUTs has been developed and the design equations are presented and compared with finite element method simulations and measured values. The use of an acoustic resonator tube to boost the output pressure and increase the bandwidth of micro-scale transducers is demonstrated. The developed fabrication process for AlN PMUTs is presented. Clamped plate transducers operating from 100-300 kHz are characterized in the mechanical, electrical, and acoustic domains. The output pressure of the transducers at 5 cm is 90 mPa/V and the receive sensitivity is 0.8 mV/Pa. A flexurally suspended design with increased linearity and a piston-like mode shape is presented and the effect of perforations in the membrane surface determined. Finally, fabrication of PMUT arrays and sources of frequency mismatch, including geometric and the effects of residual stress are discussed. Through process improvements, across-die frequency matching of 1.5% is achieved which is well within the 6.6% fractional bandwidth of the transducer. The array acoustic performance is quantified and the on axis pressure is found to increase linearly with the number of exited elements and the beam-width of a 2D array is 20°.

Download or read book Air coupled Aluminum Nitride Piezoelectric Micromachined Ultrasonic Transducers written by Ofer Rozen and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work focuses on air coupled piezoelectric ultrasonic transducers (PMUTs) for range finding and gesture recognition applications. Such applications require an array of identical PMUTs operating at center frequencies from 40-900 kHz, a fractional bandwidth greater than 5%, and center frequency variation between PMUTs within the same array that does not exceed the fractional bandwidth. The first contribution of this work aims to reduce the in-wafer and in-die variation of the resonance frequency without degrading the PMUT performance. By designing a variable thickness diaphragm, a more robust diaphragm was designed while widening its bandwidth compared to flat solid plate with the same resonant frequency. The membranes are partially etched to remove mass, in a radial ribbed pattern that maintains the stiffness of the structure. This design achieves a 10 fold lower variation in the resonance frequency, while maintaining low quality factor for PMUTs at about 200 kHz. The second contribution of this work concerns the design of PMUTs for higher frequencies. Traditionally, air couple ultrasonic transducers operate at 40-200 kHz, in order to minimize loss in air. However, for some applications, the transmission range can be traded off in order to achieve better resolution. PMUTs at resonance frequencies from 200-900 kHz were fabricated and characterized, and their loss in air was confirmed. The devices were fabricated using wafer-level bonding of a MEMS wafer to a CMOS wafer; therefore the acoustic effects due to the presence of the CMOS wafer were investigated. A back side cavity was required in order to prevent squeeze film damping between the membrane and the CMOS. Finally, a novel method to recycle the back-side acoustic pressure by redirecting it to the front-side through concentric venting rings was demonstrated. The ring diameter determines the phase-shift between the sound emerging from the front-side port and the ring, and can be adjusted to either amplify the far-field sound pressure level (SPL) or change the directivity of the output beam. Nine deferent ring designs were fabricated and characterized, and a 4.5dB increase in on-axis SPL was measured. The methods used include analytic and numeric modeling of the piezo-acoustic systems as well as fabrication and characterization of devices. Multi-physics finite element models (FEM) were conducted using COMSOL and included the piezoelectric devices and the acoustic domains. Also a general dynamic model for a PMUT system that can evaluate performance in transmission and sensing was developed. It can also be adjusted for different boundary conditions and different diaphragm shapes. The model is not limited to linear coefficient, and therefore can also be used to study the non-linearity of the system. Then, devices with an aluminum nitride (AlN) piezo layer were fabricated both at the Marvell Nanofabrication Laboratory and in an industrial foundry. Frequency responses were studied in-air, using a laser Doppler vibrometer (LDV) and acoustic measurements were conducted using a B&K high frequency microphone.

Download or read book Air Coupled Piezoelectric Micromachined Ultrasonic Transducer Array Based on Low cost and Large Remnant Polarization PZT Thin Film written by and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Micromachined Ultrasonic Transducers written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Microfabricated ultrasonic transducers have been generated which operate in both liquids and gases. Air coupled through transmission of aluminum was observed for the first time using a pair of 2.3 MHz transducers. The dynamic range of the transducers was 110 dB, and the received signal had an SNR of 30 dB. Air coupled through transmission of steel and glass has also been observed. A theoretical model for the transducers has been refined and agrees well with experimental results. A robust microfabrication process has been developed and was used to generate air transducers which resonate from 2 to 12 MHz, as well as immersion transducers that operate in water from 1 to 20 MHz with a 60 dB dynamic range. Optimized immersion and air transducers have been designed and a dynamic range above 110 dB is anticipated. This development effort finds applications in hydrophones, medical ultrasound, nondestructive evaluation, ranging, flow metering, and scanning tip force sensing and lithography.

Download or read book Large Amplitude Piezoelectric Micromachined Ultrasonic Transducers for Airborne Applications written by Yuri Kusano and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Piezoelectric micromachined ultrasonic transducers (PMUTs) have greatly advanced in the last decade opening the path to a wide range of applications, including 3D range finding, 3D gesture recognition, 3D imaging, and fingerprint sensing. This evolving ultrasonic time-of-flight sensors based on microelectromechanical systems (MEMS) technology utilize the flexural vibration of a membrane consisting of a piezoelectric thin-film. Compared to the conventional bulk ultrasonic transducers, PMUTs are small size, low power consumption, low cost, and easy to fabricate array structures. Despite many advantages, PMUTs still require further investigation to improve their bandwidth, transmission power, and nonlinear behavior that emerges at large amplitude excitations. As opposed to the immersed applications, these limitations become particularly significant for airborne applications because they demand large amplitude displacements as well as high pressure outputs. This work describes various PMUTs designed and fabricated for in-air operation, focusing on each aspect of the issues listed above. In the first part, a method to expand the bandwidth is presented using lead-zirconate-titanate (PZT) PMUTs. Wideband enables short transmission time that allows detection at a closer distance as well as higher range resolution. By optimally tuning a small DC bias of 5 V, the rectangular shaped PMUTs demonstrate comparably high bandwidth for air-coupled transducers. The second part focuses on implementing one of the new piezoelectric materials, a scandium-doped aluminum nitride (ScAlN) thin-film with high Sc concentration at 36%. Retaining many good features of AlN (e.g. CMOS compatibility, low dielectric loss, high Curie temperature, fairly simple sputtering and etching process), the ScAlN can obtain significantly improved piezoelectric properties up to the crystal phase boundary at 43%. An optimized design and fabrication process for 36% ScAlN PMUTs with high piezoelectric transduction are presented. The transmit pressure of these PMUTs operating in air at 60 kHz is 105 dB SPL at 10 cm and only 30 dB attenuation at 2 m range. The nonlinear effects of the air-coupled PMUTs are further studied in the third part of the dissertation. An empirical model to predict the mechanical spring-hardening effect that limits the dynamic range of PMUTs due to the membrane stiffening is proposed and evaluated. Understanding the nonlinear vibration at large amplitudes allows further improvement in the transducer design especially for airborne applications. Lastly, PMUTs with flexural support structures are presented as one solution to increase the actuation area and to improve the linear operating range.

Download or read book Piezoelectric and Acoustic Materials for Transducer Applications written by Ahmad Safari and published by Springer. This book was released on 2010-11-04 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book discusses the underlying physical principles of piezoelectric materials, important properties of ferroelectric/piezoelectric materials used in today’s transducer technology, and the principles used in transducer design. It provides examples of a wide range of applications of such materials along with the appertaining rationales. With contributions from distinguished researchers, this is a comprehensive reference on all the pertinent aspects of piezoelectric materials.

Download or read book Ultrasound in Food Processing written by Mar Villamiel and published by John Wiley & Sons. This book was released on 2017-04-25 with total page 764 pages. Available in PDF, EPUB and Kindle. Book excerpt: Part I: Fundamentals of ultrasound This part will cover the main basic principles of ultrasound generation and propagation and those phenomena related to low and high intensity ultrasound applications. The mechanisms involved in food analysis and process monitoring and in food process intensification will be shown. Part II: Low intensity ultrasound applications Low intensity ultrasound applications have been used for non-destructive food analysis as well as for process monitoring. Ultrasonic techniques, based on velocity, attenuation or frequency spectrum analysis, may be considered as rapid, simple, portable and suitable for on-line measurements. Although industrial applications of low-intensity ultrasound, such as meat carcass evaluation, have been used in the food industry for decades, this section will cover the most novel applications, which could be considered as highly relevant for future application in the food industry. Chapters addressing this issue will be divided into three subsections: (1) food control, (2) process monitoring, (3) new trends. Part III: High intensity ultrasound applications High intensity ultrasound application constitutes a way to intensify many food processes. However, the efficient generation and application of ultrasound is essential to achieving a successful effect. This part of the book will begin with a chapter dealing with the importance of the design of efficient ultrasonic application systems. The medium is essential to achieve efficient transmission, and for that reason the particular challenges of applying ultrasound in different media will be addressed. The next part of this section constitutes an up-to-date vision of the use of high intensity ultrasound in food processes. The chapters will be divided into four sections, according to the medium in which the ultrasound vibration is transmitted from the transducers to the product being treated. Thus, solid, liquid, supercritical and gas media have been used for ultrasound propagation. Previous books addressing ultrasonic applications in food processing have been based on the process itself, so chapters have been divided in mass and heat transport, microbial inactivation, etc. This new book will propose a revolutionary overview of ultrasonic applications based on (in the authors’ opinion) the most relevant factor affecting the efficiency of ultrasound applications: the medium in which ultrasound is propagated. Depending on the medium, ultrasonic phenomena can be completely different, but it also affects the complexity of the ultrasonic generation, propagation and application. In addition, the effect of high intensity ultrasound on major components of food, such as proteins, carbohydrates and lipids will be also covered, since this type of information has not been deeply studied in previous books. Other aspects related to the challenges of food industry to incorporate ultrasound devices will be also considered. This point is also very important since, in the last few years, researchers have made huge efforts to integrate fully automated and efficient ultrasound systems to the food production lines but, in some cases, it was not satisfactory. In this sense, it is necessary to identify and review the main related problems to efficiently produce and transmit ultrasound, scale-up, reduce cost, save energy and guarantee the production of safe, healthy and high added value foods.

Download or read book Air coupled Capacitive Micromachined Ultrasonic Transducers Based on Annular Cell Geometry written by Shuai Na and published by . This book was released on 2017 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Air-coupled ultrasound is gaining increasing industry momentum due to the demands and development of non-destructive evaluation (NDE) of aerospace composite materials. Currently, the micromachining technology has advanced such that vacuum cavities sealed by thin plates, known as Capacitive Micromachined Ultrasonic Transducers (CMUTs), can be fabricated through silicon micromachining processes in a low cost manner. Given the thin plates, a CMUT is able to vibrate with a low mechanical impedance and thus a high coupling efficiency with the ambient atmosphere. Nevertheless, air-coupled applications are still highly limited by the transmit power of air-coupled CMUTs. A circle is the routine geometry in most CMUT cell designs. Even though efforts have been put forward to address the limitations of circular design in terms of sensitivity, more investigation about other cell geometries is prudent. In this work, a novel air-coupled CMUT design with annular cell geometry is proposed. Finite element analysis and experimental studies demonstrated its significant improvement in transmit efficiency over the conventional circular-cell CMUTs. A lumped element model was constructed to facilitate a better understanding and provide an efficient design technique of the annular CMUT. Three optimization schemes were developed to optimize the transmit efficiency and achieve a reasonable comparison between the novel annular and conventional circular CMUT cells. Based on the lumped models, a design optimization flow chart was constructed to facilitate the analytical optimization of the three schemes. To further enhance the transmit power as well as offer depth focusing, a 9-element concentric annular-cell array was designed, fabricated, and characterized. A pillar-free etching process was developed to create the deep large-area cavities. The cross-talk between neighbouring cells and the plate-cracking phenomenon were discussed with suggestions for improvement being provided. This study provides a systematic framework for designing and studying annular-cell CMUTs and demonstrates their great potential in transmitting high-power ultrasound in air.

Download or read book Characteristics and Applications of Air coupled Micromachined Ultrasonic Transducers written by Andrew Graham Bashford and published by . This book was released on 2017 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanics of Microsystems written by Alberto Corigliano and published by John Wiley & Sons. This book was released on 2018-04-02 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanics of Microsystems Alberto Corigliano, Raffaele Ardito, Claudia Comi, Attilio Frangi, Aldo Ghisi and Stefano Mariani, Politecnico di Milano, Italy A mechanical approach to microsystems, covering fundamental concepts including MEMS design, modelling and reliability Mechanics of Microsystems takes a mechanical approach to microsystems and covers fundamental concepts including MEMS design, modelling and reliability. The book examines the mechanical behaviour of microsystems from a ‘design for reliability’ point of view and includes examples of applications in industry. Mechanics of Microsystems is divided into two main parts. The first part recalls basic knowledge related to the microsystems behaviour and offers an overview on microsystems and fundamental design and modelling tools from a mechanical point of view, together with many practical examples of real microsystems. The second part covers the mechanical characterization of materials at the micro-scale and considers the most important reliability issues (fracture, fatigue, stiction, damping phenomena, etc) which are fundamental to fabricate a real working device. Key features: Provides an overview of MEMS, with special focus on mechanical-based Microsystems and reliability issues. Includes examples of applications in industry. Accompanied by a website hosting supplementary material. The book provides essential reading for researchers and practitioners working with MEMS, as well as graduate students in mechanical, materials and electrical engineering.

Download or read book Capacitive Micromachined Ultrasonic Transducers for Non destructive Testing Applications written by Lawrence Lai Pong Wong and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasound is a popular technique for industrial non-destructive testing (NDT) applications. By sending ultrasonic waves into an object and observing the amplitude and the delay of the reflected or transmitted waves, one can characterize the material, measure the thickness of the object, and detect discontinuities (flaws) as well as the size, location, and orientation of the defects in the object. Traditionally, ultrasonic transducers for NDT are made with piezoelectric crystals. Meanwhile, another class of ultrasonic transducers known as capacitive micromachined ultrasonic transducers (CMUTs) have become popular in medical ultrasound research because of their large bandwidths and other attributes that allow them to be integrated into the tip of a catheter. However, CMUTs have not been widely adopted in ultrasonic NDT applications. In this thesis, three important CMUTs characteristics that could potentially make them attractive for NDT applications are introduced and demonstrated. First, CMUTs can be beneficial to NDT because the fabrication techniques of CMUTs can easily be used to implement high-frequency, high-density phased arrays, which are essential for high resolution scanning. Surface scanning using a 2-D row-column addressed CMUT array was demonstrated. Secondly, CMUTs can be integrated with supporting microelectronic circuits, thus one can implement a highly integrated transducer system, which can be useful in structural health monitoring NDT applications. Front-end microelectronic circuits that include a transmit pulser and a receive amplifier were designed, tested, and characterized. Thirdly, CMUTs are suitable for air-coupled applications because of their low acoustic impedance at resonance. Air-coupled CMUTs fabricated in a standard RF-MEMS process were characterized and tested. This thesis concludes with an analysis of the potential usefulness of CMUTs for ultrasonic NDT. While many ultrasonic NDT applications are better off being performed using conventional piezoelectric transducers, CMUTs can and should be used in certain NDT applications that can take advantage of the beneficial characteristics of this exciting transducer technology.

Download or read book Ultrasonic Transducers written by K Nakamura and published by Elsevier. This book was released on 2012-08-23 with total page 749 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasonic transducers are key components in sensors for distance, flow and level measurement as well as in power, biomedical and other applications of ultrasound. Ultrasonic transducers reviews recent research in the design and application of this important technology. Part one provides an overview of materials and design of ultrasonic transducers. Piezoelectricity and basic configurations are explored in depth, along with electromagnetic acoustic transducers, and the use of ceramics, thin film and single crystals in ultrasonic transducers. Part two goes on to investigate modelling and characterisation, with performance modelling, electrical evaluation, laser Doppler vibrometry and optical visualisation all considered in detail. Applications of ultrasonic transducers are the focus of part three, beginning with a review of surface acoustic wave devices and air-borne ultrasound transducers, and going on to consider ultrasonic transducers for use at high temperature and in flaw detection systems, power, biomedical and micro-scale ultrasonics, therapeutic ultrasound devices, piezoelectric and fibre optic hydrophones, and ultrasonic motors are also described. With its distinguished editor and expert team of international contributors,Ultrasonic transducers is an authoritative review of key developments for engineers and materials scientists involved in this area of technology as well as in its applications in sectors as diverse as electronics, wireless communication and medical diagnostics. Reviews recent research in the design and application of ultrasonic transducers Provides an overview of the materials and design of ultrasonic transducers, with an in-depth exploration of piezoelectricity and basic configurations Investigates modelling and characterisation, applications of ultrasonic transducers, and ultrasonic transducers for use at high temperature and in flaw detection systems

Download or read book High Efficient Piezoelectric Micromachined Ultrasonic Transducer Arrays written by Qi Wang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Piezoelectric micromachined ultrasonic transducers (PMUTs) have been developed for many applications such as biometric identification, medical imaging and gesture recognition as an economic and small replacement for current bulk piezoelectric ultrasonic transducers. The PMUTs fabrication process compatibility to complementary metal-oxide-semiconductor (CMOS) is an advantage for making circuit integrated systems in the same process to achieve low cost and small size, especially for mobile and wearable devices. The current PMUTs have no sufficient output pressures compare to bulk piezoelectric ultrasonic transducers. This thesis will focus on improving the efficiency of the PMUTs and their arrays from the perspective of piezoelectric materials, individual PMUT structures, arrays designs and the acoustic couplings in the arrays. Firstly, the background of the piezoelectric ultrasonic transducers will be introduced. Comparisons of the micromachined ultrasonic transducers (MUT, including piezoelectric and capacitive micromachined ultrasonic transducers) with current bulk piezoelectric ultrasonic transducers show that MUTs have the advantages in the low cost, small size for more potential applications. Then, to improve the current performance of the PMUTs, novel piezoelectric materials are utilized to fabricate PMUT arrays. Characterization results indicated that scandium aluminum nitride is a promising thin film for the future PMUT products. Furthermore, the acoustic coupling is a major source of the cross talk in the large PMUT arrays and will influence the imaging resolution. An equivalent circuit model is built and verified experimentally to improve the PMUT array designs. Meanwhile, the acoustic coupling is also utilized to achieve improved pulse-echo performance with a novel PMUT structure. Next, the PMUT array optimizations based on different structural thicknesses will be studied theoretically and experimentally in the following chapter. The results show that a thin and densely packed array is the key to achieve high performance. Current cavity SOI wafer-based fabrication process is not good enough to achieve high fill-factor for high-frequency PMUT arrays. Thus, a novel surface micromachining process is proposed to fabricate high fill-factor PMUT arrays with improved performance.

Download or read book High Frequency Piezo Composite Micromachined Ultrasound Transducer Array Technology for Biomedical Imaging written by Xiaoning Jiang and published by . This book was released on 2017 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this monograph, the authors reports the current advancement in high frequency piezoelectric crystal micromachined ultrasound transducers and arrays and their biomedical applications. Piezoelectric ultrasound transducers operating at high frequencies (>20 MHz) are of increasing demand in recent years for medical imaging and biological particle manipulation involved therapy. The performances of transducers greatly rely on the properties of the piezoelectric materials and transduction structures, including piezoelectric coefficient (d), electromechanical coupling coefficient (k), dielectric permittivity (e) and acoustic impedance (Z). Piezo-composite structures are preferred because of their relatively high electromechanical coupling coefficient and low acoustic impedance. A number of piezo-composite techniques have been developed, namely "dice and fill," "tape-casting," "stack and bond," "interdigital phase bonding," "laser micromachining" and "micro-molding". However, these techniques are either difficult to achieve fine features or not suitable for manufacturing of high frequency ultrasound transducers (>20 MHz). The piezo-composite micromachined ultrasound transducers (PC-MUT) technique discovered over the last 10 years or so has demonstrated high performance high frequency piezo-composite ultrasound transducers. In this monograph, piezoelectric materials used for high frequency transducers is introduced first. Next, the benefits and theory of piezo composites is presented, followed by the design criteria and fabrication methods. Biomedical applications using piezo composites micromachined ultrasound transducers (PC-MUT) and arrays will also be reported, in comparison with other ultrasound transducer techniques. The final part of this monograph describes challenges and future perspectives of this technique for biomedical applications.

Download or read book An Evaluation of 1 3 Connectivity Composite Transducers for Air coupled Ultrasonic Applications written by Anthony Gachagan and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional ultrasonic non-destructive evaluation techniques require some form of liquid coupling between the piezoelectric transducer and the sample under inspection to facilitate mechanical energy transfer. Under automated conditions, maintaining a consistent couplant layer can constitute a problem and is manifest in slower scanning rates. To improve scanning speed the ultrasound should ideally propagate across an intermediate airgap. This possibility has been inhibited by the lack of a suitable transducer technology to overcome the practical difficulties inherent in the air medium. The large acoustic impedance mismatch, between a piezoelectric element and air, and the large air attenuation factor ensures both poor sensitivity and resolution characteristics. This Thesis advances transducer technology, enabling these problems to be challenged effectively.Initially, the Thesis describes the creation of a wideband characterisation methodology for aircoupled ultrasonic transducers operating in the range 100kHz - 2MHz. The proposed technique utilises piezopolymer transducers in both transmission and reception modes and despite the obvious measurement difficulties, good agreement between theory and experiment is illustrated. Results are presented on the characterisation of both electrostatic and 1-3 connectivity piezocomposite devices, in which the inherent narrowband nature of the piezocomposite transducer demonstrates considerable potential for airborne applications.Subsequently, the performance of air-coupled 1-3 connectivity piezocomposite transducers is investigated using both uni-dimensional and finite element modelling techniques. Experimental verification of these techniques enables the finite element approach to be used as the benchmark for evaluation of practical transducer configurations. Consequently, a series of design guidelines are presented for practical air-coupled composite transducer systems. For many applications, the conventional method to improve system resolution, through attachment of a backing block, produces an unacceptably low system sensitivity. Hence, an alternative approach is proposed, utilising strong coupling between the fundamental thickness mode and the first lateral resonance in a 1-3 piezocomposite. Finite element analysis has been employed in the design of a laterally-coupled composite receiver and a -6dB bandwidth of 150% at a centre frequency of 1 MHz is presented. Finally, the new transducer design techniques were applied to three different airborne non-destructive testing applications. Successful detection of various defects in carbon-fibre reinforced composite plates is demonstrated.

Download or read book Nonlinear Structures Systems Volume 1 written by Matthew R.W. Brake and published by Springer Nature. This book was released on 2023-11-14 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nonlinear Structures & Systems, Volume 1: Proceedings of the 41st IMAC, A Conference and Exposition on Structural Dynamics, 2023, the first volume of ten from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of Nonlinear Dynamics, including papers on: Experimental Nonlinear Dynamics Jointed Structures: Identification, Mechanics, Dynamics Nonlinear Damping Nonlinear Modeling and Simulation Nonlinear Reduced-Order Modeling Nonlinearity and System Identification

Download or read book Permanent Contact Mode Operation of Air coupled Capacitive Micromachined Ultrasonic Transducers CMUTs for Wide Pressure Range Application written by Min-Chieh Ho and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Flare gas stacks are widely used to burn off raw natural gas as waste in oil production facilities. In areas without proper gas transportation infrastructure, collecting the natural gas for sale can be even more costly than flaring it off. About 150 billion cubic meter of natural gas is flared annually worldwide, which is equal to 25% of the US gas consumption and contributes to about 400 million tons of carbon dioxide emission each year. In recent year, therefore, it is not surprising that regulatory agencies require the oil producers to report flare emissions, and effective regulation of gas flaring relies heavily on accurate measurement. The focus of this research is to provide ultrasonic transducers for flare gas metering, with a targeted pressure range of 1 - 20 atm and temperature up to 300 degree C. Piezoelectric transducers are not a good candidate due to their limited Curie temperature. In order to operate CMUTs over a wide and varying pressure range without suffering from drastic changes in static operational point and operational frequency, we proposed a new operation mode, in which the plate is in permanent contact with the bottom of the cavity, even at zero dc bias and 1 atm pressure. This dissertation describes the design, finite element simulation, the fabrication, and characterization results for the CMUTs in permanent contact mode. Finite element analysis predicts the behavior of these CMUTs very well, and provides design guidelines that are useful in determining the device dimensions to fabricate. Improvements in device design and fabrication processes are also implemented in a second fabrication to increase the mechanical strength of the devices, and pitch-catch measurements with good SNR are demonstrated with these CMUTs up to 20 atm. This dissertation also presents the experimental results, including the charging method and charge storage long-term (29 months) stability, for pre-charged CMUTs for dc-bias-free operation.