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 Nanostructure Based Sensors for Gas Sensing from Devices to Systems written by Sabrina Grassini and published by MDPI. This book was released on 2019-10-29 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of solid state gas sensors based on microtransducers and nanostructured sensing materials is the key point in the design of portable measurement systems able to reach sensing and identification performance comparable with analytical ones. In such a context several efforts must be spent of course in the development of the sensing material, but also in the choice of the transducer mechanism and its structure, in the electrical characterization of the performance and in the design of suitable measurement setups. This call for papers invites researchers worldwide to report about their novel results on the most recent advances and overview in design and measurements for applications in gas sensors, along with their relevant features and technological aspects. Original research papers are welcome (but not limited) on all aspects that focus on the most recent advances in: (i) basic principles and modeling of gas and VOCs sensors; (ii) new gas sensor principles and technologies; (iii) Characterization and measurements methodologies; (iv) transduction and sampling systems; (vi) package optimization; (vi) gas sensor based systems and applications.
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 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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 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 Additive Manufacturing 3D Print of Air coupled Diaphragm Ultrasonic Transdrucers written by Botong Zhu and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Air-coupled ultrasound is a non-contact technology that has become increasingly common in Non Destructive Evaluation (NDE) and material evaluation. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled devices. This thesis proposes a methodology for improving the bandwidth of an air-coupled micro-machined ultrasonic transducer (MUT) without sensitivity loss by connecting a number of resonating pipes of various length to a cavity in the backplate. This design is inspired by the pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The −6 dB bandwidth of the "pipe organ" inspired air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ∼5 times wider than a custom-built standard device. After validating the concept via a series of single element low-frequency prototypes, two improved designs: the multiple element and the high-frequency single element pipe organ transducers were simulated in order to tailor the pipe organ design to NDE applications.Although the simulated and experimental performance of the pipe organ inspired transducers are proved to be significantly better than the conventional designs, conventional micro-machined technologies are not able to satisfy their required 3D manufacturing resolution. In recent years, there has been increasing interest in using additive manufacturing (3D printing) technology to fabricate sensors and actuators due to rapid prototyping, low-cost manufacturing processes, customized features and the ability to create complex 3D geometries at micrometre scale. This work combines the ultrasonic diaphragm transducer design with a novel stereolithographic additive manufacturing technique. This includes developing a multi-material fabrication process using a commercial digital light processing printer and optimizing the formula of custom-built functional (conductive and piezoelectric) materials. A set of capacitive acoustic and ultrasonic transducers was fabricated using the additive manufacturing technology. The additive manufactured capacitive transducers have a receiving sensitivity of up to 0.4 mV/Pa at their resonant frequency.
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 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 Handbook of Modern Sensors written by Jacob Fraden and published by Springer Science & Business Media. This book was released on 2006-04-29 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seven years have passed since the publication of the previous edition of this book. During that time, sensor technologies have made a remarkable leap forward. The sensitivity of the sensors became higher, the dimensions became smaller, the sel- tivity became better, and the prices became lower. What have not changed are the fundamental principles of the sensor design. They are still governed by the laws of Nature. Arguably one of the greatest geniuses who ever lived, Leonardo Da Vinci, had his own peculiar way of praying. He was saying, “Oh Lord, thanks for Thou do not violate your own laws. ” It is comforting indeed that the laws of Nature do not change as time goes by; it is just our appreciation of them that is being re?ned. Thus, this new edition examines the same good old laws of Nature that are employed in the designs of various sensors. This has not changed much since the previous edition. Yet, the sections that describe the practical designs are revised substantially. Recent ideas and developments have been added, and less important and nonessential designs were dropped. Probably the most dramatic recent progress in the sensor technologies relates to wide use of MEMS and MEOMS (micro-electro-mechanical systems and micro-electro-opto-mechanical systems). These are examined in this new edition with greater detail. This book is about devices commonly called sensors. The invention of a - croprocessor has brought highly sophisticated instruments into our everyday lives.
Download or read book Wide Bandgap Based Devices written by Farid Medjdoub and published by MDPI. This book was released on 2021-05-26 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Emerging wide bandgap (WBG) semiconductors hold the potential to advance the global industry in the same way that, more than 50 years ago, the invention of the silicon (Si) chip enabled the modern computer era. SiC- and GaN-based devices are starting to become more commercially available. Smaller, faster, and more efficient than their counterpart Si-based components, these WBG devices also offer greater expected reliability in tougher operating conditions. Furthermore, in this frame, a new class of microelectronic-grade semiconducting materials that have an even larger bandgap than the previously established wide bandgap semiconductors, such as GaN and SiC, have been created, and are thus referred to as “ultra-wide bandgap” materials. These materials, which include AlGaN, AlN, diamond, Ga2O3, and BN, offer theoretically superior properties, including a higher critical breakdown field, higher temperature operation, and potentially higher radiation tolerance. These attributes, in turn, make it possible to use revolutionary new devices for extreme environments, such as high-efficiency power transistors, because of the improved Baliga figure of merit, ultra-high voltage pulsed power switches, high-efficiency UV-LEDs, and electronics. This Special Issue aims to collect high quality research papers, short communications, and review articles that focus on wide bandgap device design, fabrication, and advanced characterization. The Special Issue will also publish selected papers from the 43rd Workshop on Compound Semiconductor Devices and Integrated Circuits, held in France (WOCSDICE 2019), which brings together scientists and engineers working in the area of III–V, and other compound semiconductor devices and integrated circuits. In particular, the following topics are addressed: – GaN- and SiC-based devices for power and optoelectronic applications – Ga2O3 substrate development, and Ga2O3 thin film growth, doping, and devices – AlN-based emerging material and devices – BN epitaxial growth, characterization, and devices
Download or read book Therapeutic Ultrasound written by Jean-Michel Escoffre and published by Springer. This book was released on 2015-10-20 with total page 459 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights advances and prospects of a highly versatile and dynamic research field: Therapeutic ultrasound. Leading experts in the field describe a wide range of topics related to the development of therapeutic ultrasound (i.e., high intensity focused ultrasound, microbubble-assisted ultrasound drug delivery, low intensity pulsed ultrasound, ultrasound-sensitive nanocarriers), ranging from the biophysical concepts (i.e., tissue ablation, drug and gene delivery, neuromodulation) to therapeutic applications (i.e., chemotherapy, sonodynamic therapy, sonothrombolysis, immunotherapy, lithotripsy, vaccination). This book is an indispensable source of information for students, researchers and clinicians dealing with non-invasive image-guided ultrasound-based therapeutic interventions in the fields of oncology, neurology, cardiology and nephrology.
Download or read book Introduction to Instrumentation and Measurements written by Robert B. Northrop and published by CRC Press. This book was released on 2018-09-03 with total page 952 pages. Available in PDF, EPUB and Kindle. Book excerpt: Weighing in on the growth of innovative technologies, the adoption of new standards, and the lack of educational development as it relates to current and emerging applications, the third edition of Introduction to Instrumentation and Measurements uses the authors’ 40 years of teaching experience to expound on the theory, science, and art of modern instrumentation and measurements (I&M). What’s New in This Edition: This edition includes material on modern integrated circuit (IC) and photonic sensors, micro-electro-mechanical (MEM) and nano-electro-mechanical (NEM) sensors, chemical and radiation sensors, signal conditioning, noise, data interfaces, and basic digital signal processing (DSP), and upgrades every chapter with the latest advancements. It contains new material on the designs of micro-electro-mechanical (MEMS) sensors, adds two new chapters on wireless instrumentation and microsensors, and incorporates extensive biomedical examples and problems. Containing 13 chapters, this third edition: Describes sensor dynamics, signal conditioning, and data display and storage Focuses on means of conditioning the analog outputs of various sensors Considers noise and coherent interference in measurements in depth Covers the traditional topics of DC null methods of measurement and AC null measurements Examines Wheatstone and Kelvin bridges and potentiometers Explores the major AC bridges used to measure inductance, Q, capacitance, and D Presents a survey of sensor mechanisms Includes a description and analysis of sensors based on the giant magnetoresistive effect (GMR) and the anisotropic magnetoresistive (AMR) effect Provides a detailed analysis of mechanical gyroscopes, clinometers, and accelerometers Contains the classic means of measuring electrical quantities Examines digital interfaces in measurement systems Defines digital signal conditioning in instrumentation Addresses solid-state chemical microsensors and wireless instrumentation Introduces mechanical microsensors (MEMS and NEMS) Details examples of the design of measurement systems Introduction to Instrumentation and Measurements is written with practicing engineers and scientists in mind, and is intended to be used in a classroom course or as a reference. It is assumed that the reader has taken core EE curriculum courses or their equivalents.
Download or read book MEMS Materials and Processes Handbook written by Reza Ghodssi and published by Springer Science & Business Media. This book was released on 2011-03-18 with total page 1211 pages. Available in PDF, EPUB and Kindle. Book excerpt: MEMs Materials and Processes Handbook" is a comprehensive reference for researchers searching for new materials, properties of known materials, or specific processes available for MEMS fabrication. The content is separated into distinct sections on "Materials" and "Processes". The extensive Material Selection Guide" and a "Material Database" guides the reader through the selection of appropriate materials for the required task at hand. The "Processes" section of the book is organized as a catalog of various microfabrication processes, each with a brief introduction to the technology, as well as examples of common uses in MEMs.
Download or read book Diagnostic Ultrasound written by Peter R. Hoskins and published by Cambridge University Press. This book was released on 2010-06-17 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: All healthcare professionals practising ultrasound in a clinical setting should receive accredited training in the principles and practice of ultrasound scanning. This second edition of Diagnostic Ultrasound: Physics and Equipment provides a comprehensive introduction to the physics, technology and safety of ultrasound equipment, with high quality ultrasound images and diagrams throughout. It covers all aspects of the field at a level intended to meet the requirements of UK sonography courses. New to this edition: • Updated descriptions of ultrasound technology, quality assurance and safety. • Additional chapters dedicated to 3D ultrasound, contrast agents and elastography. • New glossary containing definitions of over 500 terms. The editors and contributing authors are all authorities in their areas, with contributions to the scientific and professional development of ultrasound at national and international level.
Download or read book Acoustics Sound Fields and Transducers written by Leo Leroy Beranek and published by Academic Press. This book was released on 2012-09-20 with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt: Long-awaited update and expansion of a widely recognised classic in the field by pioneering acoustics expert, Leo L. Beranek Builds upon Beranek's 1954 Acoustics classic by incorporating recent developments, practical formulas and methods for effective simulation Uniquely, provides the detailed acoustic fundamentals which enable better understanding of complex design parameters, measurement methods and data Brings together topics currently scattered across a variety of books and sources into one valuable reference Includes relevant case studies, real-world examples and solutions to bring the theory to life Acoustics: Sound Fields and Transducers is a modern expansion and re-working of Acoustics, the 1954 classic reference written by Leo L. Beranek. Updated throughout and focused on electroacoustics with the needs of a broad range of acoustics engineers and scientists in mind, this new book retains and expands on the detailed acoustical fundamentals included in the original whilst adding practical formulas and simulation methods for practising professionals. Benefitting from Beranek's lifetime experience as a leader in the field and co-author Tim Mellow's cutting-edge industry experience, Acoustics: Sound Fields and Transducers is a modern classic to keep close to hand in the lab, office and design studio. Builds on Beranek's 1954 Acoustics classic by incorporating recent developments, practical formulas and methods for effective simulationUniquely provides the detailed acoustic fundamentals, enabling better understanding of complex design parameters, measurement methods and dataBrings together topics currently scattered across a variety of books and sources into one valuable referenceIncludes relevant case studies, real-world examples and solutions to bring the theory to life.
Download or read book Piezoelectric Transducers and Applications written by Antonio Arnau and published by Springer Science & Business Media. This book was released on 2004 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Piezoelectric Transducers and Applications provides a guide for graduate students and researchers to the current state of the art of this complex and multidisciplinary area. The book fills an urgent need for a unified source of information on piezoelectric devices and their astounding variety of existing and emerging applications. Some of the chapters focus more on the basic concepts of the different disciplines involved and are presented in a didactic manner. Others go deeper into the complex aspects of specific fields of research, thus reaching the technical level of a scientific paper. Among other topics resonant sensors, especially bulk acoustic wave thickness shear mode resonators, chemical and bio-sensors, as well as broadband ultrasonic systems are treated in-depth.
