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 Modeling Fabrication and Characterization of Piezoelectric Micromachined Ultrasonic Transducer Arrays written by Yipeng Lu and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents high fill-factor piezoelectric micromachined ultrasonic transducer (PMUT) arrays fabricated via a novel process using cavity SOI wafers. The simple three-mask fabrication process enables smaller diameter PMUTs (25 [mu]m) and finer pitch than previous processes requiring through-wafer etching. PMUTs were fabricated with diameters from 25 ℗æm to 50 [mu]m, resulting in center frequencies from 13 MHz to 55 MHz in air. Two types of devices, having different piezoelectric layers, lead zirconium titanate (PZT) and aluminum nitride (AlN), were fabricated and characterized. Comparing 50 [mu]m diameter devices, the PZT PMUTs show large dynamic displacement sensitivity of 316 nm/V at 11 MHz in air, which is ~20x higher than that of the AlN PMUTs. Electrical impedance measurements of the PZT PMUTs show high electromechanical coupling k(t)2 = 12.5%, and 50 Ω electrical impedance that is well-matched to typical interface circuits. Immersion tests were conducted on PZT PMUT arrays. The fluid-immersed acoustic pressure generated by an unfocused 9x9 array of 40 [mu]m diameter, 10 MHz PZT PMUTs, measured with a needle hydrophone 1.2 mm away from the array, was 58 kPa with a 25 V(pp) input. Beam-forming based on electronic phase control produced a narrow, 150 [mu]m diameter, focused beam over a depth of focus > 0.2 mm and increased the pressure to 450 kPa with 18 V(pp) input. Finally, we also demonstrated short-range (~mm) and high-resolution (

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 Interface Engineering of Capacitive Micromachined Ultrasonic Transducers for Medical Applications written by Der-Song Lin and published by Stanford University. This book was released on 2011 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs), have been widely studied in academia and industry over the last decade. CMUTs provide many benefits over traditional piezoelectric transducers including improvement in performance through wide bandwidth, and ease of electronics integration, with the potential to batch fabricate very large 2D arrays with low-cost and high-yield. Though many aspects of CMUT technology have been studied over the years, packaging the CMUT into a fully practical system has not been thoroughly explored. Two important interfaces of packaging that this thesis explores are device encapsulation (the interface between CMUTs and patients) and full electronic integration of large scale 2D arrays (the interface between CMUTs and electronics). In the first part of the work, I investigate the requirements for the CMUT encapsulation. For medical usage, encapsulation is needed to electrically insulate the device, mechanically protect the device, and maintain transducer performance, especially the access of the ultrasound energy. While hermetic sealing can protect many other MEMS devices, CMUTs require mechanical interaction to a fluid, which makes fulfilling the previous criterion very challenging. The proposed solution is to use a viscoelastic material with the glass-transition-temperature lower than room temperature, such as Polydimethylsiloxane (PDMS), to preserve the CMUT static and dynamic performance. Experimental implementation of the encapsulated imaging CMUT arrays shows the device performance was maintained; 95 % of efficiency, 85% of the maximum output pressure, and 91% of the fractional bandwidth (FBW) can be preserved. A viscoelastic finite element model was also developed and shows the performance effects of the coating can be accurately predicted. Four designs, providing acoustic crosstalk suppression, flexible substrate, lens focusing, and blood flow monitoring using PDMS layer were also demonstrated. The second part of the work, presents contributions towards the electronic integration and packaging of large-area 2-D arrays. A very large 2D array is appealing for it can enable advanced novel imaging applications, such as a reconfigurable array, and a compression plate for breast cancer screening. With these goals in mind, I developed the first large-scale fully populated and integrated 2D CMUTs array with 32 by 192 elements. In this study, I demonstrate a flexible and reliable integration approach by successfully combining a simple UBM preparation technique and a CMUTs-interposer-ASICs sandwich design. The results show high shear strength of the UBM (26.5 g), 100% yield of the interconnections, and excellent CMUT resonance uniformity ([lowercase Sigma] = 0.02 MHz). As demonstrated, this allows for a large-scale assembly of a tile-able array by using an interposer. Interface engineering is crucial towards the development of CMUTs into a practical ultrasound system. With the advances in encapsulation technique with a viscoelastic polymer and the combination of the UBM technique to the TSV fabrication for electronics integration, a fully integrated CMUT system can be realized.

Download or read book High Frequency Piezo Composite Micromachined Ultrasound Transducer Array Technology for Biomedical Imaging written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ultrasonic Transducer Materials written by O. E. Mattiat and published by Springer Science & Business Media. This book was released on 2013-03-13 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years remarkable progress has been made in the development of materials for ultrasonic transducers. There is a continuing trend towards increasingly higher frequency ranges for the application of ultrasonic trans ducers in modern technology. The progress in this area has been especially rapid and articles and papers on the subject are scattered over numerous technical and scientific journals in this country and abroad. Although good books have appeared on ultrasonics in general and ultrasonic transducers in particular in which, for obvious reasons, materials play an important part, no comprehensive treatise is available that represents the state-of-the-art on modern ultrasonic transducer materials. This book intends to fill a need for a thorough review of the subject. Not all materials are covered of which, theoretically, ultrasonic trans ducers could be made but those that are or may be of technical impor tance and which have inherent electro acoustic transducer properties, i.e., materials that are either magnetostrictive, electrostrictive, or piezoelectric. The book has been devided into three parts which somewhat reflect the historic development of ultrasonic transducer materials for important tech nical application. Chapter 1 deals with magnetostrictive materials, magnetostrictive met als and their alloys, and magnetostrictive ferrites (polycrystalline ceramics). The metals are useful especially in cases where ruggednes of the transducers are of overriding importance and in the lower ultrasonic frequency range.

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 Frequency Piezoelectric Micromachined Ultrasound Transducers written by Christine Dempster and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the current research is to fabricate 4-28 MHz Aluminum Nitride (AlN) piezoelectric micromachined ultrasound transducers (pMUTs) to be used in pulse echo imaging, such as biometric fingerprint authentication and real time 3D medical imaging. Unimorph piezoelectric plates, composed of SiO2/Mo/AlN/Al layers on a Silicon wafer, are designed and modeled in both linear and 2D arrays with single and dual electrode designs. These are designed to be fabricated, tested, and eventually integrated above CMOS on a silicon substrate. Applying a potential difference between the two electrodes of a pMUT causes the piezoelectric AlN layer to bend and generate a pressure wave, thus allowing the device to act as a transmitter. The same device acts as a receiver when a pressure wave deforms the AlN layer and generates an electrical charge. Element diaphragm diameter (30 micron to 80 micron) determines resonant frequency and thus the dimensions of an object that can most accurately be imaged by the pMUT array. PMUTs have been fabricated using the same method as in this project to successfully achieve pMUTs of larger diameters and lower effective frequencies. Decreasing the size of the pMUTs from what is currently being fabricated in should allow accurate imaging of much smaller features, something of use for highly accurate fingerprint identity authentication and minimally invasive medical imaging in real time. Since the start of this project, a finite element model (FEM) was used to determine the frequency response, maximum deflection, and response to initial stress conditions for pMUTs of 30, 50, 60, and 80 micron diameters. According to the finite element model, the smallest pMUT will have a first mode frequency of 28 MHz and the largest pMUT will have a 4 MHz response if a 1 V potential difference is applied across the piezoelectric layer. Maximum static displacement is 1.9 Å for the single electrode design and 4.9 Å for the dual electrode design. Analytical results confirm FEM findings.

Download or read book Development of a Design Platform for Piezoelectric Micromachined Ultrasonic Transducer Array 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 Capacitive Micromachined Ultrasonic Transducers CMUTs for Therapeutic Applications written by Hyo-Seon Yoon and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-intensity focused ultrasound (HIFU) is a noninvasive method to treat a variety of diseases. Most of the HIFU machines in clinic typically consist of a piezoelectric transducer array and an imaging system for temperature monitoring and anatomical location guidance. One of the limitations of piezoelectric transducers is self-heating, which requires cooling systems to protect both transducers and patients. Capacitive micromachined ultrasonic transducers (CMUTs) are another type of transducers fabricated with silicon micromachining. CMUTs are promising candidates as therapeutic transducers, as they experience a lot less self-heating compared to piezoelectric transducers. This dissertation mainly focuses on describing the design, simulation, fabrication, characterization, and experimental results of CMUTs for HIFU applications. Single-element transducers are fabricated using local oxidation of silicon (LOCOS)-wafer-bonding process. The measurement part compares the self-heating of a PZT and a CMUT, and discusses the charging issue of CMUTs. Geometric focusing using multiple single-element CMUTs is also demonstrated. The fabrication of 1-D CMUT arrays to enhance the output pressure for HIFU applications is discussed. Higher output pressure of a CMUT cell can be achieved by adding one extra fabrication step to the existing fabrication process. Two-dimensional transducer arrays are required for electronic focusing and beam steering. An 8-channel continuous wave (CW) excitation system is developed to drive a 2-D CMUT array. This 8-channel system minimizes the system complexity without significant loss of focusing capability, compared to a full system with hundreds to thousands of channels. The first successful 2-D CMUT array fabricated using the thick-buried-oxide (BOX) process is presented. The breakdown issue of the insulation layer observed in the test stage is investigated as well. Another type of 2-D CMUT array fabricated using the sacrificial-release process is also tested for HIFU applications. Using the 8-channel CW excitation system, the 2-D CMUT array has proven to be able to produce enough output pressure for thermal ablation. This dissertation presents the result of ex-vivo experiments, which created thermal lesions on bovine tissue using a CMUT array for the first time.

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 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 Transducer Arrays Suitable for Acoustic Imaging written by Charles S. DeSilets and published by . This book was released on 1978 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Real time Volumetric Ultrasound Imaging with Capacitive Micromachined Ultrasonic Transducer CMUT Probes written by Jung Woo Choe and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In ultrasound imaging, an array of ultrasonic transducers is used to generate ultrasound beams and obtain the echo data reflected by the imaging targets. The echo data are sent to a back-end imaging system and processed for image reconstruction. Currently, most of the commercial ultrasound probes in the market are made of piezoelectric transducer arrays. Capacitive micromachined ultrasonic transducers (CMUTs) are another type of transducers which emerged as an alternative to piezoelectric transducers. Being fabricated using standard micromachining processes, they have advantages in fabricating transducer arrays with arbitrary geometry or many transducer elements, as well as in integrating them with a supporting front-end electronics. 2-D transducer arrays enable volumetric imaging without mechanically scanning the probe. However, a 2-D transducer array consists of a large number of transducer elements, which increases the imaging system complexity and the data processing time. To eliminate these issues, at the expense of degraded image quality, a sparse 2-D array with fewer transducer elements can be used in volumetric imaging. The first part of this dissertation describes an optimization method to find a sparse array configuration that provides optimal image quality with limited number of transducer elements. Among the various array shapes we can implement using CMUT fabrication technologies, the ring geometry is particularly attractive in many applications including intracardiac and intravascular applications. A ring transducer array, which is a type of 2-D sparse array, enables volumetric imaging with much fewer transducer elements compared to a fully populated 2-D array. To find the optimal imaging scheme for real-time imaging with a ring array, various imaging options were investigated and compared in both simulations and experiments. Commercial ultrasound imaging systems are mainly designed for probes with standard geometry and conventional imaging techniques. Therefore, they are not readily accessible for probes with non-standard geometry, such as a ring array. In addition, it is difficult to use them with non-conventional imaging schemes that may be ideal for non-standard array geometries. For real-time volumetric imaging with various types of CMUT arrays, a flexible imaging system that works with arbitrary probe geometry and various imaging schemes including non-conventional imaging techniques was designed and implemented. The raw data obtained by the custom imaging system are transferred to a host PC, and then processed for real-time image reconstruction by custom imaging software. The custom imaging software was first developed on a multi-core CPU platform, and then on a graphics processing unit (GPU) platform for better real-time imaging performance and more functionalities, such as real-time volume rendering and dual-mode imaging with both photoacoustic and ultrasound images. Using the custom imaging system and software, real-time imaging was demonstrated for various types of CMUT probes and imaging schemes. The imaging results presented in this dissertation show successful demonstration of real-time imaging for 1-D, rectangular, and annular CMUT arrays with various imaging phantoms.

Download or read book Piezoelectric Micro machined Ultrasonic Transducers for Medical Imaging written by Katherine Marie Smyth and published by . This book was released on 2017 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Next generation medical imaging technology hinges on the development of cost effective and array compatible transducers making piezoelectric micro-machined ultrasonic transducers (pMUTs) an attractive alternative to the current bulk piezoelectric technology. This thesis aims to realize pMUT potential starting with the development of an effective single cell model that is further scaled to optimize multi-cell elements in a 1D array. In the first half of this work, a transverse mode, lead zirconate titanate (PZT) pMUT plate cell is fabricated using common micro-fabrication techniques and a PZT sol-gel deposition process. Through derivation using a novel Greens function solution technique, an equivalent circuit model with explicitly defined lumped parameters is presented and validated through electrical impedance measurements of fabricated devices and finite element modeling. The equivalent circuit is a crucial design tool as transducer performance metrics, including experimentally validated acoustic domain values, are shown to be defined directly from the lumped parameters. In the second half, figures of merit are identified from these performance metrics and an expanded multi-cell model is employed to strategically target improvements in both bandwidth and coupling while maintaining high pressure output. The resulting, optimized multicell elements in a 1D array are fabricated via a commercially viable, wafer-scale manufacturing process including a novel PZT dry etch. A top-down fabrication approach facilitates achievement of the largest active area of a multi-cell pMUT to date consisting of over 1000 cells in a 200pm x 4mm element footprint, and more substantially, results in the highest electromechanical coupling recorded for a pMUT to date measured at 9 ± 1.4% per element.

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 High performance Micromachined Ultrasonic Transducers written by Guo-Lun Luo and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With emerging micro-electromechanical system (MEMS) technology, MEMS ultrasonic transducers (MUTs) are demonstrated with the merits of smaller size, lighter weight, lower power consumption. Compared to conventional ultrasonic transducers, MUTs have better acoustic matching, CMOS compatibility, and array fabrications. This dissertation focuses on high-performance MUTs, from the perspectives of driving mechanism, structure design, material, array design, fabrication process, sealing and housing, achieving higher transmitting pressure output, higher receiving sensitivity and wider bandwidth. First, this study investigates piezoelectric MUTs (PMUTs) and capacitive MUTs (CMUTs) to propose a novel hybrid MUT (HMUT) with the highest figure of merits (FoM) of MUTs. The HMUT is developed to remain the advantages of both MUTs for higher performance. For airborne applications, the HMUT is made by a PZT PMUT with large amplitude as transmitter (TX), and a capacitive CMUT with high sensitivity, wide bandwidth, and low bias, as receiver (RX). The airborne PMUT is fabricated by a single-crystal PZT thin film with a high piezoelectric coefficient (e[subscript 31,f ~] 15 C/m2), enabling a high-pressure output of 108 dB SPL at 30 cm. The PZT PMUT with a dielectric constant ([epsilon]r = 308) as RX, shows the sensitivity of 1.9 mV/Pa, resulting in high signal-to-noise ratio (SNR) in the pulse-echo experiment, demonstrating 5-meter round-trip detectable distance. However, the PZT PMUT has generically high permittivity resulting in low receiving sensitivity, the narrow bandwidth (9%) due to high Q-factor, and TX/RX resonances mismatching, and mechanical nonlinearity. Here, we use a wide-bandwidth CMUT as a receiver to eliminate the resonances mismatching, and higher sensitivity can be achieved due to low permittivity ([epsilon]r~1). The CMUT receiver, formed by a vented diaphragm and a small gap of 2 [mu]m, and CMUT with air damping is designed and optimized to have sensitivity of 14 mV/Pa, bias voltage of 5V, and fraction bandwidth of 150% from the mechanical characterization, resulting in 7X of sensitivity and 15X of bandwidth improvement compared to the single-crystal PZT PMUT. Moreover, the 3D printed housing of airborne MUTs is designed and implemented to protect the fragile structure and provide good acoustic impedance matching with air, enabling -1.4 dB acoustic loss from the housing, -2 dB SNR in pulse-echo measurement. For immersion MUTs, we utilized surface micromachining to developed MUTs, enabling high fill-factor MUT arrays with larger active areas to increase efficiency, and the MUT cavities can be sealed in vacuum for immersion applications. First, we demonstrated an AlN PMUT array with 80% fill-factor, and the PMUT cavities were sealed in vacuum. The explicit pressure model for MUT arrays with various fill-factor, is investigated from the experiments. Moreover, the structure enhancement is demonstrated using this process, resulting in higher PMUT pressure output. Compared to fully clamped PMUTs, the sloped PMUT with a 2.5X Q-factor (2.5X) can create 3X displacement by shaping the sacrificial layer. The corrugated PMUT is also implemented to demonstrate piston-like motions with an increasing active area, showing 3.2X volume velocity. In addition, the sealing technique with acoustic coupling layer is demonstrated to increase the bandwidth for immersion. Using surface micromachining, the immersion HMUTs is discussed and proposed to have the fully monolithic PMUT/CMUT integration with high performance.