Download or read book Volumetric Ultrasound Imaging Systems Using Capacitive Micromachined Ultrasonic Transducer CMUT Arrays written by Anshuman Bhuyan and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Medical imaging has become very important in the proper diagnosis of a disease. It has eliminated the need for invasive surgery for evaluation purposes, which can be painful to the patient. There are many modes of medical imaging, ultrasound being one of the most common. Ultrasound imaging provides various advantages compared to other modes that make it very attractive for diagnostic purposes. Conventional ultrasound systems provide real-time 2-D images of the human anatomy and have been used for decades. However, 4-D ultrasound imaging is becoming increasingly popular due to the additional information it provides over conventional 2-D imaging. It makes the imaging procedure less susceptible to the errors of the sonographer and 2-D image slices can be taken at various orientations with respect to the imaging probe allowing convenient offline analysis by the doctor. There are however, several challenges in building such a system. This is because of the requirement of the frontend electronics (typically consisting of LNAs) needing to be very close to the transducer array and the large number of elements that need to be interfaced to the backend system. Also, imaging a volume space requires image processing of a very large dataset that could eventually limit the imaging volume rate. The first part of this dissertation describes a 4-D ultrasound imaging system using Capacitive Micromachined Ultrasonic Transducer (CMUT) technology. Use of CMUTs enables us to address most of the challenges in building such a 4-D ultrasound system. Integrated circuits (IC) with a transmit beamformer and receive signal conditioning circuit were designed and fabricated, and were integrated tightly with the transducer array using flip-chip bonding technology. Different techniques of integration are demonstrated, and the choice between them is dictated by the targeted application. Multi-beam transmit functionality is incorporated in the IC that addresses the issue of limited imaging volume rate in a 4-D ultrasound system. Imaging experiments are presented that illustrate a true real-time volumetric imaging capability of the system. Two other ultrasound systems are also described. One is an extension of the work presented in the first part by incorporating capabilities of therapy using High Intensity Focused Ultrasound (HIFU), in the same 4-D ultrasound imaging system. This would allow physicians to use the same probe for imaging as well as therapy. This system uses an IC similar in design to that used for developing the 4-D ultrasound imaging system. It also consists of a switch network to allow external pulsers to provide a continuous wave sinusoidal excitation to the CMUT transducer. A new high-voltage switch circuit design is presented that is used in the switch network. Finally, a wearable ultrasound probe is presented that is capable of performing 2-D imaging in real-time. Such a probe is useful for applications that require constant or periodic monitoring of body functions and therefore can be worn by the patient at all times. Again, ICs were designed and integrated closely to a 1-D CMUT array. The assembly process is described and imaging results are presented.

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 Ultrasound Imaging Systems Using Capacitive Micromachined Ultrasonic Transducer CMUT Arrays with In Probe Electronic Circuits written by Jean Lunsford Sanders and published by . This book was released on 2021 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Row column Capacitive Micromachined Ultrasonic Transducers for Medical Imaging written by Albert I-Hsiang Chen and published by . This book was released on 2016 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasound imaging plays an important role in modern medical diagnosis. Recent progress in real-time 3-D ultrasound imaging can offer critical information such as the accurate estimation of organ, cyst, or tumour volumes. However, compared to conventional 2-D ultrasound imaging, the large amount of data and circuit complexity found in 3-D ultrasound imaging results in very expensive systems. Therefore, a simplification scheme for 3-D ultrasound imaging technology is needed for a more wide-spread use and to advance clinical development of volumetric ultrasound. Row-column addressing 2-D array is one particular simplification scheme that requires only N + N addressing lines to activate each element in an N x N array. As a result, the fabrication, circuit, and processing complexity dramatically decrease. Capacitive micromachined ultrasonic transducer (CMUT) technology was chosen to fabricate the array as it offers micro-precision fabrication and a wide bandwidth, which make it an attractive transducer technology. The objective of this thesis is to investigate and demonstrate the imaging potential of row-column CMUT arrays for RT3D imaging. First, the motivation, physics, and modelling of both CMUTs and row-column arrays are described, followed by the demonstration of a customized row-column CMUT pseudo-real-time 3-D imaging system. One particular limitation about row-column arrays discovered as part of this dissertation work is the limited field-of-view of the row-column arrays' imaging performance. A curved row-column CMUT array was proposed to improve the field-of-view, and the resulting modelling of the acoustic field and simulated reconstructed image are presented. Furthermore, a new fabrication process was proposed to construct a curved row-column CMUT array. The resulting device was tested to demonstrate its flexibility to achieve the necessary curvature. Finally, a new wafer bonding process is introduced to tackle the next generation of RC-CMUT fabrication. Many of the new fabrication techniques reported in this work are useful for CMUT fabrication engineers. The analysis on row-column array also provides additional insights for 2-D array simplification research.

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 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 Capacitive Micromachined Ultrasonic Transducers with Substrate embedded Springs written by Byung Chul Lee and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: After the first capacitive micromachined ultrasonic transducer (CMUT) was invented in 1994, it became one of the candidate technologies to advance the state-of-the-art of medical ultrasound imaging. Benefiting from its fabrication technique based on the semiconductor industry, CMUT technology has broadened the medical and therapeutic applications such as real-time volumetric ultrasound imaging, catheter-based forward-looking intravascular ultrasound (IVUS), photoacoustic imaging, high-intensity focused ultrasound (HIFU) and so on. In spite of many advantages, however, CMUT technology has been criticized with its relatively low transmit sensitivity (~10 kPa/V) or low average volume displacement efficiency (0.1 nm/V) as well as large drive and bias voltage requirements (in a range of a few hundreds of volts). In order to resolve these issues and open up new potential of clinical applications, this dissertation describes the design, fabrication, and system implementation of CMUTs with substrate-embedded springs, so-called post-CMUT (PCMUT). Since PCMUT structure resembles an ideal piston transducer, the improvements in performance mainly stem from the higher average displacement of the top plate for a given gap height. The overview of the first generation PCMUT is introduced and two main issues in simulation and fabrication aspects of the first generation PCMUT is discussed. To further improve the PCMUT device, a 3D finite element analysis (FEA) model of the PCMUT is demonstrated to predict the performance of the first generation PCMUT. In addition, the design guideline of the second generation PCMUT is proposed for achieving the maximum fractional bandwidth (100 %) as well as with the highest transmit sensitivity (~28 kPa/V). The second generation PCMUT is fabricated by using three combination MEMS processes: usage of two silicon-on-insulator (SOI) wafers, wafer bonding process, and wafer polishing process. The second generation PCMUT achieves high transmit sensitivity (~21 kPa/V) or large average volume displacement efficiency (1.1 nm/V) with a low bias voltage (55 V). Compared to a commercial piezoelectric transducer, the second generation PCMUT improves 2.75 times of the maximum output pressure and 5.25 times of the average volume displacement efficiency with respect to the same voltage. After fabrication and performance characterization of the second generation PCMUT, this dissertation demonstrates the feasibility of PCMUT to use it in medical imaging system by integrating PCMUT with a custom-built integrated circuit (IC). Photoacoustic imaging is also presented for one of its application examples.

Download or read book A Dual mode Ultrasound System for Imaging and High Intensity Focused Ultrasound HIFU with a Single 2 D Capacitive Micromachined Ultrasonic Transducer CMUT Array written by Ji Hoon Jang and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultrasound imaging technology has many applications for the medical field and for the public. Thanks to ultrasound imaging, parents can meet their precious child even before the baby is born. In clinical applications, ultrasound is inexpensive, portable and reveals the structure and movement of organs in real time, allowing physicians to monitor the growth and physical development of a fetus. Because there is no ionizing radiation exposure to the patient, it is a very safe technology. In addition to diagnostic applications, ultrasound has been used for therapeutic treatment. High intensity focused ultrasound (HIFU) has been widely used to treat different types of tumors, including those of prostate, liver, breast, kidney, bone and pancreas because of its non-invasive and precise approach for tissue ablation. The basic concept of using HIFU is to focus continuous ultrasound at the focal point and a temperature increase beyond a certain point creates a lesion without damaging the surrounding tissue. For successful HIFU operation, it is important to have a reliable method for guidance and monitoring of the treatment such as ultrasound imaging. Most ultrasound image-guided HIFU systems need separate imaging and HIFU transducers, and require a cooling system due to properties of piezoelectric transducers such as narrow fractional bandwidth and self-heating. As an alternative, capacitive micromachined ultrasonic transducers (CMUTs) have a distinctive advantage over piezoelectric transducers in respect to self-heating and a wide fractional bandwidth. Thus, CMUTs are especially beneficial in dual-mode operations where a single transducer is used for both imaging and therapy. By taking advantage of this CMUT technology, I developed a compact dual-mode ultrasound system that can perform both ultrasound imaging and HIFU with a single 2-D CMUT array. A dual-mode ultrasound probe is equipped with a dual-mode application-specific integrated circuit (ASIC) and a 2-D 32x32-element CMUT array. The dual-mode ASIC consists of pulsers, transmit beamforming circuitry, and low-noise amplifiers for imaging mode and high voltage (HV) switches for HIFU mode. By turning HV switches on and off, the system can alternately operate imaging mode and HIFU mode on demand. A 2-D 32x32-element CMUT array was fabricated to have a center frequency of 5 MHz in immersion. Both ASIC and CMUT array were flip-chip bonded to a custom-designed flexible printed circuit board (flex PCB). After polydimethylsiloxane (PDMS) encapsulation, the acoustic performance of the probe was evaluated. I successfully demonstrated the imaging mode of the dual-mode probe using nylon wire phantom. Using HIFU mode, I measured 7.4 MPa peak-to-peak pressure at 8 mm focal depth. To get higher pressure for the ablation, high AC and DC voltage were used, and CMUT arrays got shorted due to the insulator breakdown. With this probe, obtaining high pressure levels needed for tissue ablation was problematic with CMUTs due to device failure at high voltages. Therefore, I re-optimized a CMUT design that can produce higher output pressure without breakdown or device failure. With CMUT simulation software, the design parameters of CMUT element were optimized with a gap height of 0.13 um and a top plate thickness of 1 um. After it was fabricated and integrated, the dual-mode probe was tested again in an acoustic setup. Compared with previous results, the device shows improved performance without device failure. The focused pressure at F-1 (8 mm) was measured to 16 MPa peak-to-peak. More importantly, most of the device can produce high pressure levels reliably without device failure. Using HIFU simulation software, the specification for HIFU ablation was explored if the dual-mode probe can ablate the tissue. It shows that even with 10 MPa peak-to-peak the dual-mode probe can create the lesion. An ablation test was successfully performed on HIFU phantom gel and ex-vivo tissue using HIFU mode of the dual-mode probe. Another important evaluation as a HIFU probe was the heating of the device. While CMUT array has very low self-heating, because of the power dissipation on HV switches of dual-mode ASIC, the ASIC was heated during HIFU mode. To reduce the heating of dual-mode ASIC, the copper heat sink rod, the chiller, and the water circulation heat sink were added to the system and it significantly reduced the heating. With the thermal management system, the probe was thermally stable around the body temperature during HIFU mode and imaging mode. Lastly, I successfully demonstrated ultrasound image-guided HIFU on HIFU phantom gel with guide wires by switching between imaging mode and HIFU mode using dual-mode ultrasound system. Our studies established a dual-mode HIFU system that will improve the non invasive ablation of tissue. This work of the dual mode system certainly shows the possibility of the new treatment application that was impossible to achieve using the conventional image-guided HIFU system.

Download or read book Photoacoustic Imaging Using Capacitive Micromachined Ultrasonic Transducers written by Srikant Vaithilingam and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the primary goals of a medical imaging procedure is to spatially localize disease in an individual. This dissertation focuses on photoacoustic imaging, which is a relatively new medical imaging modality that shows great promise for disease diagnosis - especially cancer detection. In photoacoustic imaging, short laser pulses absorbed by molecules in tissue induce ultrasonic pressure waves which are then detected to form an image. In this work, using a custom built mechanically scanned single-transducer photoacoustic imaging system, we extend photoacoustic imaging into the molecular imaging domain. In this first such demonstration, we show how an exogenous contrast agent that binds preferentially to an angiogenesis biomarker enables an early cancer diagnosis in living subjects. To accelerate the goal of taking photoacoustic imaging from the lab to the clinic, this thesis introduces capacitive micromachined ultrasonic transducer (CMUT) arrays as an enabling technology platform. CMUT technology allows the fabrication of highly sensitive, wide bandwidth, 2D transducer arrays that can be tightly integrated with electronics. This thesis shows the first results of true 3D volumetric photoacoustic imaging using CMUTs. Deep tissue photoacoustic imaging up to a depth of ~5 cm and preliminary results from real-time photoacoustic imaging are also shown. Finally, in this work, we describe a new CMUT microfabrication process called the Thick-BOX process. The Thick-BOX process promises a simpler fabrication process that produces more reliable and robust CMUTs. Experimental fabrication results of low frequency CMUT devices are presented as a proof-of-concept verification for this fabrication process.

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 Sensors and Microsystems written by G. Di Francia and published by Springer Nature. This book was released on 2020-02-21 with total page 411 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book showcases the state of the art in the field of sensors and microsystems, revealing the impressive potential of novel methodologies and technologies. It covers a broad range of aspects, including: bio-, physical and chemical sensors; actuators; micro- and nano-structured materials; mechanisms of interaction and signal transduction; polymers and biomaterials; sensor electronics and instrumentation; analytical microsystems, recognition systems and signal analysis; and sensor networks, as well as manufacturing technologies, environmental, food and biomedical applications. The book gathers a selection of papers presented at the 20th AISEM National Conference on Sensors and Microsystems, held in Naples, Italy in February 2019, the event brought together researchers, end users, technology teams and policy makers.

Download or read book Acoustical Imaging Using Capacitive Micromachined Ultrasonic Transducer Arrays written by Ömer Oralkan and published by . This book was released on 2004 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Top orthogonal to bottom electrode Capacitive Micromachined Ultrasound Transducers for Low cost 3D Ultrasound Imaging written by Alexander Sampaleanu and published by . This book was released on 2013 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasound transducers (CMUTs) offer a promising solution for three-dimensional ultrasound imaging due to their ability to be easily fabricated in two-dimensional arrays. However, channel routing is still non-trivial and cost-intensive. The subject of this thesis is a 'Top-Orthogonal-to-Bottom-Electrode' (TOBE) 2-D CMUT array architecture, along with its respective row-column addressing schemes, which can significantly reduce the channel count of a 2-D array, such that only 2N channels are required for an N x N array. Background on acoustics, ultrasound imaging, and CMUT technology is presented before the novel array architecture and imaging schemes is described. Arrays were fabricated using a sacrificial release method, and acoustic immersion and air-coupled tests, along with imaging simulations, were done to validate array functionality. Results showed that single-element actuation is possible with a row-column addressing scheme, allowing for novel imaging schemes which could result in significantly more cost-effective 3-D ultrasound imaging.

Download or read book The Design Fabrication and Characterization of Capacitive Micromachined Ultrasonic Transducers for Imaging Applications written by Andrew Stephan Logan and published by . This book was released on 2010 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) have proven themselves to be excellent candidates for medical ultrasonic imaging applications. The use of semiconductor fabrication techniques facilitates the fabrication of high quality arrays of uniform cells and elements, broad acoustic bandwidth, the potential to integrate the transducers with the necessary electronics, and the opportunity to exploit the benefits of batch fabrication. In this thesis, the design, fabrication and testing of one- and two-dimensional CMUT arrays using a novel wafer bonding process whereby the membrane and the insulation layer are both silicon nitride is reported. A user-grown insulating membrane layer avoids the need for expensive SOI wafers, permits optimization of the electrode size, and allows more freedom in selecting the membrane thickness, while also enjoying the benefits of wafer bonding fabrication. Using a row-column addressing scheme for an NxN two-dimensional array permits three-dimensional imaging with a large reduction in the complexity of the array when compared to a conventional 2D array with connections to all N2 elements. Only 2N connections are required and the image acquisition rate has the potential to be greatly increased. A simplification of the device at the imaging end will facilitate the integration of a three-dimensional imaging CMUT array into either an endoscope or catheter which is the ultimate purpose of this research project. To date, many sizes of transducers which operate at different frequencies have been successfully fabricated. Initial characterization in terms of resonant frequency and, transmission and reception in immersion has been performed on most of the device types. Extensive characterization has been performed with a linear 32 element array transducer and a 32x32 element row-column transducer. Two- and three-dimensional phased array imaging has been demonstrated.

Download or read book Investigation of Acoustic Crosstalk Effects in CMUT Arrays written by Michael Hochman and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive Micromachined Ultrasonic Transducers (CMUTs) have demonstrated significant potential to advance the state of medical ultrasound imaging beyond the capabilities of the currently employed piezoelectric technology. Because they rely on well-established micro-fabrication techniques, they can achieve complex geometries, densely populated arrays, and tight integration with electronics, all of which are required for advanced intravascular ultrasound (IVUS) applications such as high-frequency or forward-looking catheters. Moreover, they also offer higher bandwidth than their piezoelectric counterparts. Before CMUTs can be effectively used, they must be fully characterized and optimized through experimentation and modeling. Unfortunately, immersed transducer arrays are inherently difficult to simulate due to a phenomenon known as acoustic crosstalk, which refers to the fact that every membrane in an array affects the dynamic behavior of every other membrane in an array as their respective pressure fields interact with one another. In essence, it implies that modeling a single CMUT membrane is not sufficient; the entire array must be modeled for complete accuracy. :Finite element models (FEMs) are the most accurate technique for simulating CMUT behavior, but they can become extremely large considering that most CMUT arrays contain hundreds of membranes. This thesis focuses on the development and application of a more efficient model for transducer arrays first introduced by Meynier et al. [1], which provides accuracy comparable to FEM, but with greatly decreased computation time. It models the stiffness of each membrane using a finite difference approximation of thin plate equations. This stiffness is incorporated into a force balance which accounts for effects from the electrostatic actuation, pressure forces from the fluid environment, mass and damping from the membrane, etc. For fluid coupling effects, a Boundary Element Matrix (BEM) is employed that is based on the Green's function for a baffled point source in a semi-infinite fluid. The BEM utilizes the nodal mesh created for the finite difference method, and relates the dynamic displacement of each node to the pressure at every node in the array. Use of the thin plate equations and the BEM implies that the entire CMUT array can be reduced to a 2D nodal mesh, allowing for a drastic improvement in computation time compared with FEM.

Download or read book Interface Engineering of Capacitive Micromachined Ultrasonic Transducers for Medical Applications written by Der-Song Lin and published by . This book was released on 2011 with total page 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 Fundamentals and Applications of Ultrasonic Waves written by J. David N. Cheeke and published by CRC Press. This book was released on 2017-12-19 with total page 507 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written at an intermediate level in a way that is easy to understand, Fundamentals and Applications of Ultrasonic Waves, Second Edition provides an up-to-date exposition of ultrasonics and some of its main applications. Designed specifically for newcomers to the field, this fully updated second edition emphasizes underlying physical concepts over mathematics. The first half covers the fundamentals of ultrasonic waves for isotropic media. Starting with bulk liquid and solid media, discussion extends to surface and plate effects, at which point the author introduces new modes such as Rayleigh and Lamb waves. This focus on only isotropic media simplifies the usually complex mathematics involved, enabling a clearer understanding of the underlying physics to avoid the complicated tensorial description characteristic of crystalline media. The second part of the book addresses a broad spectrum of industrial and research applications, including quartz crystal resonators, surface acoustic wave devices, MEMS and microacoustics, and acoustic sensors. It also provides a broad discussion on the use of ultrasonics for non-destructive evaluation. The author concentrates on the developing area of microacoustics, including exciting new work on the use of probe microscopy techniques in nanotechnology. Focusing on the physics of acoustic waves, as well as their propagation, technology, and applications, this book addresses viscoelasticity, as well as new concepts in acoustic microscopy. It updates coverage of ultrasonics in nature and developments in sonoluminescence, and it also compares new technologies, including use of atomic force acoustic microscopy and lasers. Highlighting both direct and indirect applications for readers working in neighboring disciplines, the author presents particularly important sections on the use of microacoustics and acoustic nanoprobes in next-generation devices and instruments.