Download or read book A PolyMUMPs Capacitive Micromachined Ultrasonic Transducer written by Ming Cai and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Capacitive Micromachined Ultrasonic Transducers written by Dilruba Zaman Jeba and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) have been developed as an alternative to piezoelectric transducers for ultrasonic imaging in non-destructive testing applications. These CMUTs offer substantial advantages over their piezoelectric counterparts, which include a highly miniaturized system, easy integration with electronic control circuitry, a wider bandwidth, and a higher sensitivity. In this thesis, the design, fabrication and characterization of several single and array CMUT devices are reported. Many sizes of CMUTs, aiming to operate at different resonant frequencies, were fabricated using a PolyMUMPs sacrificial technique. An analytical and finite element model was used to further understanding of the physical behaviour of the transducer. The basic functionality of the CMUT devices was investigated through capacitance and electrical impedance measurements. These devices showed greater change in the capacitance and impedance data while operating close to their collapse voltages. This higher change in both capacitance and impedance is a result of a larger membrane displacement. The acoustic output power is directly related to the magnitude of the membrane's displacement. The transducers performance thus can be enhanced by operating close to their collapse voltage and obtained higher sensitivity. The optical characterization, performed on the single devices and on the 1-D arrays, provided a better understanding of the membrane vibration modes and displacement profiles at different resonant frequency modes. Acoustic measurements were performed to demonstrate the transmission capability of the CMUTs. The generated acoustic signals were detected using a commercial detector. These acoustic experiments demonstrated that these CMUTs can potentially be used as ultrasonic transducers alternative to piezoelectric transducers.

Download or read book Characterization of Multiple Moving Membrane Capacitive Micromachined Ultrasonic Transducer written by Md. Iftekharul Islam and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A newly developed multiple moving membrane capacitive micromachined ultrasonic transducer (M3-CMUT) is fabricated and characterized in this thesis. Unlike the single vibrating membrane in the conventional capacitive micromachined ultrasonic transducer (CMUT), the novel design involves two deflectable membranes suspended over a fixed bottom electrode. In the presence of bias, both of the membranes deflect simultaneously, which results in a smaller cavity compared to a CMUT. To understand the basics of a capacitive transducer, an equivalent mass-spring-capacitor model of CMUT was reported. The results of this analytical model were used to develop the finite element models (FEM) of CMUT and more complex M3-CMUT in COMSOL Multiphysics software. The electromechanical analysis of these models was conducted to observe their operating conditions. Following the modeling and analysis, several single-cell, 1-D, and 2-D arrays of these devices were fabricated using PolyMUMPs technology, a sacrificial fabrication technique for the MEMS transducers. The electrical and acoustic characterizations of the fabricated devices were performed to measure the actual transducer properties. The measured data and the model results were found to be in good agreement. It was observed from the electrical impedance measurements that a higher membrane deflection was achieved in the double membrane device. The reduction in the cavity of M3-CMUT enhanced the sensitivity of the transducer. The acoustic characterization using a pitch-catch experimental setup demonstrated that the novel M3-CMUT could be used as an ultrasonic transducer. The velocity and attenuation of the acoustic waves, when the transducer used as both the transmitter and the receiver, were found to be very close to the theoretical value.

Download or read book Novel Architectures for Capacitive Micromachined Sensors and Actuators written by Hani Tawfik and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "This work presents novel architectures for improving the performance of capacitive-based micromachined thermal detectors, ultrasonic transducers, and multiplexers. The proposed designs are implemented in a pure-play commercial process, which is known for its reliability and cost-effectiveness. In addition, several performance-limitation issues are tackled. Furthermore, a novel approach is proposed for implementing standalone MEMS arrays, to avoid the complicated and expensive post-processing of complementary metal-oxide-semiconductor (CMOS) wafers.The first part of this work presents a novel dual-level capacitive bimorphous thermal detector architecture that is prototyped in the commercial PolyMUMPs by MEMSCAP. The dual-level design exhibits a 6.5 fF/°C sensitivity which is over 3 times higher than traditional single-level designs and it has a base capacitance that is over twice as large. The proposed architecture mitigates an inherent trade-off between thermal sensitivity and base capacitance. Other challenges facing bimorphous thermal detectors are addressed as well. This work also presents, a compensation mechanism for shocks and the ambient temperature. In addition, a material selection study for the bimorph layers concluded a significant performance enhancement of using silicon-carbide (SiC) with polyimide. Moreover, a method was developed for utilizing a positive photoresist as a sacrificial layer that alleviates the restrictions on material-selection for the layers of the bimorphs.The second part of this study presents a reduced-gap implementation of a 3.33-MHz capacitive micromachined ultrasonic transducer (CMUT) in the PolyMUMPs technology. The design provides a bias voltage supply reduction that is four times less compared to the traditional architecture to achieve a sufficient acoustic pressure. Also, a novel operation mechanism is demonstrated for ultrasonic testing underwater, and this mechanism employs the surface-tension forces between the surfaces of the water and the ultrasonic probe. The proposed meniscus-mode mechanism amplifies the ultrasonic signal more than the traditional fully-immersed setup by a factor of 2.6; this is demonstrated experimentally in the study.The final part proposes a novel switching design for multiplexing, and it targets low-frequency applications. The inline torsional electrostatic MEMS multiplexer (ITEM2) architecture is presented. In the study, a theoretical analysis of the structure's snap-down voltage is derived. By combining the novel architectures for thermal detectors and CMUTs presented with the proposed ITEM2 design, a stand-alone MEMS array solution can be a low-cost alternative to the traditional monolithic and hybrid integration with the electronics. The study presents an implementation of an 8 × 8 thermal detectors array that is routed using micromachined bypass-bridges and MEMS multiplexers." --

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 Through wafer Interconnects written by Xuefeng Zhuang and published by . This book was released on 2008 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Capacitive Micromachined Ultrasonic Transducers CMUTs Built with Wafer bonding Technology written by Yongli Huang and published by . This book was released on 2005 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Characterization of Capacitive Micromachined Ultrasonic Transducers Using Finite Element Modeling written by Bradley John Kirchmayer and published by . This book was released on 2006 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fabrication of Capacitive Micromachined Ultrasonic Transducers Based on Adhesive Wafer Bonding written by Zhenhao Li and published by . This book was released on 2017 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capacitive micromachined ultrasonic transducers (CMUTs) can be used for medical imaging, non-destructive testing or medical treatment applications. It can also be used as gravimetric sensors for gas sensing or immersion bio-sensing. Although various CMUT fabrication methods have been reported, there are still many challenges to address. Conventional fabrication methods can be categorized as either surface micromachining or the wafer bonding method. These methods have design trade-offs and limitations associated with process complexity, structural parameter optimization and wafer materials selection. For example, surface micromachining approaches can suffer from complicated fabrication processes. In addition, structural parameters cannot be fully optimized due to feasibility concerns during fabrication. In contrast, the development of wafer bonding techniques enabled CMUTs to be fabricated in a straightforward way and structural parameters can be easily optimized when compared with a surface micromachining approach. However, the yield of the traditional wafer bonded CMUTs is very sensitive to contaminations and the surface quality at the bonding interface. Although the difficulties of the wafer bonding process are not always reported, they definitely exist for every researcher who wants to fabricate their own CMUTs. As a result, this dissertation work aims to develop a CMUT fabrication process with fewer fabrication constraints, low-cost and low process temperature for CMOS integration. The developed CMUT fabrication processes reported in the thesis applied photosensitive polymer adhesive for wafer bonding in order to make a process with good tolerance to contaminations and defects on the wafer surface, present a wide range of material selection at the bonding interface and require low process temperature (less than 250°C). These features can benefit CMUT fabrication with increased yield better design flexibility and lower cost. Having maximum process temperature of 250°C, the developed processes can also be CMOS compatible. Furthermore, a novel CMUT structure, which can only be achieved by the reported technique, was developed showing more than doubled ultrasound receive sensitivity when compared with conventional CMUT structures. The fabrication processes were developed systematically and the details of process development will be presented in this thesis.

Download or read book Minimally Invasive Capacitive Micromachined Ultrasonic Transducers Array for Biomedical Applications written by Xiaoyang Cheng and published by . This book was released on 2008 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Capacitive Micromachined Ultrasonic Transducers for Therpaeutic sic Ultrasound written by Serena H. Wong and published by . This book was released on 2008 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Capacitive Micromachined Ultrasonic Transducer CMUT Chemical Sensor and Its Interface Circuits written by Hyunjoo Jenny Lee and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Miniaturized chemical sensors based on microelectromechanical-systems (MEMS) offer competitive advantages over existing bench-top chemical analyzers, such as small size, low power consumption, low cost due to batch fabrication, and CMOS compatibility. The potential for system integration of these chemical sensors with on-chip CMOS circuitry expands the spectrum of use, including consumer, industrial, and homeland security applications. This thesis introduces a miniaturized resonant chemical sensor based on a 50-MHz capacitive micromachined ultrasonic transducer (CMUT). With a high mass sensitivity of 4.3 ag/Hz, this CMUT-based chemical sensor achieves excellent volume sensitivity of 21.2 ppt/Hz to dimethyl methylphosphonate (DMMP), a common simulant for Sarin gas. In addition, a direct application of a mesoporous silica thin-film on a CMUT for relative humidity and carbon dioxide detection is presented. Using a mesoporous silica thin-film with a pore size of ~11 nm, this sensor achieves one of the lowest volume resolutions and a sensitive detection of 5.1 × 10-4%RH/Hz to water vapor in nitrogen. In addition, a mesoporous thin-film that is functionalized with an amino-group is directly applied on the resonant sensor, which exhibits a volume sensitivity of 1.6 × 10-4%/Hz and a volume resolution of 1.82 × 10-4% to carbon dioxide in nitrogen. Lastly, this thesis describes the sensor interface circuitry for CMUT and discusses the frequency noise analysis of CMUT-based oscillators. Specifically, a multi-channel interface integrated circuit (IC) implemented using 0.18-um CMOS technology, which results in reduced area and power consumption for each channel is presented. Two-channel detection of relative humidity is demonstrated using this circuit.

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 Modeling Design and Characterization of Capacitive Micromachined Ultrasonic Transducers CMUTs written by Alessandro Caronti and published by . This book was released on 2003 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Novel Applications of Capacitive Micromachined Ultrasonic Transducers written by and published by . This book was released on 2007 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Exploring Multiple mode Vibrations of Capacitive Micromachined Ultrasonic Transducers CMUTs written by Wei You and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: