TY - CHAP A1 - Park, Kwan Kyu A1 - Kupnik, Mario A1 - Lee, Hyunjoo J. A1 - Oralkan, Ömer A1 - Khuri-Yakub, Butrus T. T1 - Zero-bias resonant sensor with an oxide-nitride layer as charge trap T2 - 2010 IEEE sensors, Waikoloa, Hawaii, USA, 1 - 4 November 2010 Y1 - 2010 SN - 978-1-4244-8168-2 SP - 1024 EP - 1028 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Park, Kwan Kyu A1 - Kupnik, Mario A1 - Lee, Hyunjoo J. A1 - Khuri-Yakub, Butrus T. T1 - Modeling CMUT of multi-cell configuration T2 - IEEE Ultrasonics Symposium (IUS), 2010, 11 - 14 Oct. 2010, Town & Country Inn & Convention Center, San Diego Y1 - 2010 SN - 978-1-4577-0381-2 SP - 431 EP - 434 PB - IEEE CY - Piscataway, NJ ER - TY - CHAP A1 - Hoffmann, Maik A1 - Unger, Alexander A1 - Ho, Min-Chieh A1 - Park, Kwan Kyu A1 - Khuri-Yakub, Butrus T. A1 - Kupnik, Mario T1 - Volumetric characterization of ultrasonic transducers for gas flow metering T2 - Proceedings, 2013 IEEE International Ultrasonics Symposium N2 - The design of ultrasonic gas flowmeters requires a thorough three dimensional characterization of the acoustic sound field. For large pipe flowmeters, such as used for flare gas metering, the transducers are operated at frequencies ranging from 20 kHz up to 150 kHz. Thus, in this work we use a commercially available calibrated 1/8-inch microphone, mounted on a 3D positioning system for performing volumetric measurements in a volume of up to 1x1x1 m. By using proper corrections in terms of angular and free-field response of the microphone, the measurement system is efficient and delivers around 30000 measurements in about only eight hours. The data then is visualized in form of 3D figures or various slices to extract all relevant information. The system has been used to identify non-uniform velocity profiles in capacitive micromachined ultrasonic transducers (CMUTs), operating in permanent contact mode. Further, the system can be used to investigate the effect of various acoustic boundary conditions the transducers are facing when mounted inside transducer port cavities and it can be used for general model validation purpose. Y1 - 2013 U6 - https://doi.org/10.1109/ULTSYM.2013.0336 SP - 1315 EP - 1318 PB - IEEE ER - TY - CHAP A1 - Unger, Alexander A1 - Hoffmann, Maik A1 - Ho, Min-Chieh A1 - Park, Kwan Kyu A1 - Khuri-Yakub, Butrus T. A1 - Kupnik, Mario T1 - Finite element analysis of mechanically amplified CMUTs T2 - Proceedings, 2013 IEEE International Ultrasonics Symposium N2 - We introduce the possibility of improving a single-cell capacitive micromachined ultrasonic transducer (CMUT) for air-coupled ultrasound by simply adding a hollow conical-shaped structure (horn) on top of the CMUT plate. The main objective is to improve both transmit and receive sensitivity by lowering the center-to-average displacement ratio, which for bending plate operated devices inherently is limited. In addition, for receive mode the force generated from the impinging sound pressure wave is concentrated to the center of the plate, resulting in larger signals and, in contrast to piston-shaped plates, the horn has the advantage of only moderately increasing the modal mass of the structure. By using finite element analysis and first sound pressure measurements of our modified CMUT, we demonstrate that this idea is feasible and promising for air-coupled CMUTs operating at frequencies below 150kHz, as it has been been proven to be successful for commercially available piezoelectric - driven bending plate devices as well. Y1 - 2013 U6 - https://doi.org/10.1109/ULTSYM.2013.0074 SP - 287 EP - 290 PB - IEEE ER - TY - CHAP A1 - Golinske, René A1 - Hoffmann, Maik A1 - Gupta, Abhinav A1 - Kupnik, Mario T1 - Calculation of diffraction loss between non-co-axial ultrasonic transducer configurations T2 - Proceedings, 2013 IEEE International Ultrasonics Symposium N2 - We derive and validate a quadruple integral expression for calculating the diffraction loss in an isotropic propagation medium between circular ultrasonic transducers with time-harmonic radiation. The distinctive feature is the generic non-coaxial configuration with arbitrary transducer size and orientation. By performing several measurements, we validate the integral expression and we demonstrate that nowadays it is feasible to perform the required numerical integration to obtain the diffraction loss over an entire volumetric sound pressure field on a state-of-the-art personal computer with reasonable computation time on the order of a few minutes only. Excellent agreement between calculated results and experiments prove the approach and the generic nature of our expression ensures its wide and simple applicability for efficient diffraction loss calculations. Y1 - 2013 U6 - https://doi.org/10.1109/ULTSYM.2013.0555 SP - 2171 EP - 2174 ER - TY - PAT A1 - Kupnik, Mario A1 - Khuri-Yakub, Butrus T. T1 - Monolithic integrated CMUTs fabricated by low temperature wafer bonding N2 - Low temperature wafer bonding (temperature of 450°C. or less) is employed to fabricate CMUTs on a wafer that already includes active electrical devices. The resulting structures are CMUT arrays integrated with active electronics by a low-temperature wafer bonding process.The use of a low-temperature process preserves the electronics during CMUT fabrication. With this approach, it is not necessary to make compromises in the CMUT or electronics designs, as is typical of the sacrificial release, such as low process control, poor design flexibility, low reproducibility, and reduced performance are avoided with the present approach. With this approach, a CMUT array can be provided with per-cell electrodes connected to the substrate integrated circuitry. This enables complete flexibility in electronically assigning the CMUT cells to CMUT array elements. Y1 - 2013 ER - TY - PAT A1 - Kupnik, Mario A1 - Khuri-Yakub, Butrus T. T1 - Sensor for measuring properties of liquids and gases N2 - The present invention provides a device that measures at least one property of the liquid or gas, where the invention is a CMUT sensor that includes a substrate, a first layer disposed on the substrate, where the first layer includes a cavity, and a compound plate, where the compound plated includes a bottom plate, an intermediate plate and a top plate. According to the invention, the intermediate plate has at least one sample inlet, a sample cavity and at least one sample outlet, where the bottom plate is disposed on the first layer, and the cavity in the first layer is sealed by the compound plate. The cavity in the first layer can be a vacuum or contain a gas. The CMUT sensor can be disposed in an array of two or more sensors and connected electrically in parallel. Y1 - 2012 ER - TY - GEN A1 - Lee, Hyunjoo J. A1 - Park, Kwan Kyu A1 - Kupnik, Mario A1 - Melosh, Nicholas A. A1 - Khuri-Yakub, Butrus T. T1 - Mesoporous thin-film on highly sensitive resonant chemical sensors for relative humidity and CO2 detection T2 - Analytical Chemistry N2 - Distributed sensing of gas-phase chemicals is a promising application for mesoporous materials when combined with highly sensitive miniaturized gas sensors. We present a direct application of a mesoporous silica thin film on a highly sensitive miniaturized resonant chemical sensor with a mass sensitivity at the zeptogram scale for relative humidity and CO2 detection. Using mesoporous silica thin-film, we report one of the lowest volume resolutions and a sensitive detection of 5.1 × 10–4% RH/Hz to water vapor in N2, which is 70 times higher than a device with a nontemplated silica layer. 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 CO2 in N2. Y1 - 2012 U6 - https://doi.org/10.1021/ac300225c SN - 1520-6882 VL - 84 IS - 7 SP - 3063 EP - 3066 ER - TY - GEN A1 - Lee, Hyunjoo J. A1 - Park, Kwan Kyu A1 - Kupnik, Mario A1 - Khuri-Yakub, Butrus T. T1 - Functionalization layers for CO2 sensing using capacitive micromachined ultrasonic transducers T2 - Sensors and Actuators B: Chemical N2 - Sensing of carbon dioxide(CO2)using inexpensive, miniaturized,and highly sensitive sensors is of great interest for environmental and consumer applications. In this paper, we present four functionalization layers that are suitable for resonant sensors based on mass-loading for CO2 detection. We compare the volume sensitivities of these layers to CO2 and relative humidity (RH) by using a highly sensitive 50-MHz capacitive micromachined ultrasonic transducer (CMUT) as a resonant sensor. Among the four function-alization layers, the layer based on a guanidine polymer exhibits the highest volume sensitivity to CO2 of 1.0 ppm/Hz in N2 and 3.8 ppm/Hz in air (∼45%RH). Furthermore, we report on other important characteristics of the guanidine polymer for sensing applications, including polymer saturation, regeneration, and repeatability. Y1 - 2012 SN - 0925-4005 IS - 174 SP - 87 EP - 93 ER - TY - CHAP A1 - Ho, Min-Chieh A1 - Kupnik, Mario A1 - Park, Kwan Kyu A1 - Khuri-Yakub, Butrus T. T1 - Long-term measurement results of pre-charged CMUTs with zero external bias operation T2 - IEEE International Ultrasonics Symposium, Dresden, Germany, 7 - 10 October 2012 N2 - We present long-term measurement results (<1.5 years) of CMUTs, which have been pre-charged for zero external bias operation. The fabrication is based on a direct wafer bonding process with a thick-buried-oxide-layer, which allows the realization of only partially connected, donut-shaped bottom electrodes. The only partially connected bottom electrode has a central portion that is completely encapsulated by 3-μm-thick thermally-grown silicon dioxide, and, thus, electrically floating. The devices are pre-charged by applying a dc voltage higher than the pull-in voltage, which injects charges into the electrically floating portion and creates a sufficiently strong intrinsic electric field in the gap. Measurements of resonant frequency at various bias voltages show that the charges have completely remained in the floating portion for the last 19 months. We prove the zero-external-bias operations with the pre-charged CMUTs by measuring the electrical input impedance, the ac signal displacement, and pitch-catch measurements under zero external dc bias voltage. Our results show that pre-charging CMUTs is feasible, and that the devices are capable of long-term, zero external bias voltage operation. Y1 - 2012 SN - 978-1-4673-4561-3 U6 - https://doi.org/10.1109/ULTSYM.2012.0022 SP - 89 EP - 92 PB - IEEE CY - Piscataway, NJ ER -