Bio


Khuri-Yakub current research interests include medical ultrasound imaging and therapy, ultrasound neuro-stimulation, chemical/biological sensors, gas flow and energy flow sensing, micromachined ultrasonic transducers, gesture imaging for man-machine interaction, and ultrasonic fluid ejectors. He is also active in developing in-situ sensors (temperature, film thickness, resist cure) for process monitoring and process control of integrated circuits manufacturing processes.

Academic Appointments


Honors & Awards


  • Award for Contributions to Nondestructive Testing, City of Bordeaux (1983)
  • Distinguished Engineering Advisor, Stanford University (1987)
  • Distinguished Lecturer, UFFC Group of IEEE (1999)
  • Outstanding Inventor, Stanford University (2004)
  • Distinguished Alumnus, American University of Beirut (2005)
  • Certificate of Appreciation for commitment to educate, mentor and inspire, Stanford Biodesign (2011)
  • Rayleigh Award, IEEE (2011)

Professional Education


  • PhD, Stanford University (1975)
  • MS, Dartmouth College (1972)
  • BS, American University of Beirut (1970)

Postdoctoral Advisees


Journal Articles


  • Packaging and Modular Assembly of Large-Area and Fine-Pitch 2-D Ultrasonic Transducer Arrays IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Lin, D., Wodnicki, R., Zhuang, X., Woychik, C., Thomenius, K. E., Fisher, R. A., Mills, D. M., Byun, A. J., Burdick, W., Khuri-Yakub, P., Bonitz, B., Davies, T., Thomas, G., Otto, B., Toepper, M., Fritzsch, T., Ehrmann, O. 2013; 60 (7): 1356-1375
  • Photoacoustic imaging of the bladder: a pilot study. Journal of ultrasound in medicine Kamaya, A., Vaithilingam, S., Chung, B. I., Oralkan, O., Khuri-Yakub, B. T. 2013; 32 (7): 1245-1250

    Abstract

    Photoacoustic imaging is a promising new technology that combines tissue optical characteristics with ultrasound transmission and can potentially visualize tumor depth in bladder cancer. We imaged simulated tumors in 5 fresh porcine bladders with conventional pulse-echo sonography and photoacoustic imaging. Isoechoic biomaterials of different optical qualities were used. In all 5 of the bladder specimens, photoacoustic imaging showed injected biomaterials, containing varying degrees of pigment, better than control pulse-echo sonography. Photoacoustic imaging may be complementary to diagnostic information obtained by cystoscopy and urine cytologic analysis and could potentially obviate the need for biopsy in some tumors before definitive treatment.

    View details for DOI 10.7863/ultra.32.7.1245

    View details for PubMedID 23804347

  • New Technologies in Clinical Ultrasound SEMINARS IN ROENTGENOLOGY Kamaya, A., Machtaler, S., Sanjani, S. S., Nikoozadeh, A., Sommer, F. G., Khuri-Yakub, B. T., Willmann, J. K., Desser, T. S. 2013; 48 (3): 214-223
  • 3-D airborne ultrasound synthetic aperture imaging based on capacitive micromachined ultrasonic transducers Ultrasonics Park, K., K., Khuri-Yakub, B., T. 2013; 53: 1355-1362
  • A Comparison Between Conventional and Collapse-Mode Capacitive Micromachined Ultrasonic Transducers in 10-MHz 1-D Arrays Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Park, K., K., Oralkan, O., Khuri-Yakub, B., T. 2013; 60 (6): 1245-1255
  • Dynamic Response of Model Lipid Membranes to Ultrasonic Radiation Force PLOS ONE Prieto, M., L., Oralkan, O., Khuri-Yakub, B., T., Maduke, M., C. 2013; 8 (10)
  • Precise Neural Stimulation in the Retina Using Focused Ultrasound J. Neuroscience Menz, M., D., Oralkan, O., Khuri-Yakub, P., T., Baccus, S., A. 2013; 33 (10): 4550-4560
  • Functionalization layers for CO2 sensing using capacitive micromachined ultrasonic transducers SENSORS AND ACTUATORS B-CHEMICAL Lee, H. J., Park, K. K., Kupnik, M., Khuri-Yakub, B. T. 2012; 174: 87-93
  • Dynamic response of an array of flexural plates in acoustic medium JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Park, K. K., Khuri-Yakub, B. T. 2012; 132 (4): 2292-2303

    Abstract

    The dynamic response of a transducer array made up of circular flexural plates in immersion is analytically calculated. The calculation method includes three steps: (1) the calculation of parallel resonant frequency and the velocity profile of each plate, (2) the calculation of mutual acoustic impedance between the plates, and (3) the calculation of velocity response, including the mechanical and acoustic impedance. The calculation method is validated by both finite element analysis and measurement results of a fabricated capacitive micromachined ultrasonic transducer. Based on the calculated velocity, the near-field pressure and the near-to-far field radiation patterns are presented. The flexural plate array in immersion displays two modes of operation. At low frequency, the mode shape of the transducer array is similar to that of a suspended plate and, at certain frequencies, two groups of plates move in opposite phase, which results in the cancellation of the average velocity. At high frequency, the mode shape is similar to that of a piston transducer; however, the near-field pressure distribution is similar to that of a resilient disk.

    View details for DOI 10.1121/1.4747613

    View details for Web of Science ID 000309650600035

    View details for PubMedID 23039426

  • Volumetric Real-Time Imaging Using a CMUT Ring Array IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Choe, J. W., Oralkan, O., Nikoozadeh, A., Gencel, M., Stephens, D. N., O'Donnell, M., Sahn, D. J., Khuri-Yakub, B. T. 2012; 59 (6): 1201-1211

    Abstract

    A ring array provides a very suitable geometry for forward-looking volumetric intracardiac and intravascular ultrasound imaging. We fabricated an annular 64-element capacitive micromachined ultrasonic transducer (CMUT) array featuring a 10-MHz operating frequency and a 1.27-mm outer radius. A custom software suite was developed to run on a PC-based imaging system for real-time imaging using this device. This paper presents simulated and experimental imaging results for the described CMUT ring array. Three different imaging methods--flash, classic phased array (CPA), and synthetic phased array (SPA)--were used in the study. For SPA imaging, two techniques to improve the image quality--Hadamard coding and aperture weighting--were also applied. The results show that SPA with Hadamard coding and aperture weighting is a good option for ring-array imaging. Compared with CPA, it achieves better image resolution and comparable signal-to-noise ratio at a much faster image acquisition rate. Using this method, a fast frame rate of up to 463 volumes per second is achievable if limited only by the ultrasound time of flight; with the described system we reconstructed three cross-sectional images in real-time at 10 frames per second, which was limited by the computation time in synthetic beamforming.

    View details for DOI 10.1109/TUFFC.2012.2310

    View details for Web of Science ID 000305760000013

    View details for PubMedID 22718870

  • Family of Enhanced Photoacoustic Imaging Agents for High-Sensitivity and Multiplexing Studies in Living Mice ACS NANO de la Zerda, A., Bodapati, S., Teed, R., May, S. Y., Tabakman, S. M., Liu, Z., Khuri-Yakub, B. T., Chen, X., Dai, H., Gambhir, S. S. 2012; 6 (6): 4694-4701

    Abstract

    Photoacoustic imaging is a unique modality that overcomes to a great extent the resolution and depth limitations of optical imaging while maintaining relatively high contrast. However, since many diseases will not manifest an endogenous photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target diseased tissue(s). Here we present a family of novel photoacoustic contrast agents that are based on the binding of small optical dyes to single-walled carbon nanotubes (SWNT-dye). We synthesized five different SWNT-dye contrast agents using different optical dyes, creating five "flavors" of SWNT-dye nanoparticles. In particular, SWNTs that were coated with either QSY(21) (SWNT-QSY) or indocyanine green (SWNT-ICG) exhibited over 100-times higher photoacoustic contrast in living animals compared to plain SWNTs, leading to subnanomolar sensitivities. We then conjugated the SWNT-dye conjugates with cyclic Arg-Gly-Asp peptides to molecularly target the ?(v)?(3) integrin, which is associated with tumor angiogenesis. Intravenous administration of these tumor-targeted imaging agents to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. Finally, we were able to spectrally separate the photoacoustic signals of SWNT-QSY and SWNT-ICG in living animals injected subcutaneously with both particles in the same location, opening the possibility for multiplexing in vivo studies.

    View details for DOI 10.1021/nn204352r

    View details for Web of Science ID 000305661300017

    View details for PubMedID 22607191

  • Deep Tissue Photoacoustic Imaging Using a Miniaturized 2-D Capacitive Micromachined Ultrasonic Transducer Array IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Kothapalli, S., Ma, T., Vaithilingam, S., Oralkan, O., Khuri-Yakub, B. T., Gambhir, S. S. 2012; 59 (5): 1199-1204

    Abstract

    In this paper, we demonstrate 3-D photoacoustic imaging (PAI) of light absorbing objects embedded as deep as 5 cm inside strong optically scattering phantoms using a miniaturized (4 mm × 4 mm × 500 ?m), 2-D capacitive micromachined ultrasonic transducer (CMUT) array of 16 × 16 elements with a center frequency of 5.5 MHz. Two-dimensional tomographic images and 3-D volumetric images of the objects placed at different depths are presented. In addition, we studied the sensitivity of CMUT-based PAI to the concentration of indocyanine green dye at 5 cm depth inside the phantom. Under optimized experimental conditions, the objects at 5 cm depth can be imaged with SNR of about 35 dB and a spatial resolution of approximately 500 ?m. Results demonstrate that CMUTs with integrated front-end amplifier circuits are an attractive choice for achieving relatively high depth sensitivity for PAI.

    View details for DOI 10.1109/TBME.2012.2183593

    View details for Web of Science ID 000303201000001

    View details for PubMedID 22249594

  • Mesoporous Thin-Film on Highly-Sensitive Resonant Chemical Sensor for Relative Humidity and CO2 Detection ANALYTICAL CHEMISTRY Lee, H. J., Park, K. K., Kupnik, M., Melosh, N. A., Khuri-Yakub, B. T. 2012; 84 (7): 3063-3066

    Abstract

    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 CO(2) 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 N(2), 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 CO(2) in N(2).

    View details for DOI 10.1021/ac300225c

    View details for Web of Science ID 000302829800006

    View details for PubMedID 22372606

  • First In Vivo Use of a Capacitive Micromachined Ultrasound Transducer Array-Based Imaging and Ablation Catheter JOURNAL OF ULTRASOUND IN MEDICINE Stephens, D. N., Truong, U. T., Nikoozadeh, A., Oralkan, O., Seo, C. H., Cannata, J., Dentinger, A., Thomenius, K., de la Rama, A., Nguyen, T., Lin, F., Khuri-Yakub, P., Mahajan, A., Shivkumar, K., O'Donnell, M., Sahn, D. J. 2012; 31 (2): 247-256

    Abstract

    The primary objective was to test in vivo for the first time the general operation of a new multifunctional intracardiac echocardiography (ICE) catheter constructed with a microlinear capacitive micromachined ultrasound transducer (ML-CMUT) imaging array. Secondarily, we examined the compatibility of this catheter with electroanatomic mapping (EAM) guidance and also as a radiofrequency ablation (RFA) catheter. Preliminary thermal strain imaging (TSI)-derived temperature data were obtained from within the endocardium simultaneously during RFA to show the feasibility of direct ablation guidance procedures.The new 9F forward-looking ICE catheter was constructed with 3 complementary technologies: a CMUT imaging array with a custom electronic array buffer, catheter surface electrodes for EAM guidance, and a special ablation tip, that permits simultaneous TSI and RFA. In vivo imaging studies of 5 anesthetized porcine models with 5 CMUT catheters were performed.The ML-CMUT ICE catheter provided high-resolution real-time wideband 2-dimensional (2D) images at greater than 8 MHz and is capable of both RFA and EAM guidance. Although the 24-element array aperture dimension is only 1.5 mm, the imaging depth of penetration is greater than 30 mm. The specially designed ultrasound-compatible metalized plastic tip allowed simultaneous imaging during ablation and direct acquisition of TSI data for tissue ablation temperatures. Postprocessing analysis showed a first-order correlation between TSI and temperature, permitting early development temperature-time relationships at specific myocardial ablation sites.Multifunctional forward-looking ML-CMUT ICE catheters, with simultaneous intracardiac guidance, ultrasound imaging, and RFA, may offer a new means to improve interventional ablation procedures.

    View details for Web of Science ID 000299717300010

    View details for PubMedID 22298868

  • Nanoscale Topography of Thermally-Grown Oxide Films at Right-Angled Convex Corners of Silicon JOURNAL OF THE ELECTROCHEMICAL SOCIETY Sarioglu, A. F., Kupnik, M., Vaithilingam, S., Khuri-Yakub, B. T. 2012; 159 (2): H79-H84
  • Large Area 1D CMUT Phased Arrays for Multi-Modality Ultrasound Imaging 2011 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS) Apte, N., Vaithilingam, S., Sarioglu, A. F., Kupnik, M., Khuri-Yakub, B. T. 2012: 612-615
  • Chemical Vapor Detection Using a Capacitive Micromachined Ultrasonic Transducer ANALYTICAL CHEMISTRY Lee, H. J., Park, K. K., Kupnik, M., Oralkan, O., Khuri-Yakub, B. T. 2011; 83 (24): 9314-9320

    Abstract

    Distributed sensing of gas-phase chemicals using highly sensitive and inexpensive sensors is of great interest for many defense and consumer applications. In this paper we present ppb-level detection of dimethyl methylphosphonate (DMMP), a common simulant for sarin gas, with a ppt-level resolution using an improved capacitive micromachined ultrasonic transducer (CMUT) as a resonant chemical sensor. The improved CMUT operates at a higher resonant frequency of 47.7 MHz and offers an improved mass sensitivity of 48.8 zg/Hz/?m(2) by a factor of 2.7 compared to the previous CMUT sensors developed. A low-noise oscillator using the CMUT resonant sensor as the frequency-selective device was developed for real-time sensing, which exhibits an Allan deviation of 1.65 Hz (3?) in the presence of a gas flow; this translates into a mass resolution of 80.5 zg/?m(2). The CMUT resonant sensor is functionalized with a 50-nm thick DKAP polymer developed at Sandia National Laboratory for dimethyl methylphosphonate (DMMP) detection. To demonstrate ppb-level detection of the improved chemical sensor system, the sensor performance was tested at a certified lab (MIT Lincoln Laboratory), which is equipped with an experimental chemical setup that reliably and accurately delivers a wide range of low concentrations down to 10 ppb. We report a high volume sensitivity of 34.5 ± 0.79 pptv/Hz to DMMP and a good selectivity of the polymer to DMMP with respect to dodecane and 1-octanol.

    View details for DOI 10.1021/ac201626b

    View details for Web of Science ID 000297946900020

    View details for PubMedID 22124375

  • Capacitive micromachined ultrasonic transducer (CMUT) as a chemical sensor for DMMP detection SENSORS AND ACTUATORS B-CHEMICAL Park, K. K., Lee, H., Kupnik, M., Oralkan, O., Ramseyer, J., Lang, H. P., Hegner, M., Gerber, C., Khuri-Yakub, B. T. 2011; 160 (1): 1120-1127
  • Capacitive micromachined ultrasonic transducers for medical imaging and therapy JOURNAL OF MICROMECHANICS AND MICROENGINEERING Khuri-Yakub, B. T., Oralkan, O. 2011; 21 (5)
  • Fabrication of Capacitive Micromachined Ultrasonic Transducers via Local Oxidation and Direct Wafer Bonding JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Park, K. K., Lee, H., Kupnik, M., Khuri-Yakub, B. T. 2011; 20 (1): 95-103
  • The Feasibility of Using Thermal Strain Imaging to Regulate Energy Delivery During Intracardiac Radio-Frequency Ablation Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Seo, C., H., Stephens, D., N., Cannata, J., Dentinger, A., Lin, F., Park, S., Khuri-Yakub, Butrus, T. 2011; 58 (7): 1406-16
  • Encapsulation of Capacitive Micromachined Ultrasonic Transducers Using Viscoelastic Polymer JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Lin, D., Zhuang, X., Wong, S. H., Kupnik, M., Khuri-Yakub, B. T. 2010; 19 (6): 1341-1351

    Abstract

    The packaging of a medical imaging or therapeutic ultrasound transducer should provide protective insulation while maintaining high performance. For a capacitive micromachined ultrasonic transducer (CMUT), an ideal encapsulation coating would therefore require a limited and predictable change on the static operation point and the dynamic performance, while insulating the high dc and dc actuation voltages from the environment. To fulfill these requirements, viscoelastic materials, such as polydimethylsiloxane (PDMS), were investigated for an encapsulation material. In addition, PDMS, with a glass-transition temperature below room temperature, provides a low Young's modulus that preserves the static behavior; at higher frequencies for ultrasonic operation, this material becomes stiffer and acoustically matches to water. In this paper, we demonstrate the modeling and implementation of the viscoelastic polymer as the encapsulation material. We introduce a finite element model (FEM) that addresses viscoelasticity. This enables us to correctly calculate both the static operation point and the dynamic behavior of the CMUT. CMUTs designed for medical imaging and therapeutic ultrasound were fabricated and encapsulated. Static and dynamic measurements were used to verify the FEM and show excellent agreement. This paper will help in the design process for optimizing the static and the dynamic behavior of viscoelastic-polymer-coated CMUTs.

    View details for DOI 10.1109/JMEMS.2010.2076786

    View details for Web of Science ID 000284875400008

    View details for PubMedID 21170294

  • Design, Synthesis, and Imaging of an Activatable Photoacoustic Probe JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Levi, J., Kothapalli, S. R., Ma, T., Hartman, K., Khuri-Yakub, B. T., Gambhir, S. S. 2010; 132 (32): 11264-11269

    Abstract

    Photoacoustic tomography is a rapidly growing imaging modality that can provide images of high spatial resolution and high contrast at depths up to 5 cm. We report here the design, synthesis, and evaluation of an activatable probe that shows great promise for enabling detection of the cleaved probe in the presence of high levels of nonactivated, uncleaved probe, a difficult task to attain in absorbance-based modality. Before the cleavage by its target, proteolytic enzyme MMP-2, the probe, an activatable cell-penetrating peptide, Ceeee[Ahx]PLGLAGrrrrrK, labeled with two chromophores, BHQ3 and Alexa750, shows photoacoustic signals of similar intensity at the two wavelengths corresponding to the absorption maxima of the chromophores, 675 and 750 nm. Subtraction of the images taken at these two wavelengths makes the probe effectively photoacoustically silent, as the signals at these two wavelengths essentially cancel out. After the cleavage, the dye associated with the cell-penetrating part of the probe, BHQ3, accumulates in the cells, while the other dye diffuses away, resulting in photoacoustic signal seen at only one of the wavelengths, 675 nm. Subtraction of the photoacoustic images at two wavelengths reveals the location of the cleaved (activated) probe. In the search for the chromophores that are best suited for photoacoustic imaging, we have investigated the photoacoustic signals of five chromophores absorbing in the near-infrared region. We have found that the photoacoustic signal did not correlate with the absorbance and fluorescence of the molecules, as the highest photoacoustic signal arose from the least absorbing quenchers, BHQ3 and QXL 680.

    View details for DOI 10.1021/0104000a

    View details for Web of Science ID 000280861300058

    View details for PubMedID 20698693

  • Ultrahigh Sensitivity Carbon Nanotube Agents for Photoacoustic Molecular Imaging in Living Mice NANO LETTERS de la Zerda, A., Liu, Z., Bodapati, S., Teed, R., Vaithilingam, S., Khuri-Yakub, B. T., Chen, X., Dai, H., Gambhir, S. S. 2010; 10 (6): 2168-2172

    Abstract

    Photoacoustic imaging is an emerging modality that overcomes to a great extent the resolution and depth limitations of optical imaging while maintaining relatively high-contrast. However, since many diseases will not manifest an endogenous photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target diseased tissue(s). Here we present a novel photoacoustic contrast agent, Indocyanine Green dye-enhanced single walled carbon nanotube (SWNT-ICG). We conjugated this contrast agent with cyclic Arg-Gly-Asp (RGD) peptides to molecularly target the alpha(v)beta(3) integrins, which are associated with tumor angiogenesis. Intravenous administration of this tumor-targeted contrast agent to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. The new contrast agent gave a markedly 300 times higher photoacoustic contrast in living tissues than previously reported SWNTs, leading to subnanomolar sensitivities. Finally, we show that the new contrast agent can detect approximately 20 times fewer cancer cells than previously reported SWNTs.

    View details for DOI 10.1021/nl100890d

    View details for Web of Science ID 000278449200033

    View details for PubMedID 20499887

  • Photoacoustic ocular imaging OPTICS LETTERS de la Zerda, A., Paulus, Y. M., Teed, R., Bodapati, S., Dollberg, Y., Khuri-Yakub, B. T., Blumenkranz, M. S., Moshfeghi, D. M., Gambhir, S. S. 2010; 35 (3): 270-272

    Abstract

    We developed a photoacoustic ocular imaging device and demonstrated its utility in imaging the deeper layers of the eye including the retina, choroid, and optic nerve. Using safe laser intensity, the photoacoustic system was able to visualize the blood distribution of an enucleated pig's eye and an eye of a living rabbit. Ultrasound images, which were simultaneously acquired, were overlaid on the photoacoustic images to visualize the eye's anatomy. Such a system may be used in the future for early detection and improved management of neovascular ocular diseases, including wet age-related macular degeneration and proliferative diabetic retinopathy.

    View details for Web of Science ID 000274196100001

    View details for PubMedID 20125691

  • Capacitive Micromachined Ultrasonic Transducers for Therapeutic Ultrasound Applications IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Wong, S. H., Kupnik, M., Watkins, R. D., Butts-Pauly, K., Khuri-Yakub, B. T. 2010; 57 (1): 114-123

    Abstract

    Therapeutic ultrasound guided by MRI is a noninvasive treatment that potentially reduces mortality, lowers medical costs, and widens accessibility of treatments for patients. Recent developments in the design and fabrication of capacitive micromachined ultrasonic transducers (CMUTs) have made them competitive with piezoelectric transducers for use in therapeutic ultrasound applications. In this paper, we present the first designs and prototypes of an eight-element, concentric-ring, CMUT array to treat upper abdominal cancers. This array was simulated and designed to focus 30-50 mm into tissue, and ablate a 2- to 3-cm-diameter tumor within 1 h. Assuming a surface acoustic output pressure of 1 MPa peak-to-peak (8.5 W/cm (2)) at 2.5 MHz, we simulated an array that produced a focal intensity of 680 W/cm (2) when focusing to 35 mm. CMUT cells were then designed to meet these frequency and surface acoustic intensity specifications. These cell designs were fabricated as 2.5 mm x 2.5 mm test transducers and used to verify our models. The test transducers were shown to operate at 2.5 MHz with an output pressure of 1.4 MPa peak-to-peak (16.3 W/cm (2)). With this CMUT cell design, we fabricated a full eight-element array. Due to yield issues, we only developed electronics to focus the four center elements of the array. The beam profile of the measured array deviated from the simulated one because of the crosstalk effects; the beamwidth matched within 10% and sidelobes increased by two times, which caused the measured gain to be 16.6 compared to 27.4.

    View details for DOI 10.1109/TBME.2009.2026909

    View details for Web of Science ID 000273565600018

    View details for PubMedID 19628448

  • Three-Dimensional Photoacoustic Imaging Using a Two-Dimensional CMUT Array IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Vaithilingam, S., Ma, T., Furukawa, Y., Wygant, I. O., Zhuang, X., de la Zerda, A., Oralkan, O., Kamaya, A., Gambhir, S. S., Jeffrey, R. B., Khuri-Yakub, B. T. 2009; 56 (11): 2411-2419

    Abstract

    In this paper, we describe using a 2-D array of capacitive micromachined ultrasonic transducers (CMUTs) to perform 3-D photoacoustic and acoustic imaging. A tunable optical parametric oscillator laser system that generates nanosecond laser pulses was used to induce the photoacoustic signals. To demonstrate the feasibility of the system, 2 different phantoms were imaged. The first phantom consisted of alternating black and transparent fishing lines of 180 mum and 150 mum diameter, respectively. The second phantom comprised polyethylene tubes, embedded in chicken breast tissue, filled with liquids such as the dye indocyanine green, pig blood, and a mixture of the 2. The tubes were embedded at a depth of 0.8 cm inside the tissue and were at an overall distance of 1.8 cm from the CMUT array. Two-dimensional cross-sectional slices and 3-D volume rendered images of pulse-echo data as well as photoacoustic data are presented. The profile and beamwidths of the fishing line are analyzed and compared with a numerical simulation carried out using the Field II ultrasound simulation software. We investigated using a large aperture (64 x 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller CMUT array (16 x 16 elements). Two-dimensional transducer arrays overcome many of the limitations of a mechanically scanned system and enable volumetric imaging. Advantages of CMUT technology for photoacoustic imaging include the ease of integration with electronics, ability to fabricate large, fully populated 2-D arrays with arbitrary geometries, wide-bandwidth arrays and high-frequency arrays. A CMUT based photoacoustic system is proposed as a viable alternative to a piezoelectric transducer based photoacoustic systems.

    View details for DOI 10.1109/TUFFC.2009.1329

    View details for Web of Science ID 000271478600010

    View details for PubMedID 19942528

  • An Integrated Circuit With Transmit Beamforming Flip-Chip Bonded to a 2-D CMUT Array for 3-D Ultrasound Imaging IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wygant, I. O., Jamal, N. S., Lee, H. J., Nikoozadeh, A., Oralkan, O., Karaman, M., Khuri-Yakub, B. T. 2009; 56 (10): 2145-2156

    Abstract

    State-of-the-art 3-D medical ultrasound imaging requires transmitting and receiving ultrasound using a 2-D array of ultrasound transducers with hundreds or thousands of elements. A tight combination of the transducer array with integrated circuitry eliminates bulky cables connecting the elements of the transducer array to a separate system of electronics. Furthermore, preamplifiers located close to the array can lead to improved receive sensitivity. A combined IC and transducer array can lead to a portable, high-performance, and inexpensive 3-D ultrasound imaging system. This paper presents an IC flip-chip bonded to a 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array for 3-D ultrasound imaging. The IC includes a transmit beamformer that generates 25-V unipolar pulses with programmable focusing delays to 224 of the 256 transducer elements. One-shot circuits allow adjustment of the pulse widths for different ultrasound transducer center frequencies. For receiving reflected ultrasound signals, the IC uses the 32-elements along the array diagonals. The IC provides each receiving element with a low-noise 25-MHz-bandwidth transimpedance amplifier. Using a field-programmable gate array (FPGA) clocked at 100 MHz to operate the IC, the IC generated properly timed transmit pulses with 5-ns accuracy. With the IC flip-chip bonded to a CMUT array, we show that the IC can produce steered and focused ultrasound beams. We present 2-D and 3-D images of a wire phantom and 2-D orthogonal cross-sectional images (Bscans) of a latex heart phantom.

    View details for DOI 10.1109/TUFFC.2009.1297

    View details for Web of Science ID 000270592000011

    View details for PubMedID 19942502

  • Minimally Redundant 2-D Array Designs for 3-D Medical Ultrasound Imaging IEEE TRANSACTIONS ON MEDICAL IMAGING Karaman, M., Wygant, I. O., Oralkan, O., Khuri-Yakub, B. T. 2009; 28 (7): 1051-1061

    Abstract

    In real-time ultrasonic 3-D imaging, in addition to difficulties in fabricating and interconnecting 2-D transducer arrays with hundreds of elements, there are also challenges in acquiring and processing data from a large number of ultrasound channels. The coarray (spatial convolution of the transmit and receive arrays) can be used to find efficient array designs that capture all of the spatial frequency content (a transmit-receive element combination corresponds to a spatial frequency) with a reduced number of active channels and firing events. Eliminating the redundancies in the transmit-receive element combinations and firing events reduces the overall system complexity and improves the frame rate. Here we explore four reduced redundancy 2-D array configurations for miniature 3-D ultrasonic imaging systems. Our approach is based on 1) coarray design with reduced redundancy using different subsets of linear arrays constituting the 2-D transducer array, and 2) 3-D scanning using fan-beams (narrow in one dimension and broad in the other dimension) generated by the transmit linear arrays. We form the overall array response through coherent summation of the individual responses of each transmit-receive array pairs. We present theoretical and simulated point spread functions of the array configurations along with quantitative comparison in terms of the front-end complexity and image quality.

    View details for DOI 10.1109/TMI.2008.2010936

    View details for Web of Science ID 000267698100008

    View details for PubMedID 19131299

  • Experimental Studies With a 9F Forward-Looking Intracardiac Imaging and Ablation Catheter JOURNAL OF ULTRASOUND IN MEDICINE Stephens, D. N., O'Donnell, M., Thomenius, K., Dentinger, A., Wildes, D., Chen, P., Shung, K. K., Cannata, J., Khuri-Yakub, P., Oralkan, O., Mahajan, A., Shivkumar, K., Sahn, D. J. 2009; 28 (2): 207-215

    Abstract

    The purpose of this study was to develop a high-resolution, near-field-optimized 14-MHz, 24-element broad-bandwidth forward-looking array for integration on a steerable 9F electrophysiology (EP) catheter.Several generations of prototype imaging catheters with bidirectional steering, termed microlinear (ML), were built and tested as integrated catheter designs with EP sensing electrodes near the tip. The wide-bandwidth ultrasound array was mounted on the very tip, equipped with an aperture of only 1.2 by 1.58 mm. The array pulse echo performance was fully simulated, and its construction offered shielding from ablation noise. Both ex vivo and in vivo imaging with a porcine animal model were performed.The array pulse echo performance was concordant with Krimholtz-Leedom-Matthaei model simulation. Three generations of prototype devices were tested in the right atrium and ventricle in 4 acute pig studies for the following characteristics: (1) image quality, (2) anatomic identification, (3) visualization of other catheter devices, and (4) for a mechanism for stabilization when imaging ablation. The ML catheter is capable of both low-artifact ablation imaging on a standard clinical imaging system and high-frame rate myocardial wall strain rate imaging for detecting changes in cardiac mechanics associated with ablation.The imaging resolution performance of this very small array device, together with its penetration beyond 2 cm, is excellent considering its very small array aperture. The forward-looking intracardiac catheter has been adapted to work easily on an existing commercial imaging platform with very minor software modifications.

    View details for Web of Science ID 000266555700007

    View details for PubMedID 19168770

  • A Family of Intracardiac Ultrasound Imaging Devices Designed for Guidance of Electrophysiology Ablation Procedures 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20 Sahn, D. J., Stephens, D. N., Cannata, J. M., Shung, K. K., Oralkan, O., Nikoozadeh, A., Khuri-Yakub, B. T., Nguyen, H., Chen, P., Dentinger, A. M., Wildes, D., Thomenius, K. E., Mahajan, A., Shivkumar, K., O'Donnell, M. 2009: 1913-1917

    Abstract

    Our Bioengineering Research Partnership grant, -High Frequency Ultrasound Arrays for Cardiac Imaging", including the individuals cited at the end of this paper - Douglas N. Stephens (UC Davis), Matthew O'Donnell (UW Seattle), Kai Thomenius (GE Global Research), Aaron M. Dentinger (GE Global Research), Douglas Wildes (GE Global Research), Peter Chen (St. Jude Medical), K. Kirk Shung (University of Southern California), Jonathan M. Cannata (University of Southern California), Butrus (Pierre) T. Khuri-Yakub (Stanford University), Omer Oralkan (Stanford University), Aman Mahajan (UCLA School of Medicine), Kalyanam Shivkumar (UCLA School of Medicine) and David J. Sahn (Oregon Health & Science University) - is in its sixth year of NIH funding, having proposed to develop a family of high frequency miniaturized forward and side-looking ultrasound imaging devices equipped with electrophysiology mapping and localization sensors and eventually to include a family of capactive micromachined ultrasonic transducer (cMUT) devices - a forward-looking cMUT MicroLinear array and a ring array capable of 3-dimensional imaging and a 5Fr lumen large enough to admit an electrode and ablation devices.

    View details for Web of Science ID 000280543601209

    View details for PubMedID 19963529

  • Wafer-Bonded 2-D CMUT Arrays Incorporating Through-Wafer Trench-Isolated Interconnects with a Supporting Frame IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Zhang, X., Wygant, I. O., Lin, D., Kupnik, M., Oralkan, O., Khuri-Yakub, B. T. 2009; 56 (1): 182-192

    Abstract

    This paper reports on wafer-bonded, fully populated 2-D capacitive micromachined ultrasonic transducer (CMUT) arrays. To date, no successful through-wafer via fabrication technique has been demonstrated that is compatible with the wafer-bonding method of making CMUT arrays. As an alternative to through-wafer vias, trench isolation with a supporting frame is incorporated into the 2-D arrays to provide through-wafer electrical connections. The CMUT arrays are built on a silicon-on-insulator (SOI) wafer, and all electrical connections to the array elements are brought to the back side of the wafer through the highly conductive silicon substrate. Neighboring array elements are separated by trenches on both the device layer and the bulk silicon. A mesh frame structure, providing mechanical support, is embedded between silicon pillars, which electrically connect to individual elements. We successfully fabricated a 16 x 16-element 2-D CMUT array using wafer bonding with a yield of 100%. Across the array, the pulse-echo amplitude distribution is uniform (rho = 6.6% of the mean amplitude). In one design, we measured a center frequency of 7.6 MHz, a peak-to-peak output pressure of 2.9 MPa at the transducer surface, and a 3-dB fractional bandwidth of 95%. Volumetric ultrasound imaging was demonstrated by chip-to-chip bonding one of the fabricated 2-D arrays to a custom-designed integrated circuit (IC). This study shows that through-wafer trench-isolation with a supporting frame is a viable solution for providing electrical interconnects to CMUT elements and that 2-D arrays fabricated using waferbonding deliver good performance.

    View details for DOI 10.1109/TUFFC.2009.1018

    View details for Web of Science ID 000262561600021

    View details for PubMedID 19213645

  • Capacitive Micromachined Ultrasonic Transducers with Piston-Shaped Membranes: Fabrication and Experimental Characterization IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Huang, Y., Zhuang, X., Haeggstrom, E. O., Ergun, A. S., Cheng, C., Khuri-Yakub, B. T. 2009; 56 (1): 136-145

    Abstract

    Capacitive micromachined ultrasonic transducers (CMUTs) featuring piston-shaped membranes (piston CMUTs) were developed to improve device performance in terms of transmission efficiency, reception sensitivity, and fractional bandwidth (FBW). A piston CMUT has a relatively flat active moving surface whose membrane motion is closer to ideal piston-type motion compared with a CMUT with uniformly thick membranes (classical CMUT). Piston CMUTs with a more uniform surface displacement profile can achieve high output pressure with a relatively small electrode separation. The improved device capacitance and gap uniformity also enhance detection sensitivity. By adding a center mass to the membrane, a large ratio of second-order resonant frequency to first-order resonant frequency was achieved. This improved the FBW. Piston CMUTs featuring membranes of different geometric shapes were designed and fabricated using wafer bonding. Fabricating piston CMUTs is a more complex process than fabricating CMUTs with uniformly thick membranes. However, no yield loss was observed. These devices achieved ~100% improvement in transduction performance (transmission and reception) over classical CMUTs. For CMUTs with square and rectangular membranes, the FBW increased from ~110% to ~150% and from ~140% to ~175%, respectively, compared with classical CMUTs. The new devices produced a maximum output pressure exceeding 1 MPa at the transducer surface. Performance optimization using geometric membrane shape configurations was the same in both piston CMUTs and classical CMUTs.

    View details for DOI 10.1109/TUFFC.2009.1013

    View details for Web of Science ID 000262561600016

    View details for PubMedID 19213640

  • 50 kHz Capacitive Micromachined Ultrasonic Transducers for Generation of Highly Directional Sound with Parametric Arrays IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wygant, I. O., Kupnik, M., Windsor, J. C., Wright, W. M., Wochner, M. S., Yaralioglu, G. G., Hamilton, M. F., Khuri-Yakub, B. T. 2009; 56 (1): 193-203

    Abstract

    In this study, we examine the use of capacitive micromachined ultrasonic transducers (CMUTs) with vacuum- sealed cavities for transmitting directional sound with parametric arrays. We used finite element modeling to design CMUTs with 40-microm- and 60-microm-thick membranes to have resonance frequencies of 46 kHz and 54 kHz, respectively. The wafer bonding approach used to fabricate the CMUTs provides good control over device properties and the capability to fabricate CMUTs with large diameter membranes and deep cavities. Each CMUT is 8 cm in diameter and consists of 284 circular membranes. Each membrane is 4 mm in diameter. Characterization of the fabricated CMUTs shows they have center frequencies of 46 kHz and 55 kHz and 3 dB bandwidths of 1.9 kHz and 5.3 kHz for the 40-microm- and 60-microm-thick membrane devices, respectively. With dc bias voltages of 380 V and 350 V and an ac excitation of 200 V peak-to-peak, the CMUTs generate average sound pressure levels, normalized to the device's surface, of 135 dB and 129 dB (re 20 microPa), respectively. When used to generate 5 kHz sound with a parametric array, we measured sound at 3 m with a 6 dB beamwidth of 8.7 degrees and a sound pressure level of 58 dB. To understand how detector nonlinearity (e.g., the nonlinearity of the microphone used to make the sound level measurements) affects the measured sound pressure level, we made measurements with and without an acoustic low-pass filter placed in front of the microphone; the measured sound levels agree with numerical simulations of the pressure field. The results presented in this paper demonstrate that large-area CMUTs, which produce high-intensity ultrasound, can be fabricated for transmitting directional sound with parametric arrays.

    View details for DOI 10.1109/TUFFC.2009.1019

    View details for Web of Science ID 000262561600022

    View details for PubMedID 19213646

  • Forward-Looking Intracardiac Ultrasound Imaging Using a 1-D CMUT Array Integrated With Custom Front-End Electronics IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Nikoozadeh, A., Wygant, I. O., Lin, D., Oralkan, O., Ergun, A. S., Stephens, D. N., Thomenius, K. E., Dentinger, A. M., Wildes, D., Akopyan, G., Shivkumar, K., Mahajan, A., Sahn, D. J., Khuri-Yakub, B. T. 2008; 55 (12): 2651-2660

    Abstract

    Minimally invasive catheter-based electrophysiological (EP) interventions are becoming a standard procedure in diagnosis and treatment of cardiac arrhythmias. As a result of technological advances that enable small feature sizes and a high level of integration, nonfluoroscopic intracardiac echocardiography (ICE) imaging catheters are attracting increasing attention. ICE catheters improve EP procedural guidance while reducing the undesirable use of fluoroscopy, which is currently the common catheter guidance method. Phased-array ICE catheters have been in use for several years now, although only for side-looking imaging. We are developing a forward-looking ICE catheter for improved visualization. In this effort, we fabricate a 24-element, fine-pitch 1-D array of capacitive micromachined ultrasonic transducers (CMUT), with a total footprint of 1.73 mm x 1.27 mm. We also design a custom integrated circuit (IC) composed of 24 identical blocks of transmit/ receive circuitry, measuring 2.1 mm x 2.1 mm. The transmit circuitry is capable of delivering 25-V unipolar pulses, and the receive circuitry includes a transimpedance preamplifier followed by an output buffer. The CMUT array and the custom IC are designed to be mounted at the tip of a 10-Fr catheter for high-frame-rate forward-looking intracardiac imaging. Through-wafer vias incorporated in the CMUT array provide access to individual array elements from the back side of the array. We successfully flip-chip bond a CMUT array to the custom IC with 100% yield. We coat the device with a layer of polydimethylsiloxane (PDMS) to electrically isolate the device for imaging in water and tissue. The pulse-echo in water from a total plane reflector has a center frequency of 9.2 MHz with a 96% fractional bandwidth. Finally, we demonstrate the imaging capability of the integrated device on commercial phantoms and on a beating ex vivo rabbit heart (Langendorff model) using a commercial ultrasound imaging system.

    View details for DOI 10.1109/TUFFC.2008.980

    View details for Web of Science ID 000262221800012

    View details for PubMedID 19126489

  • Evaluation of wafer bonded CMUTs with rectangular membranes featuring high fill factor IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wong, S. H., Kupnik, M., Zhuang, X., Lin, D., Butts-Pauly, K., Khuri-Yakub, B. T. 2008; 55 (9): 2053-2065

    Abstract

    Increasing fill factor is one design approach used to increase average output displacement, output pressure, and sensitivity of capacitive micromachined ultrasonic transducers (CMUTs). For rectangular cells, the cell-to-cell spacing and the aspect ratio determine the fill factor. In this paper, we explore the effects of these parameters on performance, in particular the nonuniformity of collapse voltage between neighboring cells and presence of higher order modes in air or immersed operation. We used a white light interferometer to measure nonuniformity in deflection between neighboring cells. We found that reducing the cell-to-cell spacing could cause bending of the center support post, which amplifies nonuniformities in collapse voltage to 18.4% between neighboring cells. Using a 2-D finite element model (FEM), we found that for our designs, increasing the support post width to 1.67 times the membrane thickness alleviated the post bending problem. Using impedance and interferometer measurements to observe the effects of aspect ratio on higher order modes, we found that the (1,3) modal frequency approached the (1,1) modal frequency as the aspect ratio of the rectangles increased. In air operation, under continuous wave (CW) excitation at the center frequency, the rectangular cells behaved in the (1,1) mode. In immersion, because of dispersive guided modes, these cells operated in a higher order mode when excited with a CW signal at the center frequency. This contributed to a loss of output pressure; for this reason our rectangular design was unsuitable for CW operation in immersion.

    View details for DOI 10.1109/TUFFC.897

    View details for Web of Science ID 000258912800020

    View details for PubMedID 18986902

  • Carbon nanotubes as photoacoustic molecular imaging agents in living mice NATURE NANOTECHNOLOGY de la Zerda, A., Zavaleta, C., Keren, S., Vaithilingam, S., Bodapati, S., Liu, Z., Levi, J., Smith, B. R., Ma, T., Oralkan, O., Cheng, Z., Chen, X., Dai, H., Khuri-Yakub, B. T., Gambhir, S. S. 2008; 3 (9): 557-562

    Abstract

    Photoacoustic imaging of living subjects offers higher spatial resolution and allows deeper tissues to be imaged compared with most optical imaging techniques. As many diseases do not exhibit a natural photoacoustic contrast, especially in their early stages, it is necessary to administer a photoacoustic contrast agent. A number of contrast agents for photoacoustic imaging have been suggested previously, but most were not shown to target a diseased site in living subjects. Here we show that single-walled carbon nanotubes conjugated with cyclic Arg-Gly-Asp (RGD) peptides can be used as a contrast agent for photoacoustic imaging of tumours. Intravenous administration of these targeted nanotubes to mice bearing tumours showed eight times greater photoacoustic signal in the tumour than mice injected with non-targeted nanotubes. These results were verified ex vivo using Raman microscopy. Photoacoustic imaging of targeted single-walled carbon nanotubes may contribute to non-invasive cancer imaging and monitoring of nanotherapeutics in living subjects.

    View details for DOI 10.1038/nnano.2008.231

    View details for Web of Science ID 000259013100014

    View details for PubMedID 18772918

  • Multifunctional catheters combining intracardiac ultrasound imaging and electrophysiology sensing IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Stephens, D. N., Cannata, J., Liu, R., Zhao, J. Z., Shung, K. K., Nguyen, H., Chia, R., Dentinger, A., Wildes, D., Thomenius, K. E., Mahajan, A., Shivkumar, K., Kim, K., O'Donnell, M., Nikoozadeh, A., Oralkan, O., Khuri-Yakub, P. T., Sahn, D. J. 2008; 55 (7): 1570-1581

    Abstract

    A family of 3 multifunctional intracardiac imaging and electrophysiology (EP) mapping catheters has been in development to help guide diagnostic and therapeutic intracardiac EP procedures. The catheter tip on the first device includes a 7.5 MHz, 64-element, side-looking phased array for high resolution sector scanning. The second device is a forward-looking catheter with a 24-element 14 MHz phased array. Both of these catheters operate on a commercial imaging system with standard software. Multiple EP mapping sensors were mounted as ring electrodes near the arrays for electrocardiographic synchronization of ultrasound images and used for unique integration with EP mapping technologies. To help establish the catheters' ability for integration with EP interventional procedures, tests were performed in vivo in a porcine animal model to demonstrate both useful intracardiac echocardiographic (ICE) visualization and simultaneous 3-D positional information using integrated electroanatomical mapping techniques. The catheters also performed well in high frame rate imaging, color flow imaging, and strain rate imaging of atrial and ventricular structures. The companion paper of this work discusses the catheter design of the side-looking catheter with special attention to acoustic lens design. The third device in development is a 10 MHz forward-looking ring array that is to be mounted at the distal tip of a 9F catheter to permit use of the available catheter lumen for adjunctive therapy tools.

    View details for DOI 10.1109/TUFFC.2008.834

    View details for Web of Science ID 000257386000020

    View details for PubMedID 18986948

  • Fabrication of flexible transducer arrays with through-wafer electrical interconnects based on trench refilling with PDMS JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Zhuang, X., Lin, D., Oralkan, O., Khuri-Yakub, B. T. 2008; 17 (2): 446-452
  • Feasibility of MR-temperature mapping of ultrasonic heating from a CMUT IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wong, S. H., Watkins, R. D., Kupnik, M., Pauly, K. B., Khuri-Yakub, B. T. 2008; 55 (4): 811-818

    Abstract

    In the last decade, high intensity focused ultrasound (HIFU) has gained popularity as a minimally invasive and noninvasive therapeutic tool for treatment of cancers, arrhythmias, and other medical conditions. HIFU therapy is often guided by magnetic resonance imaging (MRI), which provides anatomical images for therapeutic device placement, temperature maps for treatment guidance, and postoperative evaluation of the region of interest. While piezoelectric transducers are dominantly used for MR-guided HIFU, capacitive micromachined ultrasonic transducers (CMUTs) show competitive advantages, such as ease of fabrication, integration with electronics, improved efficiency, and reduction of self-heating. In this paper, we will show our first results of an unfocused CMUT transducer monitored by MR-temperature maps. This 2.51 mm by 2.32 mm, unfocused CMUT heated a HIFU phantom by 14 degrees C in 2.5 min. This temperature rise was successfully monitored by MR thermometry in a 3.0 T General Electric scanner.

    View details for DOI 10.1109/TUFFC.2008.71.5

    View details for Web of Science ID 000254783100007

    View details for PubMedID 18467225

  • Capacitive micromachined ultrasonic transducers (CMUTs) with isolation posts ULTRASONICS Huang, Y., Zhuang, X., Haeggstrom, E. O., Ergun, A. S., Cheng, C., Khuri-Yakub, B. T. 2008; 48 (1): 74-81

    Abstract

    In this paper, an improved design of a capacitive micromachined ultrasonic transducer (CMUT) is presented. The design improvement aims to address the reliability issues of a CMUT and to extend the device operation beyond the contact (collapse) voltage. The major design novelty is the isolation posts in the vacuum cavities of the CMUT cells instead of full-coverage insulation layers in conventional CMUTs. This eliminates the contact voltage drifting due to charging caused by the insulation layer, and enables repeatable CMUT operation in the post-contact regime. Ultrasonic tests of the CMUTs with isolation posts (PostCMUTs) in air (electrical input impedance and capacitance vs. bias voltage) and immersion (transmission and reception) indicate acoustic performance similar to that obtained from conventional CMUTs while no undesired side effects of this new design is observed.

    View details for DOI 10.1016/j.ultras.2007.11.006

    View details for Web of Science ID 000254854000009

    View details for PubMedID 18207212

  • Integration of 2D CMUT arrays with front-end electronics for volumetric ultrasound imaging IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wygant, I. O., Zhuang, X., Yeh, D. T., Oralkan, O., Ergun, A. S., Karaman, M., Khuri-Yakub, B. T. 2008; 55 (2): 327-342

    Abstract

    For three-dimensional (3D) ultrasound imaging, connecting elements of a two-dimensional (2D) transducer array to the imaging system's front-end electronics is a challenge because of the large number of array elements and the small element size. To compactly connect the transducer array with electronics, we flip-chip bond a 2D 16 x 16-element capacitive micromachined ultrasonic transducer (CMUT) array to a custom-designed integrated circuit (IC). Through-wafer interconnects are used to connect the CMUT elements on the top side of the array with flip-chip bond pads on the back side. The IC provides a 25-V pulser and a transimpedance preamplifier to each element of the array. For each of three characterized devices, the element yield is excellent (99 to 100% of the elements are functional). Center frequencies range from 2.6 MHz to 5.1 MHz. For pulse echo operation, the average - 6-dB fractional bandwidth is as high as 125%. Transmit pressures normalized to the face of the transducer are as high as 339 kPa and input-referred receiver noise is typically 1.2 to 2.1 mPa/pHz. The flip-chip bonded devices were used to acquire 3D synthetic aperture images of a wire-target phantom. Combining the transducer array and IC, as shown in this paper, allows for better utilization of large arrays, improves receive sensitivity, and may lead to new imaging techniques that depend on transducer arrays that are closely coupled to IC electronics.

    View details for DOI 10.1109/TUFFC.2008.652

    View details for Web of Science ID 000253358700008

    View details for PubMedID 18334340

  • Investigating Large 2D Arrays for Photoacoustic and Acoustic Imaging using CMUT Technology 2008 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-4 AND APPENDIX Vaithilingam, S., Ma, T., Furukawa, Y., Oralkan, O., Kamaya, A., Torashima, K., Kupnik, M., Wygant, I. O., Zhuang, X., Jeffrey, R. B., Khuri-Yakub, B. T. 2008: 1238-1241
  • Fabricating capacitive micromachined ultrasonic transducers with direct wafer-bonding and locos technology MEMS 2008: 21ST IEEE INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS, TECHNICAL DIGEST Park, K. K., Lee, H. J., Kupnik, M., Oralkan, O., Khuri-Yakub, B. T. 2008: 339-342
  • Capacitive micromachined ultrasonic transducers for chemical detection in nitrogen APPLIED PHYSICS LETTERS Park, K. K., Lee, H. J., Yaralioglu, G. G., Ergun, A. S., Oralkan, O., Kupnik, M., Quate, C. F., Khuri-Yakub, B. T., Braun, T., Ramseyer, J., Lang, H. P., Hegner, M., Gerber, C., Gimzewski, J. K. 2007; 91 (9)

    View details for DOI 10.1063/1.2776348

    View details for Web of Science ID 000249156100148

  • Integration of trench-isolated through-wafer interconnects with 2d capacitive micromachined ultrasonic transducer arrays SENSORS AND ACTUATORS A-PHYSICAL Zhuang, X., Ergun, A. S., Huang, Y., Wygant, I. O., Oralkan, O., Khuri-Yakub, B. T. 2007; 138 (1): 221-229

    Abstract

    This paper presents a method to provide electrical connection to a 2D capacitive micromachined ultrasonic transducer (CMUT) array. The interconnects are processed after the CMUTs are fabricated on the front side of a silicon wafer. Connections to array elements are made from the back side of the substrate via highly conductive silicon pillars that result from a deep reactive ion etching (DRIE) process. Flip-chip bonding is used to integrate the CMUT array with an integrated circuit (IC) that comprises the front-end circuits for the transducer and provides mechanical support for the trench-isolated array elements. Design, fabrication process and characterization results are presented. The advantages when compared to other through-wafer interconnect techniques are discussed.

    View details for DOI 10.1016/j.sna.2007.04.008

    View details for Web of Science ID 000248296900028

    View details for PubMedID 18037982

  • Biocompatible coatings for CMUTs in a harsh, aqueous environment JOURNAL OF MICROMECHANICS AND MICROENGINEERING Zhuang, X., Nikoozadeh, A., Beasley, M. A., Yaralioglu, G. G., Khuri-Yakub, B. T., Pruitt, B. L. 2007; 17 (5): 994-1001
  • Finite element modeling and experimental characterization of crosstalk in 1-D CMUT arrays IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Bayram, B., Kupnik, M., Yaralioglu, C. G., Oralkan, O., Ergun, A. S., Lin, D., Wong, S. H., Khuri-Yakub, B. T. 2007; 54 (2): 418-430

    Abstract

    Crosstalk is the coupling of energy between the elements of an ultrasonic transducer array. This coupling degrades the performance of transducers in applications such as medical imaging and therapeutics. In this paper, we present an experimental demonstration of guided interface waves in capacitive micromachined ultrasonic transducers (CMUTs). We compare the experimental results to finite element calculations using a commercial package (LS-DYNA) for a 1-D CMUT array operating in the conventional and collapsed modes. An element in the middle of the array was excited with a unipolar voltage pulse, and the displacements were measured using a laser interferometer along the center line of the array elements immersed in soybean oil. We repeated the measurements for an identical CMUT array covered with a 4.5-microm polydimethylsiloxane (PDMS) layer. The main crosstalk mechanism is the dispersive guided modes propagating in the fluid-solid interface. Although the transmitter element had a center frequency of 5.8 MHz with a 130% fractional bandwidth in the conventional operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 2.1 MHz, and had a cut-off frequency of 4 MHz. In the collapsed operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 4.0 MHz, and had a cut-off frequency of 10 MHz. Crosstalk level was lower in the collapsed operation (-39 dB) than in the conventional operation (-24.4 dB). The coverage of the PDMS did not significantly affect the crosstalk level, but reduced the phase velocity for both operation modes. Lamb wave modes, A0 and S0, were also observed with crosstalk levels of -40 dB and -65 dB, respectively. We observed excellent agreement between the finite element and the experimental results.

    View details for DOI 10.1109/TUFFC.2007.256

    View details for Web of Science ID 000243920900022

    View details for PubMedID 17328339

  • A co-axial scanning acoustic and. photoacoustic microscope 2007 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1-6 Vaithilingam, S., Ma, T., Furukawa, Y., de la Zerda, A., Oralkan, O., Kamaya, A., Keren, S., Gambhir, S. S., Jeffrey, R. B., Khuri-Yakub, B. T. 2007: 2413-2416
  • Advantages of capacitive micromachined ultrasonics transducers (CMUTs) for high intensity focused ultrasound (HIFU) 2007 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1-6 Wong, S. H., Kupnik, M., Butts-Pauly, K., Khuri-Yakub, B. T. 2007: 1313-1316
  • Feasibility of noncontact intracardiac ultrasound ablation and Imaging catheter for treatment of atrial fibrillation IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Wong, S. H., Scott, G. C., Conolly, S. M., Narayan, G., Liang, D. H. 2006; 53 (12): 2394-2405

    Abstract

    Atrial fibrillation (AF) affects 1% of the population and results in a cost of 2.8 billion dollars from hospitalizations alone. Treatments that electrically isolate portions of the atria are clinically effective in curing AF. However, such minimally invasive catheter treatments face difficulties in mechanically positioning the catheter tip and visualizing the anatomy of the region. We propose a noncontact, intracardiac transducer that can ablate tissue and provide rudimentary imaging to guide therapy. Our design consists of a high-power, 20 mm by 2 mm, 128-element, transducer array placed on the side of 7-French catheter. The transducer will be used in imaging mode to locate the atrial wall; then, by focusing at that location, a lesion can be formed. Imaging of previously formed lesions could potentially guide placement of subsequent lesions. Successive rotations of the catheter will potentially enable a contiguous circular lesion to be created around the pulmonary vein. The challenge of intracardiac-sized transducers is achieving high intensities (300-5000 W/cm2) needed to raise the temperature of the tissue above 43 degrees C. In this paper, we demonstrate the feasibility of an intracardiac-sized transducer for treatment of atrial fibrillation. In simulations and proof-of-concept experiments, we show a 37 degrees C temperature rise in the lesion location and demonstrate the possibility of lesion imaging.

    View details for DOI 10.1109/TUFFC.2006.188

    View details for Web of Science ID 000242390900022

    View details for PubMedID 17186922

  • Comparison of conventional and collapsed region operation of capacitive micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Huang, Y., Haeggstrom, E., Bayram, B., Zhuang, X., Ergun, A. S., Cheng, C., Khuri-Yakub, B. T. 2006; 53 (10): 1918-1933

    Abstract

    We report experimental results from a comparative study on collapsed region and conventional region operation of capacitive micromachined ultrasonic transducers (CMUTs) fabricated with a wafer bonding technique. Using ultrasonic pulse-echo and pitch-catch measurements, we characterized single elements of 1-D CMUT arrays operating in oil. The experimental results from this study agreed with the simulation results: a CMUT operating in the collapsed region produced a higher maximum output pressure than a CMUT operated in the conventional region at 90% of its collapse voltage (3 kPa/V vs. 16.1 kPa/V at 2.3 MHz). While the pulse-echo fractional bandwidth (126%) was higher in the collapsed region operation than in the conventional operation (117%), the pulse-echo amplitude in collapsed region operation was 11 dB higher than in conventional region operation. Furthermore, within the range of tested bias voltages, the output pressure monotonously increased with increased bias during collapsed region operation. It was also found that in the conventional mode, short AC pulses (larger than the collapse voltage) could be applied without collapsing the membranes. Finally, while no significant difference was observed in reflectivity of the CMUT face between the two regions of operation, hysteretic behavior of the devices was identified in the collapsed region operation.

    View details for DOI 10.1109/TUFFC.2006.125

    View details for Web of Science ID 000240860200023

    View details for PubMedID 17036801

  • Experimental measurements of mechanical dissipation associated with dielectric coatings formed using SiO2, Ta2O5 and Al2O3 CLASSICAL AND QUANTUM GRAVITY Crooks, D. R., Cagnoli, G., Fejer, M. M., Harry, G., Hough, J., Khuri-Yakub, B. T., Penn, S., Route, R., Rowan, S., Sneddon, P. H., Wygant, I. O., Yaralioglu, G. G. 2006; 23 (15): 4953-4965
  • Experimental characterization of collapse-mode CMUT operation IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Oralkan, O., Bayram, B., Yaralioglu, G. G., Ergun, A. S., Kupnik, M., Yeh, D. T., Wygant, I. O., Khuri-Yakub, B. T. 2006; 53 (8): 1513-1523

    Abstract

    This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. In collapse-mode operation, the DC bias voltage is first increased beyond the collapse voltage, then reduced without releasing the collapsed membrane. In collapse-mode operation, the center of the membrane is always in contact with the substrate. In the case of a circular membrane, the maximum AC displacement occurs along the ring formed between the center and the edge of the membrane. The experimental characterization presented in this paper includes impedance measurements in air, pulse-echo experiments in immersion, and one-way optical displacement measurements in immersion for both conventional and collapse-mode operations. A 205-microm x 205-microm 2-D CMUT array element composed of circular silicon nitride membranes is used in the experiments. In pulse-echo experiments, a custom integrated circuit (IC) comprising a pulse driver, a transmit/receive switch, a wideband low-noise preamplifier, and a line driver is used. By reducing the parasitic capacitance, the use of a custom IC enables pulse-echo measurements at high frequencies with a very small transducer. By comparing frequency response and efficiency of the transducer in conventional and collapse regimes, experimental results show that a collapsed membrane can be used to generate and detect ultrasound more efficiently than a membrane operated in the conventional mode. Furthermore, the center frequency of the collapsed membrane can be changed by varying the applied DC voltage. In this study, the center frequency of a collapsed transducer in immersion is shown to vary from 20 MHz to 28 MHz with applied DC bias; the same transducer operates at 10 MHz in the conventional mode. In conventional mode, the maximum peak-to-peak pressure is 370 kPa on the transducer surface for a 40-ns, 25-V unipolar pulse excitation. In collapse mode, a 25-ns, 25-V unipolar pulse generates 590 kPa pressure at the surface of the transducer.

    View details for Web of Science ID 000239405700015

    View details for PubMedID 16921904

  • 3-D ultrasound imaging using a forward-looking CMUT ring array for intravascular/intracardiac applications IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Yeh, D. T., Oralkan, O., Wygant, I. O., O'Donnell, M., Khuri-Yakub, B. T. 2006; 53 (6): 1202-1211

    Abstract

    Forward-viewing ring arrays can enable new applications in intravascular and intracardiac ultrasound. This work presents compelling, full-synthetic, phased-array volumetric images from a forward-viewing capacitive micromachined ultrasonic transducer (CMUT) ring array wire bonded to a custom integrated circuit front end. The CMUT ring array has a diameter of 2 mm and 64 elements each 100 microm x 100 microm in size. In conventional mode, echo signals received from a plane reflector at 5 mm had 70% fractional bandwidth around a center frequency of 8.3 MHz. In collapse mode, 69% fractional bandwidth is measured around 19 MHz. Measured signal-to-noise ratio (SNR) of the echo averaged 16 times was 29 dB for conventional operation and 35 dB for collapse mode. B-scans were generated of a target consisting of steel wires 0.3 mm in diameter to determine resolution performance. The 6 dB axial and lateral resolutions for the B-scan of the wire target are 189 microm and 0.112 radians for 8 MHz, and 78 microm and 0.051 radians for 19 MHz. A reduced firing set suitable for real-time, intravascular applications was generated and shown to produce acceptable images. Rendered three-dimensional (3-D) images of a Palmaz-Schatz stent also are shown, demonstrating that the imaging quality is sufficient for practical applications.

    View details for Web of Science ID 000238493000013

    View details for PubMedID 16846153

  • Adaptive pulse repetition frequency technique for an ultrasonic transit-time gas flowmeter for hot pulsating gases Sensors Journal, IEEE Khuri-Yakub, B., T., Kupnik, M., Schroder, A., O'Leary, P., Benes, E., Groeschl, M. 2006; 6 (4): 906-915
  • Tomographic Photoacoustic Imaging Using Capacitive Micromachined Ultrasonic Transducer (CMUT) Technology 2006 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-5, PROCEEDINGS Vaithilingam, S., Wygant, I. O., Sifferman, S., Zhuang, X., Furukawa, Y., Oralkan, O., Keren, S., Gambhir, S. S., Khuri-Yakub, B. T. 2006: 397-400
  • Volumetric Imaging Using Fan-Beam Scanning with Reduced Redundancy 2D Arrays 2006 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-5, PROCEEDINGS Wygant, I., Karaman, M., Oralkan, O., Khuri-Yakub, B. T. 2006: 2190-2193
  • Interconnection and packaging for 2D capacitive micromachined ultrasonic transducer arrays based on through-wafer trench isolation MEMS 2006: 19TH IEEE INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS, TECHNICAL DIGEST Zhuang, X. F., Ergun, A. S., Oralkan, O., Wygant, I. O., Khuri-Yakub, B. T. 2006: 270-273
  • CAPACITIVE MICROMACHINED ULTRASONIC TRANSDUCERS FOR HIGH INTENSITY FOCUSED ABLATION OF UPPER ABDOMINAL TUMORS 2006 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-5, PROCEEDINGS Wong, S. H., Ergun, A. S., Yaralioglu, G. G., Kupnik, M., Zhuang, X., Oralkan, O., Butts-Pauly, K., Khuri-Yakub, B. T. 2006: 841-844
  • Capacitive micromachined ultrasonic transducers: Fabrication technology IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Ergun, A. S., Huang, Y. L., Zhuang, X. F., Oralkan, O., Yaralioglu, G. G., Khuri-Yakub, B. T. 2005; 52 (12): 2242-2258

    Abstract

    Capacitive micromachined ultrasonic transducer (cMUT) technology is a prime candidate for next generation imaging systems. Medical and underwater imaging and the nondestructive evaluation (NDE) societies have expressed growing interest in cMUTs over the years. Capacitive micromachined ultrasonic transducer technology is expected to make a strong impact on imaging technologies, especially volumetric imaging, and to appear in commercial products in the near future. This paper focuses on fabrication technologies for cMUTs and reviews and compares variations in the production processes. We have developed two main approaches to the fabrication of cMUTs: the sacrificial release process and the recently introduced wafer-bonding method. This paper gives a thorough review of the sacrificial release processes, and it describes the new wafer-bonding method in detail. Process variations are compared qualitatively and quantitatively whenever possible. Through these comparisons, it was concluded that wafer-bonded cMUT technology was superior in terms of process control, yield, and uniformity. Because the number of steps and consequent process time were reduced (from six-mask process to four-mask process), turn-around time was improved significantly.

    View details for Web of Science ID 000234398700009

    View details for PubMedID 16463490

  • Introduction to the special issue on micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Khuri-Yakub, B. T. 2005; 52 (12): 2162-2162
  • Dynamic analysis of capacitive micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Bayram, B., Yaralioglu, G. G., Kupnik, M., Ergun, A. S., Oralkan, O., Nikoozadeh, A., Khuri-Yakub, B. T. 2005; 52 (12): 2270-2275

    Abstract

    Electrostatic transducers are usually operated under a DC bias below their collapse voltage. The same scheme has been adopted for capacitive micromachined ultrasonic transducers (cMUTs). DC bias deflects the cMUT membranes toward the substrate, so that their centers are free to move during both receive and transmit operations. In this paper, we present time-domain, finite element calculations for cMUTs using LS-DYNA, a commercially available finite element package. In addition to this DC bias mode, other new cMUT operations (collapse and collapse-snapback) have recently been demonstrated. Because cMUT membranes make contact with the substrate in these new operations, modeling of these cMUTs should include contact analysis. Our model was a cMUT transducer consisting of many hexagonal membranes; because it was symmetrical, we modeled only one-sixth of a hexagonal cell loaded with a fluid medium. The finite element results for both conventional and collapse modes were compared to measurements made by an optical interferometer; a good match was observed. Thus, the model is useful for designing cMUTs that operate in regimes where membranes make contact with the substrate.

    View details for Web of Science ID 000234398700011

    View details for PubMedID 16463492

  • Finite-element analysis of capacitive micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Yaralioglu, C. G., Ergun, A. S., Khuri-Yakub, B. T. 2005; 52 (12): 2185-2198

    Abstract

    In this paper, we present the results of finite-element analysis performed to investigate capacitive micromachined ultrasonic transducers (CMUTs). Both three-dimensional (3-D) and 2-D models were developed using a commercially available finite-element modeling (FEM) software. Depending on the dimensionality of the model, the membranes were constructed using plane or shell elements. The electrostatic gap was modeled using many parallel plate transducers. An axisymmetric model for a single membrane was built; the electrical input impedance of the device then was calculated in vacuum to investigate series and parallel resonant frequencies, where the input impedance has a minimum and a maximum, respectively. A method for decomposing the membrane capacitance into parasitic and active parts was demonstrated, and it was shown that the parallel resonant frequency shifted down with increased biased voltage. Calculations then were performed for immersion transducers. Acoustic wave propagation was simulated in the immersion medium, using appropriate elements in a 3-D model. Absorbing boundaries were implemented to avoid the reflections at the end of the medium mesh. One row of an array element, modeled with appropriate boundary conditions, was used to calculate the output pressure. The results were compared with a simpler model: a single membrane in immersion, with symmetry boundary conditions on the sidewalls that cause the calculations to reflect the properties of an infinitely large array. A 2-D model then was developed to demonstrate the effect of membrane dimensions on the output pressure and bandwidth. Our calculations revealed that the small signal transmit pressure was inversely proportional to the square root of gap height. We also compared FEM results with analytical and experimental results.

    View details for Web of Science ID 000234398700004

    View details for PubMedID 16463485

  • Femtoliter to picoliter droplet generation for organic polymer deposition using single reservoir ejector arrays IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Demirci, U., Yaralioglu, G. G., Haeggstrom, E., Khuri-Yakub, B. T. 2005; 18 (4): 709-715
  • Microfluidic sonicator for real-time disruption of eukaryotic cells and bacterial spores for DNA analysis ULTRASOUND IN MEDICINE AND BIOLOGY Marentis, T. C., Kusler, B., Yaralioglu, G. G., Liu, S. J., Haeggstrom, E. O., Khuri-Yakub, B. T. 2005; 31 (9): 1265-1277

    Abstract

    Biologic agent screening is a three-step process: lysis of host cell membranes or walls to release their DNA, polymerase chain reaction to amplify the genetic material and screening for distinguishing genetic signatures. Macrofluidic devices commonly use sonication as a lysis method. Here, we present a piezoelectric microfluidic minisonicator and test its performance. Eukaryotic human leukemia HL-60 cells and Bacillus subtilis bacterial spores were lysed as they passed through a microfluidic channel at 50 microL/min and 5 microL/min, respectively, in the absence of any chemical denaturants, enzymes or microparticles. We used fluorescence-activated cell sorting and hematocytometry to measure 80% lysis of HL-60 cells after 3 s of sonication. Real-time polymerase chain reaction indicated 50% lysis of B. subtilis spores with 30 s of sonication. Advantages of the minisonicator over macrofluidic implementations include a small sample volume (2.5 microL), reduced energy consumption and compatibility with other microfluidic blocks. These features make this device an attractive option for "lab-on-a-chip" and portable applications.

    View details for DOI 10.1016/j.ultrasmedbio.2005.05.005

    View details for Web of Science ID 000232083800013

    View details for PubMedID 16176793

  • 3-D ultrasound imaging using forward viewing CMUT ring arrays for intravascular and intracardiac applications 2005 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-4 Yeh, D. T., Oralkan, O., Wygant, I. O., O'Donnell, M., Khuri-Yakub, B. T. 2005: 783-786
  • Coherent array imaging using phased subarmys. Part II: Simulations and experimental results IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Johnson, J. A., Oralkan, O., Ergun, S., Demirci, U., Karaman, M., Khuri-Yakub, B. T. 2005; 52 (1): 51-64

    Abstract

    The basic principles and theory of phased subarray (PSA) imaging imaging provides the flexibility of reducing the number of front-end hardware channels between that of classical synthetic aperture (CSA) imaging--which uses only one element per firing event--and full-phased array (FPA) imaging-which uses all elements for each firing. The performance of PSA generally ranges between that obtained by CSA and FPA using the same array, and depends on the amount of hardware complexity reduction. For the work described in this paper, we performed FPA, CSA, and PSA imaging of a resolution phantom using both simulated and experimental data from a 3-MHz, 3.2-cm, 128-element capacitive micromachined ultrasound transducer (CMUT) array. The simulated system point responses in the spatial and frequency domains are presented as a means of studying the effects of signal bandwidth, reconstruction filter size, and subsampling rate on the PSA system performance. The PSA and FPA sector-scanned images were reconstructed using the wideband experimental data with 80% fractional bandwidth, with seven 32-element subarrays used for PSA imaging. The measurements on the experimental sector images indicate that, at the transmit focal zone, the PSA method provides a 10% improvement in the 6-dB lateral resolution, and the axial point resolution of PSA imaging is identical to that of FPA imaging. The signal-to-noise ratio (SNR) of PSA image was 58.3 dB, 4.9 dB below that of the FPA image, and the contrast-to-noise ratio (CNR) is reduced by 10%. The simulated and experimental test results presented in this paper validate theoretical expectations and illustrate the flexibility of PSA imaging as a way to exchange SNR and frame rate for simplified front-end hardware.

    View details for Web of Science ID 000226812800007

    View details for PubMedID 15742562

  • Capacitive micromachined ultrasonic transducers (CMUTs) with piston-shaped membranes 2005 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-4 Huang, Y. L., Heaggstrom, E. O., Zhuang, X. F., Ergun, A. S., Khuri-Yakub, B. T. 2005: 589-592
  • Coherent-array imaging using phased subarmys. Part I: Basic principles IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Johnson, J. A., Karaman, M., Khuri-Yakub, B. T. 2005; 52 (1): 37-50

    Abstract

    The front-end hardware complexity of a coherent array imaging system scales with the number of active array elements that are simultaneously used for transmission or reception of signals. Different imaging methods use different numbers of active channels and data collection strategies. Conventional full phased array (FPA) imaging produces the best image quality using all elements for both transmission and reception, and it has high front-end hardware complexity. In contrast, classical synthetic aperture (CSA) imaging only transmits on and receives from a single element at a time, minimizing the hardware complexity but achieving poor image quality. We propose a new coherent array imaging method--phased subarray (PSA) imaging--that performs partial transmit and receive beam-forming using a subset of adjacent elements at each firing step. This method reduces the number of active channels to the number of subarray elements; these channels are multiplexed across the full array and a reduced number of beams are acquired from each subarray. The low-resolution subarray images are laterally upsampled, interpolated, weighted, and coherently summed to form the final high-resolution PSA image. The PSA imaging reduces the complexity of the front-end hardware while achieving image quality approaching that of FPA imaging.

    View details for Web of Science ID 000226812800006

    View details for PubMedID 15742561

  • Integrated ultrasound imaging systems based on capacitive micromachined ultrasonic transducer arrays 2005 IEEE SENSORS, VOLS 1 AND 2 Wygant, I. O., Yeh, D. T., Zhuang, X. F., Vaithilingam, S., Nikoozadeh, A., Oralkan, O., Ergun, A. S., Yaralioglu, G. G., Khuri-Yakub, B. T. 2005: 704-707
  • Capacitive micromachined ultrasonic transducer design for high power transmission Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Bayram, B., Oralkan, O., Ergun, A., S., Haeggstrom, E., Yaralioglu, G., G., Khuri-Yakub, B., T. 2005; 52 (2): 326-339
  • High-resolution imaging with high-frequency 1-D linear CMUT arrays 2005 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-4 Yeh, D. T., Oralkan, O., Wygant, I. O., Ergun, A. S., Wong, J. H., Khuri-Yakub, B. T. 2005: 665-668
  • Acoustically actuated flextensional SixNy and single-crystal silicon 2-D micromachined ejector arrays IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Demirci, U., Yaralioglu, G. G., Haeggstrom, E., Percin, G., Ergun, S., Khuri-Yakub, B. T. 2004; 17 (4): 517-524
  • Wideband micromachined capacitive microphones with radio frequency detection JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Hansen, S. T., Ergun, A. S., Liou, W., Auld, B. A., Khuri-Yakub, B. T. 2004; 116 (2): 828-842

    View details for DOI 10.1121/1.1771617

    View details for Web of Science ID 000223281800019

  • Forward-viewing CMUT arrays for medical Imaging IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Demirci, U., Ergun, A. S., Oralkan, O., Karaman, M., Khuri-Yakub, B. T. 2004; 51 (7): 887-895

    Abstract

    This paper reports the design and testing of forward-viewing annular arrays fabricated using capacitive micromachined ultrasonic transducer (CMUT) technology. Recent research studies have shown that CMUTs have broad frequency bandwidth and high-transduction efficiency. One- and two-dimensional CMUT arrays of various sizes already have been fabricated, and their viability for medical imaging applications has been demonstrated. We fabricated 64-element, forward-viewing annular arrays using the standard CMUT fabrication process and carried out experiments to measure the operating frequency, bandwidth, and transmit/receive efficiency of the array elements. The annular array elements, designed for imaging applications in the 20 MHz range, had a resonance frequency of 13.5 MHz in air. The immersion pulse-echo data collected from a plane reflector showed that the devices operate in the 5-26 MHz range with a fractional bandwidth of 135%. The output pressure at the surface of the transducer was measured to be 24 kPa/V. These values translate into a dynamic range of 131.5 dB for 1-V excitation in 1-Hz bandwidth with a commercial low noise receiving circuitry. The designed, forward-viewing annular CMUT array is suitable for mounting on the front surface of a cylindrical catheter probe and can provide Doppler information for measurement of blood flow and guiding information for navigation through blood vessels in intravascular ultrasound imaging.

    View details for Web of Science ID 000222678000018

    View details for PubMedID 15301009

  • Ultrasonic mixing in microfluidic channels using integrated transducers ANALYTICAL CHEMISTRY Yaralioglu, G. G., Wygant, I. O., Marentis, T. C., Khuri-Yakub, B. T. 2004; 76 (13): 3694-3698

    Abstract

    This paper presents a microfluidic mixer that uses acoustic stirring created by ultrasonic waves. The ultrasound is introduced into the channel by integrated piezoelectric transducers. The transducers are made of a zinc oxide thin film, which is deposited on the bottom surface of a quartz substrate. The poly(dimethylsiloxane) channel is aligned to the transducers on the top surface of the substrate. The transducers are designed for operation around 450 MHz. The main mechanism of the mixing is the acoustic stirring of the fluid perpendicular to the flow direction. The radiation pressure that is generated by the transducer causes the stirring inside the microfluidic channel. The performance of the mixer is characterized by mixing phenolphthalein solution and sodium hydroxide dissolved in ethyl alcohol. Flow rates on the order of 1-100 microL/min are used. The transducers are driven by 1.2 V(rms) sinusoidal voltages at 450 MHz.

    View details for DOI 10.1021/ac035220k

    View details for Web of Science ID 000222418300038

    View details for PubMedID 15228343

  • Optimized membrane configuration improves CMUT performance 2004 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-3 Huang, Y. L., Haeggstrom, E. O., Zhuang, X. F., Ergun, A. S., Khuri-Yakub, B. T. 2004: 505-508
  • Capacitive micromachined ultrasonic transducers (CMUTS) with isolation posts 2004 IEEE ULTRASONICS SYMPOSIUM, VOLS 1-3 Huang, Y. L., Haeggstrom, E. O., Zhuang, X. F., Ergun, A. S., Khuri-Yakub, B. T. 2004: 2223-2226
  • Volumetric ultrasound Imaging using 2-D CMUT arrays IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Oralkan, O., Ergun, A. S., Cheng, C. H., Johnson, J. A., Karaman, M., Lee, T. H., Khuri-Yakub, B. T. 2003; 50 (11): 1581-1594

    Abstract

    Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as a candidate to overcome the difficulties in the realization of 2-D arrays for real-time 3-D imaging. In this paper, we present the first volumetric images obtained using a 2-D CMUT array. We have fabricated a 128 x 128-element 2-D CMUT array with through-wafer via interconnects and a 420-microm element pitch. As an experimental prototype, a 32 x 64-element portion of the 128 x 128-element array was diced and flip-chip bonded onto a glass fanout chip. This chip provides individual leads from a central 16 x 16-element portion of the array to surrounding bondpads. An 8 x 16-element portion of the array was used in the experiments along with a 128-channel data acquisition system. For imaging phantoms, we used a 2.37-mm diameter steel sphere located 10 mm from the array center and two 12-mm-thick Plexiglas plates located 20 mm and 60 mm from the array. A 4 x 4 group of elements in the middle of the 8 x 16-element array was used in transmit, and the remaining elements were used to receive the echo signals. The echo signal obtained from the spherical target presented a frequency spectrum centered at 4.37 MHz with a 100% fractional bandwidth, whereas the frequency spectrum for the echo signal from the parallel plate phantom was centered at 3.44 MHz with a 91% fractional bandwidth. The images were reconstructed by using RF beamforming and synthetic phased array approaches and visualized by surface rendering and multiplanar slicing techniques. The image of the spherical target has been used to approximate the point spread function of the system and is compared with theoretical expectations. This study experimentally demonstrates that 2-D CMUT arrays can be fabricated with high yield using silicon IC-fabrication processes, individual electrical connections can be provided using through-wafer vias, and flip-chip bonding can be used to integrate these dense 2-D arrays with electronic circuits for practical 3-D imaging applications.

    View details for Web of Science ID 000187162500021

    View details for PubMedID 14682642

  • Capacitive micromachined ultrasonic lamb wave transducers using rectangular membranes IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Badi, M. H., Yaralioglu, G. G., Ergun, A. S., Hansen, S. T., Wong, E. J., Khuri-Yakub, B. T. 2003; 50 (9): 1191-1203

    Abstract

    This paper details the theory, fabrication, and characterization of a new Lamb wave device. Built using capacitive micromachined ultrasonic transducers (CMUTs), the structure described uses rectangular membranes to excite and receive Lamb waves on a silicon substrate. An equivalent circuit model for the transducer is proposed that produces results, which match well with those observed by experiment. During the derivation of this model, emphasis is placed on the resistance presented to the transducer membranes by the Lamb wave modes. Finite element analysis performed in this effort shows that the dominant propagating mode in the device is the lowest order antisymmetric flexural wave (A0). Furthermore, most of the power that couples into the Lamb wave is due to energy in the vibrating membrane that is transferred to the substrate through the supporting posts of the device. The manufacturing process of the structure, which relies solely on fundamental IC-fabrication techniques, is also discussed. The resulting device has an 18-microm-thick substrate that is almost entirely made up of crystalline silicon and operates at a frequency of 2.1 MHz. The characterization of this device includes S-parameter and laser vibrometer measurements as well as delay-line transmission data. The insertion loss, as determined by both S-parameter and delay-line transmission measurements, is 20 dB at 2.1 MHz. When configured as a delay-line oscillator, the device functions well as a sensor with sensitivity to changes in the mass loading of its substrate.

    View details for Web of Science ID 000185519100011

    View details for PubMedID 14561035

  • A new regime for operating capacitive micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Bayram, B., Haeggstrom, E., Yaralioglu, G. G., Khuri-Yakub, B. T. 2003; 50 (9): 1184-1190

    Abstract

    We report on a new operation regime for capacitive micromachined ultrasonic transducers (cMUTs). Traditionally, cMUTs are operated at a bias voltage lower than the collapse voltage of their membranes. In the new proposed operation regime, first the cMUT is biased past the collapse voltage. Second, the bias voltage applied to the collapsed membrane is reduced without releasing the membrane. Third, the cMUT is excited with an ac signal at the bias point, keeping the total applied voltage between the collapse and snapback voltages. In this operation regime, the center of the membrane is always in contact with the substrate. Our finite element methods (FEM) calculations reveal that a cMUT operating in this new regime, between collapse and snapback voltages, possesses a coupling efficiency (k(T)2) higher than a cMUT operating in the conventional regime below its collapse voltage. This paper compares the simulation results of the coupling efficiencies of cMUTs operating in conventional and new operation regimes.

    View details for Web of Science ID 000185519100010

    View details for PubMedID 14561034

  • Photoresist deposition without spinning IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Percin, G., Khuri-Yakub, B. T. 2003; 16 (3): 452-459
  • Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Huang, Y. L., Ergun, A. S., Haeggstrom, E., Badi, M. H., Khuri-Yakub, B. T. 2003; 12 (2): 128-137
  • Capacitive micromachined ultrasonic transducers: Theory and technology JOURNAL OF AEROSPACE ENGINEERING Ergun, A. S., Yaralioglu, G. G., Khuri-Yakub, B. T. 2003; 16 (2): 76-84
  • Calculation and measurement of electromechanical coupling coefficient of capacitive micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Yaralioglu, G. G., Ergun, A. S., Bayram, B., Haeggstrom, E., Khuri-Yakub, B. T. 2003; 50 (4): 449-456

    Abstract

    The electromechanical coupling coefficient is an important figure of merit of ultrasonic transducers. The transducer bandwidth is determined by the electromechanical coupling efficiency. The coupling coefficient is, by definition, the ratio of delivered mechanical energy to the stored total energy in the transducer. In this paper, we present the calculation and measurement of coupling coefficient for capacitive micromachined ultrasonic transducers (CMUTs). The finite element method (FEM) is used for our calculations, and the FEM results are compared with the analytical results obtained with parallel plate approximation. The effect of series and parallel capacitances in the CMUT also is investigated. The FEM calculations of the CMUT indicate that the electromechanical coupling coefficient is independent of any series capacitance that may exist in the structure. The series capacitance, however, alters the collapse voltage of the membrane. The parallel parasitic capacitance that may exist in a CMUT or is external to the transducer reduces the coupling coefficient at a given bias voltage. At the collapse, regardless of the parasitics, the coupling coefficient reaches unity. Our experimental measurements confirm a coupling coefficient of 0.85 before collapse, and measurements are in agreement with theory.

    View details for Web of Science ID 000182674700012

    View details for PubMedID 12744401

  • Piezoelectric droplet ejector for ink-jet printing of fluids and solid particles REVIEW OF SCIENTIFIC INSTRUMENTS Percin, G., Khuri-Yakub, B. T. 2003; 74 (2): 1120-1127

    View details for DOI 10.1063/1.1532839

    View details for Web of Science ID 000180579500030

  • Collapsed regime operation of capacitive micromachined ultrasonic transducers based on wafer-bonding technique 2003 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Huang, Y., Haeggstrom, E., Bayram, B., Zhuang, X., Ergun, A. S., Cheng, C. H., Khuri-Yakub, B. T. 2003: 1161-1164
  • Capacitive micromachined ultrasonic transducers for robotic sensing applications IROS 2003: PROCEEDINGS OF THE 2003 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Yaralioglu, G. G., Ergun, A. S., Huang, Y., Khuri-Yakub, B. T. 2003: 2347-2352
  • New fabrication process for capacitive micromachined ultrasonic transducers MEMS-03: IEEE THE SIXTEENTH ANNUAL INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS Huang, Y., Ergun, A. S., Haeggstrom, E., Khuri-Yakub, B. T. 2003: 522-525
  • An implementation of a microfluidic mixer and switch using micromachined acoustic transducers MEMS-03: IEEE THE SIXTEENTH ANNUAL INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS Jagannathan, H., Yaralioglu, G. G., Ergun, A. S., Khuri-Yakub, B. T. 2003: 104-107
  • Acoustic heating and thermometry in microfluidic channels MEMS-03: IEEE THE SIXTEENTH ANNUAL INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS Jagannathan, H., Yaralioglu, G. G., Ergun, A. S., Khuri-Yakub, B. T. 2003: 474-477
  • Micromachined droplet ejector arrays REVIEW OF SCIENTIFIC INSTRUMENTS Percin, G., Yaralioglu, G. G., Khuri-Yakub, B. T. 2002; 73 (12): 4385-4389

    View details for DOI 10.1063/1.1517145

    View details for Web of Science ID 000179393200042

  • Capacitive micromachined ultrasonic transducers: Next-generation arrays for acoustic imaging? IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Oralkan, O., Ergun, A. S., Johnson, J. A., Karaman, M., Demirci, U., Kaviani, K., Lee, T. H., Khuri-Yakub, B. T. 2002; 49 (11): 1596-1610

    Abstract

    Piezoelectric materials have dominated the ultrasonic transducer technology. Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative technology offering advantages such as wide bandwidth, ease of fabricating large arrays, and potential for integration with electronics. The aim of this paper is to demonstrate the viability of CMUTs for ultrasound imaging. We present the first pulse-echo phased array B-scan sector images using a 128-element, one-dimensional (1-D) linear CMUT array. We fabricated 64- and 128-element 1-D CMUT arrays with 100% yield and uniform element response across the arrays. These arrays have been operated in immersion with no failure or degradation in performance over the time. For imaging experiments, we built a resolution test phantom roughly mimicking the attenuation properties of soft tissue. We used a PC-based experimental system, including custom-designed electronic circuits to acquire the complete set of 128 x 128 RF A-scans from all transmit-receive element combinations. We obtained the pulse-echo frequency response by analyzing the echo signals from wire targets. These echo signals presented an 80% fractional bandwidth around 3 MHz, including the effect of attenuation in the propagating medium. We reconstructed the B-scan images with a sector angle of 90 degrees and an image depth of 210 mm through offline processing by using RF beamforming and synthetic phased array approaches. The measured 6-dB lateral and axial resolutions at 135 mm depth were 0.0144 radians and 0.3 mm, respectively. The electronic noise floor of the image was more than 50 dB below the maximum mainlobe magnitude. We also performed preliminary investigations on the effects of crosstalk among array elements on the image quality. In the near field, some artifacts were observable extending out from the array to a depth of 2 cm. A tail also was observed in the point spread function (PSF) in the axial direction, indicating the existence of crosstalk. The relative amplitude of this tail with respect to the mainlobe was less than -20 dB.

    View details for Web of Science ID 000179224100016

    View details for PubMedID 12484483

  • Piezoelectrically actuated flextensional micromachined ultrasound droplet ejectors IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Percin, G., Khuri-Yakub, B. T. 2002; 49 (6): 756-766

    Abstract

    This paper reports a variation on the design of the flextensional transducer for use in ejecting liquids. The transducer is constructed by depositing a piezoelectric thin film to a thin, edge-clamped, circular annular plate. By placing a fluid behind one face of a vibrating compound plate that has an orifice at its center, we achieve continuous or drop-on-demand ejection of the fluid. We present results of ejection of water and isopropanol. The ejector is harmless to sensitive fluids and can be used to eject fuels as well as chemical and biological samples. Micromachined two-dimensional array piezoelectrically actuated flextensional droplet ejectors were realized using planar silicon micromachining techniques. Typical resonant frequency of the micromachined device ranges from 400 kHz to 4.5 MHz. The ejection of water thru a 5-microm diameter orifice at 3.5 MHz was demonstrated by using the developed micromachined two-dimensional array ejectors.

    View details for Web of Science ID 000176055500008

    View details for PubMedID 12075968

  • Piezoelectrically actuated flextensional micromachined ultrasound transducers - I: Theory IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Percin, G., Khuri-Yakub, B. T. 2002; 49 (5): 573-584

    Abstract

    This series of two papers considers piezoelectrically actuated flextensional micromachined ultrasound transducers (PAFMUTs) and consists of theory, fabrication, and experimental parts. The theory presented in this paper is developed for an ultrasound transducer application presented in the second part. In the absence of analytical expressions for the equivalent circuit parameters of a flextensional transducer, it is difficult to calculate its optimal parameters and dimensions and difficult to choose suitable materials. The influence of coupling between flexural and extensional deformation and that of coupling between the structure and the acoustic volume on the dynamic response of piezoelectrically actuated flextensional transducer are analyzed using two analytical methods: classical thin (Kirchhoff) plate theory and Mindlin plate theory. Classical thin plate theory and Mindlin plate theory are applied to derive two-dimensional plate equations for the transducer and to calculate the coupled electromechanical field variables such as mechanical displacement and electrical input impedance. In these methods, the variations across the thickness direction vanish by using the bending moments per unit length or stress resultants. Thus, two-dimensional plate equations for a step-wise laminated circular plate are obtained as well as two different solutions to the corresponding systems. An equivalent circuit of the transducer is also obtained from these solutions.

    View details for Web of Science ID 000175662600005

    View details for PubMedID 12046933

  • Micromachined droplet ejector arrays for controlled ink-jet printing and deposition REVIEW OF SCIENTIFIC INSTRUMENTS Percin, G., Khuri-Yakub, B. T. 2002; 73 (5): 2193-2196

    View details for DOI 10.1063/1.1468684

    View details for Web of Science ID 000175194200035

  • Piezoelectrically actuated flextensional micromachined ultrasound transducers - II: Fabrication and experiments IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Percin, G., Khuri-Yakub, B. T. 2002; 49 (5): 585-595

    Abstract

    This paper presents novel micromachined two-dimensional array piezoelectrically actuated flextensional transducers that can be used to generate sound in air or water. Micromachining techniques to fabricate these devices are also presented. Individual unimorph array elements consist of a thin piezoelectric annular disk and a thin, fully clamped, circular plate. We manufacture the transducer in two-dimensional arrays using planar silicon micromachining and demonstrate ultrasound transmission in air at 2.85 MHz with 0.15 microm/V peak displacement. The devices have a range of operating resonance frequencies starting from 450 kHz to 4.5 MHz. Such an array could be combined with on-board driving and addressing circuitry for different applications.

    View details for Web of Science ID 000175662600006

    View details for PubMedID 12046934

  • Finite element analysis of underwater capacitor micromachined ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Roh, Y., Khuri-Yakub, B. T. 2002; 49 (3): 293-298

    Abstract

    A simple electro-mechanical equivalent circuit model is used to predict the behavior of capacitive micromachined ultrasonic transducers (cMUT). Most often, cMUTs are made in silicon and glass plates that are in the 0.5 mm to 1 mm range in thickness. The equivalent circuit model of the cMUT lacks important features such as coupling to the substrate and the ability to predict cross-talk between elements of an array of transducers. To overcome these deficiencies, a flnite element model of the cMUT is constructed using the commercial code ANSYS. Calculation results of the complex load impedance seen by single capacitor cells are presented, then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Cross-talk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the cross-talk level, the effect of structural variations of the substrate are investigated, which includes a change of its thickness and etched trenches or polymer walls between array elements.

    View details for Web of Science ID 000174440200002

    View details for PubMedID 12322877

  • Piezoelectrically actuated flextensional micromachined ultrasonic transducers Ultrasonics Percin, G., Khuri-Yakub, B., T. 2002; 40: 441-448
  • Lamb wave devices based on Capacitive Micromachined Ultrasonic Transducers 2002 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Badi, M. H., Yaralioglu, G. G., Ergun, A. S., Hansen, S. T., Khuri-Yakub, B. T. 2002: 1031-1034
  • Electrical through-wafer interconnects with sub-picofarad parasitic capacitance MEMS: 2001 MICROELECTROMECHANICAL SYSTEMS CONFERENCE Cheng, C. H., Ergun, A. S., Khuri-Yakub, B. T. 2002: 18-21
  • Volumetric imaging using 2D capacitive Micromachined Ultrasonic Transducer Arrays (CMUTs): Initial results 2002 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Oralkan, O., Ergun, A. S., Cheng, C. H., Johnson, J. A., Karaman, M., Lee, T. H., Khuri-Yakub, B. T. 2002: 1083-1086
  • Broadband capacitive micromachined ultrasonic transducers ranging from 10 kHz to 60 mHz for imaging arrays and more 2002 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Ergun, A. S., Huang, Y., Cheng, C. H., Oralkan, O., Johnson, J., Jagannathan, H., Demirci, U., Yaralioglu, G. G., Karaman, M., Khuri-Yakub, B. T. 2002: 1039-1043
  • Underwater acoustic imaging using capacitive micromachined ultrasonic transducer arrays OCEANS 2002 MTS/IEEE CONFERENCE & EXHIBITION, VOLS 1-4, CONFERENCE PROCEEDINGS Oralkan, O., Ergun, A. S., Cheng, C. H., Johnson, J. A., Karaman, M., Khuri-Yakub, B. T. 2002: 2354-2360
  • Medical imaging using capacitive micromachined ultrasonic transducerarrays Ultrasonics Johnson, J., A., Oralkan, O., Demirci, U., Ergun, S., Karaman, M., Khuri-Yakub, B., T. 2002; 40: 471-476
  • Medical imaging using capacitive micromachined ultrasonic transducerarrays Ultrasonics Johnson, J., A., Oralkan, O., Demirci, U., Ergun, S., Karaman, M., Khuri-Yakub, B., T. 2002; 40: 471-476
  • Characterization of one-dimensional capacitive micromachined ultrasonic immersion transducer arrays IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Jin, X. C., Oralkan, O., Degertekin, F. L., Khuri-Yakub, B. T. 2001; 48 (3): 750-760

    Abstract

    In this paper, we report on the characterization of 1-D arrays of capacitive micromachined ultrasonic transducers (cMUT). A 275- x 5600-micron 1-D CMUT array element is experimentally characterized, and the results are found to be in agreement with theoretical predictions. As a receiver, the transducer has a 0.28-fm/square root of Hz displacement sensitivity, and, as a transmitter, it produces 5 kPa/V of output pressure at the transducer surface at 3 MHz with a DC bias of 35 V. The transducer has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging. The radiation pattern of isolated single elements, as well as those of array elements are measured, and two major sources of acoustical cross talk are identified. A weakly dispersive non-leaky interface wave (Stoneley wave) is observed to be propagating at the silicon substrate-fluid interface at a speed close to the speed of sound in the fluid. This wave causes internal reflections, spurious resonance, and radiation from the edges of the silicon substrate. The large lateral component of the particle velocity generated by the membranes at the edge of the cMUT array elements is found to be the source of this interface wave. Lowest order Lamb waves in the silicon substrate are also found to contribute to the cross talk between elements. These waves are excited at the edges of individual vibrating membranes, where they are anchored to the substrate, and result in a narrowing of the beam profile of the array elements. Several methods, such as trench isolation and wafer thinning, are proposed and implemented to modify the acoustical cross coupling between array elements.

    View details for Web of Science ID 000168589400015

    View details for PubMedID 11381699

  • Improved modeling and design of microphones using radio frequency detection with capacitive micromachined ultrasonic transducers 2001 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Hansen, S. T., Ergun, A. S., Khuri-Yakub, B. T. 2001: 961-964
  • Lamb wave devices using capacitive micromachined ultrasonic transducers APPLIED PHYSICS LETTERS Yaralioglu, G. G., Badi, M. H., Ergun, A. S., Cheng, C. H., Khuri-Yakub, B. T., Degertekin, F. L. 2001; 78 (1): 111-113
  • Capacitive micromachined ultrasonic transducer arrays for medical imaging: Experimental results 2001 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Demirci, U., Oralkan, O., Johnson, J. A., Ergun, A. S., Karaman, M., Khuri-Yakub, B. T. 2001: 957-960
  • A novel parametric-effect MEMS amplifier JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Raskin, J. P., Brown, A. R., Khuri-Yakub, B. T., Rebeiz, G. M. 2000; 9 (4): 528-537
  • Initial pulse-echo imaging results with one-dimensional capacitive micromachined ultrasonic transducer arrays 2000 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Oralkan, O., Jin, X. C., Kaviani, K., Ergun, A. S., Degertekin, F. L., Karaman, M., Khuri-Yakub, B. T. 2000: 959-962
  • An efficient electrical addressing method using through-wafer vias for two-dimensional ultrasonic arrays 2000 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Cheng, C. H., Chow, E. M., Jin, X. C., Ergun, S., Khuri-Yakub, B. T. 2000: 1179-1182
  • Micromachined piezoelectrically actuated flextensional transducers for high resolution printing IS&T'S NIP16: INTERNATIONAL CONFERENCE ON DIGITAL PRINTING TECHNOLOGIES Percin, G., Khuri-Yakub, B. T. 2000: 68-68
  • RF detection for low frequency cMUTS and its comparison to traditional detection 2000 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Ergun, A. S., Hansen, S. T., Khuri-Yakub, B. T. 2000: 935-938
  • Theory and analysis of electrode size optimization for capacitive microfabricated ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Bozkurt, A., Ladabaum, I., Atalar, A., Khuri-Yakub, B. T. 1999; 46 (6): 1364-1374

    Abstract

    Theoretical analysis and computer simulations of capacitive microfabricated ultrasonic transducers indicate that device performance can be optimized through judicious patterning of electrodes. The conceptual basis of the analysis is that electrostatic force should be applied only where it is most effective, such as at the center of a circular membrane. If breakdown mechanisms are ignored, an infinitesimally small electrode with an infinite bias voltage results in the optimal transducer. A more realistic design example compares the 3-dB bandwidths of a fully metalized transducer and a partially metalized transducer, each tuned with a lossless Butterworth network. It is found that the bandwidth of the optimally metalized device is twice that of the fully metalized device.

    View details for Web of Science ID 000084029700005

    View details for PubMedID 18244332

  • Ultrasonic sensor for photoresist process monitoring IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Morton, S. L., Degertekin, F. L., Khuri-Yakub, B. T. 1999; 12 (3): 332-339
  • Controlled ink-jet printing and deposition of organic polymers and solid particles (vol 19, pg 2375, 1998) APPLIED PHYSICS LETTERS Percin, G., Lundgren, T. S., Khuri-Yakub, B. T. 1999; 74 (10): 1498-1498
  • Fabrication and characterization of surface micromachined capacitive ultrasonic immersion transducers JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Jin, X. C., Ladabaum, I., Degertekin, F. L., Calmes, S., Khuri-Yakub, B. T. 1999; 8 (1): 100-114
  • Simulation and experimental characterization of a 2-D, 3-MHZ capacitive micromachined ultrasonic transducer (CMUT) array element 1999 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 AND 2 Oralkan, O., Jin, X. C., Degertekin, F. L., Khuri-Yakub, B. T. 1999: 1141-1144
  • Recent progress in capacitive micromachined ultrasonic immersion transducer array ISIC-99: 8TH INTERNATIONAL SYMPOSIUM ON INTEGRATED CIRCUITS, DEVICES & SYSTEMS, PROCEEDINGS Jin, X. C., Cheng, C. H., Oralkan, O., Calmes, S., Degertekin, F. L., Khuri-Yakub, B. T. 1999: 159-162
  • Controlled ink-jet printing and deposition of organic polymers and solid particles APPLIED PHYSICS LETTERS Percin, G., Lundgren, T. S., Khuri-Yakub, B. T. 1998; 73 (16): 2375-2377
  • In situ ultrasonic monitoring of photoresist development APPLIED PHYSICS LETTERS Morton, S. L., Degertekin, F. L., Khuri-Yakub, B. T. 1998; 73 (15): 2215-2217
  • The microfabrication of capacitive ultrasonic transducers JOURNAL OF MICROELECTROMECHANICAL SYSTEMS Jin, X. C., Ladabaum, I., Khuri-Yakub, B. T. 1998; 7 (3): 295-302
  • Micromachinable ultrasonic leaky wave air transducers APPLIED PHYSICS LETTERS Degertekin, F. L., Atalar, A., Khuri-Yakub, B. T. 1998; 73 (6): 741-743
  • In situ ultrasonic measurement of photoresist glass transition temperature APPLIED PHYSICS LETTERS Morton, S. L., Degertekin, F. L., Khuri-Yakub, B. T. 1998; 72 (19): 2457-2459
  • Surface micromachined capacitive ultrasonic transducers IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Ladabaum, I., Jin, X. C., Soh, H. T., Atalar, A., Khuri-Yakub, B. T. 1998; 45 (3): 678-690

    Abstract

    The current state of novel technology, surface microfabricated ultrasonic transducers, is reported. Experiments demonstrating both air and water transmission are presented. Air-coupled longitudinal wave transmission through aluminum is demonstrated, implying a 110 dB dynamic range for transducers at 2.3 MHz in air. Water transmission experiments from 1 to 20 MHz are performed, with a measured 60 dB SNR at 3 MHz. A theoretical model is proposed that agrees well with observed transducer behavior. Most significantly, the model is used to demonstrate that microfabricated ultrasonic transducers constitute an attractive alternative to piezoelectric transducers in many applications.

    View details for Web of Science ID 000073912500016

    View details for PubMedID 18244219

  • Micromachined two-dimensional array piezoelectrically actuated transducers APPLIED PHYSICS LETTERS Percin, G., Atalar, A., Degertekin, F. L., Khuri-Yakub, B. T. 1998; 72 (11): 1397-1399
  • Recent progress in surface micromachined capacitive ultrasonic transducers 1998 5TH INTERNATIONAL CONFERENCE ON SOLID-STATE AND INTEGRATED CIRCUIT TECHNOLOGY PROCEEDINGS Jin, X. C., Ladabaum, I., Degertekin, F. L., Calmes, S., Khuri-Yakub, B. T. 1998: 880-883
  • Micromachined capacitive transducer arrays for medical ultrasound imaging 1998 IEEE ULTRASONICS SYMPOSIUM - PROCEEDINGS, VOLS 1 AND 2 Jin, X. C., Degertekin, F. L., Calmes, S., Zhang, X. J., Ladabaum, I., Khuri-Yakub, B. T. 1998: 1877-1880
  • Control of a drop-ejector used as photo-resist dispenser SMART STRUCTURES AND MATERIALS 1998: MATHEMATICS AND CONTROL IN SMART STRUCTURES Roche, P. E., Hansson, A., Khuri-Yakub, B. T. 1998; 3323: 446-454
  • Micromachined 2-D array piezoelectrically actuated flextensional transducers: New designs MICROMACHINED DEVICES AND COMPONENTS IV Percin, G., Khuri-Yakub, B. T. 1998; 3514: 411-414
  • Piezoelectrically actuated droplet ejector REVIEW OF SCIENTIFIC INSTRUMENTS Percin, G., Levin, L., Khuri-Yakub, B. T. 1997; 68 (12): 4561-4563
  • In Situ Monitoring of Crystallinity and Temperature During Rapid Thermal Crystallization of Silicon on Glass J. Electrochem. Soc. Subramanian, V., Degertekin, F., L., Dankoski, P., Khuri-Yakub, B., T., Saraswat, K., C. 1997; 144: 2216-2221
  • Micromachined 2-D array piezoelectricallly actuated flextensional transducers 1997 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 & 2 Percin, G., Khuri-Yakub, B. T. 1997: 959-962
  • Dry contact ultrasonic sensors for structural monitoring STRUCTURAL HEALTH MONITORING Khuri-Yakub, B. T., Degertekin, F. L., Pei, J. 1997: 481-491
  • An improved circuit model of MUTs 1997 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 & 2 RONNEKLEIV, A., Ladabaum, I., Jin, X. C., Khuri-Yakub, B. T. 1997: 395-399
  • Air coupled through transmission of aluminum and other recent results using MUTs 1997 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 & 2 Ladabaum, I., Jin, X. C., Khuri-Yakub, B. T. 1997: 983-986
  • Analysis of micro machinable piezoelectrically driven one dimensional flexural transducers 1997 IEEE ULTRASONICS SYMPOSIUM PROCEEDINGS, VOLS 1 & 2 RONNEKLEIV, A., Roche, P. E., Khuri-Yakub, B. T. 1997: 1061-1065
  • Controlled two-step solid-phase crystallization for high-performance polysilicon TFT's Electron Device Letters, IEEE Subramanian, V., Dankoski, P., Degertekin, L., Khuri-Yakub, B., T., Saraswat, K., C. 1997; 18 (8): 378-381
  • Lamb wave excitation by Hertzian contacts with applications in NDE Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Degertekin, F., L., Khuri-Yakub, B., T. 1997; 44 (4): 769-779
  • Temperature measurement in rapid thermal processing using the acoustic temperature sensor IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Lee, Y. J., KHURIYAKUB, B. T., Saraswat, K. 1996; 9 (1): 115-121
  • Hertzian contact transducers for nondestructive evaluation J. Acoustical Society of America Degertekin, F., L., Khuri-Yakub, B., T. 1996; 99: 299-308
  • Modeling, measurement and control of rapid thermal processing TRANSIENT THERMAL PROCESSING TECHNIQUES IN ELECTRONIC MATERIALS Saraswat, K. C., Chen, Y. H., Khuri-Yakub, B. T. 1996: 3-10
  • A surface micromachined electrostatic ultrasonic air transducer Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Haller, M., I., Khuri-Yakub, B., T. 1996; 43 (1): 1-6
  • Single mode lamb wave excitation in thin plates by hertzian contacts Appl. Phys. Lett. Degertekin, F., L., Khuri-Yakub, B., T. 1996; 69: 146-148
  • Point Contact Ultrasonic Transducer of Waveguiding Structure for High-Freq. Operation Appl. Phys. Lett. Yamada, K., Khuri-Yakub, B., T. 1996; 68: 1335-1337
  • IN-SITU THIN-FILM THICKNESS MEASUREMENT WITH ACOUSTIC LAMB WAVES APPLIED PHYSICS LETTERS Pei, J., Degertekin, F. L., KHURIYAKUB, B. T., Saraswat, K. C. 1995; 66 (17): 2177-2179
  • In-situ thin film thickness measurement with acoustic lamb waves Appl. Phys. Lett. Pei, J., Degertekin, F., L., Khuri-Yakub, B., T., Saraswat, K., C. 1995; 66: 2177-2179
  • RAPID THERMAL MULTIPROCESSING FOR A PROGRAMMABLE FACTORY FOR ADAPTABLE MANUFACTURING OF ICS IEEE TRANSACTIONS ON SEMICONDUCTOR MANUFACTURING Saraswat, K. C., Apte, P. P., Booth, L., CHEN, Y. Z., DANKOSKI, P. C., Degertekin, F. L., Franklin, G. F., KHURIYAKUB, B. T., Moslehi, M. M., Schaper, C., GYUGYI, P. J., Lee, Y. J., Pei, J., Wood, S. C. 1994; 7 (2): 159-175
  • TEMPERATURE-MEASUREMENT IN RAPID THERMAL-PROCESSING USING ACOUSTIC TECHNIQUES REVIEW OF SCIENTIFIC INSTRUMENTS Lee, Y. J., KHURIYAKUB, B. T., Saraswat, K. C. 1994; 65 (4): 974-976
  • SCANNING ACOUSTIC MICROSCOPY ULTRASONICS KHURIYAKUB, B. T. 1993; 31 (5): 361-372
  • ONE-POINT CONTACT MEASUREMENT OF SPHERICAL RESONANCES APPLIED PHYSICS LETTERS Hsieh, C. P., KHURIYAKUB, B. Y. 1993; 62 (24): 3091-3093
  • Effect of surface tension on the acoustic radiation pressure-induced motion of the water-air interface Journal of the Acoustical Society of America Cinbis, C., Mansour, N., N., Khuri-Yakub, B., T. 1993; 94 (4): 2365-72
  • Effect of surface tension on the acoustic radiation pressure-induced motion of the water-air interface Journal of the Acoustical Society of America Cinbis, C., Mansour, N., N., Khuri-Yakub, B., T. 1993; 94 (4): 2365-72
  • SURFACE DEFECT INSPECTION OF SPHERICAL OBJECTS BY THE RESONANT SPHERE TECHNIQUE APPLIED PHYSICS LETTERS Hsieh, C. P., KHURIYAKUB, B. T. 1992; 60 (15): 1815-1817
  • A noncontacting technique for measuring surface tension of liquids Review of Scientific Instruments Cinbis, C., Khuri-Yakub, B., T. 1992; 63 (3): 2048-2050
  • A noncontacting technique for measuring surface tension of liquids Review of Scientific Instruments Cinbis, C., Khuri-Yakub, B., T. 1992; 63 (3): 2048-2050
  • IMAGE-PROCESSING FOR A SCANNING ACOUSTIC MICROSCOPE THAT MEASURES AMPLITUDE AND PHASE IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL REINHOLDTSEN, P. A., KHURIYAKUB, B. T. 1991; 38 (2): 141-147

    Abstract

    Several image-processing techniques for a low-frequency (3 to 10 MHz) scanning acoustic microscope (SAM) that measures amplitude and phase are described. This microscope is capable of measuring both the amplitude and phase of the reflected and transmitted signals, in contrast with most earlier implementations that only measure the amplitude. By measuring phase, the authors can carry out quantitative nondestructive evaluation (NDE) and image processing that cannot be done with amplitude or phase alone. The effective 2-D point spread function of the microscope is modified by spatial filtering of the digitized complex images. In various images, the transverse resolution is improved by about 20%, aberration of images of subsurface features is corrected, and surface features are numerically defocused. The last process is used to remove the obscuring effect of surface roughness from images of subsurface features.

    View details for Web of Science ID A1991EY70100008

    View details for PubMedID 18267568

  • Image processing for a scanning acoustic microscope that measures amplitude and phase Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on Reinholdtsen, P., A., Khuri-Yakub, B., T. 1991; 38 (2): 141-147
  • AMPLITUDE AND PHASE ACOUSTIC MICROSCOPE USING DIGITAL HETERODYNING REVIEW OF SCIENTIFIC INSTRUMENTS REINHOLDTSEN, P. A., KHURIYAKUB, B. T. 1990; 61 (4): 1236-1242
  • Switchable acoustooptic tap for optical fibers Technical Digest Series Patterson, D., B., Howell, M., D., Digonnet, M., Kino, G., S., Khuri-Yakub, B., T. 1990: 98
  • High-frequency acousto-optic mode locker for picosecond pulse generation Optics Letters Keller, U., Li, K., D., Khuri-Yakub, B., T., Bloom, D., M., Weingarten, K., J., Gerstenberger, D., C. 1990; 15 (1): 45-7
  • PHOTOTHERMAL MEASUREMENTS OF HIGH-TC SUPERCONDUCTORS APPLIED PHYSICS LETTERS FANTON, J. T., Mitzi, D. B., Kapitulnik, A., KHURIYAKUB, B. T., Kino, G. S., Gazit, D., Feigelson, R. S. 1989; 55 (6): 598-599
  • ALL-FIBER ACOUSTOOPTIC PHASE MODULATORS USING ZINC-OXIDE FILMS ON GLASS-FIBER JOURNAL OF LIGHTWAVE TECHNOLOGY Godil, A. A., Patterson, D. B., HEFFNER, B. L., Kino, G. S., KHURIYAKUB, B. T. 1988; 6 (10): 1586-1590
  • ULTRASONIC EXCITATION AND DETECTION OF CAPILLARY WAVES FOR THE MEASUREMENT OF SURFACE-FILM PROPERTIES APPLIED PHYSICS LETTERS KHURIYAKUB, B. T., REINHOLDTSEN, P. A., Chou, C. H., Vesecky, J. F., Teague, C. C. 1988; 52 (19): 1571-1572
  • GENERATION OF 7.8 PS ELECTRICAL TRANSIENTS ON A MONOLITHIC NONLINEAR TRANSMISSION-LINE ELECTRONICS LETTERS Rodwell, M. J., Madden, C. J., KHURIYAKUB, B. T., Bloom, D. M., Pao, Y. C., GABRIEL, N. S., Swierkowski, S. P. 1988; 24 (2): 100-102
  • HIGH-EFFICIENCY, MULTIPLE LAYER ZNO ACOUSTIC TRANSDUCERS AT MILLIMETER-WAVE FREQUENCIES APPLIED PHYSICS LETTERS Hadimioglu, B., LACOMB, L. J., Wright, D. R., KHURIYAKUB, B. T., Quate, C. F. 1987; 50 (23): 1642-1644
  • DEPOSITION OF ORIENTED ZINC-OXIDE ON AN OPTICAL FIBER APPLIED PHYSICS LETTERS HEFFNER, B. L., KHURIYAKUB, B. T. 1986; 48 (21): 1422-1423
  • PRECISE PHASE MEASUREMENTS WITH THE ACOUSTIC MICROSCOPE IEEE TRANSACTIONS ON SONICS AND ULTRASONICS Liang, K. K., Bennett, S. D., KHURIYAKUB, B. T., Kino, G. S. 1985; 32 (2): 266-273
  • MATERIAL CHARACTERIZATION BY THE INVERSION OF V(Z) IEEE TRANSACTIONS ON SONICS AND ULTRASONICS Liang, K. K., Kino, G. S., KHURIYAKUB, B. T. 1985; 32 (2): 213-224
  • ACOUSTIC RESONATOR TRANSDUCER FOR OPERATION IN AIR ELECTRONICS LETTERS Fox, J. D., KHURIYAKUB, B. T., Kino, G. S. 1985; 21 (16): 695-696
  • 7-GHZ ACOUSTIC TRANSMISSION THROUGH A HERTZIAN CONTACT APPLIED PHYSICS LETTERS HEFFNER, B. L., Kino, G. S., KHURIYAKUB, B. T. 1985; 47 (1): 17-18
  • ACOUSTIC MICROSCOPY IN AIR AT 2 MHZ APPLIED PHYSICS LETTERS Fox, J. D., Kino, G. S., KHURIYAKUB, B. T. 1985; 47 (5): 465-467
  • MEASUREMENT OF NORMAL SURFACE DISPLACEMENTS FOR THE CHARACTERIZATION OF RECTANGULAR ACOUSTIC ARRAY ELEMENTS JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Jungerman, R. L., Bennett, P., Selfridge, A. R., KHURIYAKUB, B. T., Kino, G. S. 1984; 76 (2): 516-524
  • EFFECT OF PHOTOCARRIERS ON ACOUSTIC-WAVE PROPAGATION FOR MEASURING EXCESS CARRIER DENSITY AND LIFETIMES IN SILICON APPLIED PHYSICS LETTERS STEARNS, R. G., KHURIYAKUB, B. T., Kino, G. S. 1984; 45 (11): 1181-1183
  • MEASUREMENTS OF ADHERENCE OF RESIDUALLY STRESSED THIN-FILMS BY INDENTATION .2. EXPERIMENTS WITH ZNO/SI JOURNAL OF APPLIED PHYSICS Rossington, C., Evans, A. G., Marshall, D. B., KHURIYAKUB, B. T. 1984; 56 (10): 2639-2644
  • OPTICAL-DETECTION OF ACOUSTIC DISPLACEMENTS FOR THE CHARACTERIZATION OF SURFACE-DEFECTS MATERIALS EVALUATION Jungerman, R. L., KHURIYAKUB, B. T., Kino, G. S. 1984; 42 (4): 444-450
  • BROAD-BAND OPTICAL CAVITIES FOR INFRARED FREE-ELECTRON LASERS - ANALYSIS AND PRELIMINARY EXPERIMENTAL RESULTS APPLIED OPTICS Cutolo, A., KHURIYAKUB, B. T., Madey, J. M. 1984; 23 (17): 2935-2943

    View details for Web of Science ID A1984TG74300021

    View details for PubMedID 18213099

  • CHARACTERIZATION OF SURFACE-DEFECTS USING A PULSED ACOUSTIC LASER PROBE APPLIED PHYSICS LETTERS Jungerman, R. L., KHURIYAKUB, B. T., Kino, G. S. 1984; 44 (4): 392-393
  • A NEW TYPE OF LASER PROBE APPLIED PHYSICS LETTERS STEARNS, R. G., Kino, G. S., KHURIYAKUB, B. T. 1983; 42 (8): 659-661
  • CONICAL TRANSDUCER FOR GENERATION OF ACOUSTIC-WAVES IN FLUIDS APPLIED PHYSICS LETTERS Baer, R. L., KHURIYAKUB, B. T., Kino, G. S. 1983; 42 (7): 573-574
  • MEASUREMENT OF PERIODIC SURFACE HEATING USING SURFACE ACOUSTIC-WAVES APPLIED PHYSICS LETTERS STEARNS, R. G., KHURIYAKUB, B. T., Kino, G. S. 1983; 43 (8): 748-750
  • OPTICAL PROBING OF ACOUSTIC-WAVES ON ROUGH SURFACES JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA Jungerman, R. L., KHURIYAKUB, B. T., Kino, G. S. 1983; 73 (5): 1838-1841
  • PRECISION-MEASUREMENT OF RAYLEIGH-WAVE VELOCITY PERTURBATION APPLIED PHYSICS LETTERS Liang, K., Bennett, S. D., KHURIYAKUB, B. T., Kino, G. S. 1982; 41 (12): 1124-1126
  • EFFECT OF NONUNIFORM PIEZOELECTRIC FILMS ON MONOLITHIC SURFACE ACOUSTIC-WAVE DEVICES APPLIED PHYSICS LETTERS Bowers, J. E., Thornton, R. L., KHURIYAKUB, B. T., Jungerman, R. L., Kino, G. S. 1982; 41 (9): 805-807
  • REACTIVE MAGNETRON SPUTTERING OF ZNO JOURNAL OF APPLIED PHYSICS KHURIYAKUB, B. T., Smits, J. G., Barbee, T. 1981; 52 (7): 4772-4774
  • ACOUSTIC SURFACE-WAVE MEASUREMENTS OF SURFACE CRACKS IN CERAMICS JOURNAL OF THE AMERICAN CERAMIC SOCIETY KHURIYAKUB, B. T., Kino, G. S., Evans, A. G. 1980; 63 (1-2): 65-71
  • A THEORY FOR THE RADIATION-PATTERN OF A NARROW-STRIP ACOUSTIC TRANSDUCER APPLIED PHYSICS LETTERS Selfridge, A. R., Kino, G. S., KHURIYAKUB, B. T. 1980; 37 (1): 35-36
  • BROAD-BAND EFFICIENT THIN-FILM SEZAWA WAVE INTERDIGITAL TRANSDUCERS APPLIED PHYSICS LETTERS Bowers, J. E., KHURIYAKUB, B. T., Kino, G. S. 1980; 36 (10): 806-807
  • GENERATION AND DETECTION OF UNIPOLAR STRESS PULSES APPLIED PHYSICS LETTERS Yu, F., LLIC, D. B., KHURIYAKUB, B. T., Kino, G. S. 1980; 36 (7): 553-555
  • SHEAR-WAVE EXCITATION IN A SOLID BY LONGITUDINAL-WAVE CONTACT TRANSDUCERS JOURNAL OF APPLIED PHYSICS Chou, C. H., Liang, K., KHURIYAKUB, B. T., Kino, G. S. 1980; 51 (10): 5257-5259
  • EDGE-BONDED SURFACE-ACOUSTIC-WAVE TRANSDUCER ARRAY APPLIED PHYSICS LETTERS TUAN, H. C., Kino, G. S., KHURIYAKUB, B. T., Selfridge, A. R. 1979; 35 (4): 320-321
  • ACOUSTIC MEASUREMENT OF STRESS INTENSITY FACTORS APPLIED PHYSICS LETTERS RESCH, M. T., KHURIYAKUB, B. T., Kino, G. S., SHYNE, J. C. 1979; 34 (3): 182-184
  • ULTRASONIC-ATTENUATION OF PIEZOELECTRIC PVF2 FILMS AT HIGH-FREQUENCIES ELECTRONICS LETTERS KHURIYAKUB, B. T., Chou, C. H. 1979; 15 (11): 308-309
  • LENGTH AND DEPTH RESONANCES OF SURFACE CRACKS AND THEIR USE FOR CRACK SIZE ESTIMATION APPLIED PHYSICS LETTERS DOMARKAS, V., KHURIYAKUB, B. T., Kino, G. S. 1978; 33 (7): 557-559
  • ULTRASONIC-ATTENUATION IN CERAMICS JOURNAL OF APPLIED PHYSICS Evans, A. G., Tittmann, B. R., Kino, G. S., Ahlberg, L., KHURIYAKUB, B. T. 1978; 49 (5): 2669-2679
  • DESIGN OF EFFICIENT BROAD-BAND WEDGE TRANSDUCERS APPLIED PHYSICS LETTERS Fraser, J., KHURIYAKUB, B. T., Kino, G. S. 1978; 32 (11): 698-700
  • NEW TECHNIQUE FOR EXCITATION OF SURFACE AND SHEAR ACOUSTIC-WAVES ON NONPIEZOELECTRIC MATERIALS APPLIED PHYSICS LETTERS KHURIYAKUB, B. T., Kino, G. S. 1978; 32 (9): 513-514
  • APPLICATION OF WIENER FILTERING TO NONDESTRUCTIVE EVALUATION APPLIED PHYSICS LETTERS Murakami, Y., KHURIYAKUB, B. T., Kino, G. S., Richardson, J. M., Evans, A. G. 1978; 33 (8): 685-687
  • ACOUSTIC PULSE ECHO MEASUREMENTS AT 200 MHZ APPLIED PHYSICS LETTERS KHURIYAKUB, B. T., Kino, G. S. 1977; 30 (2): 78-80
  • MONOLITHIC WAVEGUIDE ZINC-OXIDE-ON-SILICON CONVOLVER ELECTRONICS LETTERS KHURIYAKUB, B. T., Kino, G. S. 1976; 12 (11): 271-272
  • NEW METHOD FOR WIDEBAND EXCITATION OF INTERDIGITAL SURFACE-WAVE TRANSDUCERS ELECTRONICS LETTERS KHURIYAKUB, B. T., JOLY, R. L. 1976; 12 (11): 266-267
  • STUDIES OF OPTIMUM CONDITIONS FOR GROWTH OF RF-SPUTTERED ZNO FILMS JOURNAL OF APPLIED PHYSICS KHURIYAKUB, B. T., Kino, G. S., Galle, P. 1975; 46 (8): 3266-3272

Conference Proceedings


  • Miniaturized Ultrasound Imaging Probes Enabled by CMUT Arrays with Integrated Frontend Electronic Circuits Khuri-Yakub, B. (., Oralkan, O., Nikoozadeh, A., Wygant, I. O., Zhuang, S., Gencel, M., Choe, J. W., Stephens, D. N., de la Rama, A., Chen, P., Lin, F., Dentinger, A., Wildes, D., Thomenius, K., Shivkumar, K., Mahajan, A., Seo, C. H., O'Donnell, M., Uyen Truong, U., Sahn, D. J. IEEE. 2010: 5987-5990

    Abstract

    Capacitive micromachined ultrasonic transducer (CMUT) arrays are conveniently integrated with frontend integrated circuits either monolithically or in a hybrid multichip form. This integration helps with reducing the number of active data processing channels for 2D arrays. This approach also preserves the signal integrity for arrays with small elements. Therefore CMUT arrays integrated with electronic circuits are most suitable to implement miniaturized probes required for many intravascular, intracardiac, and endoscopic applications. This paper presents examples of miniaturized CMUT probes utilizing 1D, 2D, and ring arrays with integrated electronics.

    View details for Web of Science ID 000287964006097

    View details for PubMedID 21097106

  • A new design and manufacturing process for embedded Lamb waves interdigital transducers based on piezopolymer film Bellan, F., Bulletti, A., Capineri, L., Masotti, L., Yaralioglu, G. G., Degertekin, F. L., Khuri-Yakub, B. T., Guasti, F., Rosi, E. ELSEVIER SCIENCE SA. 2005: 379-387
  • Piezoelectrically actuated flextensional micromachined ultrasound transducers Percin, G., Khuri-Yakub, B. T. ELSEVIER SCIENCE BV. 2002: 441-448

    Abstract

    This paper presents novel micromachined two-dimensional array piezoelectrically actuated flextensional transducers that can be used to generate sound in air or water. Micromachining techniques to fabricate these devices are also presented. Individual unimorph array elements consist of a thin piezoelectric annular disk and a thin, fully clamped, circular plate. We manufacture the transducer in two-dimensional arrays using planar silicon micromachining and demonstrate ultrasound transmission in air at 2.85 MHz with 0.15 microm/V peak displacement. The devices have a range of operating resonance frequencies starting from 450 kHz up to 4.5 MHz. Such an array could be combined with on-board driving and addressing circuitry for different applications.

    View details for Web of Science ID 000176648000079

    View details for PubMedID 12159981

  • Silicon micromachined ultrasonic transducers Khuri-Yakub, B. T., Cheng, C. H., Degertekin, F. L., Ergun, S., Hansen, S., Jin, X. C., Oralkan, O. JAPAN SOC APPLIED PHYSICS. 2000: 2883-2887
  • Miniature drumheads: microfabricated ultrasonic transducers Ladabaum, I., Jin, X. C., Khuri-Yakub, B. T. ELSEVIER SCIENCE BV. 1998: 25-29
  • Plate tomography with dry contact lamb wave transducers Pei, J., Yousuf, M. I., Degertekin, F. L., HONEIN, B. V., KHURIYAKUB, B. T. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1996: 725-730
  • Lamb wave tomography and its application in pipe erosion/corrosion monitoring Pei, J., Yousuf, M. I., Degertekin, F. L., HONEIN, B. V., KHURIYAKUB, B. T. IEEE. 1995: 795-798
  • A new flexible rapid thermal processing system Saraswat, K. C., Chen, Y., Degertekin, L., KHURIYAKUB, B. T. MATERIALS RESEARCH SOC. 1995: 307-319
  • A new flexible rapid thermal processing system Saraswat, K. C., Chen, Y., Degertekin, L., KHURIYAKUB, B. T. MATERIALS RESEARCH SOC. 1995: 35-47
  • Micromachined ultrasonic transducers (MUTs) Ladabaum, I., KHURIYAKUB, B. T., Spoliansky, D., HALLER, M. I. IEEE. 1995: 501-504
  • Efficient excitation and detection of lamb waves for process monitoring and NDE Degertekin, F. L., HONEIN, B. V., KHURIYAKUB, B. T. IEEE. 1995: 787-790
  • INSITU THIN FILM THICKNESS MEASUREMENT USING ULTRASONICS WAVES Pei, J., Degertekin, F. L., HONEIN, B. V., KHURIYAKUB, B. T., Saraswat, K. C. I E E E. 1994: 1237-1240
  • 3D MODELING OF RAPID THERMAL PROCESSORS FOR DESIGN OPTIMIZATION OF A NEW FLEXIBLE RTP SYSTEM CHEN, Y. Z., Booth, L., Schaper, C., KHURIYAKUB, B. T., Saraswat, K. C. IEEE. 1994: 545-548
  • PROPAGATION IN FINITE ANISOTROPIC PLATES OF DIFFRACTING SCALAR WAVES ROCHE, P. E., KHURIYAKUB, B. T. I E E E. 1994: 679-682
  • TILTED SAMPLE ACOUSTIC MICROSCOPY FOR ANISOTROPY MEASUREMENT Degertekin, F. L., HONEIN, B. V., KHURIYAKUB, B. T. I E E E. 1994: 1433-1436
  • A SURFACE MICROMACHINED ELECTROSTATIC ULTRASONIC AIR TRANSDUCER HALLER, M. I., KHURIYAKUB, B. T. I E E E. 1994: 1241-1244
  • THIN FILM EFFECTS IN ULTRASONIC WAFER THERMOMETRY Degertekin, F. L., Pei, J., HONEIN, B. V., KHURIYAKUB, B. T., Saraswat, K. C. I E E E. 1994: 1337-1341
  • TAPERED ACOUSTIC MATCHING LAYERS HALLER, M. I., KHURIYAKUB, B. T. I E E E. 1993: 505-508
  • MATERIAL CHARACTERIZATION USING HERTZIAN POINT-CONTACT TRANSDUCERS Degertekin, F. L., Pei, J., KHURIYAKUB, B. T. I E E E. 1993: 297-299
  • IN-SITU ULTRASONIC THERMOMETRY OF SEMICONDUCTOR WAFERS Degertekin, F. L., Pei, J., Lee, Y. J., KHURIYAKUB, B. T., Saraswat, K. C. I E E E. 1993: 375-377
  • NONINVASIVE SWITCHABLE ACOUSTOOPTIC TAPS FOR OPTICAL FIBER Patterson, D. B., Howell, M. D., Digonnet, M., Kino, G. S., KHURIYAKUB, B. T. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 1990: 1304-1312
  • TEMPERATURE-MEASUREMENT OF SILICON-WAFERS USING PHOTOACOUSTIC TECHNIQUES Lee, Y. J., Chou, C. H., KHURIYAKUB, B. T., Saraswat, K., MOSLEHI, M. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1990: 1109-1114
  • A SAM BEARING BALL INSPECTION SYSTEM Chou, C. H., Parent, P., KHURIYAKUB, B. T. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1990: 2091-2096
  • PHOTOTHERMAL MEASUREMENTS OF HIGH-TC SUPERCONDUCTORS FANTON, J. T., Kapitulnik, A., Mitzi, D. B., KHURIYAKUB, B. T., Kino, G. S. SPRINGER-VERLAG BERLIN. 1990: 202-204
  • NOVEL HIGH-FREQUENCY AIR TRANSDUCERS Schiller, S., Hsieh, C. K., Chou, C. H., KHURIYAKUB, B. T. PLENUM PRESS DIV PLENUM PUBLISHING CORP. 1990: 795-798