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A Love wave sensor with a phononic parylene-C wave guiding layer is proposed to detect the VEGF secreted during the selective platelet activation process, where arrays of a different material (filling material) are fabricated in the parylene-C films. The effects of the structural design parameters (period width and period number) on the electric response of sensors are investigated. As the period...
This paper presents the characterization of frequency response and mode shape at the 1st harmonic frequency of a Micro-Opto-Mechanical Acoustic Sensors (MOMAS) with a Mach-Zehnder Interferometer (MZI) readout system. In previous research, the static modeling and characterization has been demonstrated. In this paper, we investigate the capability of using MOMAS in ultrasound domain as a Micro-Opto-Mechanical...
Long term reliability has been a challenging issue in CMUT probe development. Kolo Medical Inc. has worked on improving reliability of CMUT probes for many years. Testing methods were developed and utilized to assess long term reliability and evaluate CMUT design improvements. A large amount of long term reliability test data were collected and analyzed.
Based on the least squares method which is arranged to the problem of fitting theoretical to experimental measured variables, such as phase velocities of acoustic waves and/or resonant frequencies, the environment of the minimum sum of squares (SSQ) has been analyzed, similarly to [1]. This is done by forming a “sensitivity matrix” (or Jacobian matrix: derivatives of measured variables with respect...
The matching layer inserted between the front protection metal and piezoelectric layer has been designed when the protection metal is half-wavelength thick. This matching layer plays the role of a bonding layer. The optimum thickness ranges from λ/4 to 3λ/8 in the Mason model simulation, which has been confirmed by experiments. In the optimum range, the sensitivity was much higher and the bandwidth...
Capacitive micro-machined ultrasonic transducers (CMUTs) offer several advantages over conventional piezoelectric transducers in terms of acoustic performance and circuit integration capability. In this study, we focus on the potential of CMUTs for the high receiving sensitivity which is strongly required for photoacoustic imaging applications. We propose an advanced CMUT cell design with an ultra-narrow...
A highly sensitive capacitive micromachined ultrasound transducer (CMUT) cell with an ultra-narrow gap was investigated. The electromechanical coupling coefficient (kT) as a figure of merit of sensitivity of ultrasound transducers was 0.67 in a 30-MHz CMUT cell with a 30-nm height vacuum gap and in 100-nm thick dielectric layers, and the coefficient was superior to that of piezoelectric transducers...
This paper describes the design, fabrication, characterization and test of three sectorized array transducers: one for air-coupled operation (400 kHz, 25 mm diameter) and two for water-coupled operation (4 MHz, 10 mm diameter and 2 MHz, 5 mm diameter). The objective is to use these transducers in pulse-echo mode along with a conical reflector to generate a 2D cylindrical acoustic field with angular...
Air-coupled transducers are used to conduct fast non-contact inspections in NDT. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled NDT. This paper presents a methodology for improving the bandwidth of an air-coupled diaphragm transducer without sensitivity loss by connecting a number...
For new-generation thermal power plants, off-line non-destructive testing is not sufficient and long-term monitoring at high temperature is desired. In the previous study, ultrasonic transducers made by CaBi4Ti4O15 (CBT)/Pb(Zr, Ti)O3 (PZT) were investigated and maximum operation temperature was estimated as ∼600°C. Since operation temperature of new-generation thermal power plant will be ∼700°C, it...
We have investigated the feasibility of imaging cortical pores using ultrasound contrast agents (UCA). Cortical bone porosity and pore size are major factors in determining bone strength and toughness. Assessments on cortical pore properties can help to predict and prevent bone fractures. Because cortical pores are highly associated with blood vessels, imaging cortical bone microvascular perfusion...
Laser Induced Phased Arrays (LIPAs) use post processing to focus and steer the laser generated and detected ultrasonic beam, synthesizing a phased array. The technique is broadband, non-contact, and couplant free, making LIPAs suitable for large stand-off distances, inspection of components of complex geometries and hazardous environments. This paper presents LIPAs synthesized by capturing the Full...
Power Doppler (PD) is the preferred technique for accessing weakly scattering blood cells with low-velocity flow. However, strong clutter decreases sensitivity of the blood signals, which degrades micro-vasculature imaging. Eigen-based filtering methods have been developed to separate the independent scattering sources using both spatial and slow-time statistics of echo data. We recently found that...
Surface acoustic wave (SAW) devices have been shown recently to be an appropriate technology for harsh-environment sensor applications, such as those in the automotive, aerospace, power plant, and metallurgic industries. Usages include temperature, pressure, torque, strain, gas, liquid, biochemical, and mass sensors in structural health monitoring, industrial process monitoring, environment checking...
Eigen-filters with attenuation response adapted to clutter statistics in color flow imaging (CFI) have shown improved flow detection sensitivity in the presence of tissue motion. However, its practical adoption for routine use in clinical scanners is hindered by the long processing time required to derive the eigen-components. In this work, we seek to overcome this issue by formulating a parallel-computing...
The Capacitive Micromachined Ultrasound Transducer (CMUT) technology has been under development for more than 20 years at Universities and industry labs. One of the major limitations for commercial use of CMUT probes has been poor reliability. Kolo Medical Inc. has developed a number of methods to improve reliability of CMUT probes. Kolo performed long term reliability tests to verify the improvements...
Ultrasound contrast enhanced super resolution imaging has recently attracted extensive attention due to its extraordinary resolution. Vessels that were detected in small animals with ultrafast plane wave imaging sequences were about ten fold smaller than the resolution predicted by a the classical diffraction limit. However the imaging depth in small animals is shallow. To translate this technology...
Accurate characterization of ultrasound fields generated by diagnostic and therapeutic transducers is critical for patient safety. At high frequencies, spatial variations in the pressure over the surface of the measurement device will produce a different averaged value from that at the intended location. Using a small hydrophone as an idealised point device, this paper seeks to ascertain the spatial-averaging...
Capacitive Micromachined Ultrasound Transducers (CMUTs) have become a better alternative to traditional piezoelectric transducers because of their better impedance matching characteristic and wider bandwidth. These advantages make CMUTs ideal for medical ultrasound imaging, ultrasonic flow metering, gesture sensing and other airborne applications. However conventional vacuum CMUTs have narrow bandwidth...
This paper describes the design, fabrication, characterization and test of cylindrically focused air-coupled piezoelectric monolithic and linear-array transducers. The objective is to obtain transducers that present a similar performance compared with conventional flat transducers, but more robust for applications involving curved surfaces and/or generation/detection of Lamb waves and a better spatial...
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