Lawrence L. P. Wong

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This paper presents characterization and initial imaging results of a 32 × 32 element two-dimensional capacitive micromachined ultrasonic transducer array. The devices are fabricated using a wafer bonding process in which both the insulation layer and the membrane are user-deposited silicon nitride. The transducers use a row-column addressing scheme(More)
Creating real-time three dimensional imaging with two dimensional transducers arrays is difficult to achieve due to the large number of interconnections and processing data. One method to greatly reduce the interconnections and also processing time is by introducing the row-column addressing scheme where the top and bottom electrodes are connected by rows(More)
Capacitive micromachined ultrasonic transducers (CMUTs) are an alternative to the conventional method of generating ultrasound that increases bandwidths, simplifies fabrication, and facilitates the integration with necessary electronics. We report the fabrication, characterization, and initial-phased array imaging results of a 64-element array CMUT(More)
A novel design of an air-coupled capacitive micromachined ultrasonic transducer (CMUT) with annular cell geometry (annular CMUT) is proposed. Finite element analysis shows that an annular cell has a ratio of average-to-maximum displacement (RAMD) of 0.52-0.58 which is 58-76% higher than that of a conventional circular cell. The increased RAMD leads to a(More)
This paper presents fabrication and characterization results of two-dimensional capacitive micromachined ultrasonic transducer arrays which use a row-column addressing scheme. The devices are fabricated using a wafer bonding process where both the insulation layer and the membrane are user deposited silicon nitride. Two types of arrays with different(More)
The fabrication process and characterization results of a single element capacitive micromachined ultrasonic transducer (CMUT) are presented in this paper. The fabrication process is based on polymer adhesive wafer bonding of silicon and low pressure chemical vapor deposited silicon nitride wafers. The fabricated transducer has an average resonant frequency(More)
One shortcoming of capacitive micromachined ultrasonic transducers (CMUTs) for commercial use is the weak output power relative to traditional ultrasonic transducers. Recently, we reported an annular CMUT cell with an improved transmit efficiency over a conventional circular cell in air. Extending this paper, we designed and fabricated a nine-element(More)
Developing 2D array-based systems for 3D imaging is overall more challenging due to the complexity in addressing the transducer elements. The Row-Column (RC) scheme results in a significant reduction in electrical leads at a reasonable cost in imaging quality. This paper presents imaging analysis on RC beamforming and provides evidence on why an RC-based(More)
Capacitive micromachined ultrasonic transducers (CMUTs) exhibit wide-bandwidth and can be made into tiny 2-D arrays that are integrable with electronics. A simple implementation of such 2-D array is the row-column addressed CMUT array. However, one critical limitation of a row-column array is its narrow field of view, which can be improved by curving the(More)
The introduction of wafer-bonding technique to capacitive micromachined ultrasonic transducer (CMUT) fabrication offered advantages over the surface micromachining technique, such as simplified fabrication, better membrane uniformity, and increased active area. The conventional wafer-bonding CMUT process employs silicon-on-insulator (SOI) wafers to produce(More)