In this letter, a 400-µm × 400-µm 2-D capacitive micromachined ultrasonic transducer (cMUT) array element is experimentally characterized, and the results are found to be in good agreement with theoretical predictions. As a receiver, the transducer has a 1.8 × 10-7 nm/√Hz displacement sensitivity, and, as a transmitter, it produces 16.4 kPa/V of output pressure at the transducer surface at 3 MHz. The transducer also has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging.
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