Capacitive Micromachined Ultrasonic Transducer Array for Air-coupled Lamb Wave Detection of Plate Structure

The major challenge of air-coupled ultrasonic technology is the acoustic impedance mismatching between transducer material and air. Capacitive Micromachined Ultrasonic Transducer (CMUT) has shown the potential for non-contact air-coupled application due to its low impedance. Lamb wave has the characteristics of long propagation distance and high detection efficiency, it has been widely used in the health detection of plate structures. So the combination of CMUT and Lamb wave for defect detection is a promising application. In this work, the CMUT array is fabricated and the experiments of non-contact Lamb wave excitation and reception are carried out by using the CMUT array. In addition, the sound beam incident angle of CMUT array can be changed by customized phased array system, so as to excite Lamb waves with different modes.