Capacitive Micromachined Ultrasonic Transducers (CMUTs) for Underwater Imaging Applications

• Main Authors: Jinlong Song, Chenyang Xue, Changde He, Rui Zhang, Linfeng Mu, Juan Cui, Jing Miao, Yuan Liu, Wendong Zhang
• Format: Article
• Language: English
• Published: MDPI AG 2015-09-01
• Series: Sensors
• Subjects: CMUT; C-V characteristic curve; sound pressure; bandwidth; ultrasonic imaging
• Online Access: http://www.mdpi.com/1424-8220/15/9/23205

A capacitive micromachined ultrasonic transducer structure for use in underwater imaging is designed, fabricated and tested in this paper. In this structure, a silicon dioxide insulation layer is inserted between the top electrodes and the vibration membrane to prevent ohmic contact. The capacitance-voltage (C-V) characteristic curve shows that the transducer offers suitable levels of hysteresis and repeatability performance. The −6 dB center frequency is 540 kHz and the transducer has a bandwidth of 840 kHz for a relative bandwidth of 155%. Underwater pressure of 143.43 Pa is achieved 1 m away from the capacitive micromachined ultrasonic transducer under 20  excitation. Two-dimensional underwater ultrasonic imaging, which is able to prove that a rectangular object is present underwater, is achieved. The results presented here indicate that our work will be highly beneficial for the establishment of an underwater ultrasonic imaging system.