Design and Test of Capacitive Micro-machined Ultrasonic Transducer Array for the Air-coupled Ultrasound Imaging Applications

The Air-coupled ultrasound imaging is one of the most exciting and challenging applications for ultrasound transducer arrays. The CMUT based on MEMS technology with its unique advantages of good matching with air, has become the favorite transducer of the new generation of ultrasound imaging system. In this paper, a 16-element CMUT array for air-coupled application is designed and fabricated. The comprehensive tests in lab are provided to show the performance of the CMUT array. The resonance consistency and the selection of the driving parameters (i.e. the DC bias voltage and AC excitation amplitude) have been tested and analyzed, which can be used to optimize the driving strategy of the CMUT for better transmission and reception. A two-dimension air-coupled imaging test is performed with the CMUT array. The results show that it is feasible to image the contour and position of the object with the air-coupled CMUT array proposed in this paper. It also provides a possibility for the application of CMUT in relevant fields including human-computer interaction and gesture recognition.