Fabrication and characterization of a PVDF hydrophone array transducer

This paper reports the fabrication and characterization of PVDF hydrophone array transducers which can be used for underwater acoustic sensing and/or ultrasonic nondestructive evaluation. The transducer is made of a poled PVDF thin film with both surfaces coated with electrodes. An excimer laser micro-machining system is utilized to directly machine the electrodes into a designed pattern, and to form an array of PVDF sensing elements. The size of the element can be controlled around few hundred of micrometers. The PVDF film is then packaged with plastic backing and electronic cabling to form a PVDF hydrophone array transducer. A 1-D linear array with 14 elements and a 2-D array with 16×16 elements are both fabricated and tested. To characterization the performance of the PVDF elements as a hydrophone sensor, a calibration experiment is carried out. The calibration is conducted in a water tank with a standard ultrasound transducer for generating the acoustic waves in water, and another calibrated hydrophone as a reference hydrophone. By method of comparison, the open-load sensitivity as well as the frequency response of the fabricated PVDF hydrophone array is then determined. The 1-D PVDF hydrophone array has been used for measuring the shock waves in a bubble cavitation event. The sensitivity uniformity of the 2D PVDF array transducer has been experimental measured. Further improvements and potential applications of the PVDF hydrophone array transducer will be discussed.