Multilayered Transducers Using Polyurea Film

Abstract

We have been investigating ultrasonic transducers using a polyurea piezoelectric material, which is fabricated by vapor deposition. To enhance the transducer performance, a multilayered configuration is studied in this work. First, the fabrication and transducer design of the multilayered structure are described. A special twin-vacuum chamber is used for laminating the polyurea layers and aluminum electrodes alternately without breaking vacuum. We fabricate two- and four-layered transducers with 1.5 µm polyurea films. The calculation results show that the force factor and electromechanical coupling coefficient increase as the number of layers increases. Second, to evaluate the transducer performance, we measure the electromechanical coupling factors and electric admittances. The coupling coefficients also increase as the number of layers increases at the resonant frequencies of about 30, 65, and 100 MHz. The pulse/echo measurements are conducted to determine the transmission and receiving characteristics using a reflector. The results of the experiment show that the voltage amplitudes of the received signal increase because of multilayer lamination.