Multilayered high‐performance transducer using polyurea thin film

Abstract

Polyurea thin film exhibits useful characteristics as a high‐frequency ultrasonic transducer such as a low acoustic impedance of 70% of that of PVDF, considerably high piezoelectric constants compatible with conventional piezoelectric polymers, and a higher Curie temperature. A polyurea thin film transducer working at over 100 MHz can be made on any surfaces through vapor deposition polymerization with a high controllability of thickness. To enhance the transducer performance, a multilayered configuration is studied in this study. A special twin‐vacuum‐chamber is used for laminating the polyurea layers and the aluminum electrodes alternately. We fabricate two‐ and three‐layered transducers with 1.5‐μm polyurea thin films as well as single‐layer transducers. To evaluate the transducer performances, we measure the capacitances, the electrical admittances, the coupling factors, and the Q values. The pulse/echo measurements are also conducted to determine the transmission and receiving characteristics of the transducers using a glass plate as a reflector. The results of the pulse/echo experiments show that the received voltage amplitude of the multilayered transducer is higher than that of the single‐layer transducer.