Parylene coating for 13 MHz 1-3 composite transducer performance enhancement

Abstract

1-3 piezoelectric composite material is widely applied in medical ultrasound transducers. The acoustic impedance mismatching still exists between composite materials and human tissue, this mismatching limits the performance of the 1-3 composite transducer. In this work, Parylene coating technique is employed to enhance the performance of a 1-3 piezoelectric composite transducer whose center frequency is 13 MHz. Theory and simulation analysis is carried out to estimation and optimize the influence of the Parylene coating layer. Pulse- echo experiment is performed to verify the hypothesis of theory and simulation. The experiment results confirm that the performances of the transducer are effectively enhanced by Parylene coating and the optimum thickness of the coating Parylene layer is about 39.5 μm. Compared to the uncoated 1-3 composite transducer, the echo amplitude of 39.5 μm Parylene coated transducer increases 98.8%, the value of −6 dB pulse width decreases 39.5%, the value of −20 dB pulse width decreases 22.7%, the bandwidth increases 51.9%, and the center frequency is not affected. These results prove the feasibility and effectiveness of the Parylene coating layer in transducer performance enhancement.