Finite element modeling of a piezoelectric slender bar transducer equipped with a multilayer backing for medical imaging applications

The goal of this work is to investigate the impact of front and back matching layers properties on a piezoelectric slender bar transducer performances and to propose a novel multilayer backing absorber. Quarter-wavelength acoustic matching layers and backing are known as essential components to fabricate wideband ultrasonic transducers with good electroacoustic properties. Therefore, in order to design a highly accurate single element ultrasonic transducer, the parameters of each constituent layer must be carefully identified. For this purpose, a PZ27 slender bar transducer without front and back matching layers is modeled using Two-dimensional finite element method (FEM) and is considered as the reference case. Then, a double matching layer SU8-Epoxy resin is proposed to highly reduce the acoustic impedance mismatching problem between the piezoelectric active element and the human body. Thereafter, a monolayer backing absorber is added to the structure in order to get as close as possible to the real case. Finally, a novel multilayer backing component made of 10 Epoxy-Tungsten composite layers with different loss factors, is investigated to remedy to the limitations of the proposed monolayer backing material. The bandwidth is significantly extended with good Transmitting Voltage Response (TVR). These results confirm the effectiveness of the proposed backed single element transducer which will be the elementary structure of a whole 1D linear array in future works.