Performance Comparison Between Single Layer and Several Configurations of Bilayer P(VDF-TrFE) Transducers in Pulse-Echo Measurements

Piezoelectric copolymers such as P(VDF-TrFE) have been used over the years for the fabrication of high-frequency transducers, and particularly for medical imaging. With the aim of optimizing the sensitivity/bandwidth trade-off of this type of transducer, several manufactured bilayer P(VDF-TrFE) transducer configurations were obtained and the corresponding electroacoustic properties were compared with those of a reference single-layer transducer. In a first step, based on a previous study, performances of bilayer P(VDF-TrFE) transducers with both layers acting in emission and reception were compared with performances of a single-layer transducer. Electrical connections (parallel) and polarization direction (opposite) between piezoelectric layers were chosen. For this study, the piezoelectric layers consistently had the same thickness leading to different transducer center frequencies (a ration of 2). The bilayer configuration showed an increased sensitivity (+ 5.2 dB). In a second step, different configurations were studied, in which both piezoelectric layers acted in emission and both or only one of the layers acted in reception. Performances were compared with a reference single-layer transducer at the same frequency (10 MHz). The results showed that regardless of the bilayer configuration of our fabricated transducers, the single-layer structure had to be preferred in terms of sensitivity (+ 5 dB) at the expense of the relative bandwidth (-60 %) for imaging applications.