Inkjet-Printed P(VDF-TrFE) Film for High-Frequency Annular Array

An innovative processing to deposit poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] film on silicon wafers by an inkjet printing method was used to fabricate high-frequency (HF) annular array (AA) prototype. This prototype has a total aperture of 7.3 mm and eight active elements. A polymer-based lens with low acoustic attenuation was added to the flat deposition on the wafer, setting the geometric focus to 13.8 mm. With a thickness of around $11~\mu \text{m}$ , the electromechanical performance of P(VDF-TrFE) films was evaluated with an effective thickness coupling factor of 22%. Electronics allowing all elements to simultaneously emit as a single element transducer was developed. In reception, a dynamic focusing, based on eight independent amplifying channels, was preferred. The center frequency of the prototype was 21.3 MHz, the insertion loss (IL) was 48.5 dB, and the -6-dB fractional bandwidth was 143%. The trade-off sensitivity/bandwidth has rather favored the large bandwidth. Dynamic focusing on reception was applied and allowed to improvements in the lateral full width at half maximum (FWHM) as shown on images obtained with a wire phantom at several depths. The next step, for a fully operational multielement transducer, will be to achieve a significant increase of the acoustic attenuation in the silicon wafer.