Inkjet-printed P(VDF-TrFE) film for high-frequency annular array.

An innovative processing to deposit P(VDF-TrFE) film on silicon wafers by an inkjet printing method was used to fabricate high-frequency annular array prototype. This prototype has a total aperture of 7.3 mm and 8 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 μm, 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 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 as shown on images obtained with a wire phantom at several depths. The next step, for a fully operational multi-element transducer, will be to achieve a significant increase of the acoustic attenuation in the silicon wafer.