Abstract: We have developed an innovative, nonresonant wide bandwidth multilayer PVDF ultrasonic transducer, well suited for both conventional clinical imaging in the frequency range 3 - 15 MHz as well as for high frequency back-scatter microscopy imaging between 20 - 100 MHz. Such operation is desirable in clinical practice, eliminating the need for the separate probes used to minimize the tradeoff between achievable penetration depths and desired image resolution. The unique properties of our transducer were achieved by stacking individual PVDF layers in a parallel or anti-parallel polarization direction following a Barker coded pattern. The thickness of a single layer determines our transducer's bandwidth; its electrical properties are similar to those of conventional PZT transducers; and its overall pulse-echo sensitivity is sufficiently high for directly interfacing with a commercially available ultrasound imaging system. Using our transducer model, key parameters of the design were predicted and compared with single layer PZT and PVDF transducers in the 3 - 15 MHz and 25 - 100 MHz frequency ranges, respectively. Several prototypes of our wide bandwidth multilayer transducers were fabricated and tested in water. Agreement between experimental results and corresponding computer predictions indicate that the multilayer design outperforms the PZT transducer with respect to axial resolution and overall pulse-echo sensitivity in the frequency range 3 - 100 MHz. !21
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