Ultrasonic transducers that make use of the good piezoelectric and acoustic properties of PZT/polymer composites have not been commercialized for frequencies > 20 MHz due to the limitations of conventional dice-and-fill processing. In the proposed work tape-casting technology will be used to produce single element transducers, annuiar arrays, and linear arrays with resonance frequencies ranging from 20 to > 50MHz. By using PZT printed with a fugitive phase (such as carbon) to define kerf space, 2-2 composites can be formed with PZT beam widths less than 15 um and kerf space less than 10 um. High frequency transducers made from such composites will exhibit much higher sensitivity and bandwidth than existing high frequency technologies (monolithic PZT plates, ZnO films, and PVDF films). Such an advance will greatly improve diagnostic capabilities in ophthalmic ultrasound, Doppler flow measurements, dermal and epidermal imaging, and ultrasonic backscatter microscopy. Specific applications to be investigated on this program are diffraction grating transducers for Doppler flow, where tape-cast composites have the added advantage of low cost for disposable use; > 20 pachymeters for cornea thickness measurements; 30 to >50 MHz single element and annular arrays for ultrasound backscatter microscopy; and > 30 MHz linear arrays.
Existing commercial applications include diffraction grathing transducers for Doppler flow measurements, pachymeters for cornea thickness measurements, ultrasound backscatter microscopy, and improved image quality for > 15 MHz linear and phased arrays. Development of inteconnect and beam former technologies to drive > 30 MHz linear arrays will lead to applications in ophthalmic imaging, dermatology imaging, and articular imaging.
