Electroactive polymers will be investigated as a novel means to dynamically focus high frequency (>30 MHz), single element ultrasound transducers meant for biomedical imaging. Commercial ultrasound array technology has been limited to 20 MHz or less, and though current work is increasing the operating range, the frequency of experimental arrays still lags far behind the 50 MHz+ range necessary to achieve an adequate resolution. Single element transducers are capable of these frequencies, however, these devices only have one focus. As the lateral resolution is increased, the depth of field decreases, forcing mechanical translation along the axis to achieve the desired full image. However, by using electroactive polymers as a back plate, and air as a backing for P(VDF-TrFE) piezoelectric polymer, it will be possible to dynamically change the curvature of single element transducers, thus allowing for focusing at different depths. Using a voltage source, the electroactive polymers can change area by as much as 100%, and when using it as a diaphragm, it effects different curvatures depending upon the amplitude of the voltage. This will allow the fabrication of single element transducers with operating frequencies >30 MHz that provide dynamic focusing for high resolution imaging in applications such as ophthalmology and dermatology. For the Phase I effort feasibility will be demonstrated by fabricating a single element 30 MHz transducer using the electroactive polymer as a back plate. In Phase II, the technique will be expanded to fabrication of higher frequency devices (>50 MHz) and the feasibility for real-time imaging of biological tissues will be tested. ? ?
