Novel 1-3 piezo-composites using synchrotron radiation lithography and its application for high frequency medical imaging arrays

The Synchrotron Radiation Lithography (SRL) process was used to make novel 1-3 piezo composites for a medical imaging array. SRL is a powerful tool for high resolution, smooth surface, high aspect-ratio microfabrication of resists in the 1 to 100 micron range. A resist die with an SRL generated square hole array is negatively replicated by slurry filling, then resin mold is removed by plasma etching, and then sintered to make a small postage stamp size substrate comprising a 2D isotropic array of 25×25×180 micron PZT columns. Electrodes were sputtered on the finished composite. Using this substrate, a 48 channel imaging array was made using conventional dicing and high pressure laminating processes. Although “as-available” materials and parts for f_o=5 MHz phased array were used for backing and matching, its 2-way bandwidth, as measured, showed a significant improvement over conventional bulk PZT based design. The array was wired to mate with a conventional imaging device for general performance comparisons to standard arrays on tissue equivalent phantoms, in water tank, and finally on human subject. Although further optimization is necessary for best utilization of this method and material, SRL assisted fabrication of 1-3 piezo-composites is a proven prospective technology for high frequency medical imaging arrays