The purpose of the proposed research is to design, fabricate and characterize high-power ultrasonic transducers to create stronger acoustic fields (100-fold) in acoustofluidic microscale devices than the commonly employed single-plate transducers. Such fields would enable strong acoustic radiation force acting on the particles to be handled, so that we can find the lower size limit of acoustic focusing and later apply it to sub-micron biological particles such as water-based pathogens.