Creating a home made ultrasound transducer
Ultrasonic transducers in that frequency range are not easy to construct since the resonant element (which usually is fabricated from piezoceramic material) must be very thin and very uniform in thickness and must have conducting electrodes (usually silver or nickel) deposited on two surfaces. At present, 3D printers are not capable of manufacturing such devices as they cannot handle ceramic materials and their accuracy is not good enough at the thicknesses required.  However, you can buy reasonably priced transducers by searching online for 1 MHz transducers (e.g. http://www.steminc.com/PZT/en/mist-generation-transducer-16-mhz).