Ultrasonic spray nozzles contain piezo electric transducers that when energized cause an ultrasonic nozzles to vibrate at high frequency. These transducers are fashioned in such a way that the nozzle vibrates longitudinally, so the tip of the nozzle is vibrating in an up and down motion several thousand times per second. When a thin film of liquid is applied to the tip of an ultrasonic nozzle, capillary waves form. The amplitude of these waves can be easily controlled by an ultrasonic power generator and increased to the point that these standing capillary waves become too tall to support themselves.
Micron sized highly uniform liquid droplets begin to form as these standing waves give up material due to the continuous over extension of these standing waves. Atomization can continue for extended periods of time under proper conditions. Since their commercial introduction in the 1970’s, ultrasonic spray nozzles still maintain many of the same basic principals. The variety of frequencies has expanded as well as methods to introduce ultrasonic spray systems into hostile environments such as spray pyrolysis, CVD and vacuums.