MEMS-based MHz silicon ultrasonic nozzles for production of monodisperse drops

This paper reports production of 4.5 mu m-diameter monodisperse water drops using a micro electro-mechanical system (MEMS)-based 1 MHz 3-Fourier horn ultrasonic nozzle. The required electrical drive voltage for atomization was 6.5 V at 964 +/- 1 kHz that is in good agreements with the values obtained by impedance measurement and by the three-dimensional (3D) simulation using a commercial finite element analysis program. Such small diameter drops with geometrical standard deviation (GSD) as small as 1.2 and 90% inhale-able fine particle fraction (<5.8 mu m-diameter) were achieved in ultrasonic atomization for the first time. Therefore, the MEMS-based MHz ultrasonic nozzles should have potential application to targeted delivery of reproducible doses of medicine to the respiratory system.