Ultrasonic Transducer with Silicon Membrane for Liquid Nebulization

The possibility to drive thin Si membranes into nonlinear vibrations using thin piezoelectric ZnO layers was shown. In the driving frequency range up to 200 kHz, membrane natural vibration modes with vibration frequency fm equal the driving one fo, subharmonic (fm = fo,/2) and superharmonic (fm = 2fo,) modes were detected. A lot of the subharmonic vibration modes had vibration amplitudes of several micrometers. Surface acoustic wave (SAW) generation in liquid films was monitored. For nebulization purposes a high mode resonance together with a large vibration amplitude was necessary. The drop formation was associated with the destruction of SAWs. Suitable working regimes for nebulization were those where no self-organisation in the liquid film could take place. The process of self-organisation depended on the liquid film thickness and on the membrane vibration amplitude.