Graduation date: 2008For piezoelectric stack (PZT) driven droplet generator, the driving waveform and driving frequency effect on liquid filament shape and droplet characteristics have been experimentally studied. The experimental study was based on a PZT driven droplet generator with known geometric design parameters and working fluid properties. A lumped-element-model (LEM) constructed to study the acousticmechanical behavior of the droplet generator. The droplet generator volumetric rejection from experimental study compared with that from LEM. Results show that LEM can predict the internal acoustic-mechanical behavior with reasonable accuracy. Based on the LEM, the PZT displacement magnitude dominates the internal pressure variation within the chamber. However due to the natural response of droplet generator, the acoustic pressure in the droplet generator decays exponentially. Experimental data show that the droplet formation process can be waveform and frequency dependent. When the droplet formation process is driven in "low frequency" regime, droplet formation process is weakly affected by frequency. Meniscus interaction effects, which are the interaction of a liquid filament from different droplet generation cycles, on droplet formation process are present when droplet formation process is driven in "high frequency" regime. Due to the meniscus interaction effect, the droplet formation process at "high frequency" is waveform and frequency dependent. Results show that the droplet volume reduces slightly with PZT driving frequency, about 20%. Droplet velocity increases with driving frequency, about 40%. However the droplet break-off time and droplet velocity are weakly affect by the driving frequency.