Silicon-based high-frequency multiple-Fourier horn ultrasonic nozzles for atomization and pumping

This paper reports for the first time on successful atomization and pumping using microfabricated silicon-based high frequency ultrasonic nozzles of a novel design. The nozzle is made of a piezoelectric drive section with transducers isolated from the liquid and a silicon-resonator consisting of multiple Fourier horns with a central channel for liquid flow. Such nozzles possess a number of advantages over conventional metal-based bulk-type ultrasonic nozzles such as microelectromechanical-system (MEMS)-based microfabrication technology for mass production, much higher ultrasonic frequency and thus much smaller drop diameter, much narrower drop-size distribution, and much lower electric drive power requirement. Monodispersed droplets (mist) are produced at the resonance frequency due to pure capillary wave atomization mechanism. For example, more than 93% of the droplets 7.0 mum in diameter were produced at ultrasonic resonance frequency of 484.5 kHz. Pumping is also achieved at the resonance frequency as in atomization