Micromachined ultrasonic droplet generator based on a liquid horn structure

A micromachined ultrasonic droplet generator was developed for drop-on-demand fluid atomization. This droplet generator consists of a bulk ceramic piezoelectric transducer for ultrasound generation, as silicon micromachined liquid horn structure as the nozzle, and a reservoir for the ejection fluid. A batch microfabrication process involving the wet etching of (100) silicon in potassium hydroxide solutuion, was used for the formation of these nozzles. The acoustic fields in the cavity and electrical impedance of the device were calculated using finite-element method. The results show the occurance of droplet ejection while the transducer is excited at one of the resonances determined by the horn geometry.