Directional droplet ejection by nozzleless acoustic ejectors built on ZnO and PZT

Jae Wan Kwon, Hongyu Yu, Qiang Zou, Eun Sok Kim

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


This paper describes a technique to eject liquid droplets in almost any direction with a nozzleless self-focusing acoustic transducer (SFAT) built on a ZnO thin film as well as on a thick PZT substrate. Sectoring of the SFAT annular rings of half-wave-band sources to create a piezoelectrically inactive area causes the droplet ejections to be directed non-perpendicular (i.e., oblique) to the liquid surface. The direction of the droplet ejections depends on the size of the piezoelectrically inactive area within the area of the half-wave-band sources. Droplets are ejected from the center part of the annular rings toward the open inactive area. Various openings up to 90° of pie shape have been made and tested to show that the ejection direction becomes less vertical as the piezoelectrically inactive area in the transducer increases. Additionally, a multi-directional ejector built on ZnO film has been demonstrated to eject micron-sized liquid droplets (several microns in diameter) in any of eight predetermined directions on demand. Larger size liquid droplets (about a hundred microns in diameter) have also been directionally ejected from a sectored SFAT built on a PZT substrate.

Original languageEnglish (US)
Article number024
Pages (from-to)2697-2704
Number of pages8
JournalJournal of Micromechanics and Microengineering
Issue number12
StatePublished - Dec 1 2006
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Mechanics of Materials
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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