Nanoliter droplet coalescence in air by directional acoustic ejection

Chuang Yuan Lee, Hongyu Yu, Eun Sok Kim

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


This letter presents a controlled coalescence of nanoliter liquid droplets in air by acoustic directional ejections. An asymmetrical electric field is created within a piezoelectric transducer to produce lopsided acoustic waves, which are focused (through a lens based on the innate impedance mismatch between solid and gas) onto a spot on the liquid surface. The focused acoustic beam is shown to obliquely eject 80-μm -diameter droplets at a traveling speed of 2.3 ms. Up to four such obliquely ejected droplets coalesce in air into a single droplet, which then continue to travel, rotating at 16 000 rads and producing effective micromixing in air.

Original languageEnglish (US)
Article number223902
JournalApplied Physics Letters
Issue number22
StatePublished - 2006
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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