Nanoliter droplet coalescence in air by directional acoustic ejection

Chuang Yuan Lee, Hongyu Yu, Eun Sok Kim

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Abstract

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
Volume89
Issue number22
DOIs
StatePublished - Dec 7 2006

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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