Comprehensive two-dimensional manipulations of picoliter microfluidic droplets sampled from nanoliter samples

Kai Zhang, Qionglin Liang, Xiaoni Ai, Ping Hu, Yiming Wang, Guoan Luo

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


A facile method is presented for achieving comprehensive two-dimensional droplet manipulations in closed microstructures consisting of microwell arrays and a straight microchannel. In this method, picoliter/nanoliter droplets with controllable sizes and numbers are sampled from nanoliter samples/reagents with almost 100% efficiency. Droplet motions are precisely controlled in the ±X-direction and ±Y-direction by managing hydrostatic pressure and magnetic repulsion, respectively. As a demonstration, a fluorescein-labeled droplet and a deionized droplet are successively generated and trapped in adjacent microwells. Then their positions are quickly exchanged without cross-contamination and fusion is implemented on-demand. After operations, hydrophobic ferrofluid can be completely replaced by mineral oil and droplets still remain in microwells safely. A typical fluorescence intensity-based assay is demonstrated: droplet arrays containing copper ion are diluted disproportionately first and then detected by addition of droplet arrays containing Calcein. With the ability of comprehensive two-dimensional droplet manipulations, this method could be used in various miniaturized biochemical analyses including requirements of multistep procedures and in situ monitoring.

Original languageEnglish (US)
Pages (from-to)8029-34
Number of pages6
JournalAnalytical Chemistry
Issue number20
StatePublished - Oct 15 2011


  • Copper
  • Dimethylpolysiloxanes
  • Fluorescein
  • Fluoresceins
  • Ions
  • Microarray Analysis
  • Microfluidic Analytical Techniques
  • Mineral Oil
  • Nanotechnology


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