Controlling water transport between micelles and aqueous microdroplets during sample enrichment

Mao Fukuyama, Lin Zhou, Tetsuo Okada, Kristina V. Simonova, Mikhail Proskurnin, Akihide Hibara

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Droplet microfluidics technologies have advanced rapidly, but enrichment in droplets has still been difficult. To deterministically control the droplet enrichment, the water transport from an aqueous microdroplet in organic continuous phase containing span 80 micelles was investigated. Organic phase containing Span-80-micelles contacted a NaCl aqueous solution to control hydration degree of the micelles, prior to being used in the microfluidic device. Then, the organic phase was continuously applied to the microdroplets trappled in microwells. Here, water was transported from the microdroplet to the organic phase micelles. This spontaneous emulsification process induced the droplet shrinkage and stopped when the microdroplet reached a certain diameter. The micelle hydration degree correlated well with the final water activity of droplets. The enrichment factor can be determined by the initial microdroplet salt concentration and by the micelle hydration degree. As a proof-of-concept experiment, enrichment of fluorescent nanoparticles and dye was demonstrated, and fluorescent resonance energy transfer was observed as expected. Another demonstration of bound-free separation was performed utilizing the avidin-biotin system. This technique has the potential to be a powerful pretreatment method for bioassays in droplet microfluidics.

Original languageEnglish
Article number338212
JournalAnalytica Chimica Acta
Publication statusPublished - 2021 Mar 8


  • Droplet microfluidics
  • Sample enrichment
  • Spontaneous emulsification
  • Surfactant


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