Droplet-based microsystem for multi-step bioreactions


A droplet-based microfluidic platform was used to perform on-chip droplet generation, merging and mixing for applications in multi-step reactions and assays. Submicroliter-sized droplets can be produced separately from three identical droplet-generation channels and merged together in a single chamber. Three different mixing strategies were used for mixing the merged droplet. For pure diffusion, the reagents were mixed in approximately 10 min. Using flow around the stationary droplet to induce circulatory flow within the droplet, the mixing time was decreased to approximately one minute. The shortest mixing time (10 s) was obtained with bidirectional droplet motion between the chamber and channel, and optimization could result in a total time of less than 1 s. We also tested this on-chip droplet generation and manipulation platform using a two-step thermal cycled bioreaction: nested TaqMan® PCR. With the same concentration of template DNA, the two-step reaction in a well-mixed merged droplet shows a cycle threshold of ∼6 cycles earlier than that in the diffusively mixed droplet, and ∼40 cycles earlier than the droplet-based regular (single-step) TaqMan® PCR.

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The authors would like to gratefully acknowledge the funding of this work through the grants (5-R01-AI049541-06 and 1-R01-EB006789-01A2) from the National Institutes of Health. The authors would also like to thank the staff and members of the Lurie Nanofabrication Facility (LNF) at University of Michigan for their assistance in device fabrication.

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Correspondence to Mark A. Burns.

Electronic supplementary material

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Droplet generation and merging (3× speed) (MPEG 7582 kb)

Mixing using flow around the stationary droplet in the chamber (2× speed) (MPEG 5056 kb)

Mixing using bidirectional droplet motion (2× speed) (MPEG 4538 kb)

Movie 1

Droplet generation and merging (3× speed) (MPEG 7582 kb)

Movie 2

Mixing using flow around the stationary droplet in the chamber (2× speed) (MPEG 5056 kb)

Movie 3

Mixing using bidirectional droplet motion (2× speed) (MPEG 4538 kb)

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Wang, F., Burns, M.A. Droplet-based microsystem for multi-step bioreactions. Biomed Microdevices 12, 533–541 (2010).

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  • Droplet
  • Microfluidics
  • Merging
  • Mixing
  • Nested PCR