Microfluidics and Nanofluidics

, Volume 1, Issue 4, pp 319–327 | Cite as

A sequential injection microfluidic mixing strategy

  • Jeffrey T. Coleman
  • David Sinton
Research Paper


A novel micromixing strategy is presented, which exploits the axial diffusion of a continuous sequence of discrete samples in a microchannel expansion. Mixing of a continuous sequence in an electroosmotic flow through a sudden expansion region is first modeled assuming an ideal, square-wave injection. The effect of expansion geometry and injection frequency is investigated. To facilitate sequential injection on-chip, two new sequential sample injection schemes are developed and coupled with an expansion region. The first of these designs produces two sample pairs that flow out of separate channels into a common expansion region. This design results in high axial mixing rates but an inherent bias in the injector produces significant cross-stream concentration gradients in the output. These results indicate that the effectiveness of this micromixing strategy is critically dependant on the injection method. A second injector design effectively eliminates the effect of the injection bias using a symmetric microchannel configuration with three solution inlets. The resulting symmetrical injection micromixer produces a continuous uniform stream, 99% mixed, in only 2.3 mm.


Microfluidic Mixing Electrokinetic Sequential injection Alternating injection Computational modeling 



Financial support of this work by the Natural Sciences and Engineering Research Council (NSERC) of Canada, through research grants to D.S., is gratefully acknowledged. Financial support from the Advanced Systems Institute of British Columbia, through a research award, is also gratefully acknowledged.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of VictoriaVictoriaCanada

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