Microfluidics and Nanofluidics

, Volume 13, Issue 1, pp 9–17 | Cite as

Assessment of cross-type optical particle separation system

Research Paper


This paper describes the optical and hydrodynamic characteristics of particle motion in a cross-type optical particle separator. The retention distance modulated by the optical force on a particle was measured in three dimensions for various vertical and horizontal positions via μ-defocusing digital particle image velocimetry. The experimental data showed that the actual retention distance was smaller than the predicted retention distance under the assumption that the approaching velocity was constant through the cross-section of a microfluidic channel. The retention distance was shown to increase as the injection position of the particle shifted toward the channel side wall at a given vertical position due to a higher residence time within the region of influence of the laser beam. In contrast, the retention distance decreased as the injection position shifted toward the channel top/bottom walls at a given horizontal position. A theoretical modeling study was conducted to support and interpret the experimental measurements. The resolution of the particle separation procedure, which did not require adjusting the flow rate, laser power, or working fluid properties, was studied.


Cross-type optical particle separator Retention distance Scattering force Gradient force Poiseuille velocity field profile 



This work was supported by the Creative Research Initiatives (No. 2011-0000423) program of the National Research Foundation of Korea.


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Kang Soo Lee
    • 1
  • Sang Youl Yoon
    • 1
  • Sang Bok Kim
    • 1
  • Kyung Heon Lee
    • 1
  • Hyung Jin Sung
    • 1
  • Sang Soo Kim
    • 1
  1. 1.Department of Mechanical EngineeringKAISTDaejeonKorea

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