Hoop stress-assisted three-dimensional particle focusing under viscoelastic flow

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Three-dimensional particle focusing is a prerequisite for a wide range of lab-on-a-chip applications such as cell counting and sorting. We have demonstrated that when side-wells are inserted in a rectangular channel, the particles form an almost single stream (>99 %) within ±0.9× particle diameter from the channel centerline under viscoelastic flow. Recently, viscoelasticity-based particle focusing technique has attracted much attention since it operates by flowing particles in extremely simple channels. However, the particles move along multiple equilibrium positions in rectangular channels under elasticity-dominant flow, and this is not favorable for practical applications. We show that the hoop stress along curved streamlines in side-wells can be engineered to reduce the multiple particle lanes to a single stream. Further, we achieve highly efficient focusing under inertialess viscoelastic flow with high throughput (>2000/s). We expect that our novel method will find applications in accurate cell counting, sorting, and deformability measurement.

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This work was supported by the research programs through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (nos. 2009-0093826, NRF-2013R1A1A1A05007406, and NRF-2013R1A1A2A10004353). This research was funded by the MSIP (Ministry of Science, ICT & Future Planning), Korea in the ICT R&D Program (The core technology development of light and space adaptable energy-saving I/O platform for future advertising service) and the EEWS Research Project of the Office of the KAIST EEWS Initiative. The authors are thankful to Prof. Seong Jae Lee at The University of Suwon for kindly providing us with PS beads and also the measurement of viscosities with a rheometer (MCR 300).

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Correspondence to Sung Gap Im or Younghun Kim or Ju Min Kim.

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Special issue devoted to Novel Trends in Rheology

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Cha, S., Kang, K., You, J.B. et al. Hoop stress-assisted three-dimensional particle focusing under viscoelastic flow. Rheol Acta 53, 927–933 (2014) doi:10.1007/s00397-014-0808-9

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  • Viscoelastic
  • Particle
  • Focusing
  • Microchannel flow
  • Hoop stress