Research Highlights

Hydrophoretic Separation

The development of microfluidic separation technologies is one of the major issues in the area of lab-on-a-chip and micro total analysis system. However, previous methods on passive particle separation cannot separate microparticles without the aids of sheath flows and complex channel networks. In our laboratory, separation and sorting of microspheres and mammalian cells were demonstrated by using  a novel microfluidic mechanism, "hydrophoresis", which uses slanted or anisotropic obstacles to induce hydrodynamic interaction between the obstacles and the particles subjected to rotational flows induced by the obstacles [Lab Chip 2007, 7, 890; Lab Chip 2007, 7, 1532]. By exploiting the slanted obstacles in a microchannel, we can eliminate the needs of sheath flows and complex channel networks. In addition, we can generate a lateral pressure gradient so that microparticles can be deflected and arranged along the lateral flows induced by the gradient [Small 2008, 4, 634; Anal. Chem. 2008, 80, 3035]. The equilibrium positions of the particles by the hydrodynamic interactions depend on their size. The slanted obstacle as a microfluidic control element in a microchannel is analogous to the electric, magnetic, optical, or acoustic counterparts in that their function is to generate a field gradient. Recently, we also reported a hydrophoretic device that uses rotational flows induced by regularly patterned obstacles only on the top wall for separating biological samples, including DNA molecules and mammalian cells [Anal. Chem. 2009, 81, 50; Anal. Chem. 2009, 81, 1964]. Continuous separation of micrometer and submicrometer particles was also achieved using the obstacles, demonstrating the potential of hydrophoresis for biological sample preparation on the micro- and nanoscales, with the advantages of continuous flow and sheathless passive operation [Lab Chip 2009, 9, 1962; Small 2009, 5, 2205, Cover; Lab Chip 2010, 10, 335; Lab Chip 2011, 11, 413].

Related Articles:

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Sungyoung Choi, Taeyun Ku, Seungjeong Song, Chulhee Choi, Je-Kyun Park, "Hydrophoretic high-throughput selection of platelets in physiological shear-stress range," Lab Chip, 11 (3), 413-418 (2011).  
External link Supporting Info. (pdf, 572 KB)
External link Selected for Vir. J. Bio. Phys. Res. (2011)/ Volume 21 / Issue 3 / INSTRUMENTATION DEVELOPMENT (2011. 2.1)

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Sungyoung Choi, Je-Kyun Park, "Hydrophoretic separation method applicable to biological samples," In: S. Kakaç, B. Kosoy, D.  Li, A. Pramuanjaroenkij (eds). Microfluidics Based Microsystems: Fundamentals and Applications (NATO Science for Peace and Security Series A: Chemistry and Biology). Springer; pp. 577-594, 2010.

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Sungyoung Choi, Eujin Um, Je-Kyun Park, "Chapter 6. Focusing particles without sheath flows in microflow cytometers." In: Frances S. Ligler, Jason S. Kim, editors. The Microflow Cytometer. Pan Stanford Publishing; pp. 89-103, 2010.

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Sungyoung Choi, Seung-Hoon Kim, Je-Kyun Park, "Optical path-length modulation for three-dimensional particle measurement in mirror-embedded microchannels," Lab Chip, 10 (3), 335-340 (2010).

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Sungyoung Choi, Je-Kyun Park, "Optically coated mirror-embedded microchannel to measure hydrophoretic particle ordering in three dimensions," Small, 5 (19), 2205-2211 (2009).     
External link
Featured on the Inside Cover Article in Small.  

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Microfluidics: Small 19/2009," Small, 5 (19), Inside Cover.  

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Sungyoung Choi, Je-Kyun Park, "Tuneable hydrophoretic separation using elastic deformation of poly(dimethylsiloxane)," Lab Chip, 9 (13), 1962-1965 (2009).    
External link Supporting Info. (pdf, 322 KB)

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Sungyoung Choi, Je-Kyun Park, "Chapter 4. Hydrophoretic method for continuous blood cell separation." In: Keith E. Herold and Avraham Rasooly, editors. Lab-on-a-Chip Technology: Biomolecular Separation and Analysis. Caister Academic Press; pp. 45-55, 2009.

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Topics in Particle and Dispersion Science (TPDSci): Particle trapping, manipulation, and sorting: Nano- and microfluidic methods

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Sungyoung Choi, Seungjeong Song, Chulhee Choi, Je-Kyun Park, "Microfluidic self-sorting of mammalian cells to achieve cell cycle synchrony by hydrophoresis," Anal. Chem., 81 (5), 1964-1968 (2009).
External link Supporting Info. (pdf, 271 KB)

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Sungyoung Choi, Seungjeong Song, Chulhee Choi, Je-Kyun Park, "Hydrophoretic sorting of micrometer and submicrometer particles using anisotropic microfluidic obstacles," Anal. Chem., 81 (1), 50-55 (2009).
External link
Supporting Info. (pdf, 369 KB)

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Sungyoung Choi, Je-Kyun Park, "Mirror-embedded microchannel for three-dimensional measurement of particle position," Appl. Phys. Lett., 93 (19), 191909 (2008).
External link
Supporting Info. (pdf, 197.9 KB)

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Topics in Particle and Dispersion Science (TPDSci): Optical flow cytometry and particle counting

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Sungyoung Choi, Seungjeong Song, Chulhee Choi, Je-Kyun Park, "Sheathless focusing of microbeads and blood cells based on hydrophoresis," Small, 4 (5), 634-641 (2008). 

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Sungyoung Choi, Je-Kyun Park, "Sheathless hydrophoretic particle focusing in a microchannel with exponentially increasing obstacle arrays," Anal. Chem., 80 (8), 3035-3039 (2008).

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Sungyoung Choi, Seungjeong Song, Chulhee Choi, Je-Kyun Park, "Continuous blood cell separation by hydrophoretic filtration," Lab Chip, 7 (11), 1532-1538 (2007).  
External link Supporting Info. (mpeg movie, 2.99 MB)

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Sungyoung Choi, Je-Kyun Park, "Continuous hydrophoretic separation and sizing of microparticles using slanted obstacles in a microchannel," Lab Chip, 7 (7), 890-897 (2007).   
External link Supporting Info. (mpeg movie, 2.99 MB)