Microfluidics and Nanofluidics

, 20:128 | Cite as

Viscosity-difference-induced asymmetric selective focusing for large stroke particle separation

  • Wenchao Xu
  • Zining Hou
  • Zhenhua Liu
  • Zhigang WuEmail author
Research Paper


We developed a new approach for particle separation by introducing viscosity difference of the sheath flows to form an asymmetric focusing of sample particle flow. This approach relies on the high-velocity gradient in the asymmetric focusing of the particle flow to generate a lift force, which plays a dominated role in the particle separation. The larger particles migrate away from the original streamline to the side of the higher relative velocity, while the smaller particles remain close to the streamline. Under high-viscosity (glycerol–water solution) and low-viscosity (PBS) sheath flows, a significant large stroke separation between the smaller (1.0 μm) and larger (9.9 μm) particles was achieved in a sample microfluidic device. We demonstrate that the flow rate and the viscosity difference of the sheath flows have an impact on the interval distance of the particle separation that affects the collected purity and on the focusing distribution of the smaller particles that affects the collected concentration. The interval distance of 293 μm (relative to the channel width: 0.281) and the focusing distribution of 112 μm (relative to the channel width: 0.107) were obtained in the 1042-μm-width separation area of the device. This separation method proposed in our work can potentially be applied to biological and medical applications due to the wide interval distance and the narrow focusing distribution of the particle separation, by easy manufacturing in a simple device.


Lift Force Sample Flow Stokes Number Particle Separation Sheath Flow 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We acknowledge the Natural Science Foundation of Hubei Province of China (No. 2015CFA110) and National Natural Science Foundation of China (No. 51575216) for financial support. Wu thanks the support from the Chinese central government through its Thousand Youth Talents program.

Supplementary material

Supplementary material 1 (MP4 12352 kb)

10404_2016_1791_MOESM2_ESM.pdf (665 kb)
Supplementary material 2 (PDF 665 kb)


  1. Agrawal P, Gandhi PS, Neild A (2013) The mechanics of microparticle collection in an open fluid volume undergoing low frequency horizontal vibration. J Appl Phys 114:114904–114914. doi: 10.1063/1.4821256 CrossRefGoogle Scholar
  2. Amini H, Lee W, Di Carlo D (2014) Inertial microfluidic physics. Lab Chip 14:2739–2761. doi: 10.1039/C4LC00128A CrossRefGoogle Scholar
  3. Beech JP, Holm SH, Adolfsson K, Tegenfeldt JO (2012) Sorting cells by size, shape and deformability. Lab Chip 12:1048–1051. doi: 10.1039/C2LC21083E CrossRefGoogle Scholar
  4. Bhagat AAS, Bow H, Hou HW, Tan SJ, Han J, Lim CT (2010) Microfluidics for cell separation. Med Biol Eng Comput 48:999–1014. doi: 10.1007/s11517-010-0611-4 CrossRefGoogle Scholar
  5. Collins DJ, Alan T, Neild A (2014) Particle separation using virtual deterministic lateral displacement (vDLD). Lab Chip 14:1595–1603. doi: 10.1039/c3lc51367j CrossRefGoogle Scholar
  6. Destgeer G, Ha BH, Jung JH, Sung HJ (2014) Submicron separation of microspheres via travelling surface acoustic waves. Lab Chip 14:4665–4672. doi: 10.1039/C4LC00868E CrossRefGoogle Scholar
  7. Devendran C, Gunasekara NR, Collins DJ, Neild A (2016) Batch process particle separation using surface acoustic waves (SAW): integration of travelling and standing SAW. RSC Adv 6:5856–5864. doi: 10.1039/c5ra26965b CrossRefGoogle Scholar
  8. Di Carlo D (2009) Inertial microfluidics. Lab Chip 9:3038–3046. doi: 10.1039/B912547G CrossRefGoogle Scholar
  9. Di Carlo D, Irimia D, Tompkins RG, Toner M (2007) Continuous inertial focusing, ordering, and separation of particles in microchannels. Proc Natl Acad Sci U S A 104:18892–18897. doi: 10.1073/pnas.0704958104 CrossRefGoogle Scholar
  10. Gossett DR, Weaver WM, Mach AJ, Hur SC, Tse HTK, Lee W, Amini H, Di Carlo D (2010) Label-free cell separation and sorting in microfluidic systems. Anal Bioanal Chem 397:3249–3267. doi: 10.1007/s00216-010-3721-9 CrossRefGoogle Scholar
  11. Gossett DR, Tse HTK, Dudani JS, Goda K, Woods TA, Graves SW, Di Carlo D (2012) Inertial manipulation and transfer of microparticles across laminar fluid streams. Small 8:2757–2764. doi: 10.1002/smll.201200588 CrossRefGoogle Scholar
  12. Guan G, Wu L, Bhagat AA, Li Z, Chen PC, Chao S, Ong CJ, Han J (2013) Spiral microchannel with rectangular and trapezoidal cross-sections for size based particle separation. Sci Rep 3:1475. doi: 10.1038/srep01475 CrossRefGoogle Scholar
  13. Hansson J, Karlsson JM, Haraldsson T, Brismar H, van der Wijngaart W, Russom A (2012) Inertial microfluidics in parallel channels for high-throughput applications. Lab Chip 12:4644–4650. doi: 10.1039/C2LC40241F CrossRefGoogle Scholar
  14. Ho BP, Leal GL (1974) Inertial migration of rigid spheres in two-dimensional unidirectional flows. J Fluid Mech 65:365–400. doi: 10.1017/S0022112074001431 CrossRefzbMATHGoogle Scholar
  15. Huang Y, Joo S, Duhon M, Heller M, Wallace B, Xu X (2002) Dielectrophoretic cell separation and gene expression profiling on microelectronic chip arrays. Anal Chem 74:3362–3371. doi: 10.1021/ac011273v CrossRefGoogle Scholar
  16. Huang LR, Cox EC, Austin RH, Sturm JC (2004) Continuous particle separation through deterministic lateral displacement. Science 304:987–990. doi: 10.1126/science.1094567 CrossRefGoogle Scholar
  17. Huang SB, Chen J, Wang J, Yang CL, Wu MH (2012) A new optically-induced dielectrophoretic (ODEP) force-based scheme for effective cell sorting. Int J Electrochem Sci 7:12656–12667Google Scholar
  18. Huang SB, Wu MH, Lin YH, Hsieh CH, Yang CL, Lin HC, Tseng CP, Lee GB (2013) High-purity and label-free isolation of circulating tumor cells (CTCs) in a microfluidic platform by using optically-induced-dielectrophoretic (ODEP) force. Lab Chip 13:1371–1383. doi: 10.1039/C3LC41256C CrossRefGoogle Scholar
  19. Hur SC, Tse HTK, Di Carlo D (2010) Sheathless inertial cell ordering for extreme throughput flow cytometry. Lab Chip 10:274–280. doi: 10.1039/B919495A CrossRefGoogle Scholar
  20. Hur SC, Henderson-MacLennan NK, McCabe ERB, Di Carlo D (2011) Deformability-based cell classification and enrichment using inertial microfluidics. Lab Chip 11:912–920. doi: 10.1039/C0LC00595A CrossRefGoogle Scholar
  21. Kim YW, Yoo JY (2009) Axisymmetric flow focusing of particles in a single microchannel. Lab Chip 9:1043–1045. doi: 10.1039/B815286A CrossRefGoogle Scholar
  22. Kuntaegowdanahalli SS, Bhagat AAS, Kumar G, Papautsky I (2009) Inertial microfluidics for continuous particle separation in spiral microchannels. Lab Chip 9:2973–2980. doi: 10.1039/B908271A CrossRefGoogle Scholar
  23. Leighton D, Acrivos A (1987) The shear-induced migration of particles in concentrated suspensions. J Fluid Mech 181:415–439. doi: 10.1017/S0022112087002155 CrossRefGoogle Scholar
  24. Martel JM, Toner M (2014) Inertial focusing in microfluidics. Annu Rev Biomed Eng 16:371–396. doi: 10.1146/annurev-bioeng-121813-120704 CrossRefGoogle Scholar
  25. Matas J-P, Morris JF, Guazzelli E (2004) Lateral forces on a sphere. Oil Gas Sci Technol 59:59–70. doi: 10.2516/ogst:2004006 CrossRefzbMATHGoogle Scholar
  26. Ohta A, Chiou P, Phan H, Sherwood S, Yang J, Lau A, Hsu H, Jamshidi A, Wu M (2007) Optically controlled cell discriminationand trapping using optoelectronic tweezers. IEEE J Sel Top Quantum Electron 13:235–243. doi: 10.1109/JSTQE.2007.893558 CrossRefGoogle Scholar
  27. Park J-S, Song S-H, Jung H-I (2009) Continuous focusing of microparticles using inertial lift force and vorticity via multi-orifice microfluidic channels. Lab Chip 9:939–948. doi: 10.1039/B813952K CrossRefGoogle Scholar
  28. Rubinow SI, Keller JB (1961) The transverse force on a spinning sphere moving in a viscous fluid. J Fluid Mech 11:447–459. doi: 10.1017/S0022112061000640 MathSciNetCrossRefzbMATHGoogle Scholar
  29. Saffman PG (1965) The lift on a small sphere in a slow shear. J Fluid Mech 22:385–400. doi: 10.1017/S0022112065000824 CrossRefzbMATHGoogle Scholar
  30. Segre G (1961) Radial particle displacements in Poiseuille flow of suspensions. Nature 189:209–210. doi: 10.1038/189209a0 CrossRefGoogle Scholar
  31. Segre G, Silberberg A (1962) Behavior of macroscopic rigid spheres in Poiseuille flow. J Fluid Mech 14:136–157. doi: 10.1017/S0022112062001111 CrossRefzbMATHGoogle Scholar
  32. Seo H-K, Kim Y-H, Kim H-O, Kim Y-J (2010) Hybrid cell sorters for on-chip cell separation by hydrodynamics and magnetophoresis. J Micromech Microeng 20:095019. doi: 10.1088/0960-1317/20/9/095019 CrossRefGoogle Scholar
  33. Sethu P, Sin A, Toner M (2006) Microfluidic diffusive filter for apheresis (leukapheresis). Lab Chip 6:83–89. doi: 10.1039/B512049G CrossRefGoogle Scholar
  34. Shah GJ, Ohta AT, Chiou EP-Y, Wu MC (2009) EWOD-driven droplet microfluidic device integrated with optoelectronic tweezers as an automated platform for cellular isolation and analysis. Lab Chip 9:1732–1739. doi: 10.1039/B821508A CrossRefGoogle Scholar
  35. Sheely ML (1932) Glycerol viscosity tables. Ind Eng Chem Res 24:1060–1064. doi: 10.1021/ie50273a022 CrossRefGoogle Scholar
  36. Shi J, Mao X, Ahmed D, Colletti A, Huang TJ (2008) Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW). Lab Chip 8:221–223. doi: 10.1039/B716321E CrossRefGoogle Scholar
  37. Shields CW, Reyes CD, Lopez GP (2015) Microfluidic cell sorting: a review of the advances in the separation of cells from debulking to rare cell isolation. Lab Chip 15:1230–1249. doi: 10.1039/C4LC01246A CrossRefGoogle Scholar
  38. Takagi J, Yamada M, Yasuda M, Seki M (2005) Continuous particle separation in a microchannel having asymmetrically arranged multiple branches. Lab Chip 5:778–784. doi: 10.1039/B501885D CrossRefGoogle Scholar
  39. Vahey MD, Voldman J (2008) An equilibrium method for continuous-flow cell sorting using dielectrophoresis. Anal Chem 80:3135–3143. doi: 10.1021/ac7020568 CrossRefGoogle Scholar
  40. Wu ZG, Hjort K (2009) Microfluidic hydrodynamic cell separation: a review. Micro Nanosyst 1:181–192. doi: 10.2174/1876402910901030181 CrossRefGoogle Scholar
  41. Wu ZG, Liu AQ, Hjort K (2007) Microfluidic continuous particle/cell separation via electroosmotic-flow-tuned hydrodynamic spreading. J Micromech Microeng 17:1992–1999. doi: 10.1088/0960-1317/17/10/010 CrossRefGoogle Scholar
  42. Wu ZG, Hjort K, Wicher G, Svenningsen ÅF (2008) Microfluidic high viability neural cell separation using viscoelastically tuned hydrodynamic spreading. Biomed Microdevices 10:631–638. doi: 10.1007/s10544-008-9174-7 CrossRefGoogle Scholar
  43. Wu ZG, Willing B, Bjerketorp J, Jansson JK, Hjort K (2009) Soft inertial microfluidics for high throughput separation of bacteria from human blood cells. Lab Chip 9:1193–1199. doi: 10.1039/B817611F CrossRefGoogle Scholar
  44. Yamada M, Seki M (2005) Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics. Lab Chip 5:1233–1239. doi: 10.1039/B509386D CrossRefGoogle Scholar
  45. Yamada M, Nakashima M, Seki M (2004) Pinched flow fractionation: continuous size separation of particles utilizing a laminar flow profile in a pinched microchannel. Anal Chem 76:5465–5471. doi: 10.1021/ac049863r CrossRefGoogle Scholar
  46. Yamada M, Kano K, Tsuda Y, Kobayashi J, Yamato M, Seki M, Okano T (2007) Microfluidic devices for size-dependent separation of liver cells. Biomed Microdevices 9:637–645. doi: 10.1007/s10544-007-9055-5 CrossRefGoogle Scholar
  47. Zborowski M, Chalmers JJ (2011) Rare cell separation and analysis by magnetic sorting. Anal Chem 83:8050–8056. doi: 10.1021/ac200550d CrossRefGoogle Scholar
  48. Zhang X, Cooper JM, Monaghan PB, Haswell SJ (2006) Continuous flow separation of particles within an asymmetric microfluidic device. Lab Chip 6:561–566. doi: 10.1039/B515272K CrossRefGoogle Scholar
  49. Zhou J, Papautsky I (2013) Fundamentals of inertial focusing in microchannels. Lab Chip 13:1121–1132. doi: 10.1039/C2LC41248A CrossRefGoogle Scholar
  50. Zhou J, Giridhar PV, Kasper S, Papautsky I (2014) Modulation of rotation-induced lift force for cell filtration in a low aspect ratio microchannel. Biomicrofluidics 8:044112. doi: 10.1063/1.4891599 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Wenchao Xu
    • 1
  • Zining Hou
    • 1
  • Zhenhua Liu
    • 1
  • Zhigang Wu
    • 1
    • 2
    Email author
  1. 1.State Key Laboratory of Digital Manufacturing Equipment and TechnologyHuazhong University of Science and TechnologyWuhanChina
  2. 2.Department of Engineering Science, The Ångström LaboratoryUppsala UniversityUppsalaSweden

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