Microfluidics and Nanofluidics

, Volume 9, Issue 1, pp 1–16 | Cite as

Particle focusing in microfluidic devices

  • Xiangchun Xuan
  • Junjie Zhu
  • Christopher Church


Focusing particles (both biological and synthetic) into a tight stream is usually a necessary step prior to counting, detecting, and sorting them. The various particle focusing approaches in microfluidic devices may be conveniently classified as sheath flow focusing and sheathless focusing. Sheath flow focusers use one or more sheath fluids to pinch the particle suspension and thus focus the suspended particles. Sheathless focusers typically rely on a force to manipulate particles laterally to their equilibrium positions. This force can be either externally applied or internally induced by channel topology. Therefore, the sheathless particle focusing methods may be further classified as active or passive by the nature of the forces involved. The aim of this article is to introduce and discuss the recent developments in both sheath flow and sheathless particle focusing approaches in microfluidic devices.


Particle focusing Microfluidics Review Sheath flow Dielectrophoresis Inertia 



This work was supported by NSF under grant CBET-0853873 with Marc S. Ingber as the grant monitor. The support from Clemson University through a startup package to Xuan, the Creative Inquiry Program, and the Research Investment Initiative Fund Program is also gratefully acknowledged.


  1. Ai Y, Joo SW, Jiang Y, Xuan X, Qian S (2009) Transient electrophoretic motion of a charged particle through a converging-diverging microchannel: effect of direct current dielectrophoretic force. Electrophoresis 30:2499–2506CrossRefGoogle Scholar
  2. Ai Y, Park S, Zhu J, Xuan X, Beskok A, Qian S (2010a) DC electrokinetic particle transport in an L-shaped microchannel. Langmuir 26:2937–2944CrossRefGoogle Scholar
  3. Ai Y, Qian S, Liu S, Joo SW (2010b) Dielectrophoretic choking phenomenon in a converging-diverging microchannel. Biomicrofluidics 4:013201CrossRefGoogle Scholar
  4. Anderson JL (1989) Colloid transport by interfacial forces. Annu Rev Fluid Mech 21:61–99CrossRefGoogle Scholar
  5. Aoki R, Yamada M, Yasuda M, Seki M (2009) In-channel focusing of flowing microparticles utilizing hydrodynamic filtration. Microfluid Nanofluid 6:571–576CrossRefGoogle Scholar
  6. Asmolov ES (1999) The inertial lift on a spherical particle in a plane Poiseuille flow at large channel Reynolds number. J Fluid Mech 381:63–87zbMATHCrossRefGoogle Scholar
  7. Ateya DA, Erickson JS, Howell PB Jr, Hilliard LR, Golden JP, Ligler FS (2008) The good, the bad, and the tiny: a review of microflow cytometry. Anal Bioanal Chem 391:1485–1498CrossRefGoogle Scholar
  8. Barbulovic-Nad I, Xuan X, Lee JSH, Li D (2006) DC-dielectrophoretic separation of microparticles using an oil droplet obstacle. Lab Chip 6:274–279CrossRefGoogle Scholar
  9. Barrett LM, Skulan AJ, Singh AK, Cummings EB, Fiechtner GJ (2005) Dielectrophoretic manipulation of particles and cells using insulating ridges in faceted prism microchannels. Anal Chem 77:6798–6804CrossRefGoogle Scholar
  10. Berger A, Talbot L, Yao LS (1983) Flow in curved pipes. Annu Rev Fluid Mech 15:461–512CrossRefGoogle Scholar
  11. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2008a) Enhanced particle filtration in straight microchannels using shear-modulated inertial migration. Phys Fluid 20:101702CrossRefGoogle Scholar
  12. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2008b) Continuous particle separation in spiral microchannels using dean flows and differential migration. Lab Chip 8:1906–1914CrossRefGoogle Scholar
  13. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2009) Inertial microfluidics for continuous particle filtration and extraction. Microfluid Nanofluid 7:221–230CrossRefGoogle Scholar
  14. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2010) Inertial microfluidics for sheath-less high-throughput flow cytometry. Biomed Microdev. doi: 10.1007/s10544-009-9374-9
  15. Braschler T, Demierre N, Nascimento E, Silva T, Oliva AG, Renaud P (2008) Continuous separation of cells by balanced dielectrophoretic forces at multiple frequencies. Lab Chip 8:280–286CrossRefGoogle Scholar
  16. Chang CC, Huang ZY, Yang RJ (2007) Three-dimensional hydrodynamic focusing in two-layer polydimethylsiloxane (PDMS) microchannels. J Micromech Microeng 17:1479–1486CrossRefGoogle Scholar
  17. Chau LK, Osborn T, Wu CC, Yager P (1999) Microfabricated silicon flow-cell for optical monitoring of biological fluids. Anal Sci 15:721–724CrossRefGoogle Scholar
  18. Cheng IF, Chang HC, Hou D, Chang HC (2007) An integrated dielectrophoretic chip for continuous bioparticle filtering, focusing, sorting, trapping, and detecting. Biomicrofluidics 1:021503 (1–15)Google Scholar
  19. Cho YK, Kim S, Lee K, Park C, Lee JG, Ko C (2009) Bacteria concentration using a membrane type insulator-based dielectrophoresis in a plastic chip. Electrophoresis 30:3153–3159CrossRefGoogle Scholar
  20. Choi S, Park JK (2007) Continuous hydrophoretic separation and sizing of microparticles using slanted obstacles in a microchannel. Lab Chip 7:890–897CrossRefGoogle Scholar
  21. Choi S, Park JK (2008) Sheathless hydrophoretic particle focusing in a microchannel with exponentially increasing obstacle arrays. Anal Chem 80:3035–3039CrossRefGoogle Scholar
  22. Choi S, Song S, Choi C, Park JK (2007) Continuous blood cell separation by hydrophoretic filtration. Lab Chip 7:1532–1538CrossRefGoogle Scholar
  23. Choi S, Song S, Choi C, Park JK (2008) Sheathless focusing of microbeads and blood cells based on hydrophoresis. Small 4:634–641CrossRefGoogle Scholar
  24. Choi KH, Rehmani MAA, Doh I, Cho Y (2009a) Numerical study of particle focusing through improved lab-on-a-chip device by positive dielectrophoresis. Microsyst Technol 15:1059–1065CrossRefGoogle Scholar
  25. Choi S, Song S, Choi C, Park JK (2009b) Hydrophoretic sorting of micrometer and submicrometer particles using anisotropic microfluidic obstacles. Anal Chem 81:50–55CrossRefGoogle Scholar
  26. Choi S, Song S, Choi C, Park JK (2009c) Microfluidic self-sorting of mammalian cells to achieve cell cycle synchrony by hydrophoresis. Anal Chem 81:1964–1968CrossRefGoogle Scholar
  27. Chou CF, Zenhausern F (2003) Electrodeless dielectrophoresis for micro total analysis systems. IEEE Eng Med Biol Mag 22:62–67CrossRefGoogle Scholar
  28. Chou CF, Tegenfeldt JO, Bakajin O, Chan SS, Cox EC, Darnton N, Duke T, Austin RH (2002) Electrodeless dielectrophoresis of single- and double-stranded DNA. Biophys J 83:2170–2179CrossRefGoogle Scholar
  29. Chu H, Doh I, Cho Y (2009) A three-dimensional (3D) particle focusing channel using the positive dielectrophoresis (pDEP) guided by a dielectric structure between two planar electrodes. Lab Chip 9:686–691CrossRefGoogle Scholar
  30. Chung TD, Kim HC (2007) Recent advances in miniaturized microfluidic flow cytometry for clinical use. Electrophoresis 28:4511–4520CrossRefGoogle Scholar
  31. Church C, Zhu J, Wang G, Tzeng TJ, Xuan X (2009) Electrokinetic focusing and filtration of cells in a serpentine microchannel. Biomicrofluidics 3:044109CrossRefGoogle Scholar
  32. Clarke RW, White SS, Zhou D, Ying L, Klenerman D (2005) Trapping of proteins under physiological conditions in a nanopipette. Angew Chem 44:3747–3750CrossRefGoogle Scholar
  33. Cummings EB, Singh AK (2000) Dielectrophoretic trapping without embedded electrodes. In: Proceedings of SPIE conference micromachining microfabrication, vol 4177, pp 164–173Google Scholar
  34. Cummings EB, Singh AK (2003) Dielectrophoresis in microchips containing arrays of insulating posts: theoretical and experimental results. Anal Chem 75:4724–4731CrossRefGoogle Scholar
  35. Davison SM, Sharp KV (2008) Transient simulations of the electrophoretic motion of a cylindrical particle through a 90° corner. Microfluid Nanofluid 4:409–418CrossRefGoogle Scholar
  36. Demierre N, Braschler T, Muller R (2008) Focusing and continuous separation of cells in a microfluidic device using lateral dielectrophoresis. Sens Actuators B 132:388–396CrossRefGoogle Scholar
  37. Di Carlo D (2009) Inertial microfluidics. Lab Chip 9:3038–3046CrossRefGoogle Scholar
  38. Di Carlo D, Irimia D, Tompkins RG, Toner M (2007) Continuous inertial focusing, ordering, and separation of particles in microchannels. Proc Natl Acad Sci 104:18892–18897CrossRefGoogle Scholar
  39. Di Carlo D, Edd JF, Irimia D, Tompkins RG, Toner M (2008) Equilibrium separation and filtration of particles using differential inertial focusing. Anal Chem 80:2204–2211CrossRefGoogle Scholar
  40. Di Carlo D, Edd JF, Humphry KJ, Stone HA, Toner M (2009) Particle segregation and dynamics in confined flows. Phys Rev Lett 102:094503CrossRefGoogle Scholar
  41. Edd JF, Di Carlo D, Humphry KJ, Koester S, Irimia D, Weitz DA, Toner M (2008) Controlled encapsulation of single-cells into monodisperse picolitre drops. Lab Chip 8:1262–1264CrossRefGoogle Scholar
  42. Faivre M, Abkarian M, Bickraj K, Stone HA (2006) Geometrical focusing of cells in a microfluidic device: an approach to separate blood plasma. Biorheology 43:147–159Google Scholar
  43. Fu AY, Spence C, Scherer A, Arnold FH, Quake SRA (1999) Microfabricated fluorescence-activated cell sorter. Nat Biotechnol 17:1109–1111CrossRefGoogle Scholar
  44. Fu LM, Yang RJ, Lin C, Pan Y, Lee GB (2004) Electrokinetically driven micro flow cytometers with integrated fiber optics for on-line cell/particle detection. Anal Chim Acta 507:163–169CrossRefGoogle Scholar
  45. Fu LM, Tsai CH, Lin CH (2008) A high-discernment microflow cytometer with microweir structure. Electrophoresis 29:1874–1880CrossRefGoogle Scholar
  46. Gallo-Villanueva RC, Rodriguez-Lopez CE, Diaz-de-la-Garza RI, Reyes-Betanzo C, Lapizco-Encinas BH (2009) DNA manipulation by means of insulator-based dielectrophoresis employing direct current electric fields. Electrophoresis 30:4195–4205CrossRefGoogle Scholar
  47. Gascoyne PRC, Vykoukal JV (2002) Particle separation by dielectrophoresis. Electrophoresis 23:1973–1983CrossRefGoogle Scholar
  48. Gascoyne PRC, Vykoukal JV (2004) Dielectrophoresis-based sample handling in general-purpose programmable diagnostic instruments. Proc IEEE 92:22–42CrossRefGoogle Scholar
  49. Goddard GR, Martin JC, Graves SW, Kaduchak G (2006) Ultrasonic particle concentration for sheath-less focusing of particles for analysis in a flow cytometer. Cytometry 69A:66–74CrossRefGoogle Scholar
  50. Goddard GR, Sanders CK, Martin JC, Kaduchak G, Graves SW (2007) Analytical performance of an ultrasonicparticle focusing flow cytometer. Anal Chem 79:8740–8746CrossRefGoogle Scholar
  51. Godin J, Chen C, Cho SH, Qiao W, Tsai F, Lo Y (2008) Microfluidics and photonics for bio-system-on-a-chip: a review of advancements in technology towards a microfluidic flow cytometry chip. J Biophoton 1:355–376CrossRefGoogle Scholar
  52. Golden JP, Kim JS, Erickson JS, Hilliard LR, Howell PB, Anderson GP, Nasir M, Ligler FS (2009) Multi-wavelength microflow cytometer using groove-generated sheath flow. Lab Chip 9:1942–1950CrossRefGoogle Scholar
  53. Gossett DR, Di Carlo D (2009) Particle focusing mechanisms in curving confined flows. Anal Chem 81:2459–2465CrossRefGoogle Scholar
  54. Hairer G, Vellekoop MJ (2009) An integrated flow-cell for full sample stream control. Microfluid Nanofluid 7:647–658CrossRefGoogle Scholar
  55. Hairer G, Parr GS, Svasek P, Jachimowicz A, Vellekoop MJ (2008) Investigations of micrometer sample stream profiles in a three-dimensional hydrodynamic focusing device. Sens Actuators B 132:518–524CrossRefGoogle Scholar
  56. Hawkins BG, Smith AE, Syed YA, Kirby BJ (2007) Continuous-flow particle separation by 3D insulative dielectrophoresis using coherently shaped, DC-biased, AC electric fields. Anal Chem 79:7291–7300CrossRefGoogle Scholar
  57. Holmes D, Morgan H, Green NG (2006) High throughput particle analysis: combining dielectrophoretic particle focusing with confocal optical detection. Biosens Bioelectron 21:1621–1630CrossRefGoogle Scholar
  58. Hou HH, Tsai CH, Fu LM, Yang RJ (2009) Experimental and numerical investigation into micro-flow cytometer with 3-D hydrodynamic focusing effect and micro-weir structure. Electrophoresis 30:2507–2515CrossRefGoogle Scholar
  59. Howell PB, Golden JP, Hilliard LR, Erickson JS, Mott DR, Ligler FS (2008) Two simple and rugged designs for creating microfluidic sheath flow. Lab Chip 8:1097–1103CrossRefGoogle Scholar
  60. Hsu CH, Di Carlo D, Chen CC, Irimia D, Toner M (2008) Microvortex for focusing, guiding and sorting of particles. Lab Chip 8:2128–2134CrossRefGoogle Scholar
  61. Hughes MP (2002) Strategies for dielectrophoretic separation in laboratory-on-a-chip systems. Electrophoresis 23:2569–2582CrossRefGoogle Scholar
  62. Huh D, Gu W, Kamotani Y, Grotgerg JB, Takayama S (2005) Microfluidics for flow cytometric analysis of cells and particles. Physiol Meas 26:R73–R98CrossRefGoogle Scholar
  63. Hur SC, Tse HTK, Di Carlo D (2009) Sheathless inertial cell ordering for extreme throughput flow cytometry. Lab Chip. doi: 10.1039/b919495a
  64. Jeffrey RC, Pearson JRA (1965) Particle motion in laminar vertical tube flow. J Fluid Mech 22:721–735CrossRefGoogle Scholar
  65. Jen CP, Chen TW (2008) Selective trapping of live and dead mammalian cells using insulator-based dielectrophoresis within open-top microstructures. Biomed Microdev 11:597–607CrossRefGoogle Scholar
  66. Kang K, Kang Y, Xuan X, Li D (2006) Continuous separation of microparticles by size with DC-dielectrophoresis. Electrophoresis 27:694–702CrossRefGoogle Scholar
  67. Kang Y, Li D, Kalams SA, Eid JE (2008) DC-dielectrophoretic separation of biological cells by size. Biomed Microdev 10:243–249CrossRefGoogle Scholar
  68. Kang Y, Cetin B, Wu Z, Li D (2009) Continuous particle separation with localized AC-dielectrophoresis using embedded electrodes and an insulating hurdle. Electrochim Acta 54:1715–1720CrossRefGoogle Scholar
  69. Kersaudy-Kerhoas M, Dhariwal R, Desmulliez MPY (2008) Recent advances in microparticle continuous separation. IET Nanobiotechnol 2:1–13CrossRefGoogle Scholar
  70. Kim YW, Yoo JY (2008) The lateral migration of neutrally-buoyant spheres transported through square microchannels. J Micromech Microeng 18:065015(1–13)Google Scholar
  71. Kim YW, Yoo JY (2009a) Axisymmetric flow focusing of particles in a single microchannel. Lab Chip 9:1043–1045CrossRefGoogle Scholar
  72. Kim YW, Yoo JY (2009b) Three-dimensional focusing of red blood cells in microchannels for bio-sensing applications. Biosens Bioelectron 24:3677–3682CrossRefGoogle Scholar
  73. Kim JS, Anderson GP, Erickson JS, Golden JP, Nasir M, Ligler FS (2009) Multiplexed detection of bacteria and toxins using a microflow cytometer. Anal Chem 81:5426–5432CrossRefGoogle Scholar
  74. Kohlheyer D, Unnikrishnan S, Besselink GAJ, Schlautmann S, Schasfoort RBM (2008) A microfluidic device for array patterning by perpendicular electrokinetic focusing. Microfluid Nanofluid 4:557–564CrossRefGoogle Scholar
  75. Kulrattanarak T, van der Sman RGM, Schroen CGPH, Boom RM (2008) Classification and evaluation of microfluidic devices for continuous suspension fractionation. Adv Colloid Interface Sci 142:53–65CrossRefGoogle Scholar
  76. Kummrow A, Theisen J, Frankowski M, Tuchscheerer A, Yildirim H, Brattke K, Schmidt M, Neukammer J (2009) Microfluidic structures for flow cytometric analysis of hydrodynamically focussed blood cells fabricated by ultraprecision micromachining. Lab Chip 9:972–981CrossRefGoogle Scholar
  77. Kuntaegowdanahalli S, Bhagat AAS, Kumar G, Papautsky I (2009) Inertial microfluidics for continuous particle separation in spiral microchannels. Lab Chip 9:2973–2980CrossRefGoogle Scholar
  78. Lapizco-Encinas BH, Rito-Palmomares M (2007) Dielectrophoresis for the manipulation of nanoparticles. Electrophoresis 28:4521–4538CrossRefGoogle Scholar
  79. Lapizco-Encinas BH, Simmons BA, Cummings EB, Fintschenko Y (2004a) Dielectrophoretic concentration and separation of live and dead bacteria in an array of insulators. Anal Chem 76:1571–1579CrossRefGoogle Scholar
  80. Lapizco-Encinas BH, Simmons BA, Cummings EB, Fintschenko Y (2004b) Insulator-based dielectrophoresis for the selective concentration and separation of live bacteria in water. Electrophoresis 25:1695–1704CrossRefGoogle Scholar
  81. Lapizco-Encinas BH, Davalos RV, Simmons BA, Cummings EB, Fintschenko Y (2005) An insulator-based (electrodeless) dielectrophoretic concentrator for microbes in water. J Microbiol Method 62:317–326CrossRefGoogle Scholar
  82. Lapizco-Encinas BH, Ozuna-Chacon S, Rito-Palomares M (2008) Protein manipulation with insulator-based dielectrophoresis and DC electric fields. J Chromatogr A 1206:45–51CrossRefGoogle Scholar
  83. Leal LG (1980) Particle motions in a viscous fluid. Annu Rev Fluid Mech 12:435–476MathSciNetCrossRefGoogle Scholar
  84. Lee GB, Lin C, Chang G (2003) Micro flow cytometers with buried SU-8/SOG optical waveguides. Sens Actuators A 103:165–170CrossRefGoogle Scholar
  85. Lee GB, Chang CC, Huang SB, Yang RJ (2006) The hydrodynamic focusing effect in rectangular microchannels. J Micromech Microeng 16:1024–1032CrossRefGoogle Scholar
  86. Lee MG, Choi S, Park JK (2009) Three-dimensional hydrodynamic focusing with a single sheath flow in a single-layer microfluidic device. Lab Chip 9:3155–3160CrossRefGoogle Scholar
  87. Lewpiriyawong N, Yang C, Lam YC (2008) Dielectrophoretic manipulation of particles in a modified microfluidic H-Filter with multi-insulating blocks. Biomicrofluidics 2:034105CrossRefGoogle Scholar
  88. Lin CH, Lee GB, Fu LM, Hwey BH (2004) Vertical focusing device utilizing dielectrophoretic force and its application on microflow cytometer. J Microelectromech Syst 13:923–932CrossRefGoogle Scholar
  89. Lin R, Ho C, Liu C, Chang H (2006) Dielectrophoresis based-cell patterning for tissue engineering. Biotechnol J 1:949–957CrossRefGoogle Scholar
  90. Liu C, Stakenborg T, Peeters S, Lagae L (2009) Cell manipulation with magnetic particles toward microfluidic cytometry. J Appl Phys 105:102014CrossRefGoogle Scholar
  91. Mao X, Huang TJ (2008) Focusing fluids and light in micro/nano scale—enabling technologies for single-particle detection. IEEE Nanotechnol Mag 2:22–27CrossRefGoogle Scholar
  92. Mao X, Waldeisen JR, Huang TJ (2007) “Microfluidic drifting”—implementing three-dimensional hydrodynamic focusing with a single-layer planar microfluidic device. Lab Chip 7:1260–1262CrossRefGoogle Scholar
  93. Mao X, Lin SS, Dong C, Huang TJ (2009) Single-layer planar on-chip flow cytometer using microfluidic drifting based three-dimensional (3D) hydrodynamic focusing. Lab Chip 9:1583–1589CrossRefGoogle Scholar
  94. Morgan H, Green NG (2002) AC electrokinetics: colloids and nanoparticles. Research Studies Press, HertfordshireGoogle Scholar
  95. Morton KJ, Loutherback K, Inglis DW, Tsui OK, Sturm JC, Chou SY, Austin RH (2008) Hydrodynamic metamaterials: microfabricated arrays to steer, refract, and focus streams of biomaterials. Proc Natl Acad Sci 105:7434–7438CrossRefGoogle Scholar
  96. Ozuna-Chacon S, Lapizco-Encinas BH, Rito-Palomares M, Martínez-Chapa SO, Reyes-Betanzo C (2008) Performance characterization of an insulator-based dielectrophoretic microdevice. Electrophoresis 29:3115–3122CrossRefGoogle Scholar
  97. Pamme N (2007) Continuous flow separations in microfluidic devices. Lab Chip 7:1644–1659CrossRefGoogle Scholar
  98. Park J, Song S, Jung H (2009) Continuous focusing of microparticles using inertial lift force and vorticity via multi-orifice microfluidic channels. Lab Chip 9:939–948CrossRefGoogle Scholar
  99. Petersson F, Nilsson A, Jonsson H, Laurell T (2005) Carrier medium exchange through ultrasonic particle switching in microfluidic channels. Anal Chem 77:1216–1221CrossRefGoogle Scholar
  100. Petersson F, Aberg L, Sword-Nilsson AM, Laurell T (2007) Free flow acoustophoresis: microfluidic-based mode of particle and cell separation. Anal Chem 79:5117–5123CrossRefGoogle Scholar
  101. Pohl HA (1978) Dielectrophoresis. Cambridge University Press, CambridgeGoogle Scholar
  102. Prinz C, Tegenfeldt JO, Austin RH, Cox EC, Sturm JC (2002) Bacterial chromosome extraction and isolation. Lab Chip 2:207–212CrossRefGoogle Scholar
  103. Pysher MD, Hayes MA (2007) Electrophoretic and dielectrophoretic field gradient technique for separating bioparticles. Anal Chem 79:4552–4557CrossRefGoogle Scholar
  104. Repetti RV, Leonard EF (1964) Segré-Silberberg annulus formation: a possible explanation. Nature 203:1346–1348CrossRefGoogle Scholar
  105. Rodriguez-Trujillo R, Mills CA, Samitier J, Gomila G (2007) Low cost micro-Coulter counter with hydrodynamic focusing. Microfluid Nanofluid 3:171–176CrossRefGoogle Scholar
  106. Russom A, Gupta AK, Nagrath S, Di Carlo D, Edd JF, Toner M (2009) Differential inertial focusing of particles in curved low-aspect-ratio microchannels. New J Phys 11:075025CrossRefGoogle Scholar
  107. Saffman PG (1965) The lift on a small sphere in a slow shear flow. J Fluid Mech 22:385–400zbMATHCrossRefGoogle Scholar
  108. Scott R, Sethu P, Harnett CK (2008) Three-dimensional hydrodynamic focusing in a microfluidic Coulter counter. Rev Sci Instrum 79:046104CrossRefGoogle Scholar
  109. Segre G, Silberberg A (1961) Radial particle displacements in Poiseuille flow of suspensions. Nature 189:209–210CrossRefGoogle Scholar
  110. Seo J, Lean MH, Kole A (2007a) Membrane-free microfilltration by asymmetric inertial migration. Appl Phys Lett 91:033901CrossRefGoogle Scholar
  111. Seo J, Lean MH, Kole A (2007b) Membraneless microseparation by asymmetry in curvilinear laminar flows. J Chromatogr A 1162:126–131CrossRefGoogle Scholar
  112. 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 8:221–223CrossRefGoogle Scholar
  113. Shi J, Ahmed D, Mao D, Lin SS, Huang TJ (2009a) Acoustic tweezers: patterning cells and microparticles using standing surface acoustic waves (SSAW). Lab Chip 9:2890–2895CrossRefGoogle Scholar
  114. Shi J, Huang H, Stratton Z, Lawit A, Huang Y, Huang TJ (2009b) Continuous particle separation in a microfluidic channel via standing surface acoustic waves (SSAW). Lab Chip 9:3354–3359CrossRefGoogle Scholar
  115. Sims CE, Allbritton NL (2007) Analysis of single mammalian cells on-chip. Lab Chip 7:423–440CrossRefGoogle Scholar
  116. Tanaka Y, Sato K, Shimizu T, Yamato M, Okano T, Kitamori T (2007) Biological cells on microchips: new technologies and applications. Biosens Bioelectron 23:449–458CrossRefGoogle Scholar
  117. Thwar PK, Linderman JJ, Burns MA (2007) Electrodeless direct current dielectrophoresis using reconfigurable field-shaping oil barriers. Electrophoresis 28:4572–4581CrossRefGoogle Scholar
  118. Toner M, Irimia D (2005) Blood-on-a-chip. Annu Rev Biomed Eng 7:77–103CrossRefGoogle Scholar
  119. Tsai CG, Hou HH, Fu LM (2008) An optimal three-dimensional focusing technique for micro-flow cytometers. Microfluid Nanofluid 5:827–836CrossRefGoogle Scholar
  120. Tsutsui H, Ho CM (2009) Cell separation by non-inertial force fields in microfluidic systems. Mech Res Commun 36:92–103CrossRefGoogle Scholar
  121. Voldman J (2006) Electrical forces for microscale cell manipulation. Annu Rev Biomed Eng 8:425–454CrossRefGoogle Scholar
  122. Wang L, Lu J, Marchenko SA, Monuki ES, Flanagan LA, Lee AP (2009) Dual frequency dielectrophoresis with interdigitated sidewall electrodes for microfluidic flow-through separation of beads and cells. Electrophoresis 30:1–10zbMATHCrossRefGoogle Scholar
  123. Watkins N, Venkatesan BM, Toner M, Rodriguez W, Bashir R (2009) A robust electrical microcytometer with 3-dimensional hydrofocusing. Lab Chip 9:3177–3184CrossRefGoogle Scholar
  124. Xuan X, Li D (2005) Focused electrophoretic motion and selected electrokinetic dispensing of particles and cells in cross-microchannels. Electrophoresis 26:3552–3560CrossRefGoogle Scholar
  125. Xuan X, Raghibizadeh S, Li D (2006) Wall effects on electrophoretic motion of spherical polystyrene particles in a rectangular poly(dimethylsiloxane) microchannel. J Colloid Interface Sci 296:743–748CrossRefGoogle Scholar
  126. Yamada M, Seki M (2005) Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics. Lab Chip 5:1233–1239CrossRefGoogle Scholar
  127. Yamada M, Seki M (2006) Microfluidic particle sorter employing flow splitting and recombining. Anal Chem 78:1357–1362CrossRefGoogle Scholar
  128. 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 Microdev 9:637–645CrossRefGoogle Scholar
  129. Yamada M, Kobayashi J, Yamato M, Seki M, Okano T (2008) Millisecond treatment of cells using microfluidic devices via two-step carrier-medium exchange. Lab Chip 8:772–778CrossRefGoogle Scholar
  130. Yang RJ, Chang CC, Huang SB, Lee GB (2005) A new focusing model and switching approach for electrokinetic flow inside microchannels. J Micromech Microeng 15:2141–2148CrossRefGoogle Scholar
  131. Yi CQ, Li CW, Ji SL, Yang MS (2006) Microfluidics technology for manipulation and analysis of biological cells. Anal Chim Acta 560:1–23CrossRefGoogle Scholar
  132. Ying LM, White SS, Bruckbauer A, Meadows L, Korchev YE, Klenerman D (2004) Frequency and voltage dependence of the dielectrophoretic trapping of short lengths of DNA and dCTP in a nanopipette. Biophys J 86:1018–1027CrossRefGoogle Scholar
  133. Yu C, Vykoukal J, Vykoukal DM, Schwartz JA, Shi L, Gascoyne PRC (2005) A three-dimensional dielectrophoretic particle focusing channel for microcytometry applications. J Microelectromech Syst 14:480–487CrossRefGoogle Scholar
  134. Zeng L, Balachandar S, Fischer P (2005) Wall-induced forces on a rigid sphere at finite Reynolds number. J Fluid Mech 536:1–25zbMATHCrossRefGoogle Scholar
  135. Zhao Y, Fujimoto BS, Jeffries GDM, Schiro PG, Chiu DT (2007) Optical gradient flow focusing. Opt Express 15:6167–6176CrossRefGoogle Scholar
  136. Zhu J, Xuan X (2009a) Dielectrophoretic focusing of particles in a microchannel constriction using DC-biased AC electric fields. Electrophoresis 30:2668–2675CrossRefGoogle Scholar
  137. Zhu J, Xuan X (2009b) Particle electrophoresis and dielectrophoresis in curved microchannels. J Colloid Interface Sci 340:285–290CrossRefGoogle Scholar
  138. Zhu J, Tzeng TR, Hu G, Xuan X (2009a) DC dielectrophoretic focusing of particles in a serpentine microchannel. Microfluid Nanofluid 7:751–756CrossRefGoogle Scholar
  139. Zhu J, Tzeng JT, Xuan X (2009b) Dielectrophoretic focusing of microparticles in curved microchannels. In: Proceedings of the ASME 2009 international mechanical engineering congress and exposition, IMECE2009-11876, Lake Buena Vista, FLGoogle Scholar
  140. Zhu J, Tzeng TR, Xuan X (2010) Continuous dielectrophoretic separation of particles in a spiral microchannel. Electrophoresis. doi: 10.1002/elps.200900736 (in press)

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Xiangchun Xuan
    • 1
  • Junjie Zhu
    • 1
  • Christopher Church
    • 1
  1. 1.Department of Mechanical EngineeringClemson UniversityClemsonUSA

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