Light-actuated electrothermal microfluidic motion: experimental investigation and physical interpretation

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This paper experimentally investigates a light-actuated electrothermal (ET) flow generated by the simultaneous application of a uniform AC electric field and a focused laser and provides a detailed physical interpretation of the results based on electrokinetic theory. The ET flow is driven in deionized (DI) water in a microfluidic chip consisting of two parallel-plate electrodes and analyzed using flow visualization, particle image velocimetry and single dye-based laser-induced fluorescence thermometry. Our experimental observation and measurement find that the electrothermally induced fluid motion takes the form of a rotationally symmetric toroidal vortex. The toroidal ET vortex shows a source pattern over the electrode surface where the focused laser is located, when the applied AC electric signal is less than the charge relaxation frequency of the DI water. Focusing a laser alternately to each of the two parallel-plate electrodes reveals the forced convection nature of an ET flow. The gradual increase of temperature and applied electric potential in the DI water causes a linear and parabolic increase of the ET velocity, respectively. The increase of AC frequency leads to a rapid decrease of the flow strength. The relative size of natural convection in the ET flows is less than 10 % for most of the applied experimental conditions, but increases up to about 35 % in the AC frequency region above the liquid charge relaxation frequency. From this investigation, it is found that the transition between the two flows occurs for system characteristic lengths around 1.2 mm.

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  1. Bazant MZ (2004) Induced-charge electrokinetic phenomena: theory and microfluidic applications. Phys Rev Lett 92:66101–66104

  2. Bazant MZ, Thornton K, Ajdari A (2004) Diffuse-charge dynamics in electrochemical systems. Phys Rev E 70:0210561–24

  3. Castellanos A (1998) Electrohydrodynamics. Springer, New York

  4. Castellanos A, Ramos A, González A, Green NG, Morgan H (2003) Electrohydrodynamics and dielectrophoresis in microsystems: scaling laws. J Phys D Appl Phys 36:2584–2597

  5. Chamarthy P, Garimella SV, Wereley ST (2009) Non-intrusive temperature measurement using microscale visualization techniques. Exp Fluids 47:159–170

  6. Chamarthy P, Garimella SV, Wereley ST (2010) Measurement of the temperature non-uniformity in a microchannel heat sink using microscale laser-induced fluorescence. Int J Heat Mass Transf 53:3275–3283

  7. Chuang H-S, Gui L, Wereley ST (2012) Nano-resolution flow measurement based on single pixel evaluation PIV. Microfluid Nanofluid 13:49–64

  8. González A, Ramos A, Morgan H, Green NG, Castellanos A (2006) Electrothermal flows generated by alternating and rotating electric field in microsystems. J Fluid Mech 564:415–433

  9. Green NG, Morgan H (1999) Dielectrophoresis of Submicrometer Latex Spheres. 1. Experimental Results. J Phys Chem B 103:41–50

  10. Green NG, Ramos A, González A, Castellanos A, Morgan H (2000a) Electric field induced fluid flow on microelectrodes: the effect of illumination. J Phys D Appl Phys 33:L13–L17

  11. Green NG, Ramos A, González A, Morgan H, Castellanos A (2000b) Fluid flow induced by nonuniform ac electric fields in electrolytes on microelectrodes. I. Experimental measurements. Phys Rev E 61:4011–4018

  12. Green NG, Ramos A, González A, Castellanos A, Morgan H (2001) Electrothermally induced fluid flow on microelectrodes. J Electrostat 53:71–81

  13. Green NG, Ramos A, González A, Morgan H, Castellanos A (2002) Fluid flow induced by nonuniform ac electric fields in electrolytes on microelectrodes.III. Observation of streamlines and numerical simulation. Phys Rev E 66:26305–26311

  14. Gui L, Merzkirch W (1998) Generating arbitrarily sized interrogation windows for correlation-based analysis of particle image velocimetry recordings. Exp Fluids 24:66–69

  15. Haynes WM (2013) Handbook of chemistry and physics. CRC Press, Boca Raton

  16. Hayt WH (1967) Engineering electromagnetics. McGraw-Hill, New York

  17. Hong FJ, Bai F, Cheng P (2012) Numerical simulation of AC electrothermal micropump using a fully coupled model. Microfluid Nanofluid 13:411–420

  18. Jomeh S, Hoorfar M (2012) Study of the effect of electric field and electroneutrality on transport of biomolecules in microreactors. Microfluid Nanofluid 12:279–294

  19. Kim Y-H, Wereley ST, Chun C-H (2004) Phase-resolved flow field produced by a vibrating cantilever plate between two endplates. Phys Fluids 16:145–162

  20. Kreyszig E (2011) Advanced engineering mathematics. Wiley, Jefferson

  21. Kumar A, Williams SJ, Wereley ST (2009) Experiments on opto-electrically generated microfluidic vortices. Microfluid Nanofluid 6:637–646

  22. Kumar A, Chuang H-S, Wereley ST (2010a) Dynamic manipulation by light and electric fields: micrometer particles to microliter droplets. Langmuir 26:7656–7660

  23. Kumar A, Kwon J-S, Williams SJ, Green NG, Yip NK, Wereley ST (2010b) Optically modulated electrokinetic manipulation and concentration of colloidal particles near an electrode surface. Langmuir 26:5262–5272

  24. Kumar A, Cierpka C, Williams SJ, Kähler CJ, Wereley ST (2011a) 3D3C velocimetry measurements of an electrothermal microvortex using wavefront deformation PTV and a single camera. Microfluid Nanofluid 10:355–365

  25. Kumar A, Williams SJ, Chuang H-S, Green NG, Wereley ST (2011b) Hybrid opto-electric manipulation in microfluidics-opportunities and challenges. Lab Chip 11:2135–2148

  26. Kwon J-S, Wereley ST (2013) Towards new methodologies for manipulation of colloidal particles in a miniaturized fluidic device: optoelectrokinetic manipulation technique. J Fluids Eng 135:0213061–10

  27. Kwon J-S, Maeng J-S, Chun M-S, Song S (2008) Improvement of microchannel geometry subject to electrokinesis and dielectrophoresis using numerical simulations. Microfluid Nanofluid 5:23–31

  28. Kwon J-S, Ravindranath SP, Kumar A, Irudayaraj J, Wereley ST (2012a) Opto-electrokinetic manipulation for high-performance on-chip bioassays. Lab Chip 12:4955–4959

  29. Kwon J-S, Thakur R, Wereley ST (2012b) Rapid Electrokinetic Patterning. In: Bharat B (ed) Encyclopedia of nanotechnology. Springer, Netherland

  30. Lian M, Wu J (2009) Microfluidic flow reversal at low frequency by AC electrothermal effect. Microfluid Nanofluid 7:757–765

  31. Liao S-H, Chang C-Y, Chang H-C (2013) A capillary dielectrophoretic chip for real-time blood cell separation from a drop of whole blood. Biomicrofluidics 7:0241101–0241110

  32. Loire S, Kauffmann P, Mezić I, Meinhart CD (2012) A theoretical and experimental study of ac electrothermal flows. J Phys D Appl Phys 45:1853011–1853017

  33. Meinhart CD, Wereley ST, Santiago JG (1999) PIV measurements of a microchannel flow. Exp Fluids 27:414–419

  34. Meinhart CD, Wereley ST, Santiago JG (2000) A PIV algorithm for estimating time-averaged velocity fields. J Fluids Eng 122:285–289

  35. Mizuno A, Nishioka M, Ohno Y, Dascalescu L-D (1995) Liquid microvortex generated around a laser focal point in an intense high-frequency electric field. IEEE Trans Ind Appl 31:464–468

  36. Morgan H, Green NG (2002) AC electrokinetics: colloids and nanoparticles. Research Studies Press, Baldock

  37. Nakano M, Kurita H, Komatsu J, Mizuno A, Katsura S (2006) Stretching of long DNA molecules in the microvortex induced by laser and ac electric field. Appl Phys Lett 89:1339011–1339013

  38. Nakano M, Katsura S, Touchard GG (2007) Development of an optoelectrostatic micropump using a focused laser beam in a high-frequency electric field. IEEE Trans Ind Appl 43:232–237

  39. Ng WY, Goh S, Lam YC, Yang C (2009) DC-biased AC-electroosmotic and AC-electrothermal flow mixing in microchannels. Lab Chip 9:802–809

  40. Pashley RM, Rzechowicz M, Pashley LR, Francis MJ (2005) De-gassed water is a better cleaning agent. J Phys Chem B 109:1231–1238

  41. Ramos A, Morgan H, Green NG, Castellanos A (1998) Ac electrokinetics: a review of forces in microelectrode structures. J Phys D Appl Phys 31:2338–2353

  42. Ross D, Locascio Laurie E (2002) Microfluidic temperature gradient focusing. Anal Chem 74:2556–2564

  43. Ross D, Gaitan M, Locascio Laurie E (2001) Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Anal Chem 73:4117–4123

  44. Sigurdson M, Wang D, Meinhart CD (2005) Electrothermal stirring for heterogeneous immunoassays. Lab Chip 5:1366–1373

  45. Snoeyink C, Wereley S (2013) A novel 3D3C particle tracking method suitable for microfluidic flow measurements. Exp Fluids 54:14531–10

  46. Velasco V, Williams SJ (2013) Electrokinetic concentration, patterning, and sorting of colloids with thin film heaters. J Colloid Interface Sci 394:598–603

  47. Velasco V, Work JAH, Williams SJ (2012) Electrokinetic concentration and patterning of colloids with a scanning laser. Electrophoresis 33:1931–1937

  48. Wang D, Sigurdson M, Meinhart CD (2005) Experimental analysis of particle and fluid motion in ac electrokinetics. Exp Fluids 38:1–10

  49. Wereley ST, Gui L, Meinhart CD (2002) advanced algorithms for microscale particle image velocimetry. Am Inst Aeronaut Astronaut J 40:1047–1055

  50. Williams SJ, Kumar A, Wereley ST (2008) Electrokinetic patterning of colloidal particles with optical landscapes. Lab Chip 8:1879–1882

  51. Williams SJ, Kumar A, Green NG, Wereley ST (2009) A simple, optically induced electrokinetic method to concentrate and pattern nanoparticles. Nanoscale 1:133–137

  52. Williams SJ, Kumar A, Green NG, Wereley ST (2010) Optically induced electrokinetic concentration and sorting of colloids. J Micromech Microeng 20:1–11

  53. Wood NR, Wolsiefer AI, Cohn RW, Williams SJ (2013) Dielectrophoretic trapping of nanoparticles with an electrokinetic nanoprobe. Electrophoresis 34:1922–1930

  54. Yuan Q, Wu J (2013) Thermally biased AC electrokinetic pumping effect for Lab-on-a-chip based delivery of biofluids. Biomed Microdevices 15:125–133

  55. Zaghdoudi MC, Lallemand M (1999) Analysis of the polarity influence on nucleate pool boiling under a DC electric field. J Heat Transfer 121:856–864

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Correspondence to Steven T. Wereley.

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Kwon, J., Wereley, S.T. Light-actuated electrothermal microfluidic motion: experimental investigation and physical interpretation. Microfluid Nanofluid 19, 609–619 (2015) doi:10.1007/s10404-015-1587-z

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  • Particle Image Velocimetry
  • Natural Convection
  • Microfluidic Chip
  • Particle Image Velocimetry Measurement
  • Applied Electric Potential