Advertisement

Experiments in Fluids

, Volume 37, Issue 6, pp 872–882 | Cite as

Thermally induced velocity gradients in electroosmotic microchannel flows: the cooling influence of optical infrastructure

  • David Sinton
  • Xiangchun Xuan
  • Dongqing Li
Original

Abstract

An axially non-uniform temperature distribution is shown to induce a disturbance to the electroosmotic flow field in microchannels, causing a significant deviation from the ideal plug-like velocity profile. Such axial temperature gradients are shown to be induced passively by the increased dissipation of Joule heat through the optical infrastructure of a viewing window. A combination of caged-dye-based molecular tagging velocimetry (to determine the cross-stream velocity profiles), fluorescence-based thermometry (to determine the in-channel fluid temperatures), and electrical current measurements are employed. The temperature visualization experiments demonstrate that the fluid is locally cooled in the viewed region, resulting in a local increase in the electric field strength. When large fields are applied, measurements indicate that the fluid’s temperature in the viewed region can be as much as 30°C less than in the remainder of the capillary. Despite an increase in viscosity, this local cooling results in a locally increased electroosmotic wall velocity which induces a concave velocity profile in the viewed portion and a convex velocity profile elsewhere. Experimentally determined profiles exhibit a variation in velocity across the channel of up to 5%. The cause of this velocity profile curvature is confirmed by comparing the velocity profiles obtained at a range of fields to an analytical solution that includes the effects of temperature on the liquid conductivity and viscosity.

Keywords

Velocity Profile Electric Field Strength Electroosmotic Flow Viewing Window Electroosmotic Velocity 
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.

Notes

Acknowledgements

Financial support of this work by the Natural Sciences and Engineering Research Council (NSERC) of Canada, through post-graduate scholarships to D.S. and a research grant to D.L is gratefully acknowledged. Financial support from Glynn Williams, through a post-graduate scholarship to D.S. is also gratefully acknowledged.

References

  1. Burgi DS, Salomon K, Chien RL (1991) Methods for calculating the internal temperature of capillary columns during capillary electrophoresis. J Liq Chromatogr 14:847–867Google Scholar
  2. Chabinyc ML, Chiu DT, McDonald JC, Stroock AD, Christian JF, Karger AM, Whitesides GM (2001) An integrated fluorescence detection system in poly(dimethylsiloxane) for microfluidic applications. Anal Chem 73:4491–4498CrossRefPubMedGoogle Scholar
  3. Crabtree HJ, Cheong ECS, Tilroe DA, Backhouse CJ (2001) Microchip injection and separation anomalies due to pressure effects. Anal Chem 73:4079–4086CrossRefPubMedGoogle Scholar
  4. Erickson D, Sinton D, Li D (2003) Joule heating and heat transfer in poly(dimethylsiloxane) microfluidic systems. Lab Chip 3:141–149CrossRefPubMedGoogle Scholar
  5. Harrison DJ, Manz A, Fan Z, Ludi H, Widmer HM (1992) Capillary electrophoresis and sample injection systems integrated on a planar glass chip. Anal Chem 64:1926–1932Google Scholar
  6. Herr AE, Molho JI, Santiago JG, Mungal MG, Kenny TW, Garguilo MG (2000) Electroosmotic capillary flow with non-uniform zeta potential. Anal Chem 72:1053–1057CrossRefPubMedGoogle Scholar
  7. Hill RB, Klewicki JC (1996) Data reduction methods for flow tagging velocimetry measurements. Exp Fluids 20:142–152Google Scholar
  8. Huang X, Gordon MJ, Zare RN (1988) Current-monitoring method for measuring the electroosmotic flow rate in capillary zone electrophoresis. Anal Chem 60:1837–1838Google Scholar
  9. Hunter RJ (1981) Zeta potential in colloid science: principles and applications. Academic Press, New YorkGoogle Scholar
  10. Incropera FP, DeWitt DP (1990) Fundamentals of heat and mass transfer, 3rd edn. Wiley, New YorkGoogle Scholar
  11. Johnson TJ, Ross D, Gaitan M, Locascio LE (2001) Laser modification of preformed polymer microchannels: application to reduce band broadening around turns subject to electrokinetic flow. Anal Chem 73:3656–3661CrossRefPubMedGoogle Scholar
  12. Kim MJ, Beskok A, Kihm KD (2002) Electro-osmosis-driven micro-channel flows: a comparative study of microscopic particle image velocimetry measurements and numerical simulations. Exp Fluids 33:170–180Google Scholar
  13. Knox JH, McCormack KA (1994) Temperature effects in capillary electrophoresis. 1: internal capillary temperature and effect upon performance. Chromatographia 38:207–214Google Scholar
  14. Lempert WR, Magee K, Ronney P, Gee KR, Haugland RP (1995) Flow tagging velocimetry in incompressible flow using photo-activated nonintrusive tracking of molecular motion (PHANTOMM). Exp Fluids 18:249–257Google Scholar
  15. Martin RS, Gawron AJ, Lunte SM (2000) Dual-electrode electrochemical detection for poly(dimethylsiloxane)-fabricated capillary electrophoresis microchips. Anal Chem 72:3196–3202CrossRefPubMedGoogle Scholar
  16. Maynes D, Webb AR (2002) Velocity profile characterization in sub-millimeter diameter tubes using molecular tagging velocimetry. Exp Fluids 32:3–15CrossRefGoogle Scholar
  17. McDonald JC, Duffy DC, Anderson JR, Chiu DT, Wu H, Schueller OJA, Whitesides GM (2000) Fabrication of microfluidic systems in poly(Dimethylsiloxane). Electrophoresis 21:27–40CrossRefPubMedGoogle Scholar
  18. Meinhart CD, Wereley ST, Santiago JG (1999) PIV measurements of a microchannel flow. Exp Fluids 27:414–419CrossRefGoogle Scholar
  19. Meinhart CD, Wereley ST (2003) The theory of diffraction-limited resolution in microparticle image velocimetry. Meas Sci Technol 14:1047–1053CrossRefGoogle Scholar
  20. Molho JI, Herr AE, Mosier BP, Santiago JG, Kenny TW (2001) Optimization of turn geometries for microchip electrophoresis. Anal Chem 73:1350–1360CrossRefGoogle Scholar
  21. Mosier BP, Molho JI, Santiago JG (2002) Photobleached-fluorescence imaging for microflows. Exp Fluids 33:545–554Google Scholar
  22. Nguyen N-T, Wereley ST (2002) Fundamentals and applications of microfluidics. Artech House, Norwood, MassachusettsGoogle Scholar
  23. Paul P H, Garguilo MG, Rakestraw DJ (1998) Imaging of pressure- and electrokinetically driven flows through open capillaries. Anal Chem 70:2459–2467CrossRefGoogle Scholar
  24. Ross D, Gaitan M, Locascio LE (2001) Temperature measurement in microfluidic systems using a temperature-dependent fluorescent dye. Anal Chem 73:4117–4123CrossRefPubMedGoogle Scholar
  25. Russ JC (1999) The image processing handbook, 3rd edn. CRC Press, Boca Raton, FloridaGoogle Scholar
  26. Sakakibara J, Adrian RJ (1999) Whole field measurement of temperature in water using two-color laser induced fluorescence. Exp Fluids 26:7–15CrossRefGoogle Scholar
  27. Santiago JG (2001) Electroosmotic flows in microchannels with finite inertial and pressure forces. Anal Chem 73:2353–2365CrossRefPubMedGoogle Scholar
  28. Santiago JG, Wereley ST, Meinhart CD, Beebe DJ, Adrian RJ (1998) A particle image velocimetry system for microfluidics. Exp Fluids 25:316–319CrossRefGoogle Scholar
  29. Sharp KV, Adrian RJ, Santiago JG, Molho JI (2002) Liquid flows in microchannels. In Gad-el-Hak M (ed) The MEMS handbook. CRC Press, Boca Raton, Florida, pp 6.1–6.38Google Scholar
  30. Sinton D, Erickson D, Li D (2002a) Photo-injection based sample design and electroosmotic transport in microchannels. J Micromech Microeng 12:898–904CrossRefGoogle Scholar
  31. Sinton D, Escobedo-Canseco C, Ren L, Li D (2002b) Direct and indirect electroosmotic flow velocity measurements in microchannels. J Colloid Interf Sci 254:184–189CrossRefGoogle Scholar
  32. Sinton D, Li D (2003) Electroosmotic velocity profiles in microchannels. Colloid Surface A 222:273–283CrossRefGoogle Scholar
  33. Sinton D, Erickson D, Li D (2003a) Micro-bubble lensing induced photobleaching (μ-BLIP) with application to microflow visualization. Exp Fluids 35:178–187CrossRefGoogle Scholar
  34. Sinton D, Ren L, Li D (2003b) Visualization and numerical modelling of microfluidic on-chip injection processes. J Colloid Interf Sci 260:431–439CrossRefGoogle Scholar
  35. Sinton D (2004) Microscale flow visualization. Microfluid Nanofluid (accepted for publication)Google Scholar
  36. Stone HA, Stroock AD, Ajdari A (2004) Engineering flows in small devices: microfluidics toward a lab-on-a-chip. Annu Rev Fluid Mech 36:381–411CrossRefGoogle Scholar
  37. Taylor JA, Yeung ES (1993) Imaging of hydrodynamic and electrokinetic flow profiles in capillaries. Anal Chem 65:2928–2932Google Scholar
  38. Xuan X, Li D (2004) Analysis of electrokinetic flow in microfluidic networks. J Micromech Microeng 14:290–298CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  1. 1.Department of Mechanical and Industrial EngineeringUniversity of TorontoTorontoCanada
  2. 2.Department of Mechanical EngineeringUniversity of VictoriaVictoriaCanada

Personalised recommendations