Research Papers: Flows in Complex Systems

Unsteady Electrokinetic Flow in a Microcapillary: Effects of Periodic Excitation and Geometry

[+] Author and Article Information
Ali Jabari Moghadam

Faculty of Mechanical Engineering,
Shahrood University of Technology,
Shahrood 3619995161, Iran
e-mail: jm.ali.project@gmail.com

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received December 7, 2018; final manuscript received March 22, 2019; published online May 8, 2019. Assoc. Editor: Shizhi Qian.

J. Fluids Eng 141(11), 111104 (May 08, 2019) (13 pages) Paper No: FE-18-1810; doi: 10.1115/1.4043337 History: Received December 07, 2018; Revised March 22, 2019

Oscillatory electrokinetic flow is numerically examined in a rectangular annulus microtube under the influence of various wave forms. When the inner and outer walls of the capillary are oppositely charged, an instantaneous two-direction flow field is produced and consequently the resultant flow rate is relatively reduced. A zero or negative flow rate may be achieved by appropriate design of the channel geometrical characteristics (e.g., hydraulic diameter) as well as the walls charges. In the case of sufficiently low kinematic viscosity and/or high excitation frequency, a relatively thin transient frictional layer is established close to the walls while the bulk fluid lags behind the liquid motion in the electric double layer by a phase shift. If different waveforms are combined together, fascinating outcomes can be obtained depending on the frequency of each individual wave. Applied electric fields with equal- and unequal-frequency combined waves may have the advantages of a double velocity field and a net mass flow rate, respectively. Interestingly, a direct flow pattern may be achieved by appropriately combining various waveforms with unequal frequencies. The mass flow rate decreases, with the constancy of the electrokinetic diameter, with approximately the square of hydraulic diameter. The Poiseuille number exhibits various characteristics depending on the excitation frequency as well as the type of wave especially in combination.

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Bruus, H. , 2008, Theoretical Microfluidics, Oxford University Press, New York.
Nguyen, N. T. , and Wereley, S. T. , 2006, Fundamentals and Applications of Microfluidics, Artech House, Norwood, Cambridge, MA.
Tabeling, P. , 2005, Introduction to Microfluidics, Oxford University Press, New York.
Li, D. , 2004, Electrokinetics in Microfluidics, Elsevier Academic Press, Amsterdam, The Netherlands.
Squires, T. M. , and Bazant, M. Z. , 2004, “ Induced-Charge Electro-Osmosis,” J. Fluid Mech., 509, pp. 217–252. [CrossRef]
Arulanandam, S. , and Li, D. , 2000, “ Liquid Transport in Rectangular Microchannels by Electro-Osmotic Pumping,” Colloids Surf., A, 161(1), pp. 89–102. [CrossRef]
Dutta, P. , and Beskok, A. , 2001, “ Analytical Solution of Combined Electroosmotic/Pressure Driven Flows in Two-Dimensional Straight Channels: Finite Debye Layer Effects,” Anal. Chem., 73(9), pp. 1979–1986. [CrossRef] [PubMed]
Xuan, X. C. , and Li, D. , 2005, “ Electroosmotic Flow in Microchannels With Arbitrary Geometry and Arbitrary Distribution of Wall Charge,” J. Colloid Interface Sci., 289(1), pp. 291–303. [CrossRef] [PubMed]
Kang, Y. J. , Yang, C. , and Huang, X. Y. , 2002, “ Dynamic Aspects of Electroosmotic Flow in a Cylindrical Microcapillary,” Int. J. Eng. Sci., 40(20), pp. 2203–2221. [CrossRef]
Tsao, H. K. , 2000, “ Electroosmotic Flow Through an Annulus,” J. Colloid Interface Sci., 225(1), pp. 247–250. [CrossRef] [PubMed]
Stiles, T. , Fallon, R. , Vestad, T. , Oakey, J. , Marr, D. W. M. , Squier, J. , and Jimenez, R. , 2005, “ Hydrodynamic Focusing for Vacuum-Pumped Microfluidics,” Microfluid. Nanofluid., 1(3), pp. 280–283. [CrossRef]
Zhang, K. , Jiang, L. , Gao, Z. , Zhai, C. , Yan, W. , and Wu, S. , 2018, “ Design and Numerical Study of Micropump Based on Induced Electroosmotic Flow,” J. Nanotechnol., 2018, p. 4018503.
Zhao, C. , Zhang, W. , and Yang, C. , 2017, “ Dynamic Electroosmotic Flows of Power-Law Fluids in Rectangular Microchannels,” Micromachines, 8(2), p. 34.
Bianchetti, A. , Sanchez, S. H. , and Cabaleiro, J. M. , 2016, “ Electroosmotic Flow Profile Distortion due to Laplace Pressures at the End Reservoirs,” Microfluid. Nanofluid., 20(11), pp. 1–12.
Moghadam, A. J. , 2016, “ Two-Fluid Electrokinetic Flow in a Circular Microchannel,” Int. J. Eng., Trans. A, 29(10), pp. 1469–1477.
Erickson, D. , and Li, D. , 2003, “ Analysis of Alternating Current Electroosmotic Flows in a Rectangular Microchannel,” Langmuir, 19(13), pp. 5421–5430. [CrossRef]
Dutta, P. , and Beskok, A. , 2001, “ Analytical Solution of Time Periodic Electroosmotic Flows: Analogies to Stokes Second Problem,” Anal. Chem., 73(21), pp. 5097–5102. [CrossRef] [PubMed]
Green, N. G. , Ramos, A. , Gonzalez, A. , Morgan, H. , and Castellanos, A. , 2000, “ Fluid Flow Induced by Non-Uniform AC Electric Fields in Electrolytes on Microelectrodes I: Experimental Measurements,” Phys. Rev. E, 61(4), pp. 4011–4018. [CrossRef]
Gonzalez, A. , Ramos, A. , Green, N. G. , Castellanos, A. , and Morgan, H. , 2000, “ Fluid Flow Induced by Non-Uniform AC Electric Fields in Electrolytes on Microelectrodes II: A Linear Double Layer Analysis,” Phys. Rev. E, 61, pp. 4019–4028. [CrossRef]
Brown, A. B. D. , Smith, C. G. , and Rennie, A. R. , 2001, “ Pumping of Water With an AC Electric Field Applied to Asymmetric Pairs of Microelectrodes,” Phys. Rev. E, 63, p. 016305.
Peralta, M. , Arcos, J. , Mendez, F. , and Bautista, O. , 2017, “ Oscillatory Electroosmotic Flow in a Parallel-Plate Microchannel Under Asymmetric Zeta Potentials,” Fluid Dyn. Res., 49(3), p. 035514. [CrossRef]
Moghadam, A. J. , 2012, “ An Exact Solution of AC Electro-Kinetic-Driven Flow in a Circular Micro-Channel,” Eur. J. Mech. B/Fluids, 34, pp. 91–96. [CrossRef]
Moghadam, A. J. , 2013, “ Exact Solution of AC Electro-Osmotic Flow in a Microannulus,” ASME J. Fluids Eng., 135(9), p. 091201. [CrossRef]
Moghadam, A. J. , 2014, “ Effect of Periodic Excitation on Alternating Current Electroosmotic Flow in a Microannular Channel,” Eur. J. Mech. B/Fluids, 48, pp. 1–12. [CrossRef]
Escandon, J. , Merino, E. G. , and Hernandez, C. G. , 2016, “ Transient Electroosmotic Flow of Newtonian Fluids in a Microchannel With Heterogeneous Zeta Potentials at the Walls,” ASME Paper No. IMECE2016-65939.
Gheshlaghi, B. , Nazaripoor, H. , Kumar, A. , and Sadrzadeh, M. , 2016, “ Analytical Solution for Transient Electroosmotic Flow in a Rotating Microchannel,” RSC Adv., 6(21), pp. 17632–17641. [CrossRef]
Zhao, M. , Wang, S. , and Wei, S. , 2013, “ Transient Electro-Osmotic Flow of Oldroyd-B Fluids in a Straight Pipe of Circular Cross Section,” J. Non-Newtonian Fluid Mech., 201, pp. 135–139. [CrossRef]
Moghadam, A. J. , and Akbarzadeh, P. , 2016, “ Time-Periodic Electroosmotic Flow of Non-Newtonian Fluids in Microchannels,” IJE Trans. B, 29(5), pp. 736–744.
Moghadam, A. J. , and Akbarzadeh, P. , 2017, “ Non-Newtonian Fluid Flow Induced by Pressure Gradient and Time-Periodic Electroosmosis in a Microtube,” J. Braz. Soc. Mech. Sci. Eng., 39(12), pp. 5015–5025. [CrossRef]
Jimenez, E. M. , Escandon, J. P. , and Bautista, O. E. , 2015, “ Study of the Transient Electroosmotic Flow of Maxwell Fluids in Square Cross-Section Microchannels,” ASME Paper No. ICNMM2015-48547.
Kaushik, P. , Mandal, S. , and Chakraborty, S. , 2017, “ Transient Electroosmosis of a Maxwell Fluid in a Rotating Microchannel,” Electrophoresis, 38(21), pp. 2741–2748. [CrossRef] [PubMed]
Kirby, B. J. , 2010, Micro- and Nanoscale Fluid Mechanics, Cambridge University Press, New York.
Kandlikar, S. , Garimella, S. , Li, D. , Colin, S. , and King, M. R. , 2006, Heat Transfer and Fluid Flow in Minichannels and Microchannels, Elsevier, Waltham, MA.
Hoffman, J. D. , 2001, Numerical Methods for Engineers and Scientists, Marcel Dekker, New York.


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Fig. 1

Cross-sectional area of the microchannel

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Fig. 2

Various excitation waveforms over a period (0≤Ωθ≤2π): (a) square, (b) triangular, (c) combined (Ω1=Ω2), (d) combined (Ω1<Ω2), and (e) combined (Ω1>Ω2)

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Fig. 3

Velocity profiles over a period for (a) and (b) square, (c) and (d) triangular, and (e) and (f) combined waveforms

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Fig. 4

Velocity profiles over a period for various waveforms in combination

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Fig. 5

Variations of Q (for Dh=1) with time for (a) square, (b) triangular, (c) equal-frequency combined, and (d) unequal-frequency combined waves

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Fig. 6

(a), (b) Time variations of Q for Dh=0.9294 using square and triangular waveforms, respectively and (c), (d) time variations of Q for Dh=1 and various β values using unequal-frequency combined waves

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Fig. 7

Variations of Po with time for (a) square, (b) triangular, (c) equal-frequency combined, and (d) unequal-frequency combined waveforms

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Fig. 8

Poiseuille number over a steady period for (a) square, (b) triangular, (c) equal-frequency combined, and (d) unequal-frequency combined waveforms

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Fig. 9

Variations of velocity of representative points with time for (a) square, (b) triangular, and (c) equal-frequency combined waveforms

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Fig. 10

Effect of unequal-frequency combined waveform on transient velocities of representative points



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