Numerical simulation of electroosmotic flow in hydrophobic microchannels
Tóm tắt
Electroosmotic flow (EOF) is a promising way for driving and mixing fluids in microfluidics. For the parallel-plate microchannel with the hydrophobic surface, this paper solved the governing equations using the finite element method (FEM), and the effects of microchannel height, electric strength and ionic concentration on EOF were thus investigated. The simulation indicates that the transient characteristics of EOF are similar in hydrophobic and hydrophilic microchannels, the steady time of EOF is proportional to the square of microchannel height, and the scale is microsecond. EOF velocity is proportional to the electric strength and independent of the channel height, and decreases slowly with the ionic concentration, which is lower than that in hydrophilic microchannel due to the presence of slip length in hydrophobic microchannel. The results can provide valuable insights into the optimal design of microchannel surfaces to achieve accurate EOF control in hydrophobic microchannel.
Tài liệu tham khảo
Fang Z. Manufacture & Application of Microfluidic Chip (in Chinese). Beijing: Chemical Industry Press, 2005
Feng Y, Zhou Z, Ye X, et al. Progresses on technologies of driving and controlling micro fluids (in Chinese). Adv Mech, 2002, 32(1): 1–16
Stone H A, Stroock A D, Ajdari A. Engineering flows in small devices microfluidics toward a lab-on-a-chip. Ann Rev Fluid Mech, 2004, 36: 381–411
Chen L, Guan Y, Ma J, et al. Application of a high-pressure electro- osmotic pump using nanometer silica in capillary liquid chromatography. J Chromatogr A, 2005, 1064: 19–24
Wong P K, Wang J T, Deval J H, et al. Electrokinetic in micro devices for biotechnology applications. IEEE/ASME Trans Mechatron, 2004, 9: 366–376
Wang J, Wang M, Li Z. Lattice Boltzmann simulations of mixing enhancement by the electro-osmotic flow in microchannels. Mod Phys Lett B, 2005, 19: 1515–1518
Zhao N, Lu Xi, Zhang X, et al. Progress in superhydrophobic surfaces (in Chinese). Prog Chem, 2007, 19(6): 860–871
Vinogradova O I. Drainage of a thin liquid film confined between hydrophobic surfaces. Langmuir, 1995, 11: 2213–2220
Spikes H, Granick S. Equation for slip of simple liquids at smooth solid surfaces. Langmuir, 2003, 19: 5065–5071
Wang H, Hu Y, Guo Y. Molecular dynamics study of interfacial slip behavior of ultrathin lubricating films (in Chinese). J Tsinghua Univ (Sci & Tech), 2000, 40(4): 107–110
Joly L, Ybert C, Trizac E, et al. Liquid friction on charged surfaces: from hydrodynamic slippage to electrokinetics. J Chem Phys, 2006, 125(20): 204716
Pit R, Hervet H, Léger L. Direct experimental evidence of slip in hexadecane: solid interfaces. Phys Rev Lett, 2000, 85(5): 980–983
Ou J, Rothstein J P. Direct velocity measurements of the flow past drag-reducing ultrahydrophobic surfaces. Phys Fluids, 2005, 17: 103606
Cottin-Bizonne C, Cross B, Steinberger A, et al. Boundary slip on smooth hydrophobic surfaces: intrinsic effects and possible artifacts. Phys Rev Lett, 2005, 94(2): 056102
Cho J-H J, Law B M, Rieutord F. Dipole-dependent slip of Newtonian liquids at smooth solid hydrophobic surfaces. Phys Rev Lett, 2004, 92:166102
Yang J, Kwok D Y. Analytical treatment of electrokinetic microfluidics in hydrophobic microchannels. Anal Chim Acta, 2004, 507: 39–53
Park H M, Kim T W. Simultaneous estimation of zeta potential and slip coefficient in hydrophobic microchannels. Anal Chim Acta, 2007, 593: 171–177
Huo S, Yu Z, Li Y. Flow characteristics of water in microchannel with super-hydrophobic surface (in Chinese). J Chem Indust Eng, 2007, 58(11): 2721–2726
Tretheway D C, Meinhart C D. A generating mechanism for apparent fluid slip in hydrophobic microchannels. Phys Fluids, 2004, 14(5): 1509–1515
Eijkel J. Liquid slip in micro- and nano-fluidics: recent research and its possible implications. Lab Chip, 2007, 7: 299–301
Vourdas N, Tserepi A, Boudouvis A G, et al. Plasma processing for polymeric microfluidics fabrication and surface modification: Effect of supper-hydrophobic walls on electroosmotic flow. Microelectron Eng, 2008, 85: 1124–1127
Ngoma G D, Erchiqui F. Heat flux and slip effects on liquid flow in a microchannel. Int J Therm Sci, 2007, 46: 1076–1083.
George K, Beskok A. Micro Flows: Fundamentals and Simulation. Berlin: Springer, 2002
Choi C-H, Ulmanella U, Kim J, et al. Effective slip and friction reduction in nanograted superhydrophobic microchannels. Phys Fluids, 2006, (18): 087105-1
Zhu Y, Granick S. Limits of the hydrodynamic no-slip boundary condition. Phys Rev Lett, 2002, 88(10): 106102
Arulanandam S, Li D. Liquid transport in rectangular microchannels by electroosmotic pumping. Colloid Surf A: Physicochem Eng Aspect, 2000, 161: 89–102
Zhang Y, Wong T N, Yang C, et al. Dynamic aspects of electroosmotic flow. Microfluid Nanofluid, 2006, 2: 205–214
Yang C, Ng C B, Chan V. Transient analysis of electroosmotic flow in a slit microchannel. J Colloid Interface Sci, 2002, 248: 524–527
Ou J, Moss G R, Rothstein J P. Enhanced mixing in laminar flows using ultrahydrophobic surfaces. Phys Rev E, 2007, 76: 016304