MIXING ENHANCEMENT IN ELECTROOSMOTIC MICROMIXERS

Abstract

Micromixers have important applications in various pharmaceutical and medical fields. In the present study, the enhancement of mixing index in electroosmotic micromixer with different geometries is investigated. The commercial software COMSOL Multiphysics 5.4 is employed to solve the mathematical models. The SIMPLEC algorithm is employed for coupling the velocity and pressure fields. A second-order upwind scheme is used to reduce the artificial diffusivity. The results show a remarkable effect of the electric field on the mixing efficiency. The optimum geometry is the one with no obstacle in the mixing chamber. For the optimum geometry, it is demonstrated that the mixing efficiency increases with the voltage, however there are optimum values for frequency and inlet velocity in which the micromixer exhibits its best performance. The optimum values of frequency and inlet velocity are 8 Hz and 0.1 mm/s, respectively. It is revealed that the micromixer with no obstacle can reach the mixing efficiency of about 97%.

Keywords

• Electroosmotic Micromixer
• Numerical Simulation
• Mixing Efficiency
• Obstacle

References

1. [1] Bayareh M, Nazemi Ashani M, Usefian A. Active and passive micromixers: a comprehensive review. Chemical Engineering and Processing-Process Intensification, 2020; 147 107771. doi:10.1016/j.cep.2019.107771.
2. [2] Chen H, Meiners JC. Topologic mixing on a microfluidic chip. Applied Physics Letters, 2004;84(12):2193-2195.
3. [3] Usefian A, Bayareh M, Shateri A, Taheri N. Numerical study of electro-osmotic micro-mixing of Newtonian and non-Newtonian fluids. Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2019; 41(5):238.
4. [4] Habibi A, Shojaei S, Tehrani P. A comparative numerical design of the static and electrostatic micromixers. SN Appl. Sci. 2019;1:506. doi:10.1007/s42452-019-0491-7.
5. [5] Usefian A, Bayareh M, Ahmadi Nadooshan A. Rapid mixing of Newtonian and non-Newtonian fluids in a three-dimensional micro-mixer using non-uniform magnetic field. Journal of Heat and Mass Transfer Research, 2019; 6(1):55-61.
6. [6] Lim E, Lee L, Yeo LY, Hung YM., Tan MK. Acoustically-Driven Micromixing: Effect of Transducer Geometry. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2019; 1:1. doi:10.1109/tuffc.2019.2920683.
7. [7] Huang C, Tsou C. The implementation of a thermal bubble actuated microfluidic chip with microvalve, micropump and micromixer. Sensors and Actuators A: Physical, 2014;210:147-156. doi:10.1016/j.sna.2014.02.015 .
8. [8] Usefian A, Bayareh M. Numerical and experimental investigation of an efficient convergent-divergent micromixer. Meccanica, 2020;55:1025-1035.

9. [9] Pohl HA. Dielectrophoresis: The behavior of neutral matter in nonuniform electric fields (Cambridge Monographs on physics). Cambridge/New York: Cambridge University Press, 1978.
10. [10] Masliyah JH, Bhattacharjee S . Electrokinetic and colloid transport phenomena. John Wiley & Sons, 2006.
11. [11] Stone HA, Stroock AD, Ajdari A. Engineering flows in small devices: microfluidics toward a lab-on-a-chip. Annu. Rev. Fluid Mech. 2004;36:381-411.
12. [12] Bhattacharyya S, Bera S. Combined electroosmosis-pressure driven flow and mixing in a microchannel with surface heterogeneity. Applied Mathematical Modelling, 2015;39(15):4337–4350.
13. [13] Peng R, Li D (2015) Effects of ionic concentration gradient on electroosmotic flow mixing in a microchannel. Journal of Colloid and Interface Science 440:126–132.
14. [14] Zhang K, Ren Y, Hou L, Feng X, Chen X, Jiang H, An efficient micromixer actuated by induced-charge electroosmosis using asymmetrical floating electrodes. Microfluidics and Nanofluidics, 2018;22(11). doi:10.1007/s10404-018-2153-2.
15. [15] Wu Z, Chen X. Numerical simulation of a novel microfluidic electroosmotic micromixer with Cantor fractal structure. Microsystem Technologies, 2019;doi:10.1007/s00542-019-04311-8.
16. [16] Usefian A, Bayareh M. Numerical and experimental study on mixing performance of a novel electro-osmotic micro-mixer. Meccanica, 2019; doi:10.1007/s11012-019-01018-y.
17. [17] Keshavarzian B, Shamshiri M, Charmiyan M, Moaveni A. Optimization of an Active Electrokinetic Micromixer Based on the Number and Arrangement of Microelectrodes. Journal of Applied Fluid Mechanics, 2018;11(6):1531-1541.
18. [18] Ekiciler, R., Arslan, K. CuO/Water Nanofluid Flow over Microscale Backward-Facing Step and Analysis of Heat Transfer Performance. Heat Transfer Research, 2018;49 (15).