Enhanced Microfluidics Mixing Performance in a Grooved Serpentine Microchannel at Different Flow Rates

Abstract

Reliable and efficient mixing in microfluidic systems is crucial for various applications such as molecular diagnostics, DNA hybridization, microreactors and nanoparticle synthesis. However, achieving adequate mixing at the microscale is challenging due to the fact that flow regime in microfluidics is laminar that is characterized by low Reynolds numbers. In an attempt to tackle this challenge, active and passive strategies have been utilized to enhance mixing. Passive techniques mainly rely on the interaction between fluid and channel geometry in order to extend the interface between the components of the fluid by inducing transversal flows. Passive methods have shown their simplicity over the active methods in microfluidics by simply controlling the channel geometry and flow configurations without involving any complex external forces and components. Based on this, our work presents a passive micromixer design with trapezoidal grooves placed at the bottom of the serpentine channels. The grooves induce periodic pressure drops along the channel which create staggered transversal vortices in orthogonal directions which disturbs the symmetries in the flow that results in stirring. These combined effects result in an enhanced mixing performance especially at higher flow rates. The results suggest that the design could be integrated into lab-on-a-chip systems to achieve enhanced mixing of biological or chemical components with reduced footprint, complexity and cost.

Keywords

• microfluidics
• passive micromixers
• grooved serpentine channels
• enhanced microfluidic mixing
• computational fluid dynamics

References

1. [1]. Sackmann, E.K.; Fulton, A.L.; Beebe, D.J. The present and future role of microfluidics in biomedical research. Nature 2014, 507, 181–189.
2. [2]. Chiu, D.T.; deMello, A.J.; Di Carlo, D.; Doyle, P.S.; Hansen, C.; Maceiczyk, R.M.; Wootton, R.C.R. Small but perfectly formed? Successes, challenges, and opportunities for microfluidics in the chemical and biological sciences. Chem 2017, 2, 201–223.
3. [3]. Capretto, L.; Carugo, D.; Mazzitelli, S.; Nastruzzi, C.; Xunli, Z. Microfluidic and lab-on-a-chip preparation routes for organic nanoparticles and vesicular systems for nanomedicine applications. Adv. Drug Deliv. Rev. 2013, 65, 1496–1543.
4. [4]. Khan, S.A.; Günther, A.; Schmidt, M.A.; Jensen, K.F. Microfluidic synthesis of colloidal silica. Langmuir 2004, 20, 8604–8611.
5. [5]. Bamford, R.A.; Smith, A.; Metz, J.; Glover, G.; Titball, R.W.; Pagliara, S. Investigating the physiology of viable but non-culturable bacteria by microfluidics and time-lapse microscopy. BMC Biol. 2017, 15, 121.
6. [6]. Jayamohan, H.; Sant, H.J.; Gale, B.K. Applications of microfluidics for molecular diagnostics. Methods Mol. Biol. 2013, 949, 305–334.
7. [7]. Marasso, S.L.; Mombello, D.; Cocuzza, M.; Casalena, D.; Ferrante, I.; Nesca, A.; Poiklik, P.; Rekker, K.; Aaspollu, A.; Ferrero, S.; et al. A polymer lab-on-a-chip for genetic analysis using the arrayed primer extension on microarray chips. Biomed. Microdevices 2014, 16, 661–670.
8. [8]. Zilionis, R.; Nainys, J.; Veres, A.; Savova, V.; Zemmour, D.; Klein, A.M.; Mazutis, L. Single-cell barcoding and sequencing using droplet microfluidics. Nat. Protoc. 2017, 12, 44–73.

9. [9]. Makgwane, P.R.; Ray, S.S. Synthesis of nanomaterials by continuous-flow microfluidics: A review. J Nanosci. Nanotech. 2014, 14, 1338–1363.
10. [10]. Lee, C.-Y.; Chang, C.-L.; Wang, Y.-N.; Fu, L.-M. Microfluidic mixing: a review. Int. J. Mol. Sci. 2011, 12, 3262–3287.
11. [11]. Nguyen, N.-T. Micromixers: Fundamentals, Design and Fabrication, 2nd ed.; Elsevier: Oxford, UK, 2012; ISBN 978-1-4377-3520-8.
12. [12]. Ward, K. and Fan, Z.H., 2015. Mixing in microfluidic devices and enhancement methods. Journal of Micromechanics and Microengineering, 25(9), p.094001.
13. [13]. Wiggins, S.; Ottino, J.M. Foundations of chaotic mixing. Philos. Trans. R. Soc. London Ser. A. 2004, 362, 937–970.
14. [14]. Lee, C.Y.; Wang, W.T.; Liu, C.C.; Fu, L.M. Passive mixers in microfluidic systems: A review. Chem. Eng. J. 2016, 288, 146–160.
15. [15]. Buchegger, W.; Wagner, C.; Lendl, B.; Kraft, M.; Vellekoop, M.J. A highly uniform lamination micromixer with wedge shaped inlet channels for time resolved infrared spectroscopy. Microfluid. Nanofluid. 2011, 10, 889–897.
16. [16]. Nimafar, M.; Viktorov, V.; Martinelli, M. Experimental comparative mixing performance of passive micromixers with H-shaped sub-channels. Chem. Eng. Sci. 2012, 76, 37–44.
17. [17]. Lim, T.W.; Son, Y.; Jeong, Y.J.; Yang, D.-Y.; Kong, H.-J.; Lee, K.-S.; Kim, D.-P. Three-dimensionally crossing manifold micro-mixer for fast mixing in a short channel length. Lab Chip 2011, 11, 100–103.
18. [18]. SadAbadi, H.; Packirisamy, M.; Wüthrich, R. High performance cascaded PDMS micromixer based on split-and-recombination flows for lab-on-a-chip applications. RSC Adv. 2013, 3, 7296.
19. [19]. Kim, D.S.; Lee, S.H.; Kwon, T.H.; Ahn, C.H. A serpentine laminating micromixer combining splitting/recombination and advection. Lab Chip 2005, 5, 739–747.
20. [20]. Rhoades, T., Kothapalli, C.R. and Fodor, P.S., 2020. Mixing optimization in grooved serpentine microchannels. Micromachines, 11(1), p.61.
21. [21]. Javaid, M.U., Cheema, T.A. and Park, C.W., 2017. Analysis of passive mixing in a serpentine microchannel with sinusoidal side walls. Micromachines, 9(1), p.8.
22. [22]. Mengeaud, V.; Josserand, J.; Girault, H.H. Mixing processes in a zigzag microchannel: Finite element simulations and optical study. Anal. Chem. 2002, 74, 4279–4286.
23. [23]. Hossain, S.; Ansari, M.A.; Kim, K.Y. Evaluation of the mixing performance of three passive micromixers. Chem. Eng. J. 2009, 150, 492–501.
24. [24]. Parsa, M.K.; Hormozi, F. Experimental and CFD modeling of fluid mixing in sinusoidal microchannels with different phase shift between side walls. J. Micromech. Microeng. 2014, 24, 65018.
25. [25]. Parsa, M.K.; Hormozi, F.; Jafari, D. Mixing enhancement in a passive micromixer with convergent-divergent sinusoidal microchannels and different ratio of amplitude to wave length. Comput. Fluids 2014, 105, 82–90.
26. [26]. Afzal, A.; Kim, K.Y. Convergent-divergent micromixer coupled with pulsatile flow. Sens. Actuator B-Chem. 2015, 211, 198–205.
27. [27]. Akgönül, S.; Özbey, A.; Karimzadehkhouei, M.; Gozuacik, D.; Ko¸sar, A. The effect of asymmetry on micromixing in curvilinear microchannels. Microfluid. Nanofluid. 2017, 21, 1–15.
28. [28]. Liu, R.H.; Stremler, M.A.; Sharp, K.V.; Olsen, M.G.; Santiago, J.G.; Adrian, R.J.; Aref, H.; Beebe, D.J. Passive mixing in a three-dimensional serpentine microchannel. J. Microelectromech. Syst. 2000, 9, 190–197.
29. [29]. Holz, M., Heil, S.R. and Sacco, A., 2000. Temperature-dependent self-diffusion coefficients of water and six selected molecular liquids for calibration in accurate 1H NMR PFG measurements. Physical Chemistry Chemical Physics, 2(20), pp.4740-4742.
30. [30]. Yesiloz, G., Boybay, M.S. and Ren, C.L., 2017. Effective thermo-capillary mixing in droplet microfluidics integrated with a microwave heater. Analytical Chemistry, 89(3), pp.1978-1984.
31. [31]. Stremler, M.A., Haselton, F.R. and Aref, H., 2004. Designing for chaos: applications of chaotic advection at the microscale. Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 362(1818), pp.1019-1036.
32. [32]. Bordbar, A., Taassob, A. and Kamali, R., 2018. Diffusion and convection mixing of non‐Newtonian liquids in an optimized micromixer. The Canadian Journal of Chemical Engineering, 96(8), pp.1829-1836.
33. [33]. Cho, C.C., 2008. A combined active/passive scheme for enhancing the mixing efficiency of microfluidic devices. Chemical Engineering Science, 63(12), pp.3081-3087.