Alternating and merged droplets in a double T-junction microchannel


In this work, we report experimental and numerical studies of alternating and merged droplets in a double T-junction microchannel. The microchannel device is fabricated using PDMS substrate and experiments are performed with mineral oil with surfactant as the continuous phase and aqueous glycerol as the discrete phase. Based on the flow rate fraction ϕ and Capillary number Ca, four different flow regimes are identified: merging, stable alternating droplets, alternating droplets with transition and laminar. A numerical model that employs volume-of-fluid formulations is used to predict the alternating droplet generation process. In the stable alternating droplet regime, the effect of the discretephase flow rate ratio α on the droplet diameter ratio β is experimentally studied and compared with that predicted from the simulations. It is observed that the droplet diameter ratio β increases linearly with increase in the flow rate ratio α and a good match between experiments and simulations is observed. The diameters of droplets at different Capillary numbers Ca generated using single and double T-junction microchannels are compared and it is observed that, at low Ca, the double T-junction generates larger droplets as compared to single T-junction. In merged droplet regime, the effect of the continuous phase flow rate Q c and discrete phase viscosity μ d on diameter d m and interdistance between the droplets λ of the merged droplets are studied. It is observed that the merged droplet diameter d m is reduced and interdistance between the droplets λ increases with increase in the continuous phase flow rate Q c . As the viscosity of the discrete phase μ d increases, the diameter d m and interdistance between the droplets λ of the merged droplets decreases.

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  1. 1.

    Teh, S.Y., Lin, R., Hung, L.H. & Lee, A.P. Droplet microfluidics. Lab Chip 8, 198–220 (2008).

    Article  CAS  Google Scholar 

  2. 2.

    Schneider, T., Kreutz, J. & Chiu, D.T. The potential impact of droplet microfluidics in biology. Anal. Chem. 85, 3476–3482 (2013).

    Article  CAS  Google Scholar 

  3. 3.

    Hung, L.H. et al. Alternating droplet generation and controlled dynamic droplet fusion in microfluidic device for CdS nanoparticle synthesis. Lab Chip 6, 174–178 (2006).

    Article  CAS  Google Scholar 

  4. 4.

    Hung, L.H. & Lee, A.P. Microfluidic devices for the synthesis of nanoparticles and biomaterials. J. Med. Biol. Eng. 27, 1–6 (2007).

    Google Scholar 

  5. 5.

    Sen, A.K., Darabi, J. & Knapp, D.R. Design, fabrication and test of a microfluidic nebulizer chip for desorption electrospray ionization mass spectrometry. Sens. Actuators B Chem. 137, 789–796 (2009).

    Article  CAS  Google Scholar 

  6. 6.

    Bhardwaj, P., Bagdi, P. & Sen, A.K. Microfluidic device based on a micro-hydrocyclone for particle-liquid separation. Lab Chip 11, 4012–4021 (2011).

    Article  CAS  Google Scholar 

  7. 7.

    Zheng, B., Tice, J.D. & Ismagilov, R.F. Formation of arrayed droplets of soft lithography and two-phase fluid flow, and application in protein crystallization. Adv. Mater. 16, 1365–1368 (2004).

    Article  CAS  Google Scholar 

  8. 8.

    Tice, J.D., Lyon, A.D. & Ismagilov, R.F. Effects of viscosity on droplet formation and mixing in microfluidic channels. Analytica Chimica Acta 507, 73–77 (2004).

    Article  CAS  Google Scholar 

  9. 9.

    Gupta, A. & Kumar, R. Effect of geometry on droplet formation in the squeezing regime in a microfluidic T-junction. Microfluid Nanofluid 8, 799–812 (2009).

    Article  Google Scholar 

  10. 10.

    Wehking, J.D., Gabany, M., Chew, L. & Kumar, R. Effects of viscosity, interfacial tension, and flow geometry on droplet formation in a microfluidic T-junction. Microfluid Nanofluid 16, 441–453 (2014).

    Article  CAS  Google Scholar 

  11. 11.

    Nunes, J.K., Tsai, S.S.H., Wan, J. & Stone, H. Dripping and jetting in microfluidic multiphase flows applied to particle and fiber synthesis. J. Phys. D: Appl. Phys. 46, 1–20 (2013).

    Article  Google Scholar 

  12. 12.

    Barbier, V., Willaime, H., Tabeling, P. & Jousse, F. Producing droplets in parallel microfluidic systems. Phys. Rev. E. 74, 1–4 (2006).

    Article  Google Scholar 

  13. 13.

    Hong, J., Choi, M., Edel, J.B. & DeMello, A.J. Passive self-synchronized two-droplet generation. Lab Chip 10, 2702–2709 (2010).

    Article  CAS  Google Scholar 

  14. 14.

    Song, H., Tice, J.D. & Ismagilov, R.F. A Microfluidic System for Controlling Reaction Networks in Time. Angew. Chem. Int. Ed. 42, 767–772 (2003).

    Google Scholar 

  15. 15.

    Zheng, B., Tice, J.D. & Ismagilov, R.F. Formation of droplets of alternating composition in microfluidic channels and applications to indexing of concentrations in droplet-based assays. Anal. Chem. 76, 4977–4982 (2004).

    Article  CAS  Google Scholar 

  16. 16.

    Sajeesh, P., Doble, M. & Sen, A.K. Hydrodynamic resistance and mobility of deformable objects in microfluidic channels. Biomicrofluidics 8, 1–24 (2014).

    Article  Google Scholar 

  17. 17.

    Ward, T., Faivre, M., Abkarian, M. & Stone, H.A. Microfluidic flow focusing: Drop size and scaling in pressure versus flow rate driven pumping. Electrophoresis 26, 3716–3724 (2005).

    Article  CAS  Google Scholar 

  18. 18.

    Garstecki, P., Fuerstman, M.J., Stone, H.A. & Whitesides, G.M. Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of breakup. Lab Chip 6, 437–446 (2006).

    Article  CAS  Google Scholar 

  19. 19.

    Christopher, G.F., Noharuddin, N.N., Taylor, J.A. & Anna, S.L. Experimental observation of the squeezing-to-dripping transition in T-shaped microfluidic junctions. Phys. Rev. E 78, 1–12 (2008).

    Article  Google Scholar 

  20. 20.

    Li, X. et al. Study on the mechanism of droplet formation in T-junction microchannel. Chemical Engineering Science 69, 340–351 (2012).

    Article  CAS  Google Scholar 

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Correspondence to Ashis Kumar Sen.

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Surya, H.P.N., Parayil, S., Banerjee, U. et al. Alternating and merged droplets in a double T-junction microchannel. BioChip J 9, 16–26 (2015).

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  • Droplet
  • Double T-junction
  • Merging
  • Stable alternating droplets
  • Transition and laminar