Guiding of emulsion droplets in microfluidic chips along shallow tracks defined by laser ablation

  • Zeeshan Rashid
  • Umut Can Coşkun
  • Yağız Morova
  • Berna Morova
  • Asuman Aşıkoğlu Bozkurt
  • Ahmet Erten
  • Alexandr Jonáš
  • Selçuk Aktürk
  • Alper Kiraz
Research Paper


We demonstrate controlled guiding of nanoliter emulsion droplets of polar liquids suspended in oil along shallow hydrophilic tracks fabricated at the base of microchannels located within microfluidic chips. The tracks for droplet guiding are generated by exposing the glass surface of polydimethylsiloxane (PDMS)-coated microscope slides via femtosecond laser ablation. The difference in wettability of glass and PDMS surfaces together with the shallow step-like transverse topographical profile of the ablated tracks allows polar droplets wetting preferentially the glass surface to follow the track. In this study, we investigate guiding of droplets of two different polar liquids (water/ethylene glycol) with and without surfactant suspended in an oil medium along surface tracks of different depths of 1, 1.5, and 2 \(\upmu\)m. The results of experiments are also verified with computational fluid dynamics simulations. Guiding of droplets along the tracks as a function of the droplet composition and size and the surface profile depth is evaluated by analyzing the trajectories of moving droplets with respect to the track central axis, and conditions for stable guiding are identified. The experiments and numerical simulations indicate that while the track topography plays a role in droplet guiding using 1.5- and 2-\(\upmu\)m deep tracks, for the case of the smallest track depth of 1 \(\upmu\)m, droplet guiding is mainly caused by surface energy modification along the track rather than the presence of a topographical step on the surface. Our results can be exploited to sort passively different microdroplets mixed in the same microfluidic chip, based on their inherent wetting properties, and they can also pave the way for guiding of droplets along reconfigurable tracks defined by surface energy modifications obtained using other external control mechanisms such as electric field or light.



This work was supported by TÜBİTAK (Grant No. 112T972). Z. Rashid and B. Morova thank HEC Pakistan and ASELSAN A.S., respectively, for Ph.D. scholarships. The authors thank M. Waqas Nawaz and Z. Emami for help with initial experiments, A. Ijaz for help with interfacial tension measurements, and M. B. Yağcı for help with SEM and Raman measurements in Koç University Surface Science and Technology Center (KUYTAM).

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  1. Aas M, Jonáš A, Kiraz A, Brzobohatý O, Ježek J, Pilát Z, Zemánek P (2013) Spectral tuning of lasing emission from optofluidic droplet microlasers using optical stretching. Opt Exp 21:21380–21394CrossRefGoogle Scholar
  2. Abbyad P, Dangla R, Alexandrou A, Baroud CN (2010) Rails and anchors: guiding and trapping droplet microreactors in two dimensions. Lab Chip 115:813–821Google Scholar
  3. Abbyad P, Tharaux PL, Martin JL, Baroud CN, Alexandrou A (2010) Sickling of red blood cells through rapid oxygen exchange in microfluidic drops. Lab Chip 10:2505–2512CrossRefGoogle Scholar
  4. Ahn K, Kerbage C, Hunt TP, Westervelt RM, Link DR, Weitz DA (2006) Dielectrophoretic manipulation of drops for high-speed microfluidic sorting devices. Lab Chip 88:241041–241043Google Scholar
  5. Ansys Fluent Theory Guide (2013) vol 15.0Google Scholar
  6. Baroud CN (2014) In: Kohler JM, Cahill BP (eds) Micro-segmented flow, applications in chemistry and biology. Springer, Berlin, Chapter 2, pp 7–29Google Scholar
  7. Chetouani H, Jeandey C, Haguet V, Rostaing H, Dieppedale C, Reyne G (2006) Diamagnetic levitation with permanent magnets for contactless guiding and trapping of microdroplets and particles in air and liquids. IEEE Trans Magn 42:3557–3559CrossRefGoogle Scholar
  8. Choi J, Son G (2008) Numerical study of droplet motion in a microchannel with different contact angles. J Mech Sci Eng 22:2590–2599Google Scholar
  9. Cookey GA, Obunwo CC, Uzoma DO (2015) The effect of temperature on the micellization of an anionic surfactant in mixed solvent systems. IOSR. J Appl Chem 8:49–54Google Scholar
  10. Dangla R, Lee S, Baroud CN (2014) Trapping microfluidic drops in wells of surface energy. Phys Rev Lett 107:124501-1–124501-4Google Scholar
  11. Fradet E, McDougall C, Abbyad P, Dangla R, McGloin D, Baroud CN (2011) Combining rails and anchors with laser forcing for selective manipulation within 2D droplet arrays. Lab Chip 11:4228–4234CrossRefGoogle Scholar
  12. Franke T, Abate AR, Weitz DA, Wixforth A (2009) Surface acoustic wave (SAW) directed droplet flow in microfluidics for PDMS devices. Lab Chip 9:2625–2627CrossRefGoogle Scholar
  13. Ganesan S (2012) On the dynamic contact angle in simulation of impinging droplets with sharp interface methods. Microfluid Nanofluidics 14:615–625CrossRefGoogle Scholar
  14. Garstecki P, Fuerstman MJ, Stone HA, Whitesides GM (2006) Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up. Lab Chip 6:437–446CrossRefGoogle Scholar
  15. Gupta R, Fletcher DF, Haynes BS (2009) On the CFD modelling of Taylor flow in microchannels. Chem Eng Sci 64:2941–2950CrossRefGoogle Scholar
  16. Hummer D, Kurth F, Rainer NN, Dittrich PS (2016) Single cells in confined volumes: microchambers and microdroplets. Lab Chip 16:447–458CrossRefGoogle Scholar
  17. Jonáš A, Yalızay B, Aktürk S, Kiraz A (2014) Free-standing optofluidic waveguides formed on patterned superhydrophobic surfaces. Appl Phys Lett 104:091123CrossRefGoogle Scholar
  18. Karapetsas G, Chamakos NT, Papathanasiou AG (2016) Efficient modelling of droplet dynamics on complex surfaces. J Phys Condens Matter 28:8510-1–85101-16CrossRefGoogle Scholar
  19. Lee H, Liu Y, Westervelt RM, Ham D (2006) IC/microfluidic hybrid system for magnetic manipulation of biological cells. IEEE J Solid State Circuits 41:1471–1480CrossRefGoogle Scholar
  20. Lim HS, Han JT, Kwak D, Jin M, Cho K (2006) Photoreversibly switchable superhydrophobic surface with erasable and rewritable pattern. J Am Chem Soc 128:14458–14459CrossRefGoogle Scholar
  21. Lim CY, Lam YC (2014) Phase field simulation of impingement and spreading of micro-sized droplet on heterogeneous surface. Microfluid Nanofluidics 17:131–148CrossRefGoogle Scholar
  22. Malekzadeh S, Roohi E (2015) Investigation of different droplet formation regimes in a T-junction microchannel using the VOF technique in OpenFOAM. Microgravity Sci Technol 27:231–243CrossRefGoogle Scholar
  23. Mannetje D, Ghosh S, Lagraauw R, Otten S, Pit A, Berendsen C, Zeegers J, van den Ende D, Mugele F (2014) Trapping of drops by wetting defects. Nat Commun 5:1–7CrossRefGoogle Scholar
  24. Mei F (ed) (2008) Dual capillary electrospraying—fundamentals and applications. Pro Quest, Saint Louis, MissouriGoogle Scholar
  25. Menech MD, Garstecki P, Jousse F, Stone HA (2008) Transition from squeezing to dripping in a microfluidic T-shaped junction. J Fluid Mech 595:141–161CrossRefzbMATHGoogle Scholar
  26. Pit AM, Duits MHG, Mugele F (2015) Droplet manipulations in two phase flow microfluidics. Micromachines 6:1768–1793CrossRefGoogle Scholar
  27. Rakszewska A, Tel J, Chokkalingam V, Huck WT (2014) One drop at a time: toward droplet microfluidics as a versatile tool for single-cell analysis. NPG Asia Mater 6:1–11CrossRefGoogle Scholar
  28. Sidram MH, Bhajantri NU (2015) Exploration of normalized cross correlation to track the object through various template updating techniques. IOSR J VLSI Signal Process 5:22–35Google Scholar
  29. Teh SY, Lin R, Hung LH, Lee AP (2008) Droplet microfluidics. Lab Chip 8:198–220CrossRefGoogle Scholar
  30. Than P, Preziosi L, Josephl D, Arney M (1988) Measurement of interfacial tension between immiscible liquids with the spinning rod tensiometer. J Colloid Interface Sci 124:552–559CrossRefGoogle Scholar
  31. Tullis J, Park CL, Abbyad P (2014) Selective fusion of anchored droplets via changes in surfactant concentration. Lab Chip 14:3285–3289CrossRefGoogle Scholar
  32. Unger MA, Chou H-P, Thorsen T, Scherer A, Quake SR (2000) Monolithic microfabricated valves and pumps by multilayer soft lithography. Science 288:113–116CrossRefGoogle Scholar
  33. Wang S, Kallur A, Goshu A (2011) Fabrication and characterization of PDMS thin filmGoogle Scholar
  34. Worner M (2012) Numerical modeling of multiphase flows in microfluidics and micro process engineering: a review of methods and applications. Microfluid Nanofluidics 12:841–886CrossRefGoogle Scholar
  35. Wu L, Tsutahara M, Kim LS, Ha M (2008) Three dimensional lattice Boltzmann simulations of droplet formation in a cross-junction microchannel. Int J Multiph Flow 34:852–864CrossRefzbMATHGoogle Scholar
  36. Xu L, Lee H, Panchapakesan R, Oh KW (2012) Fusion and sorting of two parallel trains of droplets using a railroad-like channel network and guiding tracks. Lab Chip 12:3936–3942CrossRefGoogle Scholar
  37. Yoon DH, Numakunai S, Nakahara A, Sekiguchi T, Shoji S (2014) Hydrodynamic on-rail droplet pass filter for fully passive sorting of droplet-phase samples. RSC Adv 4:37721–37725CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Zeeshan Rashid
    • 1
  • Umut Can Coşkun
    • 2
  • Yağız Morova
    • 3
  • Berna Morova
    • 3
  • Asuman Aşıkoğlu Bozkurt
    • 4
  • Ahmet Erten
    • 5
  • Alexandr Jonáš
    • 3
  • Selçuk Aktürk
    • 6
  • Alper Kiraz
    • 1
    • 5
  1. 1.Department of Electrical and Electronics EngineeringKoç UniversitySariyerTurkey
  2. 2.Department of Mechanical EngineeringIstanbul Technical UniversityGümüşsuyuTurkey
  3. 3.Department of PhysicsIstanbul Technical UniversityMaslakTurkey
  4. 4.Department of PhysicsYıldız Technical UniversityEsenlerTurkey
  5. 5.Department of PhysicsKoç UniversitySariyerTurkey
  6. 6.Egercili MahallesiCarsambaTurkey

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