Microfluidics and Nanofluidics

, Volume 18, Issue 5–6, pp 1247–1254 | Cite as

In situ seriate droplet coalescence under an optical force

  • Jin Ho Jung
  • Kyung Heon Lee
  • Ghulam Destgeer
  • Kang Soo Lee
  • Hyunjun Cho
  • Byung Hang Ha
  • Hyung Jin Sung
Research Paper


We demonstrated the induced coalescence of droplets under a highly accurate optical force control. Optical scattering and gradient forces were used to push and trap the droplets prior to coalescence within a microfluidic channel. The behavior of the droplets under the influence of an optical force was predicted using an analytical model that agreed well with the experimental data. The optical gradient force accelerated and decelerated the droplet within the laser beam region, and the drag force acting on the droplet was thoroughly characterized. A description of the optical trap was presented in terms of the momentum transfer from the photons to the droplet, effectively restricting droplet motion inside the microfluidic channel prior to coalescence. A phase diagram was plotted to distinguish between the three regimes of droplet coalescence, including the absence of coalescence, coalescence, and multiple coalescence events. The phase diagram permitted the laser power input and the net flow rate in the microfluidic channel to be estimated. This technique was applied to the synthesis of biodegradable gel microparticles.


Droplet coalescence Optical force Two-phase flow Biodegradable gel Droplet trapping 



This work was supported by the Creative Research Initiatives Program (No. 2014-001493) of the National Research Foundation of Korea (MSIP).

Supplementary material

Supplementary material 1 (AVI 5178 kb)

10404_2014_1522_MOESM2_ESM.doc (56 kb)
Supplementary material 2 (DOC 56 kb)


  1. Abate AR, Hung T, Mary P, Agresti JJ, Weitz DA (2010) High-throughput injection with microfluidics using picoinjectors. Proc Natl Acad Sci USA 107:19163–19166CrossRefGoogle Scholar
  2. Ahn K, Agresti J, Chong H, Marquez M, Weitz DA (2006) Dielectrophoretic manipulation of drops for high-speed microfluidic sorting devices. Appl Phys Lett 88:264105CrossRefGoogle Scholar
  3. Ashkin A, Dziedzic JM (1971) Optical levitation by radiation pressure. Appl Phys Lett 19:283–285CrossRefGoogle Scholar
  4. Baroud CN, de Saint Vincent MR, Delville JP (2007) An optical toolbox for total control of droplet microfluidics. Lab Chip 7:1029–1033CrossRefGoogle Scholar
  5. Baroud CN, Gallaire F, Dangla R (2010) Dynamics of microfluidic droplets. Lab Chip 10:2032–2045CrossRefGoogle Scholar
  6. Chang SC, Su YC (2010) On-demand micro-encapsulation utilizing on-chip synthesis of semi-permeable alginate-PLL capsules. Microfluid Nanofluid 10:1165–1174CrossRefGoogle Scholar
  7. Christopher GF, Bergstein J, End NB, Poon M, Nguyen C, Anna SL (2009) Coalescence and splitting of confined droplets at microfluidic junctions. Lab Chip 9:1102–1109CrossRefGoogle Scholar
  8. Churski K, Kaminski TS, Jakiela S, Kamysz W, Baranska-Rybak W, Weibel DB, Garstecki P (2012) Rapid screening of antibiotic toxicity in an automated microdroplet system. Lab Chip 12:1629–1637CrossRefGoogle Scholar
  9. Dholakia K, Cizmar T (2011) Shaping the future of manipulation. Nat Photonics 5:335–342CrossRefGoogle Scholar
  10. Dholakia K, Reece P (2006) Optical micromanipulation takes hold. Nano Today 1:18–27CrossRefGoogle Scholar
  11. Grier DG (2003) A revolution in optical manipulation. Nature 424:810–816CrossRefGoogle Scholar
  12. Hoang PH, Park H, Kim DP (2011) Ultrafast and continuous synthesis of unaccommodating inorganic nanomaterials in droplet- and ionic liquid-assisted microfluidic system. J Am Chem Soc 133:14765–14770CrossRefGoogle Scholar
  13. Hung LH, Choi KM, Tseng WY, Tan YC, Shea KJ, Lee AP (2006) Alternating droplet generation and controlled dynamic droplet fusion in microfluidic device for CdS nanoparticle synthesis. Lab Chip 6:174–178CrossRefGoogle Scholar
  14. Jung JH, Lee KH, Lee KS, Ha BH, Oh YS, Sung HJ (2014) Optical separation of droplets on a microfluidic platform. Microfluid Nanofluid 16:635–644CrossRefGoogle Scholar
  15. Kim SB, Kim SS (2006) Radiation forces on spheres in loosely focused Gaussian beam: ray-optics regime. J Opt Soc Am B 23:897–903CrossRefGoogle Scholar
  16. Kotz KT, Gu Y, Faris GW (2005) Optically addressed droplet-based protein assay. J Am Chem Soc 127:5736–5737CrossRefGoogle Scholar
  17. Lee DH, Lee W, Um E, Park JK (2011) Microbridge structures for uniform interval control of flowing droplets in microfluidic networks. Biomicrofluidics 5:34117–341179CrossRefGoogle Scholar
  18. Lee KH, Kim SB, Yoon SY, Lee KS, Jung JH, Sung HJ (2012) Behavior of double emulsions in a cross-type optical separation system. Langmuir 28:7343–7349CrossRefGoogle Scholar
  19. Lorenz RM, Edgar JS, Jeffries GD, Zhao Y, McGloin D, Chiu DT (2007) Vortex-trap-induced fusion of femtoliter-volume aqueous droplets. Anal Chem 79:224–228CrossRefGoogle Scholar
  20. Luong TD, Nguyen NT, Sposito A (2012) Thermocoalescence of microdroplets in a microfluidic chamber. Appl Phys Lett 100:254105CrossRefGoogle Scholar
  21. Niu X, Gulati S, Edel JB, deMello AJ (2008) Pillar-induced droplet merging in microfluidic circuits. Lab Chip 8:1837–1841CrossRefGoogle Scholar
  22. Song H, Chen DL, Ismagilov RF (2006) Reactions in droplets in microfluidic channels. Angew Chem Int Ed 45:7336–7356CrossRefGoogle Scholar
  23. Srinivasan V, Pamula VK, Fair RB (2007) An integrated digital microfluidic lab-on-a-chip for clinical diagnostics on human physiological fluids. Lab Chip 4:310–315CrossRefGoogle Scholar
  24. Sugiura S, Oda T, Izumida Y, Aoyagi Y, Satake M, Ochiai A, Ohkohchi N, Nakajima M (2005) Size control of calcium alginate beads containing living cells using micro-nozzle array. Biomaterials 26:3327–3331CrossRefGoogle Scholar
  25. Tan YC, Ho YL, Lee AP (2006) Droplet coalescence by geometrically mediated flow in microfluidic channels. Microfluid Nanofluid 3:495–499CrossRefGoogle Scholar
  26. Teh SY, Lin R, Hung LH, Lee AP (2008) Droplet microfluidics. Lab Chip 8:198–220CrossRefGoogle Scholar
  27. Tewhey R, Warner JB, Nakano M, Libby B, Medkova M, David PH, Kotsopoulos SK, Samuels ML, Hutchison JB, Larson JW, Topol EJ, Weiner MP, Harismendy O, Olson J, Link DR, Frazer KA (2009) Microdroplet-based PCR enrichment for large-scale targeted sequencing. Nat Biotechnol 27:1025–1031CrossRefGoogle Scholar
  28. Theberge AB, Mayot E, El Harrak A, Kleinschmidt F, Huck WT, Griffiths AD (2012) Microfluidic platform for combinatorial synthesis in picolitre droplets. Lab Chip 12:1320–1326CrossRefGoogle Scholar
  29. Um E, Rha E, Choi SL, Lee SG, Park JK (2012) Mesh-integrated microdroplet array for simultaneous merging and storage of single-cell droplets. Lab Chip 12:1594–1597CrossRefGoogle Scholar
  30. van der Sman RG (2010) Drag force on spheres confined on the center line of rectangular microchannels. J Colloid Interface Sci 351:43–49CrossRefGoogle Scholar
  31. Whitesides GM (2006) The origins and the future of microfluidics. Nature 442:368–373CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Jin Ho Jung
    • 1
  • Kyung Heon Lee
    • 1
  • Ghulam Destgeer
    • 1
  • Kang Soo Lee
    • 1
  • Hyunjun Cho
    • 1
  • Byung Hang Ha
    • 1
  • Hyung Jin Sung
    • 1
  1. 1.KAISTDaejeonRepublic of Korea

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