Flow regime mapping of high inertial gas–liquid droplet microflows in flow-focusing geometries

  • Arjang Shahriari
  • Myeongsub Mike Kim
  • Siavash Zamani
  • Nirmala Phillip
  • Babak Nasouri
  • Carlos H. HidrovoEmail author
Research Paper


Confined gas–liquid droplet microflows present a lot of new perspectives for microfluidic systems that require the presence of a gaseous phase. In addition to the benefits associated with the discretization of reactive and sensing processes, the highly inertial droplets generated in these systems can enable fast efficient mixing by pair collisions as well as high system throughput due to the short convective timescales involved in the droplet transport. Presented herein is mapping of the geometry-specific droplet generation from a binary gas–liquid flow for different flow-focusing configurations. The dynamic interactions of inertia, shear stress, viscous and surface tension forces create three unique regimes in the gas–liquid flow rate space, providing adaptable flow configuration to specific applications. Analytical investigation and numerical analyses involving governing forces are also introduced to predict the effective droplet diameter versus gas flow rate. We found that the experimental results were well matched to the analytical predictions within 10 % of uncertainty.


Microfluidics Droplet generation High inertia Flow regime Flow-focusing geometry 



This work was supported by DARPA 2008 Young Faculty Award (YFA) grant HR0011-08-1-0045 and is currently being supported by an NSF CAREER Award grant CBET-1151091. Authors thank Dr. Brian Carroll and David Choi for their helpful discussions for the experimental setup and Kevin Choi for his assistance in fabrication of microfluidic chips.

Supplementary material

10404_2015_1671_MOESM1_ESM.mpg (888 kb)
Supplementary material 1 (MPG 888 kb)
10404_2015_1671_MOESM2_ESM.mpg (1004 kb)
Supplementary material 2 (MPG 1004 kb)


  1. Ahn CH, Choi J, Beaucage G, Nevin JH, Lee J, Puntambekar A, Lee JY (2004) Disposable smart lab on a chip for point-of-care clinical diagnostics. IEEE 92:154–173CrossRefGoogle Scholar
  2. Anna SL, Bontoux N, Stone HA (2003) Formation of dispersions using flow focusing in microchannels. Appl Phys Lett 82:364–366CrossRefGoogle Scholar
  3. Aryafar H, Kavehpour HP (2006) Droplet coalescence through planar surfaces. Phys Fluids 18:072105CrossRefGoogle Scholar
  4. Atencia J, Beebe J (2004) Controlled microfluidic interfaces. Nature 437:648–655CrossRefGoogle Scholar
  5. Bach GA, Koch DL, Gopinath A (2004) Coalenscence and bouncing of small aerosol droplets. J Fluid Mech 518:157–185CrossRefzbMATHGoogle Scholar
  6. Bedram A, Moosavi A (2011) Droplet breakup in an asymmetric microfluidic T Junction. Eur Phys J E Soft Matter 34:1–8CrossRefGoogle Scholar
  7. Ben-Tzvi P, Rone W (2010) Microdroplet generation in gaseous and liquid environments. Microsyst Technol 16:333–356CrossRefGoogle Scholar
  8. Bolognesi G, Hargreaves A, Ward AD, Kirby AK, Bain CD, Ces O (2015) Microfluidic generation of monodisperse ultra-low interfacial tension oil droplets in water. RSC Adv 5:8114–8121CrossRefGoogle Scholar
  9. Buie CR, Santiago JG (2009) Two-phase hydrodynamics in a miniature direct methanol fuel cell. Int J Heat Mass Transf 52:5158–5166CrossRefzbMATHGoogle Scholar
  10. Carroll B, Hidrovo CH (2012a) Droplet collision mixing diagnostics using single fluorophore LIF. Exp Fluids 53:1301–1316CrossRefGoogle Scholar
  11. Carroll B, Hidrovo CH (2012b) Experimental investigation of inertial mixing in colliding droplets. Heat Transf Eng 34:1–12Google Scholar
  12. Carroll B, Hidrovo CH (2013) Droplet detachment mechanism in a high-speed gaseous microflow. J Fluid Eng 135:071206CrossRefGoogle Scholar
  13. Chen YT, Chang WC, Fang WF, Ting SC, Yao DJ, Yang JT (2012) Fission and fusion of droplets in a 3-D crossing microstructure. Microfluid Nanofluid 13:239–247CrossRefGoogle Scholar
  14. Choi S, Park JK (2005) Microfluidic system for dielectrophoretic separation based on a trapezoidal electrode array. Lab Chip 5:1161–1167CrossRefGoogle Scholar
  15. Chong ZZ, Tor SB, Loh NH, Wong TN, Gñáan-Calvo AM, Tan SH, Nguyen NT (2015) Acoustofluidic control of bubble size in microfluidic flow-focusing configuration. Lab Chip 15:996–999CrossRefGoogle Scholar
  16. Christopher GF, Anna SL (2007) Microfluidic methods for generating continuous droplet streams. J Phys D Appl Phys 40:R319–R336CrossRefGoogle Scholar
  17. Dolovich MB, Dhand R (2011) Aerosol drug delivery: developments in device design and clinical use. Lancet 377:1032–1045CrossRefGoogle Scholar
  18. Eddings MA, Johnson MA, Gale BK (2008) Determining the optimal PDMS-PDMS bonding technique for microfluidic devices. J Micromech Microeng 18:067001CrossRefGoogle Scholar
  19. Elrod SA, Hadimioglu B, Khuri-Yakub BT, Rawson EG, Richley E, Quate CF, Mansour NN, Lundgren TS (1989) Nozzleless droplet formation with focused acoustic beams. J Appl Phys 65:3441–3447CrossRefGoogle Scholar
  20. Fair RB (2007) Digital microfluidics: is a true lab-on-a-chip possible? Microfluid Nanofluid 3:245–281CrossRefGoogle Scholar
  21. Garstecki P, Gitlin I, DiLuizio W, Whitesides GM, Kumacheva E, Stone HA (2004) Formation of monodisperse bubbles in a microfluidic flow focusing device. Appl Phys Lett 85:2649–2651CrossRefGoogle Scholar
  22. Garstecki P, Fuerstman MJ, Stone HA, Whitesides GM (2006) Formation of droplets and bubbles in T-junction—scaling and mechanism of breakup. Lab Chip 6:437–446CrossRefGoogle Scholar
  23. Gong J, Kim CJ (2008) All-electronic droplet generation on-chip with real-time feedback control for EWOD digital microfluidics. Lab Chip 8:898–906CrossRefGoogle Scholar
  24. Gong X, Miller PW, Gee AD, Long NJ, de Mello AJ, Vilar R (2012) Gas–liquid segmented flow microfluidics for screening Pd-Catalyzed carbonylation reactions. Chem Eur J 18:2768–2772CrossRefGoogle Scholar
  25. Gopinath A, Koch DL (2001) Dynamics of droplet rebound from a weakly deformable gas–liquid interface. Phys Fluid 13:3526–3532CrossRefzbMATHGoogle Scholar
  26. Haubert K, Dryer T, Beebe D (2006) PDMS bonding by means of a portable, low-cost corona system. Lab Chip 6:1548–1549CrossRefGoogle Scholar
  27. Hayward RC, Utada AS, Dan N, Weitz DA (2006) Dewetting instability during the formation of polymersomes from block-copolymer-stabilized double emulsions. Langmuir 22:4457–4461CrossRefGoogle Scholar
  28. Hindson BJ, Ness KD, Masquelier DA, Belgrader P, Heredia NJ, Makarewicz AJ, Bright IJ, Lucero MY, Hidessen AL, Legler TC, Kitano TK, Hodel MR, Petersen JF, Wyatt PW, Steenblock ER, Shah PH, Bousse KJ, Troup CB, Mellen JC, Wittmann DK, Erndt NG, Cauley TH, Koehler RT, So AP, Dube S, Rose KA, Montesclaros L, Wang S, Stumbo DP, Hodges SP, Romine S, Milanovich FP, White HE, Regan JF, Karlin-Neumann GA, Hindson CM, Saxonov S, Colston BW (2011) High-throughput droplet digital PCR system for absolute quantitation of DNA copy number. Anal Chem 83(22):8604–8610CrossRefGoogle Scholar
  29. Hu W, Ohta AT (2011) Aqueous droplet manipulation by optically induced Marangoni circulation. Microfluid Nanofluid 11:307–316CrossRefGoogle Scholar
  30. Jung JH, Lee KH, Lee KS, Ha BH, Oh YS, Sung HJ (2013) Optical separation of droplets on a microfluidic platform. Microfluid Nanofluid 16:635–644CrossRefGoogle Scholar
  31. Kim M, Moon BU, Hidrovo CH (2013) Enhancement of the thermo-mechanical properties of PDMS molds for the hot embossing of PMMA microfluidic devices. J Micromech Microeng 23:095024CrossRefGoogle Scholar
  32. Li W, Pham HH, Nie Z, Macdonald B, Guenther A, Kumacheva E (2008) Multi-step microfludic polymerization reactions conducted in droplets: the internal trigger approach. Am Chem Soc 130:9935–9941CrossRefGoogle Scholar
  33. Link DR, Grasland-Mongrain E, Duri A, Sarrazin F, Cheng ZD, Cristobal G, Marquez M, Weitz DA (2006) Electric control of droplets in microfluidic devices. Angew Chem Int Ed 45:2556–2560CrossRefGoogle Scholar
  34. Liu K, Ding H, Chen Y, Zhao XZ (2007) Droplet-based synthetic method using microflow focusing and droplet fusion. Microfluid Nanofluid 3:239–243CrossRefGoogle Scholar
  35. Lorenceau E, Utada AS, Link DR, Cristobal G, Joanicot M, Weitz DA (2005) Generations of polymerosomes from double-emulsions. Langmuir 21:9183–9186CrossRefGoogle Scholar
  36. Marine NA, Klein SA, Posner JD (2009) Partition coefficient measurements in picoliter drops using a segmented flow microfluidic device. Anal Chem 81:1471–1476CrossRefGoogle Scholar
  37. Marmottant P, Villermaux E (2004) On spray formation. J Fluid Mech 498:73–111CrossRefzbMATHGoogle Scholar
  38. Mulligan MK, Rothstein JP (2012) Scale-up and control of droplet production in coupled microfluidic flow-focusing geometries. Microfluid Nanofluid 13(1):65–73CrossRefGoogle Scholar
  39. Nunes JK, Tsai SSH, Wan J, Stone HA (2013) Dripping and jetting in microfluidic multiphase flows applied to particle and fibre synthesis. J Phys D Appl Phys 46:114002CrossRefGoogle Scholar
  40. Piorek BD, Lee SJ, Santiago JG, Moskovits M, Banerjee S, Meinhart CD (2007) Free-surface microfluidic control of surface-enhanced Raman spectroscopy for the optimized detection of airborne molecules. PNAS 104:18898–18901CrossRefGoogle Scholar
  41. Post SL, Abraham J (2002) Modeling the outcome of drop–drop collisions in Diesel sprays. Int J Multiph Flow 28:997–1019CrossRefzbMATHGoogle Scholar
  42. Priest C, Herminghaus S, Seemann R (2006) Generation of monodisperse gel emulsions in a microfluidic device. Appl Phys Lett 88:024106CrossRefGoogle Scholar
  43. Roberts CC, Rao RR, Loewenberg M, Brooks CF, Galambos P, Grillet AM, Nemer MB (2012) Comparison of monodisperse droplet generation in flow focusing devices with hydrophilic and hydrophobic surfaces. Lab Chip 12:1540–1547CrossRefGoogle Scholar
  44. Seemann R, Brinkmann M, Pfohl T, Herminghaus S (2012) Droplet based microfluidics. Rep Prog Phys 75:016601CrossRefGoogle Scholar
  45. Shabani R, Cho HJ (2013) Flow rate analysis of an EWOD-based device: how important are wetting-line pinning and velocity effects? Microfluid Nanofluid 15:587–597CrossRefGoogle Scholar
  46. Song H, Chen DL, Ismagilov RF (2006) Reactions in droplets in microfluidic channels. Angew Chem Int Ed 45:7336–7356CrossRefGoogle Scholar
  47. Song Y, Baudoin M, Manneville P, Baroud CN (2011) The air–liquid flow in a microfluidic airway tree. Med Eng Phys 33:849–856CrossRefGoogle Scholar
  48. Suh KY, Kim P, Lee HH (2004) Capillary kinetics of thin polymer films in permeable microcavities. Appl Phys Lett 85:4019–4021CrossRefGoogle Scholar
  49. Sun X, Tang K, Smith RD, Kelly RT (2013) Controlled dispensing and mixing of pico-to nanoliter volumes using on-demand droplet-based microfluidics. Microfluid Nanofluid 15:117–126CrossRefGoogle Scholar
  50. Tan YC, Cristini V, Lee AP (2006) Monodispersed microfluidic droplet generation by shear focusing microfluidic device. Sens Actuators B Chem 114:350–356CrossRefGoogle Scholar
  51. Tan SH, Murshed SMS, Nguyen NT, Wong TN, Yobas L (2008a) Thermally controlled droplet formation in flow focusing geometry: formation regimes and effect of nanoparticle suspension. J Phys D Appl Phys 41:165501CrossRefGoogle Scholar
  52. Tan YC, Ho YL, Lee AP (2008b) Microfluidic sorting of droplets by size. Microfluid Nanofluid 4:343–348CrossRefGoogle Scholar
  53. Tan SH, Nguyen NT, Chua YC, Kang TG (2010) Oxygen plasma treatment for reducing hydrophobicity of a sealed polydimethylsiloxane microchannel. Biomicrofluid 4:032204CrossRefGoogle Scholar
  54. Tanyeri M, Ranka M, Sittipolkul N, Schroeder CM (2011) A microfluidic-based hydrodynamic trap: design and implementation. Lab Chip 11:1786–1794CrossRefGoogle Scholar
  55. Thiele J, Windbergs M, Abate AR, Trebbin M, Shum HC, Forster S, Weitz DA (2011) Early development drug formulation on a chip: fabrication of nanoparticles using a microfluidic spray dryer. Lab Chip 11:2362–2368CrossRefGoogle Scholar
  56. Thorsen T, Roberts RW, Arnold FH, Quake SR (2001) Dynamic pattern formation in a vesicle-generating microfluidic device. Phys Rev Lett 86:4163–4166CrossRefGoogle Scholar
  57. Utada AS, Lorenceau E, Link DR, Kaplan PD, Stone HA, Weitz DA (2005) Monodisperse double emulsions generated from microcapillary device. Science 308:537–541CrossRefGoogle Scholar
  58. van Dijke K, Kobayashi I, Schroën Uemura K, Nakajima M, Boom R (2010) Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification. Microfluid Nanofluid 9:77–85CrossRefGoogle Scholar
  59. Wada Y, Schmidt MA, Jensen KF (2006) Flow distribution and ozonolysis reaction in gas–liquid multichannel microreactors. Ind Eng Chem Res 45:8036–8042CrossRefGoogle Scholar
  60. Wan J, Stone HA (2012) Coated gas bubbles for the continuous synthesis of hollow inorganic particles. Langmuir 28:37–41CrossRefGoogle Scholar
  61. Wheeler AR, Moon H, Bird CA, Ogorzalek Loo RR, Kim CJ, Loo JA, Garrell RL (2005) Digital microfluidics with in-line sample purification for proteomics analyses with MALDI-MS. Anal Chem 77:534–540CrossRefGoogle Scholar
  62. Xu JH, Li SW, Tan J, Luo GS (2008) Correlations of droplet formation in T-junction microfluidic devices: from squeezing to dripping. Microfluid Nanofluid 5:711–717CrossRefGoogle Scholar
  63. Xu Q, Hashimoto M, Dang TT, Hoare T, Kohane DS, Whitesides GM, Langer R, Anderson DG (2009) Preparation of monodisperse biodegradable polymer microparticles using a microfluidic flow-focusing device for controlled drug delivery. Small 5:1575–1581CrossRefGoogle Scholar
  64. Yang SM, Yao H, Zhang D, Li WJ, Kung HF, Chen SC (2015) Droplet-based dielectrophoresis device for on-chip nanomedicine fabrication and improved gene delivery efficiency. Microfluid Nanofluid 19:235–243CrossRefGoogle Scholar
  65. Yasuda T, Imamura K, Hirase K (2009) Droplet transportation using EWOD-induced wettability gradient. In: Solid-state sensors, actuators and microsystems conference (Transducers), pp 413–416Google Scholar
  66. Yobas L, Martens S, Ongand WL, Ranganathan N (2006) High-performance flow-focusing geometry for spontaneous generation of monodispersed droplets. Lab Chip 6:1073–1079CrossRefGoogle Scholar
  67. Zhang K, Liang Q, Ma S, Mu X, Hu P, Wang Y, Luo G (2009) On-chip manipulation of continuous picoliter-volume superparamagentic droplets using a magnetic force. Lab Chip 9:2992–2999CrossRefGoogle Scholar
  68. Zhou CF, Yue PT, Feng JJ (2006) Predicting sizes of droplets made by microfluidic flow-induced dripping. Phys Fluids 18:092105CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Arjang Shahriari
    • 1
  • Myeongsub Mike Kim
    • 2
  • Siavash Zamani
    • 1
  • Nirmala Phillip
    • 1
  • Babak Nasouri
    • 3
  • Carlos H. Hidrovo
    • 4
    Email author
  1. 1.Mechanical Engineering DepartmentThe University of Texas at AustinAustinUSA
  2. 2.Ocean and Mechanical EngineeringFlorida Atlantic UniversityBoca RatonUSA
  3. 3.Mechanical Engineering DepartmentThe University of British ColombiaVancouverCanada
  4. 4.Multiscale Thermal Fluids Laboratory, Mechanical and Industrial Engineering DepartmentNortheastern UniversityBostonUSA

Personalised recommendations