Microfluidics and Nanofluidics

, 23:107 | Cite as

A sheathless inertial focusing technique for optofluidic devices

  • Nishtha Panwar
  • Peiyi Song
  • Chengbin Yang
  • Swee Chuan Tjin
  • Yi-Chung TungEmail author
  • Ken-Tye YongEmail author
Research Paper


Here, we demonstrate single-position, three-dimensional (3D) focusing of cells or micron-sized particles in the range 0.175 < a/w < 0.9 (a, cell or particle diameter; w, width of the microchannel), on a single-layer, single-channel microfluidic chip, which totally alleviates the need of using any sheath flow or external force, making the microfluidic chip standalone operational. The focusing is a result of inertial microfluidic hydrodynamic forces such as inertial lift forces and Dean drag forces, which are determined by the geometry of microchannel. With the microfluidic channel comprising a series of radially increasing, uniform semi-arcs interleaved by linear sections, sheathless focusing at flow rates up to 700 μL/min is achieved in our study. The result can be well explained by a developed empirical model relating the ratio of inertial lift forces and Dean drag forces, and the geometrical parameters of the microchannel. Following this approach, we illustrate experimental characterization of micron-sized sample focusing using fluorescent microparticles, pancreatic cancer cells, and macrophages under Reynolds number flows ranging between 20 and 153. We foresee the single-position focusing outcome of the proposed sheathless chip design in developing portable microfluidic and optofluidic devices for in vitro theranostics.


Inertial focusing Hydrodynamics Optofluidic Sheathless 



The authors acknowledge the support of the School of Electrical and Electronic Engineering, Nanyang Technological University, NTU-NHG Innovation Collaboration (M4061202.040) Grant, NTU–A*STAR Silicon Technologies, Centre of Excellence (11235100003) grant, NEWRI EDB Funding, MOE Tier 2 Funding (MOE2017-T2-2-002), the Scientific Research Foundation for Newly Introduced Teachers of Shenzhen University (2019136), Guangdong Medical Science and Technology Research Fund Project (A2019359), and the School of Electrical and Electronic Engineering, NTU, Singapore.

Supplementary material

10404_2019_2270_MOESM1_ESM.docx (1011 kb)
Supplementary material 1 (DOCX 1010 kb)
10404_2019_2270_MOESM2_ESM.avi (2 mb)
Supplementary material 2 (AVI 2045 kb)
10404_2019_2270_MOESM3_ESM.avi (3.2 mb)
Supplementary material 3 (AVI 3232 kb)
10404_2019_2270_MOESM4_ESM.avi (3 mb)
Supplementary material 4 (AVI 3053 kb)
10404_2019_2270_MOESM5_ESM.avi (2.5 mb)
Supplementary material 5 (AVI 2525 kb)
10404_2019_2270_MOESM6_ESM.avi (3.1 mb)
Supplementary material 6 (AVI 3168 kb)


  1. Amini H, Lee W, Di Carlo D (2014) Inertial microfluidic physics. Lab Chip 14:2739–2761. CrossRefGoogle Scholar
  2. Asmolov ES (1999) The inertial lift on a spherical particle in a plane Poiseuille flow at large channel Reynolds number. J Fluid Mech 381:63–87. CrossRefzbMATHGoogle Scholar
  3. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2008) Enhanced particle filtration in straight microchannels using shear-modulated inertial migration. Phys Fluids 20:101702. CrossRefzbMATHGoogle Scholar
  4. Bhagat AAS, Kuntaegowdanahalli SS, Papautsky I (2009) Inertial microfluidics for continuous particle filtration and extraction. Microfluid Nanofluid 7:217–226. CrossRefGoogle Scholar
  5. Bhagat AAS, Kuntaegowdanahalli SS, Kaval N, Seliskar CJ, Papautsky I (2010) Inertial microfluidics for sheath-less high-throughput flow cytometry. Biomed Microdev 12:187–195. CrossRefGoogle Scholar
  6. Chung AJ, Gossett DR, Di Carlo D (2013a) Three dimensional, sheathless, and high-throughput microparticle inertial focusing through geometry-induced secondary flows. Small 9:685–690. CrossRefGoogle Scholar
  7. Chung AJ, Pulido D, Oka JC, Amini H, Masaeli M, Di Carlo D (2013b) Microstructure-induced helical vortices allow single-stream and long-term inertial focusing. Lab Chip 13:2942–2949. CrossRefGoogle Scholar
  8. Di Carlo D, Irimia D, Tompkins RG, Toner M (2007) Continuous inertial focusing, ordering, and separation of particles in microchannels. Proc Natl Acad Sci 104:18892–18897. CrossRefGoogle Scholar
  9. Di Carlo D, Edd JF, Humphry KJ, Stone HA, Toner M (2009) Particle segregation and dynamics in confined flows. Phys Rev Lett 102:094503. CrossRefGoogle Scholar
  10. Gossett DR, Carlo DD (2009) Particle focusing mechanisms in curving confined flows. Anal Chem 81:8459–8465. CrossRefGoogle Scholar
  11. Ho BP, Leal LG (1974) Inertial migration of rigid spheres in two-dimensional unidirectional flows. J Fluid Mech 65:365–400. CrossRefzbMATHGoogle Scholar
  12. Jiang D, Tang W, Xiang N, Ni Z (2016) Numerical simulation of particle focusing in a symmetrical serpentine microchannel. RSC Advances 6:57647–57657. CrossRefGoogle Scholar
  13. Love JD, Henry WM, Stewart WJ, Black RJ, Lacroix S, Gonthier F (1991) Tapered single-mode fibres and devices. I. Adiabaticity criteria. IEE Proc J Optoelectron 138:343–354. CrossRefGoogle Scholar
  14. Martel JM, Toner M (2012) Inertial focusing dynamics in spiral microchannels. Phys Fluids (Woodbury, NY : 1994) 24:32001. CrossRefGoogle Scholar
  15. Martel JM, Toner M (2013) Particle focusing in curved microfluidic channels. Sci Rep 3:3340. CrossRefGoogle Scholar
  16. Matas J-P, Morris JF, Guazzelli É (2004) Inertial migration of rigid spherical particles in Poiseuille flow. J Fluid Mech 515:171–195. CrossRefzbMATHGoogle Scholar
  17. Oakey J, Applegate RW, Arellano E, Carlo DD, Graves SW, Toner M (2010) Particle focusing in staged inertial microfluidic devices for flow cytometry. Anal Chem 82:3862–3867. CrossRefGoogle Scholar
  18. Ramachandraiah H, Ardabili S, Faridi AM, Gantelius J, Kowalewski JM, Mårtensson G, Russom A (2014) Dean flow-coupled inertial focusing in curved channels. Biomicrofluidics 8:034117. CrossRefGoogle Scholar
  19. Reece AE, Kaastrup K, Sikes HD, Oakey J (2015) Staged inertial microfluidic focusing for complex fluid enrichment. RSC Adv 5:53857–53864. CrossRefGoogle Scholar
  20. Segré G, Silberberg A (1962) Behaviour of macroscopic rigid spheres in Poiseuille flow Part 2. Experimental results and interpretation. J Fluid Mech 14:136–157. CrossRefzbMATHGoogle Scholar
  21. Vasseur P, Cox RG (1976) The lateral migration of a spherical particle in two-dimensional shear flows. J Fluid Mech 78:385–413. CrossRefzbMATHGoogle Scholar
  22. Wang X, Zandi M, Ho C-C, Kaval N, Papautsky I (2015) Single stream inertial focusing in a straight microchannel. Lab Chip 15:1812–1821. CrossRefGoogle Scholar
  23. Yang BH, Wang J, Joseph DD, Hu HH, Pan TW, Glowinski R (2005) Migration of a sphere in tube flow. J Fluid Mech 540:109–131. CrossRefzbMATHGoogle Scholar
  24. Zhang J, Li M, Li WH, Alici G (2013) Inertial focusing in a straight channel with asymmetrical expansion–contraction cavity arrays using two secondary flows. J Micromech Microeng 23:085023. CrossRefGoogle Scholar
  25. Zhang J, Li W, Li M, Alici G, Nguyen N-T (2014) Particle inertial focusing and its mechanism in a serpentine microchannel. Microfluid Nanofluid 17:305. CrossRefGoogle Scholar
  26. Zhao Q, Zhang J, Yan S, Yuan D, Du H, Alici G, Li W (2017) High-throughput sheathless and three-dimensional microparticle focusing using a microchannel with arc-shaped groove arrays. Scientific Reports 7:41153. CrossRefGoogle Scholar
  27. Zhou J, Papautsky I (2013) Fundamentals of inertial focusing in microchannels. Lab Chip 13:1121–1132. CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.School of Electrical and Electronic EngineeringNanyang Technological UniversitySingaporeSingapore
  2. 2.MOE Key Laboratory of Fundamental Physical Quantities Measurement and Hubei Key Laboratory of Gravitation and Quantum PhysicsHuazhong University of Science and TechnologyWuhanChina
  3. 3.Guangdong Key Laboratory for Biomedical Measurements and Ultrasound Imaging, Laboratory of Evolutionary Theranostics, School of Biomedical Engineering, Health Science CenterShenzhen UniversityShenzhenChina
  4. 4.Academia Sinica, Research Center for Applied SciencesTaipeiTaiwan

Personalised recommendations