Continuous sheath-free focusing of microparticles in viscoelastic and Newtonian fluids

  • Liang-Liang Fan
  • Xu Wu
  • Hong Zhang
  • Zhi Zhao
  • Jiang Zhe
  • Liang ZhaoEmail author
Research Paper


A simple microfluidic device is reported for continuous, sheath-free focusing of microparticles in both viscoelastic and Newtonian fluids. Gradually contracted and suddenly expanded structures in the flow direction were designed on one side of the microchannel to induce asymmetric distribution of the elastic force on the cross section in the viscoelastic fluid. Driven by the elastic force and the viscous drag force, microparticles were focused in a single position located near the straight wall of the channel. In the Newtonian fluid, these contracted and expanded structures were utilized to generate highly curved streamlines which induced momentum-change-induced inertial force on particles. Under the combined effect of this force and the inertial lift force, the particles were also focused in a single stream in the Newtonian fluid. The influences of flow rate, particle size, polymer concentration, fluid viscosity and channel geometry on the particle focusing were investigated in the paper. In comparison with other particle focusing devices, the present microchannel can focus microparticles in a single stream in both the viscoelastic and the Newtonian fluids in a short channel length without the aid of sheath flow. With simple structure and easy operation, this device could be potentially utilized in a variety of particle focusing processes in biomedical applications, such as the enrichment of cells.


Particle focusing Sheath-free Viscoelastic fluid Newtonian fluid Microfluidic 



This study was supported by the National Natural Science Foundation of China (No.: 51706175, 51876172 and 51476127), the China Postdoctoral Science Foundation (No. : 2019M653590) and the Fundamental Research Funds for the Central Universities (No. xjj2016010). J. Zhe acknowledges the partial support from National Science Foundation of USA via the research grants ECCS-1625544 and ECCS-1905786.

Supplementary material

10404_2019_2281_MOESM1_ESM.doc (5.7 mb)
Supplementary material 1 (DOC 5810 kb)


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Copyright information

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

Authors and Affiliations

  1. 1.School of Mechanical EngineeringXi’an Jiaotong UniversityXi’anPeople’s Republic of China
  2. 2.State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’anPeople’s Republic of China
  3. 3.Department of Mechanical EngineeringUniversity of AkronAkronUSA

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