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  • Research progress in microfluidic separation of bioparticles utilizing viscoelastic effects
    Author:   | Date:2015-07-29   | Click Rate:    | 【Close

    Continuous manipulation and separation of particles and cells is important for a wide range of applications in biology,1 medicine, and industry. Particles and cells can be separated based on the size-dependent nature of hydrodynamic forces, including inertial and viscoelastic effects. Briefly, the inertial lift scales as and the viscoelastic lift scales as , where a is the particle diameter. Inertial migration in Newtonian fluids has been intensively studied and implemented in high-throughput label-free separation microfluidic devices for cell separation. However, inertial focusing pattern becomes more complex at higher Reynolds number, often resulting in unfavorable multiple lateral equilibrium positions. Moreover, for successful inertial focusing of smaller particles, the microchannel cross-section has to be scaled down with decreasing particle sizes.

    The researchers from the State Key Laboratory of Nonlinear Mechanics at the Institute of Mechanics, CAS demonstrated label-free, sheathless, and inexpensive separations of particles and cells by size in straight rectangular microchannels for the first time. Interestingly, large particles will migrate towards the lateral positions near the two side walls, which is different from the traditional focusing pattern of one focusing position at the channel centerline. Exploiting this unexpected mechanism, they realized complete separation of particles with a wide range of length scales—the large components were focused near the side walls whereas the small components were focused along the centerline. High-quality separation of two types of binary mixtures of biparticles—MCF-7 cells/RBCs and E. coli bacteria/RBCs—can also be easily achieved due to their difference in size. In addition, by engineering the rheological properties of the carrier medium, the operational flow rates can reach one order of magnitude higher than those in existing studies. The sample throughput can be further improved due to the excellent parallelizability of this extremely simple design using straight microchannels. The proposed method could broaden the applications of viscoelastic microfluidic devices to particle/cell separation due to the enhanced sample throughput and simple channel design.

    This research has appeared in Analytical Chemistry (http://dx.doi.org/ 10.1021/acs.analchem.5b00516). The corresponding author is Dr. Guoqing Hu and the first author is Chao Liu, a PhD candidate who won both Excellence Award of CAS President and Guo Yonghuai Prize in 2015. The same group has previously published works on Newtonian microfluidic inertia in Lab on a Chip, Biomicrofluidics, and Physics of Fluids. This work is supported by the Ministry of Science and Technology and the National Natural Science Foundation of China.

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