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.
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
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.
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.