Enhanced particle self-ordering in a double-layer channel
Springer Science+Business Media, LLC, part of Springer Nature 2018
In this work, a novel double-layer microfluidic device for enhancing particle focusing was presented. The double-layer device
consists of a channel with expansion-contraction array and periodical slanted grooves. The secondary flows induced by the
grooves modulate the flow patterns in the expansion-contraction-array (ECA) channel, further affecting the particle migration.
Compared with the single ECA channel, the double-layer channel can focus the particles over a wider range of flow rate. Due to
the differentiation of lateral migration, the double-layer channel is able to distinguish the particles with different sizes.
Furthermore, the equilibrium positions could be modulated by the orientation of grooves. This work demonstrates the possibility
to enhance and adjust the inertial focusing in an ECA channel with the assistance of grooves, which may provide a simple and
portable platform for downstream filtration, separation, and detection.
Keywords Double-layer channel
Focusing particles into a single stream is a significant step for
downstream counting, detection, concentration or sorting,
which is useful for a wide range of applications in environ-
ment, food technology and biomedicine (Xiang et al. 2015a;
Yan et al. 2014; Zhao et al. 2017). For instance, the flow
cytometry is a technique for counting, detection and sorting
particles (Simonnet and Groisman 2006) that utilizes a sheath
flow to confine the particles into a tight stream. The confined
particles can pass the detection point one by one in a tube.
Except for flow cytometry, microfluidics can also focus parti-
cles in a simple, rapid way at the minimal cost of reagents and
labor. Unlike flow cytometry that required bulky equipment,
the miniaturized microfluidic chip enables the device to be
portable for outfield research (Yan et al. 2018).
Microfluidic focusing can be divided into sheath flow-
assisted and sheathless methods. Sheath flow-assisted method
is a simple and powerful tool to achieve the particle focusing
by the hydrodynamic force, which can be used for media
exchange (Yuan et al. 2016), quantifications of cellular defor-
mation (Moehlenbrock et al. 2006), and cell washing (Yuan
et al. 2017). However, it highly depends on the accurate flow
control. Any interruption of pumping will defocus their initial
position and lead to a poor focusing performance. To over-
come this drawback, several microfluidic techniques have
been proposed to focus particles without sheath flow, such
as dielectrophoresis (DEP) and acoustophoresis (AP). Two-
and three-dimensional electrodes were fabricated to enable
the DEP focusing in a microchannel (Chu et al. 2009;Li
et al. 2013; Jia et al. 2015;Tangetal.2013). Acoustic methods
used the acoustic radiation force for focusing of microbeads
(Goddard et al. 2006; Shi et al. 2011) and mammalian cells
(Chen et al. 2014). Although these active approaches show a
promising aspect in focusing particles, they require the com-
plicated fabrication processes such as patterning of
piezoceramic plates and metal-electrodes (Choi et al. 2008).
Therefore, the sheathless, passive microfluidic device can ad-
dress this issue due to its advantage of lower fabrication cost
and simple fabrication process.
In the last decade, inertia-based methods have been
extensively used for successfully focusing particles due
to their advantages of simplicity, passiveness, preciseness,
and high-throughput (Zhang et al. 2016; Xiang et al.
Sheng Yan and Yuxing Li contributed equally to this work.
* Sheng Yan
* Weihua Li
School of Mechanical, Materials, Mechatronic and Biomedical
Engineering, University of Wollongong, Wollongong, NSW 2522,
Biomedical Microdevices (2018) 20:23