Abstract
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This article presents a dielectrophoresis (DEP)-
based microfluidic device with the three-dimensional (3D)
microelectrode configuration for concentrating and separating
particles in a continuous throughflow. The 3D electrode
structure, where microelectrode array are patterned on
both the top and bottom surfaces of the microchannel, is
composed of three units: focusing, aligning and trapping.
As particles flowing through the microfluidic channel, they
are firstly focused and aligned by the funnel-shaped and
parallel electrode array, respectively, before being captured
at the trapping unit due to negative DEP force. For a mixture
of two particle populations of different sizes or dielectric
properties, with a careful selection of suspending medium
and applied field, the population exhibits stronger negative
DEP manipulated by the microelectrode array and, therefore,
separated from the other population which is easily
carried away toward the outlet due to hydrodynamic force.
The functionality of the proposed microdevice was verified
by concentrating different-sized polystyrene (PS) microparticles
and yeast cells dynamically flowing in the
microchannel. Moreover, separation based on size and
dielectric properties was achieved by sorting PS microparticles,
and isolating 5 lm PS particles from yeast cells,
respectively. The performance of the proposed microconcentrator
and separator was also studied, including the
threshold voltage at which particles begin to be trapped,
variation of cell-trapping efficiency with respect to the
applied voltage and flow rate, and the efficiency of separation
experiments. The proposed microdevice has various
advantages, including multi-functionality, improved
manipulation efficiency and throughput, easy fabrication
and operation, etc., which shows a great potential for biological,
chemical and medical applications.