Electrorotation method is a useful technique for characterizing dielectric properties of individual cells or particles.
During the electrorotation process, a dielectric cell is subjected to rotating electric field of high frequency and its rotation
speed is monitored. As high conductivity buffer is used in the process, heat is generated which in turn affects cell
rotation performance. In this work, we present temperature analytical results of a 4-electrode electrorotation chip using
finite element method. The simulation conditions include variation of applied voltage, buffer conductivity and material
of the chip. We found that the applied voltage and conductivity of buffer used are two main factors affecting temperature
rise in electrorotation process.
Liquid pumping, mixing and biological cells/reagents delivery in micro- or nano-liter volume is critical in lab-on-chip
systems. We describe a novel AC electro-osmosis device for delivering reagents/cells over large distances without a
global pressure gradient. Our device features facile transport range scalability in x- and y-axes, using continuous flow
in a serpentine microchannel realized by microelectrode pairs arrayed in a unique antiparallel-asymmetric configuration.
Co-planar microelectrodes on glass substrate are fabricated from gold with chromium as seed layer using micro-electromechanical
system (MEMS) technology. Sealed upon the micro-electrodes is an open-ended serpentine microchannel
having width 80μm and depth 45μm; formed by micromolding PDMS with a silicon-based mold. AC signals at 3.5Vpp
and 0.5V DC offset is used to energize the microelectrodes, and polystyrene beads with diameter 5.0μm are used as
tracer particles to visualize flow. Maximum velocity of 871 μm/s was recorded using AC signals at 8 kHz. The ease
of scaling up transport distance range in 2-axes is unique to our device. Scalability in x-axis is achieved by varying the
number of microelectrode pairs; and in y-axis by varying the number of microelectrodes iterations and the
corresponding number of turns in the serpentine microchannel. Being scalable in transporting fluidic volume with high
efficiency under small driving voltages makes our device suitable for miniaturization in a micro-total-analytical-system.
Our device could be applied towards multiple point reagents, biological cells and particles delivery and mixing in a
lab-on-chip.
We present the design and fabrication of a micro-electromechanical system (MEMS) device for cell and particle
delivery using a combination of AC electrokinetic fluidic flow and negative dielectrophoresis (DEP) force. An array of
interdigitated asymmetric microelectrode pairs were used in the planar device. The electrodes produced a net charge in
the surrounding fluid, generating an AC electrokinetic fluidic motion. A non-uniform electric field with low actuation
frequency from the microelectrode pairs resulted in a negative DEP force, which was responsible for pushing delivery
particles away from sedimentation. The experimental results showed that the flow velocity increased rapidly from 267
μm/min to 394 μm/min when the applied frequency was increased from 10 kHz to 70 kHz for a cell-suspending medium
buffer solution with a conductivity of 4.7 μS/cm. A maximum delivery velocity of 801 μm/min was obtained when the buffer conductivity was increased to 47 μS/cm with an actuation frequency of 100 kHz.
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