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In a microbiological device, cell or particle manipulation and characterization require the use of electric field on different electrodes in several configurations and shapes. To efficiently design microelectrodes within a microfluidic channel for dielectrophoresis focusing, manipulation and characterization of cells, the designer will seek the exact distribution of the electric potential, electric field and hence dielectrophoresis force exerted on the cell within the microdevice. In this paper we describe the approach attaining the analytical solution of the dielectrophoretic force expression within a microchannel with parallel facing same size electrodes present on the two faces of channel substrates, with opposite voltages on the pair electrodes. Simple Fourier series mathematical expressions are derived for electric potential, electric field and dielectric force between two distant finite-size electrodes. Excellent agreement is found by comparing the analytical results calculated using MATLAB™ with numerical ones obtained by Comsol. This analytical result can help the designer to perform simple design parametric analysis. Bio-microdevices are also designed and fabricated to illustrate the theoretical solution results with the experimental data. Experiments with red blood cells show the dielectrophoretic force contour plots of the analytical data matched to the experimental results.

Electrokinetics manipulation and separation of living cells employing microfluidic devices require good knowledge of the strength and distribution of electric field in such devices. AC dielectrophoresis is performed by generating non-uniform electric field using microsize electrodes. Among the several applications of dielectrophoretic phenomenon, this present study considers the recently introduced phenomenon of moving dielectrophoresis. An analytical solution using Fourier series is presented for the electric field distribution and dielectrophoretic force generated inside a microchannel. The potential at the upper part of the microchannel has been found by solving the governing equation of the electric potential with specific boundary conditions. The solutions for the electric field and dielectrophoretic force show excellent agreement with the numerical results. Microdevices were fabricated and experiments were carried out with living cells confirming and validating the analytical solutions.

The paper presents the principles and the results of the implementation of dielectrophoresis for separation and identification of rare cells such as circulation tumor cells (CTCs) from diluted blood specimens in media and further label-free identification of the origins of separated cells using radio-frequency (RF) imaging. The separation and the identification units use same fabrication methods which enable system integration on the same platform. The designs use the advantage of higher surface volume ratio which represents the particular feature for micro-and nanotechnologies. Diluted blood in solution of sucrose-dextrose 1-10 is used for cell separation that yields more than 95.3% efficiency. For enhanced sensitivity in identification, RF imaging is performed in 3.5-1 solution of glycerol and trypsin. Resonance cavity performance method is used to determine the constant permittivity of the cell lines. The results illustrated by the signature of specific cells subjected to RF imaging suggest a reliable label-free single cell detection method for identification of the type of CTC.

This article provides the design and fabrication details of a new technique to build a microfluidic device with two parallel substrates and a silicone gasket. The fabrication process uses screen printing technology offering fast and low-cost microdevices without the need for high-cost fabrication equipment and special photoresist processes. Hermetic microfluidic channels of 300 mm width and 50 mm height having parallel facing electrodes on two substrates are made with simple serigraphy technique using silicone rubber. The fabricated devices were experimentally tested for detection and characterization of polystyrene particles and living cells by negative and positive dielectrophoresis. The reported technique enables simple manipulation, centering, detection and characterization of living cells at low and high frequencies.