Embedded Passivated-electrode Insulator-based Dielectrophoresis
Pathogens in drinking water are the cause of over 1.5 million deaths around the world every year, mostly in developing countries. Practical, cheap, and effective tools for detection of these pathogens are critical to advance public health in many areas around the globe. Micro electro-mechanical systems (MEMS) are miniaturized structures that can be used for a variety of purposes, including, but not limited to, small scale sensors. Therefore, MEMS can be used in place of expensive laboratory equipment and offer a cheap and practical tool for pathogen detection.
The presented work's research objective is to introduce a new technique called embedded passivated-electrode insulator-based dielectrophoresis (EπDEP) for preconcentration, separation, or enrichment of bioparticles, including living cells. This new method combines traditional electrode-based DEP and insulator-based DEP with the objective of enhancing the electric field strength and capture efficiency within the microfluidic channel while alleviating direct contact between the electrode and the fluid. The EπDEP chip contains embedded electrodes within the microfluidic channel covered by a thin passivation layer of only 4 μm. The channel was designed with two nonaligned vertical columns of insulated microposts (200 μm diameter, 50 μm spacing) located between the electrodes (600 μm wide, 600 μm horizontal spacing) to generate the nonuniform electric field lines to concentrate cells while maintaining steady flow in the channel. The performance of the chip was demonstrated using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial pathogens in aqueous media. Trapping efficiencies of 100% were obtained for both pathogens at an applied AC voltage of 50 V peak-to-peak and flow rates as high as 10 uL/min.