Concentration of bacteria in high conductive medium using negative dielectrophoresis

Rapid and sensitive detection of pathogenic bacteria has been an important concern in various fields such as bioscience research, medical diagnosis and hazard analysis in the food industry. The requirement for highly efficient bacterial detection has pointed to the need for new and innovative sample concentration technologies. In this study, a new microfluidic device was demonstrated to enable concentration of bacteria by using negative dielectrophoresis (n-DEP) in high conductive medium. A special design of the electrode system, which was covered with patterned dielectric films, was tested in order to control the electric field distribution in the device so that n-DEP force could drive cells to a point for concentration as well as Joule heating of the suspension medium could be suppressed to avoid heat-induced cell damage. The electrode design was optimized using numerical calculation results of cell motion trajectories and the suspension medium temperature in the device. It was experimentally proved that proposed microfluidic device could concentrate E. coli cells in a continuous flow of cell suspension.