A comparison of insulator-based dielectrophoretic devices for the monitoring and separation of waterborne pathogens as a function of microfabrication technique

We present the selective trapping, concentration, and release of various biological organisms and inert beads utilizing insulator-based dielectrophoresis (iDEP) with discrete post arrays inside a polymeric microfluidic device. The arrays of insulating posts used to constrict electric field lines within the microchannel were fabricated using two of the most common fabrication techniques: chemical isotropic and reactive ion anisotropic etching. These fabrication methods, therefore, produce structures with distinct transverse profiles-the reactive ion etch produces relatively straight sidewalls, whereas the chemical etch produces tapered sidewalls. The devices were utilized to selectively separate and concentrate a variety of biological simulants and organisms. The dielectrophoretic responses of the organisms were observed to be a function of the applied electric field as well as post size and channel geometry. We then compare the device performance as a function of microfabrication methodology and through comparing experimental results and those predicted by computational modeling. We have found that there is a direct dependence on the cross-section profile of the channel and the non-uniform electric field gradients generated. This variation has a significant impact on the resultant performance and separation efficiency of the device.