Sensitivity improvement of dielectrophoretic impedance measurement by bacteria concentration using negative dielectrophoresis

Dielectrophoretic impedance measurement (DEPIM) is a method to detect bacteria in an aqueous solution. DEPIM consists of two simultaneous processes: dielectrophoretic trapping of the target bacteria onto a microelectrode and measurement of impedance change caused by trapping bacteria. In this study, a new bacterial concentration process was combined with DEPIM to improve its sensitivity. The concentration process was based on negative dielectrophoresis of bacteria caused by specific configuration of parallel electrodes. A ditched dielectric thin layer deposited on one of the parallel electrodes causes non-uniform electric field resulting in occurring negative dielectrophoresis. Two electrode configurations, one is for the bacteria concentration and the other is for DEPIM, were fabricated in a microchannel. As a result, the detection sensitivity of DEPIM increased about 1.6 times by combining the concentration.