Dielectrophoresis (DEP), the motion of a particle due to its polarization in the presence of a non-uniform electric field, can be used as an alternative to current sample enrichment techniques [1]. While the technique has been proven effective, most DEP devices must be manufactured using complicated processes. Insulator-based dielectrophoresis (iDEP) is a practical method to obtain the selectivity of dielectrophoresis while overcoming the robustness issues associated with traditional dielectrophoresis platforms [2]. While both of these methods allow for the differentiation of cells based upon their intrinsic electrical properties, they require direct contact between electrodes and a sample fluid, which can induce fouling, bubble formation and unwanted electrochemical effects [3]. We have developed an alternative method to provide the spatially non-uniform electric field required for DEP in which electrodes are not in direct contact with the biological sample. In this method, an electric field is created in the sample microchannel using electrodes inserted into two other microchannels (filled with conductive solution), which are separated from the sample microchannel by thin insulating barriers. These insulating barriers exhibit a capacitive behavior and therefore an electric field can be produced in the main channel by applying an AC field across them. The absence of contact between electrodes and the sample fluid inside the channel prevents bubble formation and avoids any contaminating effects the electrodes may have on the sample.

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