Rafael V Davalos - Contactless Dielectrophoresis (cDEP) - 3-10-10

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Abstract: ;Dielectrophoresis (DEP), the motion of a particle due to its polarization in the presence of a non- uniform electric field, can be used to differentiate cell types based upon their intrinsic electrical properties. A number of applications based upon this principle have been effectively demonstrated. Unfortunately, cellular isolation techniques employing conventional DEP generally require direct contact between electrodes and a sample fluid, which can induce fouling, bubble formation and unwanted electrochemical effects. We have invented 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 channel 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 the barriers. The absence of contact between electrodes and the sample fluid inside the channel prevents bubble formation and avoids any contaminating effects that the electrodes may have on the sample. We have designed and fabricated microfluidic devices based on this new technique and have observed DEP responses (DEP trapping and cell chaining) in multiple cancer cells, including human leukemia, breast, and prostate cancer cells. The major advantages of contactless dielectrophoresis are lack of extensive sample preparation (no antibody labeling, one needs only prepare a single cell preparation), the speed of isolation (minutes from the time of sample acquisition), and a simplified inexpensive fabrication process.
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