Molecular dielectrophoresis of biopolymers

Dielectrophoresis (DEP) has found wide applications in manipulations of micrometer-sized particles such as biological cells. However, it has been considered less effective for nanometer-sized particles such as biological macromolecules where DEP effects may be overwhelmed by Brownian motion. Here, the authors use the fluid integrated circuit (FIC) concept to fabricate micrometer-sized electrodes, with which a very high-intensity, steady-state, high-frequency field, over 1×10⁶ V/m at 1 kHz to 10 MHz, is created. The observation of molecular DEP using avidin (68 kD) and other biopolymers is made, and it is found that DEP occurs at the field strength of 0.4-1.0×10⁶ V/m, which is substantially lower than DEP theory predicts. As applications of molecular DEP, a novel molecular patterning method and “dielectrophoretic chromatography” are proposed. In the latter, biopolymer solution is moved through a high-intensity field region created in a FIC, and the polymer is analyzed and/or separated by the difference in the DEP attraction