Anomalous, Dielectrophoretic Transport of Molecules in Non-Electrolytes

The electric field dielectric polarization-based separations mechanism represents a novel method for separating solutions at small length scales. An electric field gradient with a maximum strength of $\mathrm{0.4~MV/m}$ applied across a $\mathrm{10~\mu m}$ deep channel is shown to increase the concentration inside the low electric field region by $\approx \mathrm{40}\%$ relative to the high electric field region. This concentration change is two orders of magnitude higher than the estimated change predicted using the classical equilibrium thermodynamics for the same electric field. The deviation between the predicted and the experimental results suggests that the change in volumetric electric field energy with solute concentration is insufficient to explain this phenomenon. The study also explores the effect of varying strength of electric field and frequency of supplied voltage on the dielectric polarization-based separation efficiency. While the increase in the former increases the separation efficiency, the increase in the latter reduces the degree of concentration change due to ineffective charging of the electrodes.