Continuous flow separation of particles with insulator-based dielectrophoresis chromatography

The development of insulator-based dielectrophoresis chromatography is proposed here as a novel hybrid technique that capitalizes on the simplicity of insulator-based dielectrophoresis (iDEP) and the well-known chromatographic theory. Chromatographic parameters are employed to characterize dielectrophoretic separation of particles with particles being eluted from the system as enriched particle peaks. By varying the characteristics of the insulating posts, it was possible to manipulate the interactions of the particles with the insulating post array which acted as the stationary phase. The present work studied how the characteristics of the particles affected the particle retention. Different types of particles have distinct interactions with the post array; these interactions depend on particle properties (size, electrical charge, and polarizability). This work includes mathematical modeling with COMSOL and extensive experimentation. Particles ranging from 1 to 10 μm in diameter were tested for retention time and eluted as peaks in the iDEP chromatography devices. Separation results were reported in the form of dielectropherograms including the estimation of retention time (t_R), separation efficiency (N/meter), and separation resolution (R_s). Two full separations were demonstrated: a separation by charge between two types of particles of similar size (~ 10 μm) with different electrical surface charges and a separation by size between 2- and 5-μm particles with similar surface charge (difference in ζ_P of 4 mV). The achieved separation resolutions were R_s = 1.8 and R_s = 3.5, respectively. This is the first study on DEP chromatography to assess performance in terms of resolution and separation efficiency, demonstrating the unique potential of iDEP chromatography.