Continuous-mode dielectrophoretic gating for highly efficient separation of analytes in surface micromachined microfluidic devices

Here, we describe a dielectrophoretic (DEP) gating technique for preconcentrating and separating biological and non-biological particles in a microfluidic device. The microfluidic devices are surface-micromachined on silicon substrates and are fully encapsulated without substrate bonding procedures. DEP gates in the devices consist of embedded microelectrodes that are coupled to the fluid channels for analyte manipulation with electric fields. We consider several different microelectrode designs such as low and high radius-of-curvature edges, and we detail the time- and frequency-dependent preconcentration of particles. Simulations of the particle motion under the manipulation of DEP forces are found to be in good agreement with the experimental results. Experimental results show that bioparticles such as Penicillium brevicompactum (PBC), T-cells and Escherichia coli (E. coli) undergo positive DEP and are trapped in regions of large electric-field gradient adjacent to the DEP gate. In contrast to our previous demonstration of batch-mode separation of particles with different dielectric properties, here we perform a continuous-mode separation of latex particles and E. coli from a mixture.