Characterization of particle capture in a sawtooth patterned insulating electrokinetic microfluidic device.

Here we present a scheme to separate particles according to their characteristic physical properties, including size, charge, polarizability, deformability, surface charge mobility, dielectric features, and local capacitance. Separation is accomplished using a microdevice based on direct current insulator gradient dielectrophoresis that can isolate and concentrate multiple analytes simultaneously at different positions. The device is dependent upon dielectrophoretic and electrokinetic forces incorporating a global longitudinal direct current field as well as using shaped insulating features within the channel to induce local gradients. This design allows for the production of strong local field gradients along a global field causing particles to enter, initially transported through the channel by electrophoresis and electroosmosis (electrokinetics), and to be isolated via repulsive dielectrophoretic forces that are proportional to an exponent of the field gradient. Sulfate-capped polystyrene nano and microparticles (20, 200 nm, and 1 μm) were used as probes to demonstrate the influence of channel geometry and applied longitudinal field on separation behavior. These results are consistent with models using similar channel geometry and indicate that specific particulate species can be isolated within a distinct portion of the device, whereas concentrating particles by factors from 10(3) to 10(6).