Opposing electrokinetic and hydrodynamic flows: Particle mixing and concentration devices

We present a novel, low voltage particle mixing and concentration paradigm that exploits the interplay between electrokinetic, dielectrophoretic, and pressure-driven flows. Applying electrokinetic and pressure-driven forces of similar magnitudes in opposite directions largely cancels these two forces and results in the smaller dielectrophoretic force becoming significant. The sum of these three forces throughout the microchannel results in particle concentration and mixing regions. The devices presented utilize weak DC fields (5-25 V/cm) and patterned, insulating microfluidic channels. This approach has been applied to latex beads varying in size by two orders of magnitude (2 μm - 20 nm) using one channel geometry and has been applied to both biological and synthetic particles