Andrew J. Skulan

Particle mixing and concentration through competing electrokinetic and hydrodynamic flows

We have developed a novel, low voltage particle concentration and separation paradigm that exploits the interplay between electrokinetic, dielectrophoretic, and pressure-driven flows. The devices presented utilize weak DC fields (5-25 V/cm) and patterned, insulating microfluidic channels. This approach has been applied to species varying in size by two orders of magnitude on the same chip (2 /spl mu/m-20 nm), can be applied to both biological and synthetic particles, and permits the channel geometry to be optimized to a specific size range.

Insulating dielectrophoresis for the continuous separation and concentration of Bacillus subtilis

This paper presents a novel microdevice for the dielectrophoretic manipulation of particles and cells for sample preparation and analysis. A two level isotropic etch of a glass substrate was used to create insulating ridges in micron sized channels. These ridges created a non-uniform field when a direct current field was applied across the channel and the dielectrophoretic force that resulted from the ridge was used to manipulate particles. We show the continuous concentration and separation of Bacillus subtilis from a two component sample mixture. When the applied voltage is at or above 30V/mm the flow of Bacillus subtilis was restricted to the central channel as a result of negative DEP away from the field concentration produced by the insulating ridges. Under the same applied electric fields the 200-nm polystyrene particles DEP away from the insulating ridges was negligible for the 200-nm particles, which flowed uninhibited down the three exit channels.

Continuous Particle Filtration and Concentration by Multigradient Dielectrophoresis

A novel methodology for designing selective particle concentrators in electrokinetic flows is presented. The technique is based on two-level etching of channels to produce ridges along which field gradients are patterned. The field gradients are then used to deflect particles using dielectrophoresis. Using uniform-field designs as a basis, fields in the vicinity of a single ridge are examined both experimentally and numerically. Although isotropic etching causes local deviations from piecewise continuous fields, ridges are found to serve as selective particle deflectors in experiments with both polystyrene beads and Bacillus subtilis. Sequences of parallel ridges are also tested, illustrating the efficacy of corrugated ridge structures for selective particle concentration.Copyright