Field amplified sample stacking (FASS) is used to increase sample concentrations in electrokinetic flows. The technique uses conductivity gradients to establish a non-uniform electric field that accumulates ions within a conductivity gradient, and can be readily integrated with capillary electrophoresis. Conductivity gradients also cause gradients in near-wall electroosmotic flow velocities. Th...

A difficulty with the design and operation of an electrokinetically operated DNA hybridization microfluidic chip is the opposite direction of the electroosmotic flow and electrophoretic mobility of the oligonucleotides. This makes it difficult to simultaneously deliver targets and an appropriate hybridization buffer simultaneously to the probe sites. In this work we investigate the possibility ...

In this paper, a simple but accurate modeling method for obtaining analytical solutions for the fundamental characteristics of electroosmotic ow through rectangular pumping channels without the Debye–Hückel approximation is presented. The Poisson–Boltzmann equation without the ebye–Hückel approximation for the electric potential distribution and the momentum equation for the velocity profile ar...

Control of EOF in microfluidic devices is essential in applications such as protein/DNA sizing and high-throughput drug screening. With the growing popularity of poly(methyl methacrylate) (PMMA) as the substrate for polymeric-based microfludics, it is important to understand the effect of surfactants on EOF in these devices. In this article, we present an extensive investigation exploring chang...

The electroosmotic flow (EOF) in a poly(dimethylsiloxane) (PDMS) separation channel can be altered and controlled by adding a carboxylic acid to the prepolymer prior to curing. When the prepolymer is doped with 0.5 wt % undecylenic acid (UDA), the electroosmotic mobility in a modified PDMS channel rises to (7.6 +/- 0.2) x 10(-4) cm(2) V(-1) s(-1) (in HEPES buffer at pH 8.5), which is nearly twi...

S. Devasenathipathy and J.G. Santiago The advent of microfabricated chemical analysis systems has led to a growing interest in microfabricated fluidic systems with characteristic scales in the range of a micron to a millimeter. A motivation to integrate components in a manner analogous to modern microelectronics is coupled with a potential for achieving massively parallel functions, and the fie...

A 330-pL chromatographic bed was fabricated on a glass substrate as part of an electroosmotically pumped microfluidic system. Two weirs within a sample channel formed a cavity in which octadecylsilane (ODS) coated silica beads (1.5-4 microns diameter) were trapped. ODS beads were mobilized into and out of the cavity using electroosmotic flow through a bead-introduction channel which accessed th...

A simple coating procedure employing a sol-gel process to modify the inner surface of a bare fused-silica capillary with a positively charged quaternary ammonium group is established. Scanning electron microscopic studies reveal that a smooth coating with 1 to approximately 2 microm thickness can be obtained at optimized coating conditions. With 40 mM citrate as a running electrolyte, the plot ...

Sample pre-concentration can be a critical element to improve sensitivity of integrated microchip assays. In this work a converging Y-inlet microfluidic channel with integrated coplanar electrodes was used to investigate transverse DNA and protein migration under uniform direct current (DC) electric fields to assess the ability to concentrate a sample prior to other enzymatic modifications or c...