Microfluid systems have found many uses in science and technology, especially where miniaturization provides significant advantages. They have been developed for applications ranging from combustion, micromechanical systems, and microelectronics, to drug delivery, chemical analysis, and biodetection technologies. Sandia has an extensive research and development program focusing on the application of microfluidics and separations to the detection and analysis of chemical and biological warfare agents.

As part of this effort, the Defense Advanced Research Projects Agency (DARPA) has funded work at Sandia aimed at achieving an understanding of the effect of uncertainty in material properties and reaction rates on microfluidics biodetection device operation. This collaborative project with Johns Hopkins University (JHU) involved the detailed modeling of the transport and labeling of protein samples in electroosmotically driven microchannel analytical devices. It focused on understanding the effect of uncertainties in material properties and reaction rates on device operation, particularly with respect to dispersion of protein samples and peak signal reduction.

DARPA is funding a extension of this work as a collaboration between Sandia, JHU, and Stanford University with a focus on analyte sample dispersion in regions of electroosmotically driven microchannel flow with high electric field gradients. Such high gradients are commonly used in field amplified sample stacking (FASS) strategies for concentrating analytes in the microfluid system upstream of the detector, thereby enhancing the signal-to-noise ratio and sensitivity of the device. On the other hand, strong electric field gradients, developed by employing highly discontinuous buffers, can lead to instability of the fluid motions in the high-gradient region, leading to dispersion of the analyte sample and counteracting the sample concentration increase by FASS. Achieving high stacking ratios, while avoiding this dispersion due to electrokinetic instability, is a serious challenge. We are addressing this challenge using both experimental measurements and detailed modeling studies. By enhancing understanding of these instabilities, and evaluating improved designs to ameliorate them, this work will enable increased sensitivity of microfluidic instruments using FASS for chem/bio agent detection.

Microfluidics web site