Publications

Abstract not provided.

Microfluidic devices have been proposed for 'Lab-on-a-Chip' applications for nearly a decade. Despite the unquestionable promise of these devices to allow rapid, sensitive and portable biochemical analysis, few practical devices exist. It is often difficult to adapt current laboratory techniques to the microscale because bench-top methods use discrete liquid volumes, while most current microfluidic devices employ streams of liquid confined in a branching network of micron-scale channels. The goal of this research was to use two phase liquid flows, creating discrete packets of liquid. Once divided into discrete packets, the packets can be moved controllably within the microchannels without loss of material. Each packet is equivalent to a minute test tube, holding a fraction from a separation or an aliquot to be reacted. We report on the fabrication of glass and PDMS (polydimethylsiloxane) devices that create and store packets.

This report describes the continued development of a low-power, portable detector for the rapid identification of pathogens such as B. anthracis and smallpox. Based on our successful demonstration of the continuous filter/concentrator inlet, we believe strongly that the inlet section will enable differentiation between viable and non-viable populations, between types of cells, and between pathogens and background contamination. Selective, continuous focusing of particles in a microstream enables highly selective and sensitive identification using fluorescently labeled antibodies and other receptors such as peptides, aptamers, or small ligands to minimize false positives. Processes such as mixing and lysing will also benefit from the highly localized particle streams. The concentrator is based on faceted prisms to contract microfluidic flows while maintaining uniform flowfields. The resulting interfaces, capable of high throughput, serve as high-, low-, and band-pass filters to direct selected bioparticles to a rapid, affinity-based detection system. The proposed device is superior to existing array-based detectors as antibody-pathogen binding can be accomplished in seconds rather than tens of minutes or even hours. The system is being designed to interface with aerosol collectors under development by the National Laboratories or commercial systems. The focused stream is designed to be interrogated using diode lasers to differentiate pathogens by light scattering. Identification of particles is done using fluorescently labeled antibodies to tag the particles, followed by multiplexed laser-induced fluorescence (LIF) detection (achieved by labeling each antibody with a different dye).