| Microfluidic technologies offer much promise to aid in the development of biodetection instrumentation through improved front-end sample preparation, sample amplification, and sample separation strategies. This thesis reports on three microfluidic technologies: (1) a high-surface-area DNA purification system, (2) a novel buoyancy-driven re-circulating polymerase chain reaction device, and (3) the thermal aspects of temperature gradient focusing (TGF) architectures. Both numerical modeling and experimental testing help understand and predict the device performance and limitations in these three systems.; The nucleic acid extraction system demonstrates DNA concentrations of >1,000-fold, PCR inhibition purification, and the ability to process large volumes (>75 mL) in a handheld, flow-through device using spiked environmental aerosol samples and unprocessed 'raw-sewage' water. Multiple chip designs and extraction protocols are experimentally studied to determine critical performance parameters (e.g. capture and elution efficiencies, throughput, binding capacity, reusability).; A new class of PCR instruments uses a buoyancy-driven re-circulating flow to thermally cycle the DNA sample and benefits from reduced cycle times, low sample volumes, a miniaturized format, and low power consumption. This thesis analyzes a specific buoyancy PCR device in a micro-channel 'race-track' geometry to determine key parameters about PCR cycle times, thermal profiles, and other figures of merit as functions of device dimensions.; A complete thermal characterization is performed for a device designed to simultaneously separate, concentrate and/or purify biomolecules and cells based on TGF. The thermal characterization improves analyte separations and fractionations by mapping local temperatures and local temperature gradients to the separation resolution in TGF. The results are experimentally verified and provide useful design rules from the thermal perspective to optimize TGF based separations, concentrations and purifications. |
