| Miniaturization of chemical reactors, such as medical diagnostics and environmental monitors, can provide many advantages over more traditional macroscopic processes and has become an increasingly active area of research. Microfluidics, a key component of this miniaturization process, can be thought of as chemical engineering on a micro-scale, in which the chemical reactors have at least one dimension of less than one millimeter. At such small scales, fluid flow is predominately laminar, viscous effects dominate over momentum effects, and ‘scale down’ is not straightforward. Novel techniques not possible in the macro-scale become feasible as scaling laws become more favorable.; One of the first applications of microfluidics, microfluidic implementation of capillary electrophoresis and isoelectric focusing (IEF), continues to be growing area of research. However, the devices and techniques associated with those implementations are limited to batch processes and typically have high power requirements. When the research presented in this report was initiated, there were no standard methods for microfluidic free flow electrophoresis or IEF, primarily because no devices existed in which the electric field could be applied perpendicular to flow. Therefore, a significant fraction of this research has been devoted to the design and fabrication of such microfluidic electrochemical flow cells (μEFC) and to methods for characterizing their behavior. The primary motivation of this project was sample preconditioning; to develop a suite of techniques designed to prepare ‘real-world’ samples for analysis by removing particles that could interfere with analysis and concentrating particles of interest. Since the immediate goal was integration into a miniaturized biological warfare agent detection system, the sample preconditioning techniques themselves had to microfluidic in nature.; A functional, easy-to-fabricate, μEFC is described, as well as two complementary methods of device characterization: optical, quantitative pH gradient measurement and a two-dimensional, steady-state mathematical model. The μEFC is shown to have successfully concentrated vegetative bacteria and proteins in continuous flow operation. Such concentrations are of immediate interest in the context of sample preconditioning:... |
