| Microfluidic devices are now well established in a variety of scientific areas as a means of making or assisting in analytical determinations. The majority of such devices are sensors, often using an optical, chemical, or electrochemical signal to determine the concentration of a particular cell or analyte. Other microfluidic applications involve sample preconditioning and delivery, where a sample is often fractionated before reaching a downstream detector. The vast interest in microfluidics is driven by several fundamental advantages over existing technologies. The most significant is the ability to perform analysis on very small samples. Small device dimensions lead to very fast interdiffusion times, often making microfluidic assays much faster than their macro-scale counterparts. Another key advantage is the ability to mass-produce most microfluidic devices by a number of different fabrication methods. The T-sensor is a microfluidic device that uses pressure-driven flow to bring continuous input streams in contact. Interdiffusion of key analytes and indicators between the input streams produces a measurable signal that is associated with a parameter of interest, such as a diffusion coefficient, concentration, or kinetic constant. The three-dimensional hydrodynamics of pressure-driven flow present a series of complicating phenomena that affect the behavior of diffusing, reacting analytes. This research presents the development of microfluidic assays, including a protein assay and an enzyme assay, as well as a series of fundamental studies on diffusion in microchannels. In addition, multiple custom numerical simulations were developed as tools for the analysis of experimental data and design of new microfluidic assays. The overall goals of this work were to establish microfluidics as a viable assay format and to demonstrate the quantitative design and analysis of particular assays of interest. |
