| Analytical microdevices are quickly becoming the platform of choice for many applications in industrial, governmental, and academic laboratories. The advantages of using these systems over conventional instrumentation include reduced sample size and waste production, lower cost, quicker analysis times, smaller device footprint, and ease of multiplexed fabrication. As sample size decreases, especially for important, costly biological molecules, the minimization of dispersive forces on the sample plug is important for maximized fluidic control and analysis.; The theme of this dissertation is to provide solutions for improved microfluidic manipulations on analytical microdevices. These include systems designed for analyte concentration, careful manipulation, and sensitive detection. A novel technique, termed electrophoretic focusing, was developed to accomplish concentration without the need of chromatographic supports or discontinuous buffer systems. By using counterbalanced flow techniques (electrophoretic migration versus bulk flow), concentration can be accomplished in a relatively simple manner.; In terms of careful fluidic manipulation, electroosmosis provides an ideal transport mechanism with minimized dispersive effects. A study of dynamic electroosmotic flow control via externally applied potentials has shown the ability to efficiently manipulate analytes (40x higher efficiency) on analytical microdevices compared to fused-silica systems. While small-volume fluidic manipulations must be optimized, so must the detection system which attempts to probe these small volumes. A novel flow-through heterogeneous microimmunoassay system was developed using paramagnetic particles. The characteristically high surface area to volume ratios, fast reaction times, and simple manipulation of the packed bed by magnetic fields shows the great potential of this detection scheme in heterogeneous sandwich immunoassays on analytical microdevices.; Other applications to small-volume fluidic manipulations are also presented by way of induced patterning effects caused by magnetic field interactions on paramagnetic microspheres. This gives rise to dynamic, carefully controlled paramagnetic supraparticle structures that may be manipulated by induced magnetic fields. The induced pattern effect may be applied to such items as microfluidic mixing, careful cellular manipulation, integration of micro-optical devices, some fabrication applications, and reaction distance studies. All of these projects have led to an increased understanding of small-volume fluidic manipulations and how such may be improved on analytical microdevices. |
