| In this work the complete motivation, design, fabrication, and characterization of a microscale electrical field-flow fractionation (ElFFF) system is presented. The general theory for field flow-fractionation (FFF) systems is reviewed and demonstrates that miniaturization, while providing some advantages, does not purport to improve the capabilities of FFF systems. A closer look, specifically at the ElFFF system, though, indicates the numerous potential advantages for miniaturizing ElFFF systems. The advantages from miniaturization are explored thoroughly and a determination is made that a microscale ElFFF system could provide numerous benefits such as improved resolution and reduced analysis times, as well other advantages. The components involved in ElFFF systems are then reviewed and a design for a microscale ElFFF system is developed. The fabrication for a mu-ElFFF system is outlined and the micromachining processes used in fabrication described. A completed mu-ElFFF system is demonstrated and characterized with regard to most of the important parameters regarding ElFFF systems. These parameters include plate heights, resolution, equilibration times, electrode time constants, and effective electric fields, as well as several other parameters. The capabilities of the fabricated system are demonstrated by retaining and separating polymer particles by both size and surface charge, polymer particles with attached proteins, and by retaining and separating whole blood. Thus, the microscale system is shown to function in accordance with theory, and to meet the expectations developed before the system was fabricated.; In addition to the mu-ElFFF system, the design and fabrication of a microscale electrical impedance detector is presented. The detector is characterized with regard to its detection abilities using three different modes of operation. Each of these modes, either DC, AC, or impedance spectroscopy, has their own unique advantages and disadvantages, but each is clearly able to detect the type of particles currently of interest for analysis in ElFFF systems. The detector is shown to improve the operation of the mu-ElFFF by reducing plate heights in the complete system. The detector in electrical impedance spectroscopy mode also demonstrates the potential for making particle size measurements, further increasing the analytical capabilities of the complete mu-ElFFF system. |
