| Microfluidic devices find application in the fields of medicine, defense, and research, because they are often less expensive and more efficient than traditional devices, and potentially disposable. The marriage of microfluidic devices with organic polymers has accelerated their advancement because of the ease and speed with which they can be prototyped. The first section of this thesis describes two aspects of the development of microfluidic systems in poly(dimethylsiloxane)—general methods of fabrication and functional components for specialized applications.; Chapter 1 provides an overview of recent progress in three-dimensional channel systems and Chapter 2 presents in detail one of the first, general methods for fabricating such systems-the “membrane sandwich” method. This technique consists of overlaying different levels of features to build up a network of microfluidic channels with any connectivity. It enables the assembly and sealing of a stack of membranes to an arbitrary height and without tedious alignment steps.; As a step closer to fully integrated devices with multiple functions, and towards the original inspiration of the “lab-on-a-chip”, components for microfluidic systems are being developed to diverse ends. Valves, pumps, mixers, and sensors control the way fluid flows in microfluidic channels. Chapter 3 presents the fabrication of some of these components and demonstrates their capabilities. In particular, the biomimetic “lymphatic” valve that functions similarly to its biological counterpart (from which its structure was adapted) highlights the parallels between microfluidic systems and living systems—which, is shown here to be useful as an engineering tool.; The second part of this thesis addresses an important question in physical-organic chemistry and drug design: to what extent can residues on a protein communicate with other residues or ligands by electrostatic forces in aqueous solution? The present study combines organic syntheses, capillary electrophoresis, and mathematical modeling of kinetics. Its results are consistent with theory that invokes electrostatic potential alone as the stimulus for a change in the association behavior of residues as far away as 30 Å at ionic strength of 130 mM. |
