| This thesis describes the fabrication of microfluidic devices in poly(dimethylsiloxane) (PDMS) that can be used in analytical applications. Chapter 1 (and Appendix 3) reviews microfluidic devices fabricated in PDMS. The main advantages of PDMS for fabricating devices are that the polymer is inexpensive and microfluidic channels are easily formed in it. Casting PDMS against a suitable “master” (or mold) is the basis of forming channels. The emphasis in Chapter 1, and the entire work, is on functional devices that rely on the intrinsic properties of PDMS for fabrication or actuation.; Typically the masters used to form channels are produced by photolithography, which is a planar process (Appendix 1). Chapter 2 details a non-photolithographic technique for the fabrication of masters—solid-object printing. In solid-object printing, a CAD file is printed directly into a master in one step without the need for masks. The advantage of the method is that masters with multilevel features (Appendices 4–5), tall (>1 mm) features, and large areas can be fabricated in one printing.; One challenge associated with microfluidic devices is the ability to store and dispense liquids on the device. Chapter 3 describes a single-use configurable device that can store and deliver solutions on demand. Storage occurs in initially disconnected channels. To dispense the stored fluid, connections between these channels are opened through the intentional electrical breakdown of the PDMS separating the channels. Once connected, fluid can be pumped between the channels. A device for an enzyme-linked immunosorbent assay (ELISA) is used as a demonstration of this technique.; Detection of analytes is a key component in microfluidic devices. A common method of detection is fluorescence, but the necessary components for this method are often large and expensive compared to the channel system. Chapter 4 details the integration of the optical components of a system for fluorescence detection into a microfluidic device for capillary electrophoresis. The system consists of an optical fiber for excitation of fluorophores and a micro-avalanche photodiode for detection. The components for detection are inexpensive, easily embedded in PDMS, and provide a compact design. |
