Microfabrication of optical and electronic devices by soft lithography

This thesis describes the fabrication of optical and electronic devices by soft lithography---a suite of techniques that uses low-cost materials and minimal infrastructure to pattern a wide range of materials. These methods facilitate the rapid prototyping of useful devices such as optical waveguides, electronic elements, and microfluidic channels. Contributions from both research and industrial laboratories, in terms of materials and techniques, have expanded the capabilities of soft lithography. Chapter 1 reviews the developments in soft lithographic techniques during 1999--2004.; The combination of microcontact printing (MCP) and wet-chemical etching is used commonly to pattern thin films of metals. Features patterned in palladium by this soft-lithographic technique have densities of defects much lower than features in the coinage metals (gold, silver, and copper) patterned by the same technique (Chapter 2 and Appendix VII); this characteristic improves reproducibility of operating properties of microelectronic devices. The origin of this improved resistance to etching is discussed in Appendix VIII. Chapter 2 also describes the fabrication of palladium-based wires and an H2 sensor by muCP.; Electrical microcontact printing (E-muCP) is a technique that uses a metal-coated PDMS stamp to pattern the flow of current through a substrate. Chapter 3 describes the use of this technique to pattern planar, optical waveguides in a thin film of phloxine B-doped poly(4-vinylphenol). This technique patterns large areas (>1 cm2) rapidly (<90 s), and thus is useful for the rapid prototyping of optical splitters.; Most planar optical waveguides have limited tunability because the core and cladding materials are static in their composition and geometry. Chapter 4 introduces optical waveguides comprising a liquid core and a liquid cladding ("liq/liq waveguides") flowing in microfluidic channels made of PDMS. Liq/liq waveguides are dynamic in that their geometry and function depend on the continuous flow of the core and cladding fluids. The liquid/liquid interface is optically smooth because the liquids flow at low Reynolds numbers in microchannels; this property leads to low optical loss due to scattering at the interfaces. This system is useful for fabricating of tunable optical devices such as evanescent couplers, optical splitters, and optical filters (Chapter 5).