Micropatternable multifunctional nanocomposite polymers for flexible soft MEMS applications

This thesis describes the fabrication, micro-machining, and characterization of novel multifunctional nanocomposite polymers for flexible microsystems.Various elastomers, primarily polydimethylsiloxane (PDMS), a silicone based elastomer, are chosen as substrate materials to create new flexible microsystems because of numerous benefits of PDMS including flexibility, biocompatibility, low cost, low toxicity, high oxidative and thermal stability, optical transparency, low permeability to water, low electrical conductivity, and ease of micropatterning. However, most devices to date based on PDMS are passive, as making active devices out of PDMS is extremely challenging.When PDMS is bonded to substrates with conventionally-realized active components like electrodes, heaters, sensors, actuators, etc., it is rendered inflexible – defeating one of its key benefits. For example, the common method of bonding PDMS with glass renders the resulting devices completely inflexible.If metals or alloys are deposited on PDMS, the weak adhesion between them and PDMS leads to microcracks when the substrates are flexed,bent,or twisted.This leads to electrical disconnection and device failure.The focus of this thesis is the development of novel approaches to the realization of active-component based highly flexible microsystems employing PDMS and/or other elastomer materials.To overcome problems with incorporating active devices while maintaining system flexibility, various new materials and methods of microfabricating them are developed.These newly developed electrically conductive and magnetic nanocomposite polymers deliver flexibility similar to undoped and insulating PDMS, yet provide functionality for active device development similar to the inclusion of inflexible metals and other functional materials.These new polymers can also be easily micromicromolded using conventional PDMS processing, such as soft lithography techniques. A new hybrid microfabrication process for combining micromolded nanocomposite with undoped PDMS polymer is also developed to demonstrate the potential of the new polymers to be incorporated into fully flexible systems containing active components. Poly(methyl methacrylate) (PMMA) is also explored as a new molding substrate for small and large area microfabrication. Applications of these multifunctional nanocomposites include shape-conformable microelectrodes, hard magnetic microactuators, signal routing for Lab on a Chip (LOC) and many other devices requiring flexible microsystems and electronics.