Design of nanocomposite polymer coatings for MEMS applications

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Julthongpiput, Duangrut
Major Professor
Vladimir V. Tsukruk
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Materials Science and Engineering

The Department of Materials Science and Engineering teaches the composition, microstructure, and processing of materials as well as their properties, uses, and performance. These fields of research utilize technologies in metals, ceramics, polymers, composites, and electronic materials.

The Department of Materials Science and Engineering was formed in 1975 from the merger of the Department of Ceramics Engineering and the Department of Metallurgical Engineering.

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The recent evolution in microelectronics of combining electrical and mechanical functions has brought about the exciting field of microelectromechanical system (MEMS). As the dimensions of the components shrink, adhesion, stiction, friction, and wear become a significant technological barrier for the successful development of durable microdevices. In this thesis, we investigate wear-resistant, nanocomposite, molecular coatings from advanced polymers with controlled nanomechanical and nanotribological properties from the prospective of long-term applications for MEMS. We discuss fundamentals governing the mechanical and tribological properties on a micro scale associated with the morphology and microstructure of these molecular coatings.;In order to fabricate wear-resistant and superelastic molecular coatings, several types of the molecular designs are proposed and tested in this work. All designs are based on chemical attachment of the polymer layers onto a functionalized silicon surface. We focus on developing two different kinds of molecular coatings: reinforced elastomeric layers from grafted block-copolymers and polymer brush layers grown by the "grafted to" technique. A more complicated design included bilayered nanocomposite coatings consisting of a hard polymer layer placed on the top of an elastomeric layer to regulate surface adhesion and to increase surface stiffness of nanocomposite bilayers. Another design incorporates a paraffinic oil component to assure the presence of highly mobile molecules inside of the elastomeric phase. This oily fraction can be a source of an instant supply of mobile lubricant to a deformed contact area, thus providing potential self-lubrication and self-healing mechanisms for surface areas affected by excessive deformation. We observed that the interfacial assemblies, as presented in this paper, exhibited very low friction coefficient, low stiction, and better wear stability as compared to other, non-structured, non-tethered, or non-reinforced organic molecular lubrication coatings widely used as boundary lubricants. These results have interesting implications for the use of ultrathin grafted polymers as molecular lubricants.

Wed Jan 01 00:00:00 UTC 2003