Doctoral Dissertations

Date of Award

8-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Michael J. Sepaniak

Committee Members

David C. Joy, Bin Zhao, Ziling Xue

Abstract

Recent developments in microelectro-mechanical systems have enabled the exploration of transduction modes that involve mechanical energy and are based primarily on mechanical phenomena. As a result an innovative family of chemical and biological sensors has emerged which utilize a transducer in the form of microcantilevers (MCs). MCs offer greater sensitivity than comparable mass-responding sensors due in large part to their small dimension. These low cost devices can be deployed for remote testing, providing real-time information for the analyst. An additional advantage is the ability to employ MCs in an arrayed fashion adding a unique selectivity not available to many sensing platforms. The goal of this research is to explore improvements and advances in surface modification strategies for MC design. A practical application has been demonstrated for H2 related detection.

The initial research (Chapter 2) focused on a novel surface structuring technique for introducing a molecular recognition phase (MRP) onto a MC transducer. The MRP in this study was introduced via spontaneous galvanic displacement reaction (SGDR) and has been implemented for H2 detection. Combining the advantages of a MC sensing platform with a high active surface area of nano-porous (np-Pd) created by a SGDR, a fast, selective, and sensitive means to detect hydrogen gas has been achieved.

A second study (Chapter 3) investigates the nature of np-Pd systems created by the SGDR process. Experimental evidence is provided to support a mechanistic model which allowed a better understanding of both processing and material properties related to this strategy to create np-Pd films. This study has provided information for H2 related issues including catalysis, storage, and sensing applications.

A final study (Chapter 4) explores improvements in the properties of materials used for MC design. A nano-laminate composite (NLC) surface composed of alternating layers of SiNx/SiO2 has shown advantages for MC design in comparison to conventional materials used for MCs. The NLC-MCs fabricated using this method exhibit superior reflectivity for optical read-out. The NLC materials experience less thermal induced drift compared to MCs that use metalized surfaces. The asymmetric layering of the NLC material used for MC design show promise for flexible functionalization strategies.

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