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ZnO nanowires (NWs) are good candidates for chemical sensing because of their high surface-to-volume ratio. In this work, ZnO nanobridge sensors were fabricated utilizing a novel method which uses carbonized photoresist (C-PR) as a nucleation layer. The use of C-PR allows simultaneous growth and integration of NWs to lithographically-defined features. The nanobridge sensors are shown to be sensitive to the presence of O₂, H₂O, CO, and H₂/N₂ gas. However, since ZnO dissolves in water, a protective layer is necessary for these sensors to be used in the liquid or vapor phase. A chemical vapor deposition (CVD) process for amino-[2,2]paracyclophane (parylene-A) was developed and used to successfully protect the NWs. Gas sensing measurements were performed on bare and parylene-A coated devices with and without UV illumination. The parylene-A layer was found to attenuate sensitivity to O₂ and H₂O, and UV illumination was found to decrease the response time. / Graduation date: 2012

Numerous applications in the present day ranging from testing humidity in air to detecting miniscule quantities of potentially hazardous chemical and biological agents in the air or water supplies require the development of chemical sensors capable of analyte detection with high sensitivity and selectively. Further, it has become desirable to create lab-on-chip systems that can detect multiple chemical agents and allow for sampling and testing of environments at locations distant from conventional laboratory facilities. Current challenges in this area include design, development and characterization of low detection limit sensors, development of low-noise readout methods, positive identification of analytes and, identification and reduction of the effect of various noise sources - both intrinsic and extrinsic to the sensor. The current work examines the performance limits of a 10-cantilever piezoresistive microcantilever array (PµCA) sensor. The microcantilevers measure analyte concentration in terms of the surface stress associated with analyte binding to the functionalized cantilever surface. The design, fabrication, characterization and testing of this measurement platform is presented. A novel aspect of the sensors developed is the use of n-type doping which increases the sensitivity of the device by one order of magnitude. In addition, design rules for surface stress-based chemical sensors have been developed. Extensive thermal characterization of the piezoresistive microcantilevers has been performed for DC and AC electrical excitation and values of heat transfer coefficient for the associated microscale phenomena are reported. Further, a method of low-noise measurement of cantilever resistance has been developed based on phase-sensitive detection techniques and this has been integrated with a multiplexing circuit to measure piezoresistance change in multiple cantilevers. Finally, the two novel techniques of chemical sensing- double-sided sensing and thermal array-based sensing have been investigated. These methods are presented as a means of extending the applicability and functionality of piezoresistive microcantilever sensors for chemical sensing.

Thesis (M.S.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 31, 2008) Includes bibliographical references (p. 33-36).

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: David R. Walt. Submitted to the Dept. of Chemistry. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 207-225).

Thesis (Ph.D.) -- McMaster University, 2003. / Includes bibliographical references (leaves 134-141). Also available via World Wide Web.

Thesis (Ph. D.)--Michigan State University. Dept. of Packaging, 2006. / Title from PDF t.p. (viewed on Nov. 20, 2008) Includes bibliographical references (p. 275-287). Also issued in print.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Systems Science and Industrial Engineering, 2007. / Includes bibliographical references.