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Spring 2009 Seminar Series
Friday, June 5, at 3:30 p.m.
Room 264 MacQuigg Labs
Elvin Beach
PhD Candidate advised By Dr. Patricia Morris
Department of Materials Science and Engineering
The Ohio State University
Picoliter Drop Deposition Of Oxide Nanoparticles:
A Route To High Performance Microsensor Arrays
Abstract
Picoliter drop deposition (PDD), based on the drop-on-demand ink-jet principle, was investigated as a method for fabricating nanostructured metal oxide-based chemiresistor gas sensors on microhotplate substrates. This technique shows promise for reproducible deposition of minute quantities of material with a high level of both placement precision and thin-film microstructure organization, but many interrelated variables must be controlled, including the pre-formed metal oxide nanoparticles and the processing characteristics of the deposition ink itself. First, metal oxide nanoparticles, which are the heart of robust gas sensing devices, were synthesized (including, SnO2, NiO and TiO2) using hydrothermal and solvothermal techniques. Second, the preparation of stable suspensions is of critical importance for generating picoliter drops with consistent size, shape and trajectory. A study of oxide nanoparticle-laden suspensions has been carried out to identify how critical variables such as surface tension and solvent evaporation rate influence the PDD process is also described here. Control of the deposition process is important for consistent materials placement; however, it is only the first step in making high performance sensing materials. Drying and annealing to form useful micro/nanostructured films for chemiresistive sensing is equally important. The unique capabilities of microhotplate substrate arrays allows for efficient, almost combinatorial, study on the influence of the heating rate and maximum temperature applied during drying and annealing to microstructural feature formation. Investigations of the nanoparticle thin-film microstructures were carried out using cross-sectional electron microscopy. Correlations between the nanoparticle-laden suspension properties, PDD processing parameters and the final thin film microstructure were revealed that led to films with optimized gas sensor performance. Temperature-programmed sensing (TPS) was utilized to determine the operating temperatures that showed the highest level of gas sensitivity for each material and fixed-temperature sensing (FTS) was used to examine the response and recovery characteristics of each oxide film.
Bio
Elvin graduated in 2000 with a B.S. in Metallurgical Engineering and 2001 with an M.S. in Materials Science & Engineering from Michigan Technological University. Elvin was a research scientist in the surface science and electron microscopy group at The Dow Chemical Company in Midland, MI from 2001--2005 before returning to pursue a Ph.D. Ohio State University.
