PhD Defense by Milad Navaei
PhD Defense Presentation
Tuesday, July 21, 2015 , 11:00 a.m.
109 Love Building
Peter Hesketh, PhD (Georgia Institute of Technology)
Mostafa Ghiaasiaan, PhD (Georgia Institute of Technology)
Albert Frazier, PhD (Georgia Institute of Technology)
Oliver Brand, PhD (Georgia Institute of Technology)
Jean-Marie Dimanja, PhD (Spelman College)
Todd Sulchek, PhD (Georgia Institute of Technology)
Integration of a Micro-Gas Chromatography System for Detection of Volatile Organic Compounds
The focus of this dissertation is on the design and micro-fabrication of an all gas chromatography column with a novel two dimensional resistive heater and its integration with an ultra-low power TCD sensor for fast separation and detection of Volatile Organic Compounds (VOC). The major limitations of the current MEMS-GC column are: direct bonding of silicon to silicon, and peak band broadening due to slow temperature programming. Direct fusion bonding of silicon to silicon is not an effective technique for proper sealing of a high density micro-machined surface such as a GC column. This technique requires extremely smooth and clean surfaces, otherwise small voids and unbonded areas occur. As part of this thesis, a new gold eutectic-fusion bonding technique is developed to improve the sealing of the column. The time and power required to ramp and sustain the column’s temperature are very high for the current GC columns. To reduce the time required to separate the compounds, a new temperature gradient programming heating method was developed to generate temperature gradients along the length of the column. This novel heating method refocuses eluding bands and counteract the part of the chromatographic band spreading. At the end, a low power TCD sensor was designed and integrated for a faster and more accurate measurement of the VOC gases separated with the MEMS GC column. These features enable the MEMS-GC system to analyze live and fast detection of the VOC gases released by pathogenic species of Armellaria fungus.