Dissertation Defense


Karthik Chinna Balareddy

Gas chromatography (GC) is a powerful tool in the analysis of volatile organic compound (VOC) mixtures. It has found applications in healthcare, industrial safety, homeland security, and environmental studies. However to extend its use from lab based to in-situ based applications it is vital to miniaturize the systems to develop so called micro-gas chromatographs ( µGC). There are a multitude of issues associated with developing  µGC systems. This dissertation present to the development of optical and electrical sensors aimed at alleviating some of these issues, through high sensitivity, analyte pattern analysis, robust design and ease of integration.
The first optical sensor sensors developed consists of a polymer sensing film coated on silicon substrate via a variety of methods including, spin coating, drop coating, and spray coating. Several issues with the Fabry-Pérot (FP) are discussed and solved including non-uniformity of responses, reproducibility, dead volumes due to integration, and sensors arrays. The sensor showed excellent sensitivity, with detection limits as low as 0.7 pg. An array of these sensors was also demonstrated and showed promise for use in pattern analysis and analyte discrimination.
The second optical sensor characterized, worked on the principle of localized. The sensor was shown be capable of differentiating between vapors without the need for an array, i.e. with the use of only a single sensor. However the low sensitivity is still a stumbling block for this type of sensor.
The final sensor detailed within this dissertation is a high frequency graphene field effect transistor sensor (gr-FET). The detailed testing results described herein indicate unprecedented sensitivity for a pristine graphene nanoelectronic sensor along with ideal response and desorption times. The sensors were also tested for their response to a series of eluted analytes separated using standard GC techniques.
All three proposed sensors have a small footprint and low power consumption which are critical for  µGC applications.

Sponsored by

Xudong (Sherman) Fan & Yogesh Gianchandani