Microsystems for optical gas sensing incorporating the solvatochromic dy

The work presented in this thesis demonstrates three Microsystems using microstructure glass (MSG), polymers and Flame Hydrolysis Deposition (FHD) glass as optical gas sensors, which incorporate the solvatochromic dyes, Nile red and Reichardt's dye in various supporting polymers. Sensor fabrication techniques were developed and their performance was tested and discussed. MSG and SU-8 polymer based devices containing the polymer/dye sensors were used to produce fluorescence from the dye in the presence of analytes, including hexane, methanol and butan-2-ol, and their performances were compared. The fluorescence response, detected via an epifluorescence microscope and imaging CCD camera, showed that the MSG devices are superior to their SU-8 analogues, with respect to sensor response and response recovery, in detecting these analytes. These results can be attributed to the physical properties of, and the interactions between, the polymer/dye complex and the analytes, as well as the structure of the support for the sensors. By taking advantage of the emission shift phenomenon of the solvatochromic dye in environments with different polarities, similar to the bathochromic shift seen for the dye within different solvent solutions, the responses of the sensors at two different wavelengths show potential for gas identification and discrimination. For example, the MSG devices were found to have both superior sensitivity to analytes (up to 7 times greater) and better recovery times (up to 50% faster) than structures made in SU-8. Finally, this research has also demonstrated that the FHD technique can be used as a flexible and adaptable method for fabricating total analytical systems (mu-TAS), such as those used in Lab-on-a-Chip technology. A summary of conclusions and ideas for future work are included.