| Fiber-optic chemical sensors (FOCS) are now well-established as an effective tool for solving a plethora of real-world detection problems for a wide range of applications. FOCS are commonly noted for their ease of miniaturization, remote-sensing capabilities, and freedom from electrical interferences, to name just a few. This thesis describes the first application of the cross-reactive array technique to optically-based chemical sensors.; Initially, sensor fabrication methods such as dip-coating and photopolymerization have been implemented. Various formats for building the array using different types of fiber-optics have been studied. A previously developed method for site-selective photopolymerization on imaging fibers has been successfully applied to vapor sensing elements for use in the cross-reactive array format.; Through collaborative efforts with several other research groups, the optical array has been applied to a number of different problems. The sensor array was used to discriminate between organic vapors differing by as little as one carbon atom. The array was also used to discriminate between a large set of analytes across many different classes and including complex mixtures, showing 90% correction prediction. Several different methods of gleaning multi-wavelength information from the sensors were developed. Multi-wavelength data was shown to enhance the optical array's ability to detect TCE in mixtures over single-wavelength data. The optical array was used successfully for the detection and qualitative discrimination between fragrances, but showed only limited success in discriminating between coffees and beers.; A new method for reducing the detection limits of the vapor sensor array by nearly three orders of magnitude was developed. The technique employs the direct incorporation of common adsorbents into the fiber-optic sensing layer. Solvatochromic dyes were directly adsorbed to the surface of porous alumina and silica particles and adhered to the distal face of an optical fiber. The resulting sensors exhibited unique solvatochromic behavior, rapid response times, high sensitivity, and good reversibility.; A new approach for rapid, simple generation of uniquely-responding sensors for use in polymer-based sensor arrays was developed using combinatorial polymer synthesis methods. Polymerization reactions between different combinations of two starting materials were found to lead to many new, unique sensors with responses not simply related to the proportion of the starting materials.; Finally, a new approach is described that involves the design of an artificial nose sensor array based on high density optical arrays that directly incorporate a number of structural and operational features of the olfactory system. The arrays are comprised of thousands of microsphere (bead) sensors, each belonging to a discrete class, randomly dispersed across the face of an etched optical imaging fiber. Beads are recognized and classified after array assembly by their unique,'self-encoded' response pattern to a selected vapor pulse. (Abstract shortened by UMI.)... |
