Chemically diverse sensor arrays based on conducting polymers in sensing characterization and application

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Iyogun, Akin Augustine
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There has been a growing need to develop an artificial mimic of mammalian olfaction in a manner analogous to charged coupled device (CCD) chip in machine vision. This need is motivated by the existence of devices to mimic the five senses except the sense of smell and taste, generally known as perception. One major challenge is the limited number of chemically different sensing surfaces that are to be useful as multi sensor array in a device, comparable with olfaction in its capacity to engage ≈1000 unique olfactory receptors to discriminate odorants. To be technically viable, such a device will involve the development and incorporation of several chemically distinct sensors to perform similar functions as its natural counterpart. An approach to create such a multi sensor array was explored in this research involving the electrosynthesis of homopolymers and copolymers sensor films. The modification of these polymers was performed through the growth of sensor films at different oxidation potentials, or holding the individual ‘as grown’ sensor films to different redox potential after growth. While variable signature resistance responses were generated from sensors interaction with analytes, differential response patterns were created to discriminate between them. The task of identifying unique patterns for analytes and the classification of each analyte as A or B hence, the uniqueness of each sensor was also investigated to ascertain that chemical variation of these sensors occurred. Pattern recognition algorithms involving techniques such as principal component analysis and linear discriminant analysis were relevant to relate the measured resistance responses in the form of clusters or numerical separation of clusters to differentiate patterns as a function of the sensor analyte interactions. This created the needed discrimination, as the resolving power of the arrays was investigated with linear discriminant analysis as a function of analytes or sensors. An ensemble of all the homopolymer, copolymer and conducting polymer composites created in this research resulted in broadly responsive, partially selective arrays which progressively tend towards realizing the number of olfactory receptors utilized by mammalian olfaction in performing odor discriminatory function. A real world application of these arrays as ‘fuel sensor’ has been investigated and is included in this thesis.
Sensors, Sensor arrays, Conducting polymer, Electrodeposition