M.Sc Thesis

M.Sc StudentKahn Nicole
SubjectGold Nanoparticle-based Sensors on Flexible Substrates for
Diagnostic Sensing Applications
DepartmentDepartment of Chemical Engineering
Supervisor PROF. Hossam Haick
Full Thesis textFull thesis text - English Version


Chemiresistive films based on molecularly-capped gold nanoparticles deposited on flexible substrates allow spatial organizational changes that occur with bending or stretching to influence the electrical characteristics, in addition to a well-characterized analyte response. Analyte adsorption leads to changes in the dielectric constant of the film matrix and/or film swelling in an analyte type and concentration-dependent manner. Current rigid cross-reactive nanoparticle sensor arrays utilize this analyte response and pattern recognition methods to develop diagnostic tools. In this study, the potential of flexible sensor integration in a similar system was evaluated. Because a single flexible sensor has multiple bending states, each of which responds individually to a single analyte concentration, a significant increase in the number of features extracted from each sensor can be achieved.

            Electrodes based on various flexible substrates were overlaid with molecularly-modified gold nanoparticles using the layer-by-layer method. The ability of an array of such sensors was used to identify analyte type using only bending-related features. Simulations of both ovarian cancer and control breath were easily separated, and a diagnostic experiment using clinical samples collected from 43 women both with and without ovarian cancer provided a sensitivity of 81.3%, specificity of 82.9%, and accuracy of 83.6%. The ability of individual sensors to discriminate between diagnostic groups was assessed. Response of such sensors under exposure to a variety of volatile organic compounds under multiple concentrations and strain exertions was measured, allowing the assessment of effect of capping ligand type and film thickness, as well as a greater understanding of specific response mechanisms.

            This study successfully exhibited how flexible sensor arrays can be tailored for sensitivity and specificity, and used in a clinical setting for disease diagnosis from exhaled breath. The interdependent strain and analyte responses allow for the extraction of significantly more data than the rigid chemiresistors currently used in such arrays. In this study, only ovarian cancer was investigated, and additional diseases in larger-scale studies should be planned.