Novel optofluidic sensor systems for quantitative chemical imaging and on-chip sensor calibration

The design, fabrication and characterization of optofluidic biosensor systems for quantitative oxygen imaging with a color charge-coupled device (CCD) camera as well as on-chip self-calibration of sensors utilizing gas bubbles was investigated. This dissertation was prepared in publication format. The first and second papers demonstrate that color imaging devices can be used in quantitative chemical analysis. The final paper explores the feasibility of using electrolytically generated bubbles for a novel functionality of reagentless, on-chip, in situ calibration of optical biosensors. Work in the first paper includes the use of a color CCD camera for fluorescence intensity imaging. This involves extracting the red color element to determine the dissolved oxygen content from the color image of a sample. The linearity and sensitivity of oxygen detection based on the red intensity analysis was improved to those of spectrometric measurement and total color intensity analysis. In the second paper, the color extraction technique used in the dissolved oxygen sensor was extended to gaseous oxygen detection to eliminate the need of optical filters and replace the blue light emitting diode (LED) excitation source with a general broad-band white LED. This new method has potential applications in multi-analyte monitoring and simultaneous structural/functional imaging of biological samples with a single broad-band light source. In the final paper, a double-layered optofluidic system was developed to demonstrate on-chip, self-calibration of dissolved oxygen sensor. A multilayers of dry film resist was used for preparing a 3-D fluidic structure. A thin black polydimethylsiloxane membrane was used for oxygen diffusion and optical isolation. The sensor calibration result with the on-chip bubble was shown to be in good agreement with that of standard calibrants --Abstract, page iv