An Optofluidic Ring Resonator Platform for Rapid and Robust Sensing

Ring resonators show great potential as sensitive optical detectors for studies of biomolecular interactions, drug screening, and point-of-care diagnostics. They are sensitive to minute changes in the refractive index of the surrounding medium, which enables them to detect and quantify sub-femtomolar concentrations of target molecules. This thesis investigates the advantages of an optofluidic ring resonator platform that employs a differential measurement scheme for reducing environmental noise due to temperature and pressure fluctuations. Through simulations and experiments, I determine the sensitivity of the platform to changes in the target analyte concentration and to environmental noise, and demonstrate the benefits of employing a second, reference, ring resonator. A crucial step in achieving versatile biosensing platforms is the integration of the high sensitivity resonators into platforms with short assay times and robust chemical functionalization. I focus on the development of robust chemistry protocols for depositing linker silane layers for biomolecular interaction studies. Moreover, since the fluid handling scheme strongly influences the response time of the platform, I design and test two fluidic platforms integrated with elastomeric valves that show excellent response times. To further increase the response time of the sensing platform, I explore the effects of a patterned channel geometry on the enhancement of mass transport to the sensor in low Reynolds number flows.