Optofluidic Ring Resonator: A Versatile Microfluidic Platform for Chemical Vapor Detection and Intra-Cavity Biomolecular Analysis.

Abstract

In the past few years, the optical ring resonator has emerged as a new sensing technology capable of detecting bio/chemical molecules in both liquid and vapor phase rapidly and sensitively. The ring resonator sensing relies on the whispering gallery mode (WGM) that forms due to total internal reflection of light at the curved resonator surface. The WGM has an extremely high Q-factor (>106). It circulates along the resonator circumference and repetitively interacts with the analyte near the resonator surface, thus resulting in an effective WGM-analyte interaction length of tens of centimeters. The optofluidic ring resonator (OFRR) is based on a thin-walled glass capillary whose circular cross section forms the ring resonator. The OFRR uniquely integrates the highly sensitive ring resonator technology and the superior fluidic handling capability of the capillary, and provides a very versatile technology platform for bio/chemical analysis. This thesis investigates two major OFRR sensing areas: chemical vapor detection and microfluidic laser intra-cavity biodetection. In the first area, the OFRR vapor sensing feasibility is first demonstrated with detection of representative gas analytes, followed by the theoretical analysis using a four-layer Mie model. Then the OFRR technology is integrated with micro-gas chromatography (mGC) to develop a highly sensitive and selective OFRR-mGC system. The dual use of the OFRR capillary as a separation column and an optical detector renders the OFRR-mGC system unique multi-point on-column detection capability. Using the OFRR-mGC system, rapid and sensitive detection of dinitrotoluene vapor out of interfering background is demonstrated. A tandem-column setting of the OFRR-mGC system is also explored to enhance the chromatographic resolution. A vapor mixture of twelve analytes of different volatilities and polarities are separated and detected within four minutes. In the second area, a bio-compatible optofluidic laser is developed based on the OFRR. A DNA scaffold is incorporated into the laser gain medium and controls the lasing emission properties through efficient fluorescence resonant energy transfer. This platform is further employed for highly-selective intra-cavity DNA detection. Two orders of magnitude improvement in detection selectivity is achieved over the conventional fluorescence detection method in differentiating the target and the single-base mismatched DNA sequences.Ph.D.Biomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89639/1/yuze_1.pd