Dissertation Defense: Shuang Hao, "Fundamentals and Applications of Label-Free FLOWER-Based Sensing for Ultra-sensitive Detection of Single Particles and Molecules"

Abstract:

Detection techniques for single particles and molecules play a crucial role in advancing basic science, disease diagnostics, and nanomaterial investigations. The Frequency Locked Optical Whispering Evanescent Resonator (FLOWER) system, utilizing Whispering Gallery Mode (WGM) optical microcavities, emerges as a sensitive tool for label-free biomolecular sensing due to its ultrahigh quality (Q) factor and small mode volume. This dissertation explores the properties of the FLOWER system through numerical simulations, highlighting key parameters and their impact on Signal-to-Noise Ratio (SNR), with a demonstrated ability to detect resonance shifts of 0.05 attometers.

Moreover, experimental assays involving a microtoroid functionalized with the T1R2/T1R3 heterodimer sweet taste receptor showcase FLOWER's label-free measurement capabilities in exploring sweet ligand binding responses. The research contributes insights into G-protein-coupled receptor (GPCR) signaling pathways, deepening our understanding of receptor activation.

Additionally, the microtoroid, when applied in photothermal microscopy for single-particle detection, exhibits outstanding sensitivity, spatially detecting 5 nm diameter quantum dots (QDs) with a remarkable SNR exceeding 10,000. Integration with an amplitude modulated pump laser and a Proportional-Integral-Derivative (PID) controller significantly reduces noise, enhancing signal stability.  This photothermal microscopy demonstrates potential applications across diverse fields, including biological sciences, nanotechnology, materials science, chemistry, and medicine.

Please email Shuang Hao (shuanghao@arizona.edu) or me (jini@optics.arizona.edu) for the Zoom link.