Manipulation, Detection, and Characterization of Single Nanoparticles: From Dielectric Nanoantennas to Interferometric Electrohydrodynamic Tweezers

Abstract

The manipulation, detection, and characterization of nanoscale particles are central challenges in nanophotonics, optical sensing, and nanoscale analysis. Conventional optical tweezers enable precise control of microscopic objects, but their performance is limited for nanoparticles because the optical gradient force decreases with particle volume and the diffraction limit prevents subwavelength light confinement. In addition, high optical powers can induce photothermal heating, sample damage, and unwanted fluidic motion. This dissertation addresses these limitations by engineering resonant nanophotonic structures and interferometric platforms for low-power trapping, label-free detection, and single-particle characterization. First, this work demonstrates that optical anapole states in all-dielectric nanoantennas provide strong near-field enhancement while suppressing far-field scattering and minimizing photothermal heating. By integrating silicon anapole nanoantennas with distributed Bragg reflector substrates and double-nanohole apertures, the enhanced electromagnetic field becomes accessible to nanoscale biological particles. This design enables low-power optical trapping of extracellular vesicles and supermeres with negligible temperature rise, overcoming key limitations of conventional and plasmonic nanotweezers. Second, this dissertation explores anapole-enhanced photothermal effects for controlled particle transport and manipulation. By exciting anapole nanoantennas at visible wavelengths, localized heating generates thermophoretic and diffusiophoretic forces in polymer-containing solutions. These forces are engineered to transport and trap nanoparticles across anapole arrays, demonstrating a hybrid mechanism that combines near-field optical gradient forces with thermally driven diffusiophoresis. Third, this work introduces interferometric electrohydrodynamic tweezers, a multifunctional platform that combines AC electro-osmotic flow with interferometric scattering microscopy. This system enables label-free trapping, transport, and characterization of multiple nanoparticles without fluorescence labeling. Using interferometric scattering contrast, Brownian motion analysis, particle tracking, and AI-assisted segmentation, the platform provides a route toward high-throughput characterization of extracellular vesicles and other nanoscale biological particles. Finally, this dissertation extends the resonator-based design concept beyond particle manipulation to thermal photonics. Nonlocal magnetic anapole metasurfaces are investigated to control mid-infrared thermal radiation, enabling directional, multiband, and narrowband thermal emission. Together, these studies show that resonant nanophotonic structures can tailor light–matter interactions across nanoscale manipulation, sensing, characterization, and thermal emission.