Laser-Induced Nanoparticle Transfer and Super-Resolution Imaging

Date of Award

8-1-2024

Degree Name

Ph.D. in Electro-Optics

Department

Department of Electro-Optics and Photonics

Advisor/Chair

Chenglong Zhao

Abstract

This dissertation explores advanced techniques in nanofabrication and super-resolution imaging, focusing on the use of laser-induced transfer methods and fiber-coupled photonic nanojet (PNJ). The research demonstrates both numerically and experimentally the potential of microsphere-fiber PNJ lenses in achieving super-resolution imaging. Key findings highlight the successful excitation and imaging of quantum dots, emphasizing the method's precision in locating single quantum dots and achieving high-resolution imaging. First, we introduce the mechanisms and applications of several laser-induced nanoparticle transfer techniques. The investigation highlighted the differences and advantages of methods such as laser ablation in liquid (LAL), laser-induced forward transfer (LIFT), and the novel opto-thermal mechanical (OTM) approach. Each method's unique benefits and limitations were examined, with a particular focus on the OTM method due to its simplicity, cost-effectiveness, and versatility in transferring various types of nanoparticles (NPs). The OTM method was demonstrated to efficiently transfer NPs from a soft substrate to a receiver substrate using a continuous wave (CW) laser, offering a low-cost alternative to more complex and expensive femtosecond laser systems. In Chapter 3, the study investigates the release probability of gold nanoparticles (AuNPs) from various substrates under CW laser illumination. The research reveals that plasma cleaning of the substrate, although common, reduces the release probability due to increased particle adhesion. Additionally, the study finds that the mechanical properties of the substrate significantly influence the release probability, with more flexible substrates facilitating easier release of NPs. These insights are crucial for optimizing nanoparticle transfer technology for various applications. Chapter 4 extends the investigation to the sorting of AuNPs from polymethyl methacrylate (PMMA) substrates. The research demonstrates that adjusting the thickness of the PMMA layer can control the release angle of AuNPs, allowing precise manipulation and placement of NPs. This capability is further utilized to sort AuNPs of different sizes, showcasing the method's potential for nanoparticle purification and separation. Chapter 5 focuses on the development of a fiber-coupled high numerical aperture microlens system to achieve super-resolution microscopy via PNJs. The study compares various super-resolution techniques and demonstrates the capability of the microsphere-attached fiber to generate PNJs, achieving sub-diffraction-limit resolution. The simulation results support the experimental findings, highlighting the system's potential for high-resolution imaging applications. Future work will focus on improving the super-resolution imaging capabilities of the microsphere-fiber PNJ lens. Planned experiments include exciting quantum dots using the PNJ lens and collecting fluorescence through a CCD or spectrometer. Additionally, the research aims to explore the use of supercontinuum lasers to achieve a wide wavelength range of focus and investigate other techniques, such as fiber-based zone plates, to enhance super-resolution imaging further. By advancing the understanding and application of these techniques, this dissertation contributes to the development of versatile and powerful tools for scientific and industrial applications, paving the way for future innovations in nanofabrication and imaging.

Keywords

Laser-induced nanoparticle transfer; Opto-thermal mechanical transfer; Super-resolution imaging; Fiber-coupled photonics nanojet.

Rights Statement

Copyright © 2024, author.

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