Date of Graduation

12-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics (PhD)

Degree Level

Graduate

Department

Physics

Advisor/Mentor

Wang, Yong

Committee Member

Chen, Jingyi

Second Committee Member

Li, Jiali

Third Committee Member

Kumar, Pradeep

Keywords

bacteria; kinetics; lasers; motility; nanoparticles; photoluminescence

Abstract

This dissertation has two focus areas: nanoparticle nanowelding and bacteria motility in the presence of micrometer sized structures. There are two main projects for the nanoparticle nanowelding studies: “Real-time imaging of laser-induced nanowelding in solution” and “Two-color laser-induced nanostructure shape modulation.” For the real-time imaging project, I used a fluorescence microscope, a 405 nm laser, and various python packages to quantify the average size of nanowelded nanostructures as a function of time and found that the average nanostructure growth over time fit the parameters of A¯(t) ∝ c0(1−e−t/τ), where c0 represents the initial concentration of nanoparticles in the solution and τ is a parameter that depends on the power of my laser. For the two-color laser-induced nanostucture project, I used a combination of a 405 nm lase rand a 532 nm laser to see how nanostructure shape depends on the combination of laser wavelengths. Bacteria motility connects to my nanoparticle nanowelding projects through the research processes I used and the practical applications in various fields like energy generation and environmental remediation. I will discuss three projects related to bacterial motility in this paper: two simulation projects and one microscopy project that is still in progress. For the simulation projects, I looked at bacteria in the presence of micrometer-sized Tesla valves and bacteria in the presence of micro-pillars with different surface structures. For the microscopy project I started looking at what I will refer to as ‘potential wells’ to see how bacteria motility effects their ability to be trapped-in and escape from micrometer-sized well structures.

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