Nanoparticle suspensions are utilized for depositing thin films on solid substrates by a process called nano electrospray laser deposition. In this research, three deposition methods, contact liquid line laser printing, nano-electrospray laser sintering and evaporative optical Marangoni convection are investigated experimentally and analytically. Thin silver lines are printed on indium tin oxide-coated silicon substrates by dispensing silver nanoparticle suspension with a micropipe of inner diameter 51µm and subsequently sintering the nanoparticles with a CO2 laser beam of Bessel intensity profile. The deposited silver lines of 65µm width and 1µm height have good resistivity which can be used to manufacture silver fingers on solar cells by stacking multiple layers, or coat the substrate with a single silver layer to form a smooth surface for subsequently depositing thicker silver fingers. An analytical conduction model is developed for the Bessel beam heating of the substrate to predict the temperature distribution in the silicon substrate, which can be used to guide the substrate speed as well as the range of laser power for sintering. Another analytical model is also developed for the Bessel beam heating of the nanosuspension microdrops and the substrate to predict the droplet thermal behavior (i.e., explosion characteristics) in mid-air and on the substrate that are observed in nano-electrospray laser sintering. Due to laser illumination, the droplet suspension undergoes changes in optical properties and surface tension-dominated Marangoni convection. This evaporative optical Marangoni convection has been modeled for an incident UV beam to understand the deposition patterns on the substrate. An analytical solution of stream function is shown to predict surface patterns that compare well with experiments.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Li, Tianyi, "Laser-microdrop Interactions in Nanoparticle Deposition on Solid Substrates" (2021). Electronic Theses and Dissertations, 2020-. 724.