Gas-Phase Transport and Redeposition of Nano- and Micro-Particulates During Laser Cleaning From Solid Substrates

Theoretical modeling and experimental studies were performed to investigate basic processes underlying transport of model submicron spherical particles in still air and thin liquid layers of variable thickness after their laser-assisted detachment from dry and 2-propanol–dosed Si surfaces. Viscous drag and diffusive Brownian motion were found to mostly affect transport of nano- and micro-particles removed from solid substrates in the used or other viscous media removed by laser cleaning, resulting in their undesirable redeposition. A crucial parameter of particle transport—liftoff distances—has been experimentally measured as a function of laser fluence for these particles using thin 2-propanol layers, and the distances can be scaled for other viscous media accounting for their corresponding viscosities. Experimental and theoretical results of this work can be related to optimization of transport processes in laser cleaning and laser-induced forward transfer applications for nano- and

micro-features of arbitrary shapes.