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The rising speed and dissolution rate of a carbon dioxide bubble in slightly contaminated water were investigated experimentally and numerically. We developed an experimental system that uses a charged-coupled device (CCD) camera coupled with a microscope to track the rising bubble. By precisely measuring the bubble size and rising speed, we were able to accurately estimate the drag coefficient and the Sherwood number for the dissolution rate of gas bubbles at Reynolds numbers below 100 in the transient regime, where the bubble changes from behaving as a fluid sphere to behaving as a solid particle. We also numerically estimated the drag coefficient and Sherwood number of the ‘stagnant cap model’ by directly solving the coupled Navier–Stokes and convection–diffusion equations. We compared our experimental results with our numerical results and proposed equations for estimating the drag coefficient and Sherwood number of the bubble affected by contamination and clarified that the gas–liquid interface of the carbon dioxide bubble in water is immobile. We also show that the experimental and numerical results are in good agreement and the stagnant cap model can explain the mechanism of the transient process where the bubble behaviour changes from that of a fluid sphere to that of a solid particle.

Laser ablation has become a widely recognized tool for materials processing. In the area of polymeric materials, applications of UV lasers for surface modification, microlithography, cutting, and boring have been explored. With the addition of dopants into the bulk, it has become possible to sensitize most known classes of polymers for UV laser ablation at any desired wavelength, including fluoropolymers. Important features of dopant-induced ablation are the reduction of threshold energy fluence required for ablation, and the enhancement of the etching rate by factors higher than ten. In the present review the investigated dopant/polymer systems are summarized and compared. Based on the available information, a general scheme including all relevant pathways is suggested, revealing that in each particular case the dominant mechanism depends on the specific system under study.