Controlling Long-Pulsed Laser-Induced Cavitation Through Nanoparticle Doping: A Numerical Analysis

Previous studies indicate that the medium's laser absorption coefficient () influences laser energy transmission and fluid/bubble dynamics in long-pulsed laser-induced cavitation. However, few studies explore the strategies to change the medium’s  and the resulting impacts on the dynamics and transmission. In this talk, we present an experimental method in which the absorption coefficient of water is modified by introducing PEDOT nanoparticles, achieving a range from 2.6 to 31.3  for the Holmium: YAG laser as concentration increases from 0% to 1 wt.%. We then conduct numerical simulations for laser-induced cavitation with seven selected absorption coefficients within this range to explore the effect of varying . These simulations utilize a new computational model that couples multiphase fluid dynamics with laser radiation and phase transition (vaporization). The simulated bubble evolution aligns well with experimental results in water with 0% PEDOT. Results indicate that increasing  leads to earlier bubble nucleation (16.4 vs. 4.4 s) and a transition from round to long, conical bubble shape, with lower temperature observed inside the conical vapor bubble. Moreover, the impact on laser energy transmission highly depends on the distance from measurement position to the laser source. At shorter distances (≤0.25 mm), higher  enhances energy delivery due to the Moses effect, while at longer distances (≥1.5 mm), lower  is more effective in reducing energy absorption. In intermediate ranges, energy transmission shows a non-linear relationship with increasing .