Liquid-Assisted Laser Ablation, Micro-Machining and Functional Surface Structuring: Insights into Process Variants, Mechanisms, and Challenges

Laser ablation is one of the widely used processes in micro and nano engineering applications. Owing to the limitations of re-deposition of melt debris, heat-affected zones, spatter adhesion, deep ablation difficulties, surface morphological issues, thermal damage, and compromises over the geometrical accuracies, the dry laser ablation is extended to laser ablation under wet media. The ablation performed under the coupling effect of laser parameters and the liquid medium parameters facilitates the flushing of melt debris, the cooling effect around the irradiated zones, reduction in heat-affected zones, less thermal damage, and improved accuracy of the ablated micro- and nano-features. The process has several variants, such as underwater laser ablation, waterjet-guided laser ablation, micro-machining under liquid laser ablation, underwater laser surface structuring, etc. In this review, these variants of the laser ablation process are systematically discussed to understand what distinct competencies are offered by this category of laser ablation under wet media. Under each of these variants, different attributes are systematically presented and discussed, such as process fundamentals, the principle of material removal phenomenon, process capabilities to deal with different engineering materials, types of lasers used in each case, performance measures, parametric effects, and the challenges within each of these process variants. At the end, important conclusions are inferred and supported with a proposed set of future research directions for the researchers’ community to explore further deep insights in this area of laser ablation under wet media.