Femtosecond Laser Ablation of Porous PVDF and PES Membranes: Ablation Behaviors and In‐Plane Cross‐Sectioning

Laser ablation is emerging as an effective method for fabricating and modifying polymeric membranes. However, the interaction between laser energy and polymers is intricate, being governed by photothermal, photochemical, and photophysical processes. With the added complexity of porous structures, it is challenging to achieve controlled ablation of membranes. Despite many recent demonstrations, a systematic experimental study of laser–porous membrane interactions is still lacking. Here we report detailed studies of the ablation of two commonly used membranes, polyvinylidene fluoride (PVDF) and polyether sulfone (PES), using a femtosecond UV laser. The ablation rates were quantified under varying laser parameters (pulse number and fluence) and membrane characteristics (chemistry, pore size, and porosity). Under single‐pulse ablation, both PVDF and PES membranes displayed pore size independent ablation rates at low fluences. At high fluences, the membranes displayed reduced ablation rates but did not exhibit the shielding effect that dominated dense polymer films. Similar trends were observed for multi‐pulse ablation of the membranes. Interestingly, the multi‐pulse/single‐pulse ablation depth ratios showed a power‐law‐like dependence on the pulse number, which is analogous to the equation describing “incubation effect” observed for analyzing ablation thresholds. By leveraging these findings, we demonstrated laser ablation as a controlled in‐plane sectioning methodology for characterizing the pore structures of an asymmetric PES membrane at varying depths. The results provide critical insights into the interaction between femtosecond UV laser and porous membranes, which is important for the continuous development of laser ablation as a method for membrane fabrication and characterization.