Design of Surfaces with Persistent Antimicrobial Properties on Stainless Steel Developed Using Femtosecond Laser Texturing for Application in "High Traffic" Objects.

Metal-based high-touch surfaces used for diverse applications in everyday use, like handrails, playground grab handles, doorknobs, ATM touch pads, and desks, are the most common targets for pollution with a variety of microbes; there is thus a need to improve their antimicrobial properties, an issue which has become a challenge in recent years, particularly after the COVID-19 pandemic. According to the World Health Organization (WHO), drug-resistant pathogens are one of the main concerns to global health today, as they lead to longer hospital stays and increased medical costs. Generally, the development of antimicrobial surfaces is related to the utilization of chemical methods via deposition on surfaces in the forms of various types of coatings. However, the addition of chemical substances onto a surface can induce unwanted effects, since it causes surface chemistry changes and, in some cases, cannot provide long-lasting results. A novel approach of utilising ultra-short laser radiation for the treatment of metallic surfaces by inducing a variety of micro- and nanostructuration is elaborated upon in the current research, estimating the optimum relation between the wettability and roughness characteristics for the creation of antimicrobial properties for such high-touch surfaces. In the current study, AISI 304-304L stainless steel metal was used as a benchmark material. Surface texturing via laser ablation with femtosecond laser pulses is an effective method, since it enables the formation of a variety of surface patterns, along with the creation of bimodal roughness, in one-step processing. In this investigation, a precise approach toward developing hydrophobic stainless steel surfaces with tunable adherence using femtosecond laser-induced modification is described. The impact of basic femtosecond laser processing parameters, like the scanning velocity, laser energy, and wettability properties of the laser-processed stainless steel samples, are examined. It is identified that the topography and morphology of laser-induced surface structures can be efficiently changed by adapting the laser processing parameters to create structures, which facilitate the transfer of surface properties from extremely low to high surface wettability.