PFAS-free Superhydrophobic Surfaces using Femtosecond Laser Processing and Hot-Filament Chemical Vapor Deposition

Ultrashort-pulsed laser technology has revolutionized surface modification and can be a key part to generate biomimetic, superhydrophobic properties on a large scale. However, laser- structured surfaces exhibit a high surface energy directly after light-material interaction and thus need post-processing techniques to control the surface chemistry. Current research has been chiefly based on perfluorinated and polyfluorinated alkyl compounds (PFAS) to lower the surface energy, for which severe ecological and physiological concerns exist. Using hot-fila- ment chemical vapor deposition, we demonstrate the development of an, compared to fluorine- containing coatings, more environmentally friendly coating based on siloxane components, which we successfully applied on laser-structured surfaces. Creating two surface designs with a femtosecond laser, we showed that even nanoscaled protrusions are not overlaid by the ho- mogenous chemical vapor deposited polymer film. Combining a hierarchical surface topogra- phy and thin film deposition, superhydrophobic surfaces with a static contact angle of 171.6°, a contact angle hysteresis of 8.6°, a sliding angle of 4.5° and low lateral adhesion forces (FLA=9 µN) were achieved. These findings highlight the potential impact of combined ultra- short-pulsed laser technology and chemical vapor deposition polymerization for large-scale ap- plications, emphasizing an environmental alternative to PFAS.