Design of Chemical Surface Treatment for Laser-Textured Metal Alloys to Achieve Extreme Wetting Behavior

Extreme wetting activities of laser-textured metal alloys have received significant interest due to their superior performance in a wide range of commercial applications and fundamental research studies. Fundamentally, extreme wettability of structured metal alloys depends on both the surface structure and surface chemistry. However, compared with the generation of physical topology on the surface, the role of surface chemistry is less explored for the laser texturing processes of metal alloys to tune the wettability. This work introduces a systematic design approach to modify the surface chemistry of laser textured metal alloys to achieve various extreme wettabilities, including superhydrophobicity/superoleophobicity, superhydrophilicity/superoleophilicity, and coexistence of superoleophobicity and superhydrophilicity. Microscale trenches are first created on the aluminum alloy 6061 surfaces by nanosecond pulse laser surface texturing. Subsequently, the textured surface is immersion-treated in several chemical solutions to attach target functional groups on the surface to achieve the final extreme wettability. Anchoring fluorinated groups (-CF₂- and -CF₃) with very low dispersive and nondispersive surface energy leads to superoleophobicity and superhydrophobicity, resulting in repelling both water and diiodomethane. Attachment of the polar nitrile (-C≡N) group with very high nondispersive and high dispersive surface energy achieves superhydrophilicity and superoleophilicity by drawing water and diiodomethane molecules in the laser-textured capillaries. At last, anchoring fluorinated groups (-CF₂- and -CF₃) and polar sodium carboxylate (-COONa) together leads to very low dispersive and very high nondispersive surface energy components. It results in the coexistence of superoleophobicity and superhydrophilicity, where the treated surface attracts water but repels diiodomethane.

A bioinspired approach to produce parahydrophobic properties using PEDOP conducting polymers with branched alkyl chains

In nature, several plants and insects, such as the Rosa montana petals or the gecko foot, are highly hydrophobic but with an extremely high water adhesion. These properties are called parahydrophobic. Here, in order to reproduce such properties we have developed original 3,4-ethylenedioxypyrrole monomers containing branched alkyl chains in order to have intrinsically hydrophilic polymers. In certain conditions, the electrodeposited conducting polymer films are parahydrophobic due to the presence fibrous structures forming large agglomerates. On such surfaces, a water droplet deposited on them remains stuck even after a substrate inclination of 180°. Such properties are extremely interesting for applications in water harvesting, for example.