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

Abstract

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.

Stretchable and Superwettable Colorimetric Sensing Patch for Epidermal Collection and Analysis of Sweat

“…In Figure e, the highly textured SEBS substrate is generated by replica molding from a piece of textured aluminum plate prepared by laser ablation (details available in the Experimental Section). According to optical topographic images shown in Figure S5, the texture substrate consists of an array of microscale grooves formed as a result of the laser scan path. , As compared with the smooth elastomeric film with a characteristic contact angle of 103.4 ± 3.6°, the roughened substrate exhibits a notably increased water contact angle of 132.5 ± 4.2° as a result of the additional surface area to boost hydrophobicity (see Figure f). , Subsequently, the decoration of fluorinated silica NPs over the roughened SEBS substrate further increases the water contact angle to 156.6 ± 3.8°. , As shown in Figure e, the heterarchical micro/nanostructures that resemble the surface morphology of a lotus leaf achieve superhydrophobicity by effective trapping of air pockets. − …”

“…According to optical topographic images shown in Figure S5, the texture substrate consists of an array of microscale grooves formed as a result of the laser scan path. 45,46 As compared with the smooth elastomeric film with a characteristic contact angle of 103.4 ± 3.6°, the roughened substrate exhibits a notably increased water contact angle of 132.5 ± 4.2°as a result of the additional surface area to boost hydrophobicity (see Figure 2f). 47,48 Subsequently, the decoration of fluorinated silica NPs over the roughened SEBS substrate further increases the water contact angle to 156.6 ± 3.8°.…”

Laser-Induced Slippery Liquid-Infused Surfaces with Anticorrosion and Wear Resistance Properties on Aluminum Alloy Substrates

“…After modification with fluoroalkyl silane, a water droplet on the base Al alloy surface exhibits hydrophobicity with a CA of 102.5 ± 2.1° (Figure c). Fluorination treatment can reduce the surface free energy and increase the hydrophobicity of the surface, but the CA of the water droplet is not greater than 120°. , The perfluorinated lubricant is injected into the hydrophobic surface and the CA is 93.9 ± 1.5°. When the surface is turned 90°, the water droplets still adhere to the surface (Figure d).…”

Enabling Superhydrophobicity-Guided Superwicking in Metal Alloys via a Nanosecond Laser-Based Surface Treatment Method

“…Therefore, it is also expected to show capillary wicking in the fabricated surface. On the other hand, the presence of fluorocarbon groups (−CF 2 – and −CF 3 ) is known in surface chemistry to reduce the dispersive component of surface energy. − As a result, the surface behaves as a repellent to water molecules. The combination of repellent surface chemistry and surface nanostructures induces extreme repellency toward water molecules leading to superhydrophobicity.…”