Regulating Underwater Oil Adhesion on Superoleophobic Copper Films through Assembling n-Alkanoic Acids

Abstract

Controlling liquid adhesion on special wetting surface is significant in many practical applications. In this paper, an easy self-assembled monolayer technique was advanced to modify nanostructured copper substrates, and tunable adhesive underwater superoleophobic surfaces were prepared. The surface adhesion can be regulated by simply varying the chain length of the n-alkanoic acids, and the tunable adhesive properties can be ascribed to the combined action of surfaces nanostructures and related variation in surface chemistry. Meanwhile, the tunable ability is universal, and the oil-adhesion controllability is suitable to various oils including silicon oil, n-hexane, and chloroform. Finally, on the basis of the special tunable adhesive properties, some applications of our surfaces including droplet storage, transfer, mixing, and so on are also discussed. The paper offers a novel and simple method to prepare underwater superoleophobic surfaces with regulated adhesion, which can potentially be applied in numerous fields, for instance, biodetection, microreactors, and microfluidic devices.

A Review of Femtosecond‐Laser‐Induced Underwater Superoleophobic Surfaces

“…Contrary to the fish scales, if the oil adhesion of a superoleophobic surface is very high rather than ultralow, the oil droplet will be able to stick to the surface no matter the substrate is tilted at any angle. Such high adhesive surface can be used to transport small oil droplet without any volume loss . Because of the important applications in manipulating oil droplets on the target materials, the multifunctional superoleophobic surfaces showing controllable adhesion (from low to high) to oil droplet have attracted growing interest among the researchers …”

“…The adhesion between the underwater oil droplet and the solid substrate is primarily determined by the wetting state of the droplet . The hierarchical periodic microislands fabricated at the scanning speed of 2 mm s −1 and the shift of scanning lines of 2 µm are rough enough.…”

“…Inspired by the underwater superoleophobicity of fish scales, various technologies have been developed to fabricate underwater superoleophobic surfaces following the design principle of “from in‐air superhydrophilicity to underwater superoleophobicity,” such as lithography, templating, chemical etching, hydrothermal method, self‐assembly, electrochemical deposition, electrochemical anodization, and spray/dip coating . The same as the superhydrophobic surfaces, the artificial underwater superoleophobic surfaces have also attracted much attention recently owning to their significant applications in antioil coatings, oil/water separation, manipulation of oil microdroplets, self‐cleaning, bioadhesion, antiblocking, guiding the movement of oil droplets, floating on oil, and oil droplets patterning . Underwater superoleophobic surfaces can be successfully prepared by the above‐mentioned traditional methods, but those methods, more or less, have to face their inherent limitations, such as complex fabrication process, tight restriction on special materials, and lack flexibility.…”

“…This tilted angle of the substrate is SA (Figure b). In general, the value of the SA can reflect the degree of the adhesion between the solid substrate and the liquid droplets . A higher liquid adhesion usually gives rise to a larger SA value.…”

Underwater superoleophobicity, anti-oil and ultra-broadband enhanced absorption of metallic surfaces produced by a femtosecond laser inspired by fish and chameleons

“…Zhang et al reported a series of underwater superoleophobic Ni/NiO surfaces with controlled oil adhesion by combining electrodeposition and heating techniques16. Cheng et al proposed a self-assembled monolayer technique to modify nanostructured copper substrates to prepare tuneable adhesive underwater superoleophobic surfaces17. However, these manufacturing processes are difficult to control, and the reported underwater superoleophobic surfaces only exhibit improved oil wettability, greatly limiting their application to underwater devices such as oil-repellent military submarines and amphibious military aircraft and tanks, which also require optical stealth.…”