Fluorocarbon lubricant impregnated nanoporous oxide for omnicorrosion-resistant stainless steel

Multifunctional Edible Oil-Impregnated Nanoporous Oxide Layer on AISI 304 Stainless Steel

Slippery liquid-infused porous surface (SLIPS) realized on commercial materials provides various functionalities, such as corrosion resistance, condensation heat transfer, anti-fouling, de/anti-icing, and self-cleaning. In particular, perfluorinated lubricants infused in fluorocarbon-coated porous structures have showed exceptional performances with durability; however, they caused several issues in safety, due to their difficulty in degradation and bio-accumulation. Here, we introduce a new approach to create the multifunctional lubricant-impregnated surface with edible oils and fatty acid, which are also safe to human body and degradable in nature. The edible oil-impregnated anodized nanoporous stainless steel surface shows a significantly low contact angle hysteresis and sliding angle, which is similar with general surface of fluorocarbon lubricant-infused systems. The edible oil impregnated in the hydrophobic nanoporous oxide surface also inhibits the direct contact of external aqueous solution to a solid surface structure. Due to such de-wetting property caused by a lubricating effect of edible oils, the edible oil-impregnated stainless steel surface shows enhanced corrosion resistance, anti-biofouling and condensation heat transfer with reduced ice adhesion.

Combining Topography and Chemistry to Produce Antibiofouling Surfaces: A Review

Despite decades of research on the reduction of surface fouling from biomolecules or micro-organisms, the ultimate antibiofouling surface remains undiscovered. The recent covid-19 pandemic strengthened the crucial need for such treatments. Among the numerous approaches that are able to provide surfaces with antibiofouling properties, chemical, biological, and topographical strategies have been implemented for instance in the marine, medical, or food industries. However, many of these methods have a biocidal effect and, with antibioresistance and biocide resistance a growing threat on humanity, strategies based on reducing adsorption of biomolecules and micro-organism are necessary for long-term solutions. Bioinspired strategies, combining both surface chemistry and topography, are currently at the heart of the best innovative and sustainable solutions. The synergistic effect of micro/nanostructuration, together with engineered chemical or biological functionalization is believed to contribute to the development of antibiofouling surfaces. This review aims to present approaches combining hydrophobic or hydrophilic chemistries with a specific topography to avoid biofouling in various industrial environments and healthcare facilities.

Overview of the development of slippery surfaces: Lubricants from presence to absence

The superhydrophobic surfaces inspired by the lotus have excellent performances and are known for their low contact angle hysteresis and smooth surfaces. However, there are still some problems, such as the unstable structure, poor durability, high product cost and so on that need to be improved. Those issues can be avoided via liquid-infused surfaces(LIS), which are inspired by Nepenthes and consist of a mico-nano structured substrate and a smooth continuous atomic-grade lubricant. Compared with superhydrophobic surfaces, LIS not only achieves the same hydrophobic properties but also has smaller contact angle hysteresis, smoother surface, more stable structure and lower preparation cost. Although the existence of a lubricant layer improves the performance of the material, it also leaves a hidden danger, which is easy to lose and leads to the deterioration of the durability of the material. Therefore, the lubricant-free slipper materials have attracted more and more attention in recent years due to their low volatility, good durability and excellent lubrication performance. In this review, the types of LIS lubricants and their physicochemical properties were summarized at the beginning and then the applications of LIS in various fields were introduced. At the end of this paper, some solid lubricants and their applications were described, and the future development prospects of LIS lubricants also were expected.

Design of Robust Lubricant-Infused Surfaces for Anti-Corrosion

A lubricant-infused surface such as an oil-impregnated porous surface has great potentials for various applications due to its omniphobicity. However, the drainage and depletion of the lubricant liquid oil remain practical concerns for real applications. Here, we investigate the effect of a specially designed bottle-shaped nanopore of anodic aluminum oxide, which has a smaller pore diameter in the upper region than the lower one, on the oil retentivity and anti-corrosion efficacy. The effects of the viscosity and volatility of the lubricant oil were further investigated for synergy. Results show that the bottle-shaped pore helps to stably immobilize the lubricant oil in the nanostructure and significantly enhances the robustness and anti-corrosion efficacy, compared to the conventional cylindrical pores with straight walls as well as the hybrid one featured with additional pillar structures. Moreover, the enlarged oil capacity in the bottle-shaped pore allows the oil to cover the underlying metallic surface effectively at cracks, enhancing the damage tolerance with a unique self-healing capability. The oil with a higher viscosity further enhances the benefits so that the bottle-shaped pore impregnated with a higher-viscosity oil shows greater anti-corrosion efficacy. It suggests that the combination of the geometric features of nanopores and the fluid properties of lubricant liquid can lead to a maximized longevity and anti-corrosion efficacy of the liquid-infused surfaces for real applications.

Robust and durable liquid-repellent surfaces

This review provides a comprehensive summary of characterization, design, fabrication, and application of robust and durable liquid-repellent surfaces.

Dewetting of non-polar thin lubricating films underneath polar liquid drops on slippery surfaces

HYPOTHESIS

The stability of thin lubricating fluid-coated slippery surfaces depends on the surface energy of the underlying solid surface. High energy solid surfaces coated with thin lubricating oil lead to the dewetting of the oil films upon depositing aqueous drops on them. Hence such surfaces are very suitable to investigate dewetting of thick films (thickness > 500 nm), which otherwise is not possible using a conventional dewetting system.

EXPERIMENTS

Lubricating films of different thicknesses are coated on hydrophilic solid surfaces, and glycerol drops are deposited on them. Fluorescence imaging of lubricating films and macroscopic wetting behavior of glycerol drops are analyzed to understand the dewetting phenomenon.

FINDINGS

Underneath lubricating films undergo initial thinning and subsequently dewet. The dewetting dynamics during hole nucleation and growth and the final pattern of the dewetted oil droplets depend strongly on the thickness of the lubricating films. Ultrathin films dewet spontaneously via homogeneous nucleation, whereas thicker films dewet via heterogeneous nucleation. During dewetting, the apparent contact angle and radius of glycerol drops follow universal scaling behavior.

Life and death of liquid-infused surfaces: a review on the choice, analysis and fate of the infused liquid layer

We review the rational choice, the analysis, the depletion and the properties imparted by the liquid layer in liquid-infused surfaces – a new class of low-adhesion surface.