Fabrication of Slippery Lubricant-Infused Porous Surface for Inhibition of Microbially Influenced Corrosion

Droplet Manipulation on Bioinspired Slippery Surfaces: From Design Principle to Biomedical Applications

Droplet manipulation with high efficiency, high flexibility, and programmability, is essential for various applications in biomedical sciences and engineering. Bioinspired liquid-infused slippery surfaces (LIS), with exceptional interfacial properties, have led to expanding research for droplet manipulation. In this review, an overview of actuation principles is presented to illustrate how materials or systems can be designed for droplet manipulation on LIS. Recent progress on new manipulation methods on LIS is also summarized and their prospective applications in anti-biofouling and pathogen control, biosensing, and the development of digital microfluidics are presented. Finally, an outlook is made on the key challenges and opportunities for droplet manipulation on LIS.

Synthesis, Characterization, and Applications of Rare-Earth-Based Complexes with Antibacterial and Antialgal Properties

The pursuit of environmentally friendly and highly effective antifouling materials for marine applications is of paramount importance. In this study, we successfully synthesized novel rare earth-based complexes by coordinating cerium (Ce III), samarium (Sm III), and europium (Eu III) with pyrithione (1-hydroxy-2-pyridinethione; PT). Extensive characterizations were performed, including single-crystal X-ray analysis, which revealed the intriguing binuclear structure of these complexes. This structural motif comprises two rare-earth ions intricately double-bridged by two oxygen atoms from the PT ligand, resulting in a distinctive and intriguing geometry. Furthermore, the central rare earth ion is surrounded by three sulfur atoms and two additional oxygen atoms, forming a unique distorted bicapped trigonal prismatic configuration. Compared with conventional antifouling biocides such as sodium pyrithione (NaPT), copper pyrithione (CuPT), and zinc pyrithione (ZnPT), these newly synthesized rare-earth complexes exhibited a remarkable boost in their in vitro antibacterial efficacy against both Gram-positive and Gram-negative bacteria. Additionally, these complexes demonstrated significant potential as antialgal agents, displaying impressive activity against marine planktonic organisms. These findings underscore the promising application prospects of these rare-earth complexes in the field of marine antifouling.

Double Immobilized Superhydrophobic and Lubricated Slippery Surface with Antibacterial and Antifouling Properties

A "double immobilized" superhydrophobic and lubricated slippery surface was prepared by simultaneously immobilizing lubricating oil and bactericide molecules. The coordination function of metal organic frameworks (MOFs) was utilized to immobilize trimesic acid, a fungicide, as a ligand of the MOF by the cathodic electrodeposition technique. Aminated silicone oil was used as a lubricating oil and was immobilized to the superhydrophobic MOF film by the curing reaction with isocyanates. This technique is a facile strategy to conductive substrates for fabricating superhydrophobic and lubricated slippery surfaces with satisfactory antibacterial and antifouling properties.

Biofilm formation of Pseudomonas aeruginosa in spaceflight is minimized on lubricant impregnated surfaces

The undesirable, yet inevitable, presence of bacterial biofilms in spacecraft poses a risk to the proper functioning of systems and to astronauts' health. To mitigate the risks that arise from them, it is important to understand biofilms' behavior in microgravity. As part of the Space Biofilms project, biofilms of Pseudomonas aeruginosa were grown in spaceflight over material surfaces. Stainless Steel 316 (SS316) and passivated SS316 were tested for their relevance as spaceflight hardware components, while a lubricant impregnated surface (LIS) was tested as potential biofilm control strategy. The morphology and gene expression of biofilms were characterized. Biofilms in microgravity are less robust than on Earth. LIS strongly inhibits biofilm formation compared to SS. Furthermore, this effect is even greater in spaceflight than on Earth, making LIS a promising option for spacecraft use. Transcriptomic profiles for the different conditions are presented, and potential mechanisms of biofilm reduction on LIS are discussed.

Engineering of Graphdiyne-Based Functional Coatings for the Protection of Arbitrary Shapes of Copper Substrates

Copper-based materials are very important for many application fields from marine industry to energy management and electronic devices. For most of these applications, the copper objects require long-term contact to a wet and salty environment, which leads to serious corrosion of copper. In this work, we report a thin graphdiyne layer directly grown on arbitrary shapes of copper objects at mild conditions, which could function as a protective coating for the copper substrates in artificial seawater with corrosion inhibition efficiency of ∼99.75%. To further improve the protective performance of the coating, the graphdiyne layer is fluorinated and followed by infusion with a fluorine-containing lubricant (i.e., perfluoropolyether). As a result, a slippery surface is obtained, which shows enhanced corrosion inhibition efficiency of ∼99.99% as well as excellent antibiofouling properties against microorganisms, such as protein and algae. Finally, the coatings are successfully applied in the protection of a commercial copper radiator from long-term attack of artificial seawater without disturbing its thermal conductivity. These results demonstrate the great potential of graphdiyne-based functional coatings for the protection of copper devices in aggressive environments.

Boosted photocatalytic effect of binary AgI/Ag2WO4 nanocatalyst: characterization and kinetics study towards ceftriaxone photodegradation

In modern chemistry, great interest has been paid to introducing outstanding photocatalysts for degrading organic pollutants. Herein, a highly efficient binary AgI/Ag₂WO₄ photocatalyst was prepared from AgI and Ag₂WO₄ nanoparticles (NPs) and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), and Fourier transform infrared (FT-IR) techniques. In the Scherrer model, the average crystallite sizes of 34.9, 42.0, and 24.1 nm were estimated for the AgI, Ag₂WO₄, and the binary catalyst, while the values were 91, 13, and 85 nm by the Williamson-Hall model. FTIR confirmed the presence of W-O-W, O-W-O, Ag-I, and O-Ag-O bonds in the coupled material. DRS results showed absorption edge wavelengths of 451, 462, and 495 nm (corresponding to the band gap values of 2.75, 2.68, and 2.51 eV) for Ag₂WO₄, AgI, and AgI/Ag₂WO₄ catalyst, respectively. Synergistic photocatalytic activity of the coupled system was achieved towards ceftriaxone (CTX) in an aqueous solution (about 33% 10 ppm CTX solution was degraded without any optimization in the initial conditions of catal dose 0.3 g/L (Ag₂WO₄:AgI with mole ratio 1:2 and 30 min abrasion time), and irrad. time 45 min, C_CTX). This boosted effect depended on the AgI:Ag₂WO₄ mole ratio and grinding time for the mechanical preparation of the binary catalyst (optimums: mole ratio of 4:1 and time 30 min). The photodegradation kinetics obeyed the Hinshelwood model with the apparent first-order rate constant (k) of 0.013 min^-1 (t_1/2 = 53.30 min). Performing the COD on the photodegraded CTX solutions got a Hinshelwood plot with a slope of 0.019 min^-1 (t_1/2 = 36.5 min).

Limiting nitrate triggered increased EPS film but decreased biocorrosion of copper induced by Pseudomonas aeruginosa

Biocorrosion of Cu remains a significant challenge in marine engineering but the mechanism is still not clear. The nutrients in marine environment affect the microbe's growth and the formation of biofilm, and then affect biocorrosion of metal to a large extent. In this study, the effect of NO3- concentration in Pseudomonas aeruginosa (P. aeruginosa) medium on the formation of extracellular polymer substance (EPS) film and biocorrosion of Cu were studied. The experiments results showed that limiting NO3- in culture medium triggered increased EPS film but decreased biocorrosion of Cu induced by P. aeruginosa. With increase of NO3- content in the culture medium, the Cu surface attached less polysaccharides and proteins, but the Cu corrosion rate was accelerated. The weight loss of Cu and the maximum pit depth were both increased with increase of NO3- content. The XPS and XRD analyses indicated that the major corrosion product is Cu2O. The increased corrosion rate with increase of the NO3- level were attributed to the EET-MIC route, the formation of Cu(NH3)2+, and the more loose EPS film.

Multifunctional Slippery Polydimethylsiloxane/Carbon Nanotube Composite Strain Sensor with Excellent Liquid Repellence and Anti-Icing/Deicing Performance

In this paper, a multifunctional slippery polydimethylsiloxane/carbon nanotube composite strain sensor (SPCCSS) is prepared using a facile template method. Benefitting from the slippery surface, the SPCCSS shows excellent liquid repellence properties, which can repel various liquids such as oil, cola, yogurt, hot water and some organic solvents. Meanwhile, the SPCCSS has a large strain sensing range (up to 100%), good sensitivity (GF = 3.3) and stable response with 500 cyclic stretches under 20% strain. Moreover, it is also demonstrated that the SPCCSS displays outstanding corrosion resistance (from pH = 1 to pH = 14) and anti-icing (8 min at −20 °C)/photothermal deicing (104 s with NIR power density of 1 W/cm²) properties, broadening its application in extreme acid, alkali and low-temperature conditions. Therefore, the multifunctional SPCCSS with the liquid repellence, anti-corrosion, and anti-icing/deicing properties has potential applications in wearable human motion monitoring tools under complex harsh environments.

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.

Designing a MOF-based slippery lubricant-infused porous surface with dual functional anti-fouling strategy

Material that resists biofouling adhesion is needed in a complex marine environment, but few of them can combine ultra-low fouling and environmental friendliness. Slippery lubricant-infused porous surface (SLIPS) is such a material, but it lacks the contact-killing ability, which limits its stability and anti-fouling efficiency. Here, we report a metal organic framework (MOF-based) Slippery ionic liquid-infused surface with excellent antifouling performance via synergistic release and contact-killing defense strategy. The dense needle-like MIL-110 array, grown in situ on the aluminum surface, is conducive to the stable storage of quaternary ammonium salt (QAS) ionic liquid. Compared to the control group with mature biofilm formed on the surface, SLIPS showed non-fouling performance in a 10-day test and another 21-day test under more challenging conditions. The adsorption amount of lipopolysaccharide (LPS) on SLIPS was 50% lower than that on the aluminum sheet and the aluminum sheet with MIL-110 grown on the surface as the control groups within three hours. The relationship between bacterial adhesion and LPS adsorption indicated that the anti-adhesion performance of SLIPS was mediated by the weak adhesion and easy release property of its surface to extracellular fouling molecules. This study provides the possibility to systematically reveal the antifouling mechanism of SLIPS on bacterial adhesion.

Slippery Liquid-Infused Porous Surfaces on Aluminum for Corrosion Protection with Improved Self-Healing Ability

Slippery liquid-infused porous surfaces (SLIPSs) can be formed by impregnating lubricants in porous surfaces with low surface energy. In this study, SLIPSs have been obtained on practically important aluminum with a porous anodic alumina layer by impregnating lubricants containing organic additives. The additive-containing lubricants change the surface slippery even without prior organic coating of the porous alumina surface. The additive-containing SLIPSs reveal a low water sliding angle of <5° and markedly improved corrosion resistance in an acetic acid solution containing chloride. The SLIPSs are formed by the in situ adsorption of the organic additives on the porous alumina surface. The scratched defects induce corrosion of the organic coating-type SLIPSs, whereas the additive-containing SLIPSs sustain high corrosion resistance even after introducing scratch defects. The adsorption of the organic additive in lubricants and refilling of the lubricant are responsible for the self-healing of the corrosion resistance. Thus, the additive-containing SLIPSs are promising self-healing corrosion-resistant surfaces.

Designing a Highly Stable Slippery Organogel on Q235 Carbon Steel for Inhibiting Microbiologically Influenced Corrosion

Microbiologically influenced corrosion (MIC) accelerates the corrosion and degradation of metal materials due to the settlement of microorganisms on the surface. However, environmentally friendly and efficient methods to fabricate antifouling and anticorrosion surfaces are still lacking. Inspired by Nepenthes, a slippery liquid-infused porous surface (SLIPS) has been proven to be an efficient way to inhibit settlement of microorganisms on the metal surface and the following MIC due to the existence of a mobile defect-free lubricant layer. However, the stability of the lubricant layer and substrate of the SLIPS prevented its long-term antifouling and anticorrosion application. Herein, a highly stable slippery organogel was fabricated by depositing a homogeneous mixture of PDMS (base and curing agent), silicone oil, triethoxyvinylsilane, and SiO₂ on Q235 and curing in an oven. Triethoxyvinylsilane was not only able to cross-link with the curing agent of PDMS through hydrosilylation but also able to interlink the organogel and Q235 through condensation between the -OH of the metal surface and hydrolyzed siloxane. As a result, the adhesion force between the organogel without triethoxyvinylsilane and the substrate (0.45 MPa) increased to 1.50 MPa for the organogel with triethoxyvinylsilane and SiO₂. Also, the tensile strength of the organogel without SiO₂ (0.97 MPa) increased to 3.88 MPa for the organogel with 2 wt % SiO₂ because of the high elastic modulus of SiO₂, which was important to improving its stability under external force. In addition, the organogel showed stable oil distribution and slippery performance after spinning at 4000 rpm for 30 s. Then, the bacterial settlement demonstrated that the organogel could effectively inhibit Pseudoalteromonas sp. settlement on the substrate under both static and dynamic conditions. Finally, an electrochemical test indicated that the MIC could be effectively mitigated by the organogel. This study provides an efficient method to fabricate a highly stable slippery surface on a metal surface for its potential application in mitigating MIC.

Innovative fouling-resistant materials for industrial heat exchangers: a review

Fouling of heat exchangers (HEs) has become a major concern across the industrial sector. Fouling is an omnipresent phenomenon but is particularly prevalent in the dairy, oil, and energy industries. Reduced energy performance that results from fouling represents significant operating loss in terms of both maintenance and impact on product quality and safety. In most industries, cleaning or replacing HEs are currently the only viable solutions for controlling fouling. This review examines the latest advances in the development of innovative materials and coatings for HEs that could mitigate the need for costly and frequent cleaning and potentially extend their operational life. To better understand the correlation between surface properties and fouling occurrence, we begin by providing an overview of the main mechanisms underlying fouling. We then present selected key strategies, which can differ considerably, for developing antifouling surfaces and conclude by discussing the current trends in the search for ideal materials for a range of applications. In our presentation of all these aspects, emphasis is given wherever possible to the potential transfer of these innovative surfaces from the laboratory to the three industries most concerned by HE fouling problems: food, petrochemicals, and energy production.

Brushable Lubricant-Infused Porous Coating with Enhanced Stability by One-Step Phase Separation

Slippery lubricant-infused porous surface (SLIPS) is a promising solution to undesired adhesion. Unfortunately, the complicated fabrication process and limited coating area block its practical applications. Herein, we report a one-step strategy to fabricate polypropylene-based SLIPS coatings through thermally induced phase separation, in which the lubricant is in situ infiltrated within a polymer network formed during cooling. The solid-liquid-phase separation process was monitored by an in situ hot-stage microscope. Such coating performs outstanding self-cleaning, anti-corrosion, and anti-bacterial performance, as well as enhanced stability of the lubricant layer because the lubricant is well adapted in the structure.

How to Efficiently Prepare Transparent Lubricant-Infused Surfaces: Inspired by Candle Soot

Poly(dimethylsiloxane) is a common dispersant, modifier, and binder in the field of bioinspired wettability. Herein, the soot production when poly(dimethylsiloxane) was burning was used to directly construct a superhydrophobic coating with the water contact angle reaching 159.7°. After the lubricant was infused, its transparency was greater than 80% of air in the visible light range of the human eye. In addition, the sliding angle and contact angle of the coating were stable for 15 days. It showed excellent oil-locking ability and stability. Even if the superhydrophobic coating was immersed in various organic solvents for 15 days, its hydrophobicity did not change. Moreover, the coating had an excellent anti-fouling ability and self-cleaning ability to meet actual application conditions. Furthermore, the preparation method was simple and rapid, without the participation of fluorine-containing modifiers, and provides a brand-new method for preparing transparent lubricant-infused surfaces.

Nanomechanical Insights into Versatile Polydopamine Wet Adhesive Interacting with Liquid-Infused and Solid Slippery Surfaces

Mussel-inspired polydopamine (PDA) can be readily deposited on almost all kinds of substrates and possesses versatile wet adhesion. Meanwhile, slippery surfaces have attracted much attention for their self-cleaning capabilities. It remains unclear how the versatile PDA adhesive would interact with slippery surfaces. In this work, both liquid-infused poly(tetrafluoroethylene) (PTFE) (LI-PTFE) and solid slippery surfaces (i.e., self-assembly of small thiol-terminated organosilane, polysiloxane covalently attached to substrates) were fabricated to investigate their capability to prevent PDA deposition. It was found that PDA particles could be easily deposited on a PTFE membrane and the two types of solid slippery surfaces, which resulted in the alternation of their surface wettability and slippery behavior of water droplets. Adhesion was detected between a PDA-coated silica colloidal probe and the PTFE membrane or solid slippery surfaces through quantitative force measurements using an atomic force microscope (AFM), mainly due to van der Waals (vdW) and hydrophobic interactions, which led to the PDA deposition phenomenon. In contrast, LI-PTFE with a thin liquid lubricant film could effectively prevent PDA deposition, with negligible changes in surface morphology, wettability, and slippery characteristics. Although PDA particles could be loosely attached to the lubricant/water interface for LI-PTFE based on the capillary adhesion measured by AFM, they could be readily removed by gentle rinsing with water, as demonstrated by the ultralow friction over LI-PTFE as compared to PTFE using lateral force microscopy (LFM). Our results indicate that LI-PTFE possesses excellent antifouling and self-cleaning properties even when interacting with the versatile PDA wet adhesives. This work provides new insights into the deposition of PDA on slippery surfaces and their interaction mechanism at the nanoscale, with useful implications for the design and development of novel slippery surfaces.

Polysiloxane Nanofilaments Infused with Silicone Oil Prevent Bacterial Adhesion and Suppress Thrombosis on Intranasal Splints

Like all biofluid-contacting medical devices, intranasal splints are highly prone to bacterial adhesion and clot formation. Despite their widespread use and the numerous complications associated with infected splints, limited success has been achieved in advancing their safety and surface biocompatibility, and, to date, no surface-coating strategy has been proposed to simultaneously enhance the antithrombogenicity and bacterial repellency of intranasal splints. Herein, we report an efficient, highly stable lubricant-infused coating for intranasal splints to render their surfaces antithrombogenic and repellent toward bacterial cells. Lubricant-infused intranasal splints were prepared by creating superhydrophobic polysiloxane nanofilament (PSnF) coatings using surface-initiated polymerization of n-propyltrichlorosilane (n-PTCS) and further infiltrating them with a silicone oil lubricant. Compared with commercially available intranasal splints, lubricant-infused, PSnF-coated splints significantly attenuated plasma and blood clot formation and prevented bacterial adhesion and biofilm formation for up to 7 days, the typical duration for which intranasal splints are kept. We further demonstrated that the performance of our engineered biointerface is independent of the underlying substrate and could be used to enhance the hemocompatibility and repellency properties of other medical implants such as medical-grade catheters.

Design novel three-dimensional network nanostructure for lubricant infused on titanium alloys towards long-term anti-fouling

Titanium alloys, recognized as a marine material with great potential, are currently facing serious biofouling problems, which greatly limits its application range. To improve the antifouling performance of titanium alloys, three unique surface of three-dimensional network, grass-like and linear nanostructures were obtained on titanium alloys via hydrothermal treatment in this work. Further, slippery liquid-infused porous surfaces (SLIPSs) were fabricated on titanium alloys via infusing PFPE lubricant into these nanostructures. Water contact angles and sliding angles of SLIPSs were measured to evaluate the effect of nanostructures on the stability of PFPE lubricant layer. Anti-fouling capability of SLIPSs were investigated by quantifying the cells of chlorella and phaeodactylum tricornutum (P. tricornutum)adhered to titanium alloys. The results shows that all the SLIPSs exhibited remarkable inhibition capacity for the settlement of chlorella and P. tricornutum. Among them, the SLIPS with three-dimensional network nanostructure displayed the longest-term anti-fouling performance, and its reduction rate of P. tricornutum and chlorella reaching 77.2 % and 84.5 % after being cultivated for 21 days, respectively, indicating that there existed a positive correlation between the stability of lubricant layer in the artificial seawater and the antifouling effect.

Inhibition Effectiveness of Laser-Cleaned Nanostructured Aluminum Alloys to Sulfate-reducing Bacteria Based on Superwetting and Ultraslippery Surfaces

This paper is a continued study on laser cleaning removal of marine microbiofouling from Al alloy surfaces. According to our previous study, it is noted that the antifouling functions of the generated laser-cleaned metallic surfaces must be highlighted. In this work, the inhibition effectiveness of the laser-cleaned Al alloy surfaces was evaluated using a type of vital marine microorganism, sulfate-reducing bacteria (SRB) Desulfovibrio desulfuricans subsp. desulfuricans, in a dynamic bacterial solution. Before the immersion tests, the laser-cleaned surfaces with nanostructures were chemically processed into superhydrophilic, superhydrophobic, and ultraslippery surfaces. SRB attachment behaviors as well as inhibition mechanisms of the three surfaces to the SRB settlement were characterized and revealed. The SRB adhering to the above surfaces presented three different morphologies, i.e., broken, dented, and plump cells. Superhydrophilic surfaces unexpectedly showed a not inferior antibacterial ability. A piercing effect of the nanostructures caused nontoxic mechanical damage to the cell membranes. The antiadhesion property of superhydrophobic solid-air hybrid surfaces was unreliable due to the loss of air bubbles. The morphology of the last surviving SRB cells left on the ultraslippery surfaces was basically plump. The stable repellent function of the surfaces was responsible for the vigorous prevention of the adhesion of the SRB. The research results offer an insight into the antibacterial/antiadhesion properties of the laser-cleaned surfaces and a practical value for the periodic service of marine high-end equipment.

Single and multi-functional coating strategies for enhancing the biocompatibility and tissue integration of blood-contacting medical implants

Device-associated clot formation and poor tissue integration are ongoing problems with permanent and temporary implantable medical devices. These complications lead to increased rates of mortality and morbidity and impose a burden on healthcare systems. In this review, we outline the current approaches for developing single and multi-functional surface coating techniques that aim to circumvent the limitations associated with existing blood-contacting medical devices. We focus on surface coatings that possess dual hemocompatibility and biofunctionality features and discuss their advantages and shortcomings to providing a biocompatible and biodynamic interface between the medical implant and blood. Lastly, we outline the newly developed surface modification techniques that use lubricant-infused coatings and discuss their unique potential and limitations in mitigating medical device-associated complications.

Extreme Antiscaling Performance of Slippery Omniphobic Covalently Attached Liquids

Scale formation presents an enormous cost to the global economy. Classical nucleation theory dictates that to reduce the heterogeneous nucleation of scale, the surface should have low surface energy and be as smooth as possible. Past approaches have focused on lowering surface energy via the use of hydrophobic coatings and have created atomically smooth interfaces to eliminate nucleation sites, or both, via the infusion of low-surface-energy lubricants into rough superhydrophobic substrates. Although lubricant-based surfaces are promising candidates for antiscaling, lubricant drainage inhibits their utilization. Here, we develop methodologies to deposit slippery omniphobic covalently attached liquids (SOCAL) on arbitrary substrates. Similar to lubricant-based surfaces, SOCAL has ultralow roughness and surface energy, enabling low nucleation rates and eliminating the need to replenish the lubricant. To enable SOCAL coating on metals, we investigated the surface chemistry required to ensure high-quality functionalization as measured by ultralow contact angle hysteresis (<3°). Using a multilayer deposition approach, we first electrophoretically deposit (EPD) silicon dioxide (SiO₂) as an intermediate layer between the metallic substrate and SOCAL. The necessity of EPD SiO₂ is to smooth (<10 nm roughness) as well as to enable the proper surface chemistry for SOCAL bonding. To characterize antiscaling performance, we utilized calcium sulfate (CaSO₄) scale tests, showing a 20× reduction in scale deposition rate than untreated metallic substrates. Descaling tests revealed that SOCAL dramatically decreases scale adhesion, resulting in rapid removal of scale buildup. Our work not only demonstrates a robust methodology for depositing antiscaling SOCAL coatings on metals but also develops design guidelines for the creation of antifouling coatings for alternate applications such as biofouling and high-temperature coking.

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.

Role of trapped air and lubricant in the interactions between fouling and SiO2 nanoparticle surfaces

Both biomimetic superhydrophobic surfaces and biomimetic slippery liquid-infused porous surfaces (SLIPSs) have been developed as potential alternatives for solving the problem of biofouling. Herein, a facile method was used to construct superhydrophobic surfaces and liquid infused porous surfaces on stainless steels for antifouling applications. The nano-structures were formed by electrostatic attraction between polycations and negatively charged SiO₂ nanoparticles, providing a structural basis for superhydrophobic surfaces and liquid infused surfaces. Biofouling testing suggested excellent antifouling performances of the liquid infused porous surfaces by decreasing the adhesion of Chlorella pyrenoidosa by 93% and of Phaeodactylum tricornutum by 71%. The thermodynamic interpretation further indicated that the air layer captured by the superhydrophobic surfaces and the lubricant layer entrapped by the liquid infused porous surfaces played the dominant role in their antifouling performances. The inspiring results might show great potential for liquid infused porous surfaces in antifouling applications.

Designing a Superhydrophobic Surface for Enhanced Atmospheric Corrosion Resistance Based on Coalescence-Induced Droplet Jumping Behavior

Coalescence-induced droplet jumping behavior of superhydrophobic surfaces has attracted increasing attention for condensation heat transfer, antifrosting, self-cleaning, and electrostatic energy harvesting applications. The potential of applying such functionalized behavior for atmospheric corrosion protection, however, is unknown. Herein, we experimentally demonstrate, for the first time, the feasibility of applying coalescence-induced droplet jumping behavior of a superhydrophobic surface for atmospheric corrosion protection. Based on the rational fabrication of two kinds of superhydrophobic surfaces that are advantageous and not advantageous for coalescence-induced droplet jumping behavior, we reveal a novel atmospheric corrosion protection mechanism by studying the correlations of the surface structure, droplet jumping behavior, and atmospheric corrosion resistance of the two surfaces. Our results demonstrate that the superhydrophobic surface with coalescence-induced droplet jumping behavior presents a better atmospheric corrosion resistance than the superhydrophobic surface without coalescence-induced droplet jumping behavior. This is because coalescence-induced droplet jumping behavior of the superhydrophobic surface offers a possible mechanism to switch the droplets from a partial wetting state to the mobile Cassie state, and this switch is critical for facilitating the recovery of the air film trapped in the microstructure of a surface. In particular, the recovered air film enhances the atmospheric corrosion resistance of a superhydrophobic surface due to its barrier-like character. The insights gained from this work not only open a new avenue for designing first-rank anticorrosion materials but also offer new opportunities for understanding the physics of jumping droplets in other promising applications.

Fluorocarbon lubricant impregnated nanoporous oxide for omnicorrosion-resistant stainless steel

Corrosion protection coatings have been required for long-term uses of metallic materials applied in various environments incorporating liquid and/or vapor phase corrosion reactants. In this study, we introduce a fluorocarbon lubricant impregnated nanoporous oxide (FLINO) coating on stainless steel for realizing effective resistances against corrosive media in both liquid and vapor phases. The FLINO layer on stainless steel significantly enhances corrosion resistances with superior durability and self-healing capability. The combination of nanoporous structure and fluorocarbon lubricant layer provides an outstanding atmospheric corrosion resistance, which has been a serious issue to be overcome on corrosion-resistant coatings. Therefore, the FLINO coating exhibiting stable and remarkable corrosion resistance against both liquid and vaporized corrosive media, called omnicorrosion-resistance, gives a new route for the versatile protection of metallic materials in various environments encompassing both underwater and atmospheric applications.

Icephobic performance of one-step silicone-oil-infused slippery coatings: Effects of surface energy, oil and nanoparticle contents

HYPOTHESIS

State-of-the-art superhydrophobic surfaces (SHSs) usually do not function in high humidity and frosty climate conditions. Lubricant-infused slippery surfaces (LISSs) with a homogeneous and ultraslippery surface are expected to be a reliable icephobic technique. Hence, the fabrication of simple and scalable bioinspired LISSs is important for practical applications.

EXPERIMENTS

Durable one-step LISSs consisting of silicone oil and polymer mixtures were fabricated. A grid map based on added oil and silica nanoparticles was developed to tune wettability, morphology, and slippery behavior of surfaces. A similar framework for ice adhesion of lubricant-infused coatings was also presented for the design of optimal icephobic materials.

FINDINGS

LISSs with slight hydrophobicity yield slippery properties, resulting in an order of magnitude lower ice adhesion compared to SHSs. The stable 20-w% silicone-oil-infused slippery coating with slight hydrophobicity and silica nanoparticles was found to be effective in anti-icing. The nanoparticles firmly anchor the oil overlayer and eliminate contamination by drying the surface. The LISSs made of polymers with surface energy ranging from 29 to 31 mJ/m² show the potential to achieve low ice adhesion. As a result, the use of systematic frameworks highlights the role of material parameters. One-production strategy can be broadly used to design icephobic materials.

Enhancement of Corrosion Resistance of Aluminum 7075 Surface through Oil Impregnation for Subsea Application

This study investigated the corrosion resistance of oil impregnated anodic aluminum oxide (AAO) surfaces of aluminum 7075 for subsea application. Although aluminum 7075 has high strength, it is scarcely used in the subsea industry because of its corrosion issue. Some treatment of aluminum 7075 is required for subsea application. In this study not only a plate shape but also a cylindrical shape were investigated because a cylindrical shape is frequently used in the subsea industry for electronic device housing. Contact angles of bare aluminum and oil impregnated AAO surfaces of aluminum 7075 were measured after a salt spray test and a pressure test. The results showed that the contact angle of bare aluminum was considerably decreased after the salt spray test, whereas the oil impregnated AAO surface presented a relatively high contact angle after the salt spray test and the pressure test. These results showed that the corrosion resistance of aluminum 7075 could be enhanced by oil impregnation on the AAO surface, and thus can be utilized in the subsea industry.

Liquid-Infused Structured Titanium Surfaces: Antiadhesive Mechanism to Repel Streptococcus oralis Biofilms

To combat implant-associated infections, there is a need for novel materials which effectively inhibit bacterial biofilm formation. In the present study, the antiadhesive properties of titanium surface functionalization based on the "slippery liquid-infused porous surfaces" (SLIPS) principle were demonstrated and the underlying mechanism was analyzed. The immobilized liquid layer was stable over 13 days of continuous flow in an oral flow chamber system. With increasing flow rates, the surface exhibited a significant reduction in attached biofilm of both the oral initial colonizer  Streptococcus oralis and an oral multispecies biofilm composed of S. oralis, Actinomyces naeslundii, Veillonella dispar, and Porphyromonas gingivalis. Using single cell force spectroscopy, reduced S. oralis adhesion forces on the lubricant layer could be measured. Gene expression patterns in biofilms on SLIPS, on control surfaces, and expression patterns of planktonic cultures were also compared. For this purpose, the genome of S. oralis strain ATCC 9811 was sequenced using PacBio Sequel technology. Even though biofilm cells showed clear changes in gene expression compared to planktonic cells, no differences could be detected between bacteria on SLIPS and on control surfaces. Therefore, it can be concluded that the ability of liquid-infused titanium to repel S. oralis biofilms is mainly due to weakened bacterial adhesion to the underlying liquid interface.

Polymer-Based Marine Antifouling and Fouling Release Surfaces: Strategies for Synthesis and Modification

In marine industries, the accumulation of organic matter and marine organisms on ship hulls and instruments limits performance, requiring frequent maintenance and increasing fuel costs. Current coatings technology to combat this biofouling relies heavily on the use of toxic, biocide-containing paints. These pose a serious threat to marine ecosystems, affecting both target and nontarget organisms. Innovation in the design of polymers offers an excellent platform for the development of alternatives, but the creation of a broad-spectrum, nontoxic material still poses quite a hurdle for researchers. Surface chemistry, physical properties, durability, and attachment scheme have been shown to play a vital role in the construction of a successful coating. This review explores why these characteristics are important and how recent research accounts for them in the design and synthesis of new environmentally benign antifouling and fouling release materials.

Flow-Induced Long-Term Stable Slippery Surfaces

Slippery lubricant-infused surfaces allow easy removal of liquid droplets on surfaces. They consist of textured or porous substrates infiltrated with a chemically compatible lubricant. Capillary forces help to keep the lubricant in place. Slippery surfaces hold promising prospects in applications including drag reduction in pipes or food packages, anticorrosion, anti-biofouling, or anti-icing. However, a critical drawback is that shear forces induced by flow lead to depletion of the lubricant. In this work, a way to overcome the shear-induced lubricant depletion by replenishing the lubricant from the flow of emulsions is presented. The addition of small amounts of positively charged surfactant reduces the charge repulsion between the negatively charged oil droplets contained in the emulsion. Attachment and coalescence of oil droplets from the oil-in-water emulsion at the substrate surface fills the structure with the lubricant. Flow-induced lubrication of textured surfaces can be generalized to a broad range of lubricant-solid combinations using minimal amounts of oil.

Study of Biofilm Growth on Slippery Liquid-Infused Porous Surfaces Made from Fluoropor

Undesired growth of biofilms represents a fundamental problem for all surfaces in long-term contact with aqueous media. Mature biofilms resist most biocide treatments and often are a pathogenic threat. One way to prevent biofilm growth on surfaces is by using slippery liquid-infused porous surfaces (SLIPS). SLIPS consist of a porous substrate which is infused with a lubricant immiscible with the aqueous medium in which the bacteria are suspended. Because of the lubricant, bacteria cannot attach to the substrate surface and thus formation of the biofilm is prevented. For this purpose, we manufactured substrates with different porosity and surface roughness values via UV-initiated free-radical polymerization in Fluoropor. Fluoropor is a class of highly fluorinated bulk-porous polymers with tunable porosity, which we recently introduced. We investigated the growth of the biofilm on the substrates, showing that a reduced surface roughness is beneficial for the reduction of biofilm growth. Samples of low roughness effectively reduced Pseudomonas aeruginosa biofilm growth for 7 days in a flow chamber experiment. The low-roughness samples also become transparent when infused with the lubricant, making such surfaces ideal for real-time observation of biofilm growth by optical examination.

Influence of long-range forces and capillarity on the function of underwater superoleophobic wrinkled surfaces

Underwater superoleophobic surfaces can be considered a particular type of lubricant-infused surface, that have anti-fouling properties by virtue of a trapped water layer that repels oils. However, as their function relies on a water layer being trapped in the surface roughness, it is crucial to understand the factors that determine the layer stability. In this work, the forces that are responsible for the stability of thin liquid films within structured surfaces were quantified, and the conclusions were tested against the performance of wrinkled surfaces as underwater superoleophobic coatings. Here, the system studied was a family of wrinkled surfaces made of hydrophilic poly(4-vinylpyridine) (P4VP), whereby the wrinkle width could be controllably tuned in the range 90 nm to 8000 nm. The van der Waals free energy was quantified and the capillary forces trapping water in the surface micro- and nano-wrinkle structure were estimated. P4VP surfaces with micro-scale wrinkles had underwater superoleophobic properties, and low adhesion to different oils with droplet roll-off angle below 6° ± 1°. Despite the van der Waals free energy of the system pointing to the dewetting of a water film under oil on top of a smooth P4VP film, the wrinkled structure is sufficient to induce a Cassie state with a trapped water layer. The micro-scale wrinkles (average width 4-12 μm) were found to be particularly effective in the trapping of the water in a Cassie non-adhesive state. The P4VP wrinkled surfaces are superamphiphobic, as when they were first infused with oil, and then exposed to a droplet of water under oil, they exhibited superhydrophobic behavior. The P4VP wrinkles have the additional useful feature of being transparent underwater, which makes them useful candidates for the protection of underwater cameras and sensors.

A Lubricant-Sandwiched Coating with Long-Term Stable Anticorrosion Performance

Lubricant-infused surface(s) (LIS) bioinspired by the Nepenthes pitcher plant are receiving enormous attention owing to their excellent hydrophobicity as well as their self-healing ability. Thus, they have been applied as anticorrosion coatings. However, the loss of lubricant mediated by vapor or other liquids deteriorates their functions. Herein, we introduce a lubricant-inserted (sandwiched) microporous triple-layered surface (LIMITS) that prevents the sudden loss of lubricant. The sandwiched lubricant gradually self-secretes toward the surface, resulting in long-term stability even under water. The LIMITS prevented the corrosion of the Fe plate for at least 45 days, which is much superior to a conventional LIS coating. This work opens an avenue for the application of slippery coating materials that are stable under water and will also promote the development of anticorrosion coating in various industries.

Icephobic Behavior of UV-Cured Polymer Networks Incorporated into Slippery Lubricant-Infused Porous Surfaces: Improving SLIPS Durability

Ice accretion causes damage on power generation infrastructure, leading to mechanical failure. Icephobic materials are being researched so that ice buildup on these surfaces will be shed before the weight of the ice causes catastrophic damage. Lubricated materials have imposed the lowest-recorded forces of ice adhesion, and therefore lubricated materials are considered the state-of-the-art in this area. Slippery lubricant-infused porous surfaces (SLIPS) are one type of such materials. SLIPS are initially very effective at repelling ice, but the trapped fluid layer that affords their icephobic properties is easily depleted by repeated icing/deicing cycles, even after one deicing event. UV-cured siloxane resins were infused into SLIPS to observe effects on icephobicity and durability. These UV-cured polymer networks enhanced both the icephobicity and longevity of the SLIPS; values of ice adhesion below 10 kPa were recorded, and appreciable icephobicity was maintained up to 10 icing/deicing cycles.