Slippery Liquid-infused Porous Surfaces Research Articles

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.

Design of Lubricant-Infused Surfaces Based on Mussel-Inspired Nanosilica Coatings: Solving Adhesion by Pre-Adhesion.

Slippery liquid-infused porous surfaces (SLIPSs) have attracted wide interest with regard to their excellent liquid repellency properties and broad applications in various fields associated with anti-adhesion. However, the preparation processes depending on the chemical properties of the substrate and the poor stability of the lubricant layer hinder the practical applications. In this work, a facile method to fabricate SLIPSs based on the mussel-inspired polydopamine (PDA)-mediated nanosilica structures is demonstrated. A variety of substrates can be decorated with SLIPSs by successive treatment of PDA-assisted sol-gel process, fluorination, and lubricant filling. The robust uniform and nanotextured silica coating, mediated by the pre-adhered PDA layer, shows enhanced lubricant-locking ability even when subjected to increased evaporation and high shear from flowing water or spinning compared with hierarchical silica rough structures. The obtained SLIPSs exhibit high transparency and excellent resistance against adhesion of liquid/solid contaminants and biofoulings through this pre-adhesion of PDA strategy. The well-defined nanosilica coating of high decoration covering micron-scaled pore walls enables improved durability of the slippery surfaces for antifouling of the porous membrane under pressure-driven filtration and this may be employed as a potential candidate for fouling resistance of porous materials.

Highly Efficient Self-Repairing Slippery Liquid-Infused Surface with Promising Anti-Icing and Anti-Fouling Performance.

Smart slippery liquid-infused porous surfaces (SLIPSs) have aroused remarkable attention owing to tremendous application foreground in biomedical instruments and industry. However, challenges still remain in fabricating durable SLIPSs. In this work, a fast and highly efficient self-repairing slippery surface (SPU-60M) was fabricated based on a polyurethane membrane and silicone oil. By introducing a great quantity of reversible disulfide bonds into the polymer backbone and hydrogen bonds in the polymer interchain, this SLIPS material could be quickly repaired in 15 min with 97.8% healing efficiency. Moreover, the self-healing efficiency could be maintained at 42.75% after the 10th cutting-healing cycle. Notably, SPU-60M showed excellent self-repairing ability not only in an ambient environment but also in an underwater environment and at ultralow temperatures. Besides, the icing delay time (DT) of SPU-60M could be prolonged to 1182 s at -15 °C, and the ice adhesion strength was only 10.33 kPa at -30 °C. In addition, SPU-60M had excellent anti-fouling performance with BSA adsorption of 2.41 μg/cm2 and Escherichia coli CFU counts of 41 × 104. These findings provide a facile way to design highly efficient self-repairing SLIPSs with multifunctionality.

Experimental Investigation on the Wind-driven Runback Motion of Water Droplets over Solid Surfaces with Different Wettabilities

Aircraft icing is widely recognized as one of the most serious weather hazards to flight safety. Specially designed hydro-/ice-phobic coatings are currently undergoing development for aircraft icing mitigation. It was found that hydro-/icephobic coatings would delay the ice accretion iover airframe surfaces so that the impacted supercooled water droplets could be blown away by the airflow from the airframe surface before being frozen into ice. It is of fundamental importance to understand the wind-driven runback behavior of water droplets over surfaces treated with different coatings, since the corresponding knowledge would be very helpful and essential to develop more efficient anti-/de-icing systems for aircraft icing protection. With the rapid development of surface engineering, a series of specially designed surface coatings succeed in icing mitigation using airflow to remove the remained water. While various hydro-/ice-phobic coatings/surfaces have been developed in recent years, the “state-of-the-art” icephobic coatings/surfaces can be generally divided into three categories, i.e., 1). Lotus-leaf-inspired superhydrophobic surfaces (SHS) with micro-/nano-scale surface textures to achieve very high contact angles (typically &gt; 150°); 2). Pitcherplant-inspired slippery liquid infused porous surfaces (SLIPS) with a layer of liquid lubricant (which is immiscible with water) being sandwiched between ice and solid substrate materials; and 3). Icephobic elastic materials/surfaces with deformable structures/surfaces. SHS has a water droplet contact angle (CA) larger than 150° and a sliding angle (SA) less than 10° . SHS always has a hierarchical structure which is similar to the lotus leaf, and water droplets on SHS appear as water beads which can easily roll off the surface by wind or gravity before frozen. Another strategy to reduce ice adhesion strength to a solid surface is to use a layer of liquid lubricant, which is immiscible with water, between ice and the solid surface. The use of such lubricated surfaces was investigated as early as 1960s, and has gained increasing attentions again recently with the introduction of a concept called Slippery Liquid-Infused Porous Surfaces (SLIPS). SLIPS concept is inspired by the Nepenthes pitcher plants, which have evolved highly slippery, liquidinfused micro-textured rim to capture insects. SLIPS surfaces were not only found to be able to suppress ice/frost accretion by effectively removing condensed moisture even in high humidity conditions, but also exhibit at least an order of magnitude lower ice adhesion than most SHS coatings. More recently, elastic materials/surfaces, such as Polydimethylsiloxane or PDMS in short, which would be structurally deformed/altered dynamically upon applying extra mechanical stress, have also been suggested for icing mitigation. Elastic materials display ultra-low adhesion to ice due to their low work of adhesion and liquidlike deformability, while maintaining good mechanical durability due to their solid-like rigidity. It is found that water droplets would not only be more readily rebounding away from the surface after impingement, but also be able to roll away before frozen due to the hydrophobicity of PDMS. Considering the differences in wettabilities and mechanisms of water repellency, it is necessary to have a systematic understanding of how efficient the surfaces are when the aerodynamic force is applied to remove the adhered water droplets. In the present study, a comprehensive experimental campaign was conducted to characterize the transient runback behaviors of wind-driven water droplets over the surfaces of test plates coated with different hydro-/icephobic coatings (i.e., SHS, SLIPS and PDMS). A high-resolution Particle Image Velocimetry (PIV) system was used to achieve quantitative measurements of the velocity field of the airflow around the wind-driven water droplets on the test surfaces with different wettabilities. With the detailed PIV measurements of the airflow field around the runback water droplets and the droplet profiles, the aerodynamic forces and the adhesion forces acting on the water droplets were estimated. While Fig. 1 shows the experimental setup used in the present study, Fig. 2 to Fig. 3 given some of the typical measurement results. More measurement results and comprehensive analysis and discussions will be provided in the full version of this research paper.

Delayed Lubricant Depletion of Slippery Liquid Infused Porous Surfaces Using Precision Nanostructures.

Slippery liquid infused porous surfaces (SLIPS) are an important class of repellent materials, comprising micro/nanotextures infused with a lubricating liquid. Unlike superhydrophobic surfaces, SLIPS do not rely on a stable air-liquid interface and thus can better manage low surface tension fluids, are less susceptible to damage under physical stress, and are able to self-heal. However, these collective properties are only efficient as long as the lubricant remains infused, which has proved challenging. We hypothesized that, in comparison to a nanohole and nanopillar morphology, the "hybrid" morphology of a hole within a nanopillar, namely a nanotube, would be able to retain and redistribute lubricant more effectively, owing to capillary forces trapping a reservoir of lubricant within the tube, while lubricant between tubes can facilitate redistribution to depleted areas. By virtue of recent fabrication advances in spacer defined intrinsic multiple patterning (SDIMP), we fabricated an array of silicon nanotubes and equivalent arrays of nanoholes and nanopillars (pitch, 560 nm; height, 2 μm). After infusing the nanostructures (prerendered hydrophobic) with lubricant Krytox 1525, we probed the lubricant stability under dynamic conditions and correlated the degree of the lubricant film discontinuity to changes in the contact angle hysteresis. As a proof of concept, the durability test, which involved consecutive deposition of droplets onto the surface amounting to 0.5 L, revealed 2-fold and 1.5-fold enhancements of lubricant retention in nanotubes in comparison to nanopillars and nanoholes, respectively, showing a clear trajectory for prolonging the lifetime of a slippery surface.

Drops Sliding on Non-SLIPS Structures.

Inspired by a plant leaf, a slippery liquid-infused porous surface (SLIPS) exhibits attractive nonwetting and self-cleaning abilities. However, rigorous requirements for the infused liquid layer and its inevitable loss limit its practical use. Here, we propose a model structure defined as a non-SLIPS by introducing solid nanostructures covered with a discontinuous lubricant film. This non-SLIPS tuned by solid wettability achieves the excellent self-cleaning feature with a small sliding angle comparable to the counterpart of a typical SLIPS. This sliding angle α* can be further reduced to a saturated plateau by a slight enhancement of hydrophobicity of the solid nanostructures. Interestingly, the sliding velocity remains almost constant for all of these non-SLIPS samples at a given tilt angle, independent of solid wettability. We formulate the slippery mechanism by defining an energy barrier responsible for the sliding initiation on the non-SLIPS. This energy barrier of the non-SLIPS is correlated, with a qualitative agreement, to the molecular adsorption on the solid nanostructures. The antibiological contamination is confirmed for this non-SLIPS, indicating its excellent self-cleaning ability. The findings suggest that the new surfaces, even with the gradual depletion of the infused oil layer, exhibit the nondegradation of the self-cleaning performance.

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.

Liquid Crystal-Infused Porous Polymer Surfaces: A "Slippery" Soft Material Platform for the Naked-Eye Detection and Discrimination of Amphiphilic Species.

We report the design and characterization of liquid crystal (LC)-infused porous polymer membranes that can detect and report on the presence of natural and synthetic amphiphiles in aqueous solution. We demonstrate that thermotropic LCs can be infused into nanoporous polymer membranes to yield LC-infused surfaces that exhibit slippery behaviors in contact with a range of aqueous fluids. In contrast to conventional liquid-infused surfaces (LIS) or slippery liquid-infused porous surfaces (SLIPS) prepared using isotropic oils, aqueous solutions slide over the surfaces of these LC-infused materials at speeds that depend strongly upon the composition of the fluid, including the presence, concentration, or structure of a dissolved surfactant. In general, the sliding times of aqueous droplets on these LC-infused surfaces increase significantly (e.g., from times on the order of seconds to times on the order of minutes) with increasing amphiphile concentration, allowing sliding times to be used to estimate the concentration of the amphiphile. Additional experiments revealed other intrinsic and extrinsic variables or parameters that can be used to further manipulate droplet sliding times and discriminate among amphiphiles of similar structure. Our results are consistent with a physical picture that involves reversible changes in the interfacial orientation of anisotropic LCs mediated by the interfacial adsorption of amphiphiles. These materials thus permit facile "naked-eye" detection and discrimination of amphiphiles in aqueous samples using equipment no more sophisticated than a stopwatch. We demonstrate the potential utility of these LC-infused surfaces for the unaided, naked-eye detection and monitoring of amphiphilic biotoxins in small droplets of fluid extracted directly from cultures of two common bacterial pathogens (Pseudomonas aeruginosa and Staphylococcus aureus). The ability to translate molecular interactions at aqueous/LC interfaces into large and readily observed changes in the sliding times of small aqueous droplets on surfaces could open the door to new applications for antifouling, liquid-infused materials in the context of environmental sensing and other fundamental and applied areas.

Slippery Antifouling Polysiloxane-Polyurea Surfaces with Matrix Self-Healing and Lubricant Self-Replenishing.

The inferior mechanical properties and the difficulty in repairing damaged substrates and lubricant films of slippery liquid-infused porous surfaces significantly hampered their practical applications. To solve this problem, we fabricated a polysiloxane-polyurea slippery elastomer with lubricant self-replenishing and matrix self-healing properties by encapsulating silicone oil into the thermoplastic elastomers. By optimizing the chemical compositions and molecular interactions, the obtained slippery elastomer exhibits unique mechanical properties with a maximum breaking strength of 0.12 MPa, elongation of 1600%, and self-healing efficiency of 98%. Moreover, the lubricant stored in the capsule of the slippery elastomer can be controlled released under mechanical stimulation, further realizing surfaces' self-lubricating and liquid manipulation switching between slippery and pinning states. Furthermore, the textile-reinforced slippery elastomer with superior mechanical strength also exhibited liquid repellency, anti-biofouling, and drag reduction properties. Therefore, this textile-reinforced omniphobic surface with high mechanical property, matrix self-healing, and lubricant self-replenishing property shows a broad application prospect in surface protection, underwater antifouling, and drag reduction.

Slippery surfaces: A decade of progress

Slippery surfaces have received great attention for more than a quarter-century. In particular, during the last decade, interest has increased exponentially, resulting in thousands of articles concerning three types of slippery surfaces: superhydrophobic, superoleophobic, and omniphobic. This review focuses on recent developments and significant findings in naturally inspired slippery surfaces. Superhydrophobicity can be characterized by water droplets beading on a surface at significantly high static contact angles and low contact-angle hystereses. Microscopically rough hydrophobic surfaces could entrap air in their pores, resulting in a portion of a submerged surface with an air–water interface, which is responsible for the slip effect and drag reduction. Suberhydrophobicity enhances the mobility of droplets on lotus leaves for self-cleaning purposes, the so-called lotus effect. Surface hydrophobicity can be advanced to repel low-surface-tension liquids, i.e., become superoleophobic. Another kind of slippery coating is the slippery liquid-infused porous surfaces (SLIPS), which are omniphobic coatings. Certain plants such as the carnivorous Nepenthes pitcher inspired SLIPS. Their interior surfaces have microstructural roughness, which can lock in place an infused lubricating liquid. The lubricant is then utilized as a repellent surface for other liquids or substances such as water, blood, crude oil, ice, insects, and bio-fouling. In this review, we discuss different slippery mechanisms in nature. We also cover recent advances in manufacturing, texturing, and controlling slippery surface at the micro- and nanoscales. We further discuss the performance, sustainability, and longevity of such surfaces under different environmental conditions. Very-recent techniques used to characterize the surfaces are also detailed.

Research Progress on Corrosion Resistance of Magnesium Alloys with Bio-inspired Water-repellent Properties: A Review

Thanks to its excellent mechanical properties, magnesium alloys have many potential applications in the aerospace and other fields. However, failure to adequately solve corrosion problems of magnesium alloy becomes one of the factors restricting its wide use in many industrial fields. Inspired by nature, researchers designed and fabricated bio-inspired water-repellent (superhydrophobic and slippery liquid-infused porous surface) surfaces with special wetting properties by exploring the surface microstructures of plants and animals such as lotus leaf and nepenthes pitcher, exhibiting excellent corrosion-resistant performance. This article summarizes the research progress on corrosion resistance of magnesium alloys with bio-inspired water-repellent properties in recent years. It mainly introduces the corrosion reasons, types of corrosion of magnesium alloys, and the preparation of magnesium alloys with bio-inspired water-repellent properties to improve corrosion resistance. In particular, it is widely used and effective to construct water-repellent and anti-corrosion coating on the surface of magnesium alloy by surface treatment. It is hoped that the research in this review can broaden the application range of magnesium alloys and provide a powerful reference for the future research on corrosion resistance of magnesium alloys.

Construction of ultra-long service life self-cleaning slippery surface on superhydrophobicity functionalized by ATRP treatment

Benefiting from its low surface energy, low surface tension and high efficiency of droplet mobility, Slippery liquid infused porous surfaces (SLIPS) are being applied in the fields like self-cleaning, anti-icing, thermal transfer etc. Nevertheless, the short service life and the complex preparation procedures are still hindering its further practical applications. In this work, with the combination of UV-curing technique and atom transfer radical polymerization (ATRP) treatment, superhydrophobic surface (SHS) with a chemical stability in a corrosive environment and an excellent mechanical resistance is prepared in a facile way. Profiting from the ultra-high affinity between SHS and lubricant oil, as-prepared SLIPS based on SHS exhibited an ultra-long service life. Compared with other commonly used SLIPS, the service life of resultant SLIPS in this work extends 50 times, which can bear a 3000 mL of continuous water droplet washing. As-prepared SLIPS is a promising candidate for the application in self-cleaning.

Corrosion derived lubricant infused surfaces on X65 carbon steel for improved inorganic scaling performance

Slippery Liquid Infused Porous Surfaces (SLIPS) are a relatively new and promising development in the surface engineering world. Bio-inspired with superior omniphobicity and robustness, SLIPS have enjoyed success in several scientific applications, spanning multiple industries from the marine environment to the medical field. Inorganic fouling is one such challenge SLIPS have managed to overcome by disrupting both the deposition and adhesion mechanics of scale. To date, the primary focus has been on adapting stainless steels while more prevalent pipeline materials, such as carbon steel, have been overlooked. Here a unique and simple SLIPS system has been fabricated from X65 carbon steel, with the potential for creation of a SLIPS system in situ. Utilizing the topographical features of an FeCO3 layer derived from CO2 corrosion, two SLIPS, one with perfluorinated Krytox oil and another with 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide have been tested. The SLIPS have been validated with prevailing models in SLIPS design literature and shed further insight into how this is determined experimentally. This SLIPS combination spares the use of a functionalization layer between the substrate/lubricant interface and displays enhanced anti-fouling capabilities in a calcium carbonate (CaCO3) scaling brine.

Novel corrosion-resistant behavior and mechanism of a biomimetic surface with switchable wettability on Mg alloy

Enlightened by anti-wetting living creature surfaces in nature, the superhydrophobic surface (SHS) and slippery liquid-infused porous surface (SLIPS) have been constructed on metal materials for solving engineering problems. In this research, we design a switchable surface between the SHS and SLIPS on Mg alloy to improve corrosion resistance and provide different water-repellent properties. The SHS and SLIPS are fabricated based on a laser-ablated polydimethylsiloxane@Al2O3@Fe2O3 coating (PAFC). After laser processing, the irradiated PAFC consists of micro/nanostructured texture resulting in excellent superhydrophobicity. The SLIPS is fabricated by filling the lubricant into the laser-structured texture of the SHS. Then, the surface can be easily switched between the SHS and SLIPS by alcohol washing and lubricant-infusion. The non-irradiated PAFC acts as a superior and durable corrosion barrier. Notably, the switchable surface exhibits an excellent anti-corrosion ability (with large impedance modulus at 10−2 Hz about 1011 Ω cm2) in both surface states, which does not have any degradation after being immersed in 3.5 wt% NaCl aqueous solution for 60 days. The SHS and SLIPS have durable air and lubricant layers, respectively, repelling the corrosive species during the immersion test. Simultaneously, the SHS and SLIPS can delay corrosion at an artificial defect area. The SLIPS performs better in the above abilities than the SHS owing to the lubricant layer's stability and self-healing property. The SHS with droplet rolling mode has better droplet transportability, water shielding ability, and self-cleaning ability than those of the SLIPS with droplet sliding mode in dealing with dynamic droplets. Meaningfully, the surface with switchable wettability exhibits long-term corrosion protection and promises a wide range of application prospects of metals such as anti-icing, drag reduction, anti-fouling, etc.

Ice-resistant surface with three dimensional spherical halloysite aerogel: Construction and anti-icing mechanism

A novel 3D microsphere fabricated with halloysite nanotubes was reported in our previous work. The hollow tubular structure in nano-scale of halloysite and the hollow structure in micro-scale of microsphere have attracted our attention. In this paper, phase change materials (methylmyristate and n-dodecane) were loaded in the spaces for the construction of anti-icing surface, and the related behavior and mechanism were investigation. The anti-icing performance of slippery liquid-infused porous surfaces (SLIPSs) were characterized by ice adhesion strength, freezing temperature and ice nucleation rate. The results showed that the phase change materials loaded in anti-icing coating eliminated the possibility of water vapor condensation in porous structure, greatly reduced the probability of nucleation on a concave surface, thus showed better anti-icing effect. Phase change materials play an important role in supercooling, effectively increasing the substrate temperature by 5.4 °C. Phase change anti-icing coating is a kind of functional material with great development potential.

Lubricant-Infused Surfaces for Low-Surface-Tension Fluids: The Extent of Lubricant Miscibility.

Lubricant-infused surfaces (LISs) and slippery liquid-infused porous surfaces (SLIPSs) have shown remarkable success in repelling low-surface-tension fluids. The atomically smooth, defect-free slippery surface leads to reduced droplet pinning and omniphobicity. However, the presence of a lubricant introduces liquid-liquid interactions with the working fluid. The commonly utilized lubricants for LISs and SLIPSs, although immiscible with water, show various degrees of miscibility with organic polar and nonpolar working fluids. Here, we rigorously investigate the extent of miscibility by considering a wide range of liquid-vapor surface tensions (12-73 mN/m) and different categories of lubricants having a range of viscosities (5-2700 cSt). Using high-fidelity analytical chemistry techniques including X-ray photoelectron spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and two-dimensional gas chromatography, we quantify lubricant miscibility to parts per billion accuracy. Furthermore, we quantify lubricant concentrations in the collected condensate obtained from prolonged condensation experiments with ethanol and hexane to delineate mixing and shear-based lubricant drainage mechanisms and to predict the lifetime of LISs and SLIPSs. Our work not only elucidates the effect of lubricant properties on miscibility with various fluids but also develops guidelines for developing stable and robust LISs and SLIPSs.

Fabrication of slippery liquid-infused porous surfaces for anti-fouling applications

Lubricant-infused textured surfaces have gained much attention as liquid-repellent surfaces owing to high surface stability compared to their superhydrophobic counterparts. In this study, polydimethylsiloxane (PDMS) micro-structures (width: 20 μm, height: 80 μm), were fabricated using soft lithography. Effects of micro-structural geometry, including pillar-type (pillar, discrete ridge) and hole-type (hole, continuous ridge, circular rings with eight stripe supporters), on infiltration capability of the lubricants with different viscosity (Krytox-103; η: 0.131 Pa.s, Krytox-105; η: 0.737 Pa.s, paraffin oil; η: 0.112 Pa.s) were investigated. Partial infiltration was observed on the pillar-type micro-structures, while more completed infiltration was obtained on the hole-type micro-structures. More viscous Krytox-105 resulted in completed infiltration for all micro-structures, thus creating a slippery liquid-infused porous surface (SLIPS). The best SLIPS, signified by a low sliding angle and a fast speed of water droplet, prepared from the hole pattern infused with Krytox-105 exhibited good anti-fouling performance against chlorophyll and milk yogurt.

An engineering-oriented approach to construct rough micro/nano-structures for anticorrosion and antifouling application

Slippery liquid-infused porous surfaces (SLIPS) have attracted considerable attention because of their multiple beneficial applications. In this report, styrene-butadiene-styrene triblock copolymer (SBS) and SBS-SiO2 films with 3D interconnected net-like structures were constructed via a simple solution blow spinning method. The original films exhibited excellent hydrophobicity with a contact angle of 145°, after infiltration with the lubricant, the contact angle of SLIPS was reduced to 110°. The antifouling and anticorrosion performance of the hydrophobic surfaces and SLIPS were also studied. The hydrophobic surfaces showed inferior antifouling and anticorrosion performance because of the large pores in the films, significantly, the lubricant-infused surface demonstrated dramatically improved antifouling and anticorrosion performance. More interestingly, compared with a silicone oil-infused surface, the perfluoropolyether oil-infused surface displayed durable anticorrosion properties over increased immersion durations. The failure mechanism of lubricants was explored. The combined anticorrosion and antifouling capability of the constructed microstructure has excellent potential application in marine environments.

Corrosion behavior of a slippery liquid infused porous surface on anodized stainless steel

In this work we present fabrication of slippery liquid infused porous surface (SLIPS) for anodized stainless steel AISI 316L. First, a porous sponge-like oxide layer was grown that subsequently was functionalized with perfluorinated molecules and finally infused with fluorinated Krytox oil. Morphology, composition analysis and wettability (also after corrosion testing) were characterized. Furthermore, corrosion behavior was studied with potentiodynamic polarization curves in 0.1 M H2SO4 and 0.1 M NaCl electrolytes. Our results demonstrate that the SLIPS coating protects the underlying material from corrosion, and the self-healing properties of the oil layer allow to recover localized damage during corrosion experiments.

Citrus-peel-like durable slippery surfaces

• A citrus-peel-like micro-cavity structure for stability enhancement of SLIPS. • A droplet manipulation technique joining advantages of active and passive methods. • A versatile platform for various applications like biological/chemical reactions. We present a citrus-peel-like micro-cavity structure for the design of durable Slippery Liquid-Infused Porous Surfaces (SLIPSs). Owing to the re-entrant and enclosed nature of micro-cavity, lubricant oils can be stabilized by mitigating mass loss resulting from liquid displacement and shear drainage, respectively. Citrus-peel-like micro-cavity SLIPS displays two orders of magnitude enhancement in durability in the droplet-sliding test when compared with micro-pillar SLIPS and smooth lubricant surface. We demonstrated precise droplet manipulation without liquid loss and cross-contamination by harnessing the Marangoni effect with photo-thermal control. Cavity-smooth SLIPS with large adhesion contrast was patterned to initiate multiple droplet coalescences for on-demand neutralization reaction. The citrus-peel-like micro-cavity SLIPS would be beneficial to various applications, such as multi-step chemical reactions and bio-detections that require loss-free, contamination-free, and programmable droplet manipulation.