Fouling-resistant behavior of liquid-infused porous slippery surfaces

Self-healing, antibiofouling and anticorrosion properties enabled by designing polymers with dynamic covalent bonds and responsive linkages

Coating metal structures with a protective material is a popular strategy to prevent their deterioration due to corrosion. However, maintaining the barrier properties of coatings after their mechanical damage is challenging. Herein, we prepared multifunctional coatings with self-healing ability to conserve their anticorrosion performance after damage. The coating was formed by blending synthesized redox-responsive copolymers with the ability to release a corrosion inhibitor upon the onset of corrosion with synthesized self-healing polyurethanes containing disulfide bonds. The corrosion rate of steel substrates coated with a blend is approximately 24 times lower than that of steel coated with only self-healing polyurethane. An exceptional healing efficiency, as high as 95%, is obtained after mechanical damage. The antibiofouling property against bacterial and microalgal attachments on coatings is facilitated by the repellent characteristic of fluorinated segments and the biocidal activity of the inhibitor moieties in the copolymer.

Slippery lubricant-infused silica nanoparticulate film processing for anti-biofouling applications

Microbial biofilm build-up in water distribution systems can pose a risk to human health and pipe material integrity. The impact is more devastating in space stations and to astronauts due to the isolation from necessary replacement parts and medical resources. As a result, there is a need for coatings to be implemented onto the inner region of the pipe to minimize the adherence and growth of biofilms. Lubricant-infused surfaces has been one such interesting material for anti-biofouling applications in which their slippery property promotes repellence to many liquids and thus prevents bacterial adherence. Textured and porous films are suitable substrate candidates to infuse and contain the lubricant. However, there is little investigation in utilizing a nanoparticulate thin film as the substrate material for lubricant infusion. A nanoparticulate film has high porosity within the structure which can promote greater lubricant infusion and retention. The implementation as a thin film structure aids to reduce material consumption and cost. In our study, we utilized a well-studied nanoporous thin film fabricated via layer-by-layer assembly of polycations and colloid silica and then calcination for greater stability. The film was further functionalized to promote fluorinated groups and improve affinity with a fluorinated lubricant. The pristine nanoporous film was characterized to determine its morphology, thickness, wettability, and porosity. The lubricant-infused film was then tested for its lubricant layer stability upon various washing conditions and its performance against bacterial biofilm adherence as a result of its slippery property. Overall, the modified silica nanoparticulate thin film demonstrated potential as a base substrate for lubricant-infused surface fabrication that repelled against ambient aqueous solvents and as an anti-biofouling coating that demonstrated low biofilm coverage and colony forming unit values. Further optimization to improve lubricant retention or incorporation of a secondary function can aid in developing better coatings for biofilm mitigation.

Slippery 3-dimensional porous bioabsorbable membranes with anti-adhesion and bactericidal properties as substitute for vaseline gauze

Vaseline gauze is a common type of wound dressing that consist of absorbent gauze impregnated with white petrolatum. It has excellent anti-adhesive property which can reduce trauma during dressing changes. However, this kind of wound dressing doesn't have bacterial killing property. Thus, a new kind of wound dressing that has anti-adhesive and bactericidal properties is needed urgently. Creating slippery liquid-impregnated porous surfaces (SLIPS) that insensitive to the structure of porous solid are generally viewed as a new anti-adhesion strategy. To expand the potential utility of SLIPS as substitute for vaseline gauze, dual-functional slippery membranes with anti-adhesion and bactericidal properties by using triclosan, vegetable oils and polylactic acid (PLA) were prepared. It's demonstrated that the triclosan-loaded/vegetable oils-infused PLA membranes (T/V-PM) has good cytocompatibility in vitro. Notably, the T/V-PM can gradually release biocide molecule into surrounding aqueous media. Moreover, the T/V-PM can kill planktonic bacterial cells without loss of their antifouling property. The in vivo study revealed that the T/V-PM can prevent the secondary injuries during wound dressing changes. This simple and low-cost strategy can be applied to inhibit blood and bacterial adhesion, and prevent tissue adhesion at the wound site. It's confirmed that the T/V-PM have great potential as substitute for vaseline gauze.

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.

Antibiotic-Impregnated Liquid-Infused Coatings Suppress the Formation of Methicillin-Resistant Staphylococcus aureus Biofilms

Medical device-associated infections are an ongoing problem. Once an implant is infected, bacteria create a complex community on the surface known as a biofilm, protecting the bacterial cells against antibiotics and the immune system. To prevent biofilm formation, several coatings have been engineered to hinder bacterial adhesion or viability. In recent years, liquid-infused surfaces (LISs) have been shown to be effective in repelling bacteria due to the presence of a tethered liquid interface. However, local lubricant loss or temporary local displacement can lead to bacteria penetrating the lubrication layer, which can then attach to the surface, proliferate, and form a biofilm. Biofilm formation on biomedical devices can subsequently disrupt the chemistry tethering the slippery liquid interface, causing the LIS coating to fail completely. To address this concern, we developed a "fail-proof" multifunctional coating through the combination of a LIS with tethered antibiotics. The coatings were tested on a medical-grade stainless steel using contact angle, sliding angle, and Fourier transform infrared spectroscopy. The results confirm the presence of antibiotics while maintaining a stable and slippery liquid interface. The antibiotic liquid-infused surface significantly reduced biofilm formation (97% reduction compared to the control) and was tested against two strains of Staphylococcus aureus, including a methicillin-resistant strain. We also demonstrated that antibiotics remain active and reduce bacteria proliferation after subsequent coating modifications. This multifunctional approach can be applied to other biomaterials and provide not only a fail-safe but a fail-proof strategy for preventing bacteria-associated infections.

A Bioinspired Slippery Surface with Stable Lubricant Impregnation for Efficient Water Harvesting

Inspired by Nepenthes pitcher plants, slippery liquid-infused porous surfaces (SLIPS) have recently attracted increasing attention for directional transport and movement manipulation of water droplets. Nevertheless, infused lubricants are generally instable and easy to deviate from such surfaces during applications, resulting in the lost control on the fog capture and motion of droplets as well as serious risk of water safety. Here, a highly stable SLIPS with improved lubricant storage is developed through the structure design of synergistically constructing regular micro-pincushion and nanoparticles. Notably, on the basis of the microstructure, the presence of nano-architecture shows great contribution to obviously increased capillary force as well as suppressed lubricant loss during water collection. Featuring the stable surface-slippery property, the biomimetic SLIPS displays well maintained dropwise coalescence of water from fog and efficient water harvesting performance. The water collection efficiency is as high as 852 mg cm^-2 h^-1 and is stable within continuous 20 h application. This fundamental illustration of structural synergism can be further applied to construct more new water manipulation and harvesting platforms with stably slippery surfaces/interfaces.

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.

Droplet Morphology and Mobility on Lubricant-Impregnated Surfaces: A Molecular Dynamics Study

Slippery liquid-infused porous surfaces (SLIPS) are gaining remarkable attention and have advanced performance in many fields. Although all SLIPS are related to lubricant-impregnation within nano/microstructures on a surface, they differ in many aspects, such as the morphology of droplets, the state of cloaking, the wetting edge, and the lubricant thickness. Requirements of the droplet morphology on SLIPS might change according to a specific application. A molecular-dynamics-based numerical model that can correctly simulate SLIPS is developed and is validated by comparing against the theoretical predictions for all possible stable states for a given droplet, lubricant, and solid surface. On the basis of this model, a detailed analysis of the equilibrium states is conducted. In particular, we discover that the four possible stable states on SLIPS predicted by theoretical studies can be extended to eight states by considering the effects of lubricant thickness and surface geometry in addition to the interfacial tension and surface wettability. These findings could be used to determine the conditions under which a thermodynamically stable state exists on SLIPS. The dynamic behavior of a nanodroplet on SLIPS is also studied, which provides insight into how a proper increase in the lubricant thickness might increase the sliding velocity. The above findings and developed model are expected to provide significant guidelines for designing SLIPS.