Liquid-infused Porous Surfaces Research Articles

Continuous Fabrication of Slippery Liquid-Infused Coatings on Rolls of Flexible Materials

We report continuous, spray-based methods for the fabrication of antifouling “slippery” liquid-infused porous surfaces (SLIPS) on rolls or sheets of thin, flexible materials relevant in a broad range of consumer and industrial applications. Our approach is based on the simultaneous spraying of two reactive polymers and leads to uniform and conformal coatings with (i) useful levels of nano- and microscale porosity and (ii) levels of residual azlactone reactivity that enable the facile introduction of hydrophobic character needed to infuse and retain lubricating oils. This approach can be used to fabricate transparent and mechanically robust SLIPS-based materials that resist fouling by a broad range of fluids and gels, including food-based substances, on rolls of polymer films and foils commonly used to design consumer packaging. These spray-on methods are compatible with continuous (e.g., roll-to-roll) processing approaches used in many commercial and industrial settings. We demonstrate proof of concept of this continuous approach to SLIPS fabrication using a benchtop roll-to-roll setup to coat meter-scale lengths of flexible plastic film. SLIPS-coated film produced using this roll-to-roll approach was then used to design models of flexible food packaging (e.g., transparent bags or sachets), containers, and adhesive “SLIPS-strips” that can be affixed manually to secondary surfaces to impart temporary nonadhesive properties. The approaches reported here enable fabrication of antifouling materials on scales and in forms that would be difficult to achieve using many existing methods for the design of SLIPS and open the door to additional potential practical applications of liquid-infused materials.

Fabrication of Slippery Liquid-Infused Coatings in Flexible Narrow-Bore Tubing.

We report a layer-by-layer suction-and-flow approach that enables the fabrication of polymer-based "slippery" liquid-infused porous surfaces (SLIPS) in the confined luminal spaces of flexible, narrow-bore tubing. These SLIPS-coated tubes can prevent or strongly reduce surface fouling after prolonged contact, storage, or flow of a broad range of complex fluids and viscoelastic materials, including many that are relevant in the contexts of medical devices (e.g., blood and urine), food processing (beverages and fluids), and other commercial and industrial applications. The robust and mechanically compliant nature of the nanoporous coating used to host the lubricating oil phase allows these coated tubes to be bent, flexed, and coiled repeatedly without affecting their inherent slippery and antifouling behaviors. Our results also show that SLIPS-coated tubes can prevent the formation of bacterial biofilms after prolonged and repeated flow-based exposure to the human pathogen Staphylococcus aureus and that the anti-biofouling properties of these coated tubes can be further improved or prolonged by coupling this approach with strategies that permit the sustained release of broad-spectrum antimicrobial agents. The suction-and-flow approach used here enables the application of slippery coatings in the confined luminal spaces of narrow-bore tubing that are difficult to access using several other methods for the fabrication of liquid-infused coatings and can be applied to tubing of arbitrary length and diameter. We anticipate that the materials and approaches reported here will prove useful for reducing or preventing biofouling, process fouling, and the clogging or occlusion of tubing in a wide range of consumer, industrial, and healthcare-oriented applications.

Evaluation of the Durability of Slippery, Liquid-Infused Porous Surfaces in Different Aggressive Environments: Influence of the Chemical-Physical Properties of Lubricants

Liquid-repellent surfaces have been extensively investigated due to their potential application in several fields. Superhydrophobic surfaces achieve outstanding water repellence, however their limited durability in severe operational conditions hinders their large-scale application. The Slippery, Liquid-Infused Porous Surface (SLIPS) approach solves many of the durability problems shown by superhydrophobic surfaces due to the presence of an infused liquid layer. Moreover, SLIPS show enhanced repellence towards low surface tension liquids that superhydrophobic surfaces cannot repel. In this perspective, SLIPS assume significant potential for application in harsh environments; however, a systematic evaluation of their durability in different conditions is still lacking in the literature. In this work, we report the fabrication of SLIPS based on a ceramic porous layer infused with different lubricants, namely perfluoropolyethers with variable viscosity and n-hexadecane; we investigate the durability of these surfaces by monitoring the evolution of their wetting behavior after exposure to severe environmental conditions like UV irradiation, chemically aggressive solutions (acidic, alkaline, and saline), and abrasion. Chemical composition and viscosity of the infused liquids prove decisive in determining SLIPS durability; especially highly viscous infused liquids deliver enhanced resistance to abrasion stress and chemical attack, making them candidates for applicable, long-lasting liquid-repellent surfaces.

Slippery Liquid-Attached Surface for Robust Biofouling Resistance.

Materials for biodevices and bioimplants commonly suffer from unwanted but unavoidable biofouling problems due to the nonspecific adhesion of proteins, cells, or bacteria. Chemical coating or physical strategies for reducing biofouling have been pursued, yet highly robust antibiofouling surfaces that can persistently resist contamination in biological environments are still lacking. In this study, we developed a facile method to fabricate a highly robust slippery and antibiofouling surface by conjugating a liquid-like polymer layer to a substrate. This slippery liquid-attached (SLA) surface was created via a one-step equilibration reaction by tethering methoxy-terminated polydimethylsiloxane (PDMS-OCH3) polymer brushes onto a substrate to form a transparent "liquid-like" layer. The SLA surface exhibited excellent sliding behaviors toward a wide range of liquids and small particles and antibiofouling properties against the long-term adhesion of small biomolecules, proteins, cells, and bacteria. Moreover, in contrast to superomniphobic surfaces and liquid-infused porous surfaces (SLIPS) requiring micro/nanostructures, the SLA layer could be obtained on smooth surfaces and maintain its biofouling resistance under abrasion with persistent stability. Our study offers a simple method to functionalize surfaces with robust slippery and antibiofouling properties, which is promising for potential applications including medical implants and biodevices.

Application of anti-icing coating based on adsorption of functional substances by microporous sphere

The occurrence of ice accretion on cold surfaces such as airplanes, power lines and wind turbines can cause various degrees of damage such as flight failure and power outage. Therefore, the reduction of ice adhesion is of great significance and widen application in aviation field. Based on the research status of anti-icing liquid-infused porous surfaces (LIPS) materials, this work attempts to use high specific surface area microporous silica as the carrier to adsorb a large content of functional substances with properties of lubricity and moisture retention, such as silicone oil and polyethylene glycol, and elastic polydimethylsiloxane (PDMS) crosslink polymer was selected as the substrate system. The functional substances are uniformly mixed in different proportions to construct different functional surfaces, which can form an oil/water lubricating layer interface between the cold air and the solid surface to reduce the ice adhesion strength. The functional coating in this work has a certain delaying frosting ability compared with uncoated aluminum plate and pure silicone rubber material in the low temperature environment of −10 °C to −15 °C. By testing the shear force between the ice and the cold surface, the ice adhesion strength on the functional substance dispersed material compared to the pure silicone rubber material can be reduced by 1/3 to 1/5, and can be reduced by 1/5 to 1/8 compared to the aluminum plate. It has a good low ice adhesion strength effect and can be used as anti-icing materials potentially.

Liquid-Infused Nanostructured Surfaces with Extreme Anti-Ice and Anti-Frost Performance

Ice-repellent coatings can have significant impact on global energy savings and improving safety in many infrastructures, transportation, and cooling systems. Recent efforts for developing ice-phobic surfaces have been mostly devoted to utilizing lotus-leaf-inspired superhydrophobic surfaces, yet these surfaces fail in high-humidity conditions due to water condensation and frost formation and even lead to increased ice adhesion due to a large surface area. We report a radically different type of ice-repellent material based on slippery, liquid-infused porous surfaces (SLIPS), where a stable, ultrasmooth, low-hysteresis lubricant overlayer is maintained by infusing a water-immiscible liquid into a nanostructured surface chemically functionalized to have a high affinity to the infiltrated liquid and lock it in place. We develop a direct fabrication method of SLIPS on industrially relevant metals, particularly aluminum, one of the most widely used lightweight structural materials. We demonstrate that SLIPS-coated Al surfaces not only suppress ice/frost accretion by effectively removing condensed moisture but also exhibit at least an order of magnitude lower ice adhesion than state-of-the-art materials. On the basis of a theoretical analysis followed by extensive icing/deicing experiments, we discuss special advantages of SLIPS as ice-repellent surfaces: highly reduced sliding droplet sizes resulting from the extremely low contact angle hysteresis. We show that our surfaces remain essentially frost-free in which any conventional materials accumulate ice. These results indicate that SLIPS is a promising candidate for developing robust anti-icing materials for broad applications, such as refrigeration, aviation, roofs, wires, outdoor signs, railings, and wind turbines.