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

Abstract

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.

Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

“…The addition of a lubricant to form a SLIPS coating drastically reduces the adhesion of ice by more than one order of magnitude compared to the superhydrophobic substrate (by decoupling the ice formation from the solid substrate). The measured ice adhesion strength on the transparent SLIPS coating (10 ± 7 kPa) is in excellent agreement with our previous results on SLIPS coatings on aluminium 21 , suggesting that the surface properties are governed by the lubricant layer and not the solid substrate itself.…”

“…The strong adhesion of ice to most common surfaces, causing safety and economic issues in any technology subjected to subzero environments, is another example where the direct contact of the material with the substrate is the principal cause for its detrimental effects. We recently demonstrated that SLIPS coatings based on highly textured polypyrrole drastically lower strength of ice adhesion to aluminium substrates 21 . Of further importance is the ability to impart transparency to such icerepellent coatings.…”

“…Of further importance is the ability to impart transparency to such icerepellent coatings. Figure 3g compares the adhesion strength of ice (measured at À 40°C using a custom ice adhesion setup adapted from literature) 21,40 for different glass substrates. The strong adhesion of ice to hydrophilic glass (1318 ± 63 kPa) decreases with fluorination of the surface but is still substantial (743±334 kPa).…”

“…To maintain stable repellency, such a surface needs to be optimized in a way that the lubricant layer is not displaced from the solid's surface: if the free energy of the solid/lubricant/liquid system is minimal for the situation where the test liquid resides on the lubricant layer without replacing it, the liquid/liquid interface effectively eliminates pinning points, leading to superrepellent surfaces with extremely low sliding angles-even for liquids with very low surface tensions. Additionally, the fluid nature of the interface possesses self-healing characteristics, allows for remarkable pressure-stability 19 and has been shown to effectively prevent the attachment of bacteria 20 and ice 21 , thus overcoming many of the challenges of conventional repellent surfaces.…”

“…In initial attempts, perfluorinated lubricants were wicked into porous Teflon membranes that provided both matching fluorinated surface functionalities as well as a nanoporous confinement. 19 Additionally, chemically functionalized micron-scale roughness features prepared by conventional and soft lithography 19,20,22,23 , electrodeposition of polypyrrole nanostructures 21 and sol-gel derived aluminium oxide nanostructures 24,25 have recently been successfully employed as structured solids for lubricant infiltration.…”