Icephobic Surfaces Research Articles

Moth-Eye Mimicking Solid Slippery Glass Surface with Icephobicity, Transparency, and Self-Healing

Slippery liquid-infused porous surfaces (SLIPSs) have been actively studied to improve the limitations of superhydrophobic (SHP) surfaces, especially the defects of the nonwetting chemical coating layer and the weak mechanical robustness of surface micro/nanostructures. However, the SLIPSs also have several drawbacks including volatilization and leakage of lubricant caused by long-term usage. In this study, we suggest the use of icephobic, highly transparent, and self-healing solid slippery surface to overcome the limitations of both surfaces (SLIPS and SHP) by combining specific biomimetic morphology and intrinsic properties of paraffin wax. A moth-eye mimicking nanopillar structure was prepared instead of a porous structure and was coated with solid paraffin wax for water repellence. Moth-eye structures enable high surface transparency based on antireflective effect, and the paraffin layer can recover from damage due to sunlight exposure. Furthermore, the paraffin coating on the nanopillars provides an air trap, resulting in a low heat transfer rate, increasing freezing time and reducing adhesion strength between the ice droplet and the surface. The heat transfer model was also calculated to elucidate the effects of the nanopillar height and paraffin layer thickness. The antireflection and freezing time of the surfaces are enhanced with increase in nanopillar height. The paraffin layer slightly deteriorates the transmittance but enhances the icephobicity. The solar cell efficiency using a biomimetic solid slippery surface is higher than that of bare glass due to the antireflective effect. This integrated biomimetic solid slippery surface is multifunctional due to its self-cleaning, anti-icing, antireflection, and self-healing properties and may replace SLIPS and SHP surfaces.

Potential anti-icing applications of encapsulated phase change material–embedded coatings; a review

Abstract Icephobic surfaces are highly sought-after materials as there is a need to reduce the catastrophic outcomes of ice formation on outdoor surfaces. Existing anti-icing strategies, including superhydrophobic surfaces (SHPSs) and slippery liquid–infused porous surfaces (SLIPS), are often ineffective against frost formation or have a limited durability. As such, new approaches are required, and the incorporation of phase change materials (PCMs) into polymeric matrices offers a potential means of delaying ice formation and reducing ice adhesion on exposed surfaces. Homogeneously dispersed encapsulated PCMs (EPCMs) of uniform size inside a binder can release high amounts of latent heat and produce local shear stresses on surfaces—due to their volume change—during icing conditions, thereby reducing ice adhesion strength. Furthermore, surface protrusions produced by the EPCMs can also impart hydrophobicity or even superhydophobicity onto a surface to delay ice formation. This contribution reviews recent progress in the development of ECPM-based anti-icing surfaces. We also discuss the advantages and challenges of using PCM materials for anti-icing applications, summarize existing encapsulation methods, and outline the ECPM-based mechanisms that hinder ice formation and lower ice adhesion.

In situ ice growth kinetics on water-repellent coatings under atmospheric icing conditions

Superhydrophobic surfaces represent a promising avenue to mitigate icing on aircraft from micrometric Supercooled Water Droplets (SWD). In the present work, we developed a novel laser-based in situ ice growth monitoring system to investigate, under realistic icing conditions, the role of wettability on the ice growth kinetics and the icephobic performance of water-repellent coatings during SWD ice accretion. This approach records the laser beam displacement and spreading, allowing one to measure ice thickness as well as assess ice microstructural changes in real time during the ice growth. Three surfaces were studied: hydrophilic Ti-6Al-4V alloy, hydrophobic spray coating, and superhydrophobic spray coating. The ice grows instantaneously on the hydrophilic and hydrophobic surfaces as pinned droplets freeze, and ice quickly covers the surface with a continuous layer. On the superhydrophobic sample, droplets bounce before freezing delaying ice nucleation by 26 ± 5 s. In this case, the island-mode growth is driven by hydrophilic droplet-pinning defects in the coating. When ice has formed a continuous layer the growth rate is linear and it increases with increasing hydrophobicity, 28% faster on the superhydrophobic surface compared to the hydrophilic substrate. This new approach highlights the role of wettability during ice accretion and will guide the development of new icephobic surfaces for aeronautics.

Evaluating the effect of processing parameters on the replication quality in the micro compression molding of silicone rubber

ABSTRACT Given the role of micro-nanostructures in producing superhydrophobic and icephobic surfaces and the importance of high-quality replication of these micro-nanostructures in direct replication processes, we evaluated the effect of processing parameters on the superhydrophobicity, icephobicity, and replication quality of silicone rubber surfaces created via micro-compression molding. Molding pressure, mold temperature, curing time, and part thickness were selected as the processing parameters to be assessed. We used a response surface methodology to illustrate the optimal values of the selected processing parameters. Molding pressure and part thickness were the main influencing parameters to attain the superhydrophobicity. In a second set of experiments, we assessed the replication quality of silicone rubber surfaces of variable thickness subjected to different molding pressures. Each part thickness had an optimal molding pressure for obtaining the best replication quality. Surfaces having the highest replication quality also demonstrated the longest freezing delay and confirmed their potential use as anti-icing surfaces. Although all developed superhydrophobic surfaces showed icephobicity, the influence of processing parameters affecting ice adhesion was complex.

Superhydrophobic photothermal icephobic surfaces based on candle soot

Ice accumulation causes various problems in our daily life for human society. The daunting challenges in ice prevention and removal call for novel efficient antiicing strategies. Recently, photothermal materials have gained attention for creating icephobic surfaces owing to their merits of energy conservation and environmental friendliness. However, it is always challenging to get an ideal photothermal material which is cheap, easily fabricating, and highly photothermally efficient. Here, we demonstrate a low-cost, high-efficiency superhydrophobic photothermal surface, uniquely based on inexpensive commonly seen candle soot. It consists of three components: candle soot, silica shell, and polydimethylsiloxane (PDMS) brushes. The candle soot provides hierarchical nano/microstructures and photothermal ability, the silica shell strengthens the hierarchical candle soot, and the grafted low-surface-energy PDMS brushes endow the surface with superhydrophobicity. Upon illumination under 1 sun, the surface temperature can increase by 53 °C, so that no ice can form at an environmental temperature as low as -50 °C and it can also rapidly melt the accumulated frost and ice in 300 s. The superhydrophobicity enables the melted water to slide away immediately, leaving a clean and dry surface. The surface can also self-clean, which further enhances its effectiveness by removing dust and other contaminants which absorb and scatter sunlight. In addition, after oxygen plasma treatment, the surface can restore superhydrophobicity with sunlight illumination. The presented icephobic surface shows great potential and broad impacts owing to its inexpensive component materials, simplicity, ecofriendliness, and high energy efficiency.

Recent Advances in Hydrophobic and Icephobic Surface Treatments of Concrete

In this review, we present a survey on hydrophobic surface treatments of concrete, important protection tools against deterioration and corrosion phenomena. In the frame of a standardized distinction in coatings, pore blockage, and impregnation methods, we highlight the huge variety of compounds and formulations utilized, and the different performances reached in terms of water contact angle, water absorption, chloride penetration, and, rarely reported, anti-icing/icephobic action. Our view covers the spectrum of the surface treatments, but also makes a comparison with hydrophobic bulk modifications of concrete, procedures often utilized as well; further, novel proposals of more sustainable routes are presented. We note that coating and impregnation, preferably when based on polyurethane and silane/siloxane, respectively, appear more effective against water ingress. The achieved wetting character is hydrophobic or, at most, overhydrophobic. Superhydrophobic coatings for concrete have been obtained by embedding nano-powders in hydrophobic emulsions, allowing to add a nanotexture to the preexisting complex roughness of the material. Concrete treated with this type of coating has also recently shown a pronounced icephobic character, a parameter that goes beyond the freeze–thaw characterization usually conducted on cement-based materials.

Thermally Sprayed Coatings: Novel Surface Engineering Strategy Towards Icephobic Solutions.

Surface engineering promotes possibilities to develop sustainable solutions to icing challenges. Durable icephobic solutions are under high interest because the functionality of many surfaces can be limited both over time and in icing conditions. To solve this, one potential approach is to use thermally sprayed polymer or composite coatings with multifunctional properties as a novel surface design method. In thermal spraying, coating materials and structures can be tailored in order to achieve different surface properties, e.g., wetting performance, roughness and protection against several weathering and wearing conditions. These, in turn, are beneficial for excellent icephobic performance and surface durability. The icephobicity of several different surfaces are tested in our icing wind tunnel (IWiT). Here, mixed-glaze ice is accreted from supercooled water droplets and the ice adhesion is measured using a centrifugal adhesion tester (CAT). The present study focuses on the icephobicity of thermally sprayed coatings. In addition, surface-related properties are evaluated in order to illustrate the correlation between the icephobic performance and the surface properties of differently tailored thermally sprayed coatings as well as compared those to other coatings and surfaces.

Reducing Static and Impact Ice Adhesion with a Self-Lubricating Icephobic Coating (SLIC)

Ice accumulation and adhesion can problematically occur on many engineering systems, such as electrical power networks, wind turbines, communication towers, and aircraft. An optional solution to these icing problems is the use of surfaces/coatings with low ice adhesion properties: Icephobic surfaces. Icephobic surfaces/coatings are very beneficial, as they facilitate the removal of ice or retard its formation and do not require the use of any sort of energy. A compact icing research tunnel (CIRT) was employed to measure ice tensile adhesion strength for both impact and static ice on a conventional metal surface (aluminum) and on a Self-Lubricating Icephobic Coating (SLIC) surface. The static ice consisted of deionized water slowly poured over the surface and left to be frozen on the test specimen surface at stationary conditions, while impact ice consisted of droplets of mean volumetric diameter (MVD) of 13 μm impacting the test specimen surface at a velocity of 40 m/s and freezing and accreting dynamically. The results revealed that static ice has an ice tensile adhesion stress higher than that of impact ice for the conditions used, consistent with previous studies. Additionally, a reduction of more than half was observed in ice tensile adhesion stress for SLIC compared to aluminum for both impact and static ice, and this performance stayed consistent even after multiple icing tests on the same sample. The SLIC coating hydrophobicity (roll-off angle and contact angle) also demonstrated resilience to icing and mechanical abrasion, confirming the self-healing properties.

Design Rules for Laser‐Treated Icephobic Metallic Surfaces for Aeronautic Applications

AbstractIce accretion on external aircraft surfaces due to the impact of supercooled water droplets can negatively affect the aerodynamic performance and reduce the operational capability and, therefore, must be prevented. Icephobic coatings capable of reducing the adhesion strength of ice to a surface represent a promising technology to support thermal or mechanical ice protection systems. Icephobicity is similar to hydrophobicity in several aspects and superhydrophobic surfaces embody a straightforward solution to the ice adhesion problem. Short/ultrashort pulsed laser surface treatments are proposed as a viable technology to generate superhydrophobic properties on metallic surfaces. However, it has not yet been verified whether such surfaces are generally icephobic under representative icing conditions. This study investigates the ice adhesion strength on Ti6Al4V, an alloy commonly used for aerospace components, textured by means of direct laser writing, direct laser interference patterning, and laser‐induced periodic surface structures laser sources with pulse durations ranging from nano‐ to femtosecond regimes. A clear relation between the spatial period, the surface microstructure depth, and the ice adhesion strength under different icing conditions is investigated. From these observations, a set of design rules can be defined for superhydrophobic surfaces that are icephobic, too.

Durable ice-lubricating surfaces based on polydimethylsiloxane embedded silicone oil infused silica aerogel

The anti-ice coatings play a key role to save huge social and economic costs required for ice removal from variety of ice accreted structures. Typically, icephobic surfaces are defined by a low ice adhesion strength (τice) of less than 100 kPa, and current developments aim at much lower values (τice < 20 kPa) known as the upper threshold for self-removal of ice. In this direction, lubricant-infused polymers are considered as an effective icephobic coating materials, however, they usually suffer from lubricant runout with ice removal. In this work, we utilized silica aerogels to effectively captivate silicone oil by themselves in the polydimethylsiloxane matrix. As an outcome, our developed films demonstrated extremely low ice adhesion strength (τice < 20 kPa) along with durability for 20 icing/deicing cycles. Furthermore, the use of silica aerogels improved the mechanical strength of the film. This icephobic coating has high transparency (>90%) and can be effectively applied over colored surfaces.

Robust icephobic epoxy coating using maleic anhydride as a crosslinking agent

In severely cold regions, it is very difficult to prevent the formation of ice on solid surfaces, even on superhydrophobic (SH) surfaces. Compared with anti-icing surfaces, icephobic surfaces are more useful in practice. In this work, a traditional epoxy coating was modified by using maleic anhydride (MAH) as a crosslinking agent, in addition to filling a small amount of epoxy resin grafted with fluorine containing chains (FEP). The wettability and the mechanical properties of the modified coating, as well as the adhesive strength of ice on the coating surface and the stability of the icephobic properties of the coating, were systematically studied. The results showed that the modified coating surface became more hydrophobic and the force required to remove ice from the surface was less than that needed for removing on the unmodified coating surface. Furthermore, the modified coating has excellent mechanical properties. After sanding with abrasive paper, the unmodified coating surface is more hydrophilic, whereas the modified coating surface retains its hydrophobicity. X-ray photoelectron spectroscopy (XPS) indicates that compared with crosslinking by traditional polyamides, crosslinking using MAH greatly reduces the number of polar groups on the coating surface. The FEP introduction further reduces the free energy of the coating surface. As a result, the modified epoxy coating exhibits excellent icephobic performance. This study will be helpful for the design of icephobic epoxy coatings for use in practical applications. For example, it may make the de-icing on the underside of trains running in cold regions becomes more easily.

Ice-phobic glass-substrate surfaces coated with polypeptides inspired by antifreeze protein

Abstract The development of ice-phobic glass-substrate surfaces for industrial applications, such as preventing the formation of ice on vehicle windshields, is important. We have previously developed a glass surface coated with a polypeptide whose amino acid sequence is identical to part of an antifreeze protein. For this polypeptide, we showed that the ice adhesion strength was reduced by the coexistence of smooth surface parts exposing hydrophobic amino-acid residues and protrusion surface parts exposing hydrophilic amino-acid residues. In this report, we improve the experimental methods and conduct experiments on the freezing of water disks in steel washers on polypeptide-coated and uncoated surfaces. Under constant cooling surface temperatures, the ice adhesion strength of the coated surfaces decreased by up to 67% when compared with that of uncoated surfaces. Atomic force microscopy observations of the polypeptide-coated glass revealed small and large protrusions on the surface, which were formed by the aggregation of polypeptide. These protrusions and the smooth surface are primarily responsible for the reduced ice adhesion strength. In addition, repeated freezing of the water disks on the surfaces revealed that the coated surfaces could maintain their characteristics for up to 100 repetitions. In addition, the transparency of the glass plate was not changed by the coating. Thus, this polypeptide coating technique should be suitable for improving deicing properties of windshields, traffic lights, and surveillance cameras.

Versatile and Scalable Icephobization of Airspace Composite by Surface Morphology and Chemistry Tuning

The design of the icephobic surface represents an urgent challenge in the field of surface engineering with high application potential. In this work, we proposed the introduction of icephobic surface properties on the technically relevant material—polyetheretherketone/carbon fibers (PEEK/CF) composite. The developed method utilizes the simple and scalable electrochemical etching to induce a significant increase of surface roughness and subsequent chemical grafting for attachment of hydrophobic fluoro-containing chemical moieties. The surface morphology was characterized at different scales, using the profilometer, confocal microscopy, and atomic force microscopy (AFM) measurements. The success of chemical grafting was confirmed using the X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) measurements. The surface properties were tuned to reach the superhydrophobic and Cassie–Baxter water drop states, minimizing the contact area between the drop and sample surface. The icephobic surface properties were tested through the measurements of the time delay of ice formation, precooled drop slipping, and estimation of ice removal force. It was convincingly demonstrated that optimal combination of physical and chemical treatment allows us reaching the icephobic properties on PEEK/CF composite. The main advantages of proposed procedure are its simplicity and scalability, which makes it highly attractive for the practical introduction of icephobic properties in the field of aircraft materials.

Correction: Stress-localized durable icephobic surfaces

Correction for ‘Stress-localized durable icephobic surfaces’ by Peyman Irajizad et al., Mater. Horiz., 2019, 6, 758–766, DOI: 10.1039/C8MH01291A.

Interfacial parameters in correlation with anti-icing performance

ABSTRACT In this work, we investigated the correlation between interfacial parameters with anti-icing performance in terms of adhesive strength. Samples with different morphologies and surface energies ranging from superhydrophilic to superhydrophobic were evaluated in relationship with contact angle, contact angle hysteresis, water – glass work of adhesion and ice-glass work of adhesion. Superhydrophobic surfaces with well-textured nanopillars were fabricated via dry etching process following by low-energy chemical compound coating. In addition, flat quartz substrates with low wetting states achieved through UVO expose method were also examined. The results demonstrated the relationship between interfacial parameters and anti-icing performance with important considerations on surface coating material and wetting state. This insight should lead to an understanding of icing phenomena and the design of icephobic surfaces.

Intelligent Icephobic Surface toward Self-Deicing Capability

Superhydrophobic surfaces show attractive anti-icing properties. However, it remains a challenge for them to achieve icephobicity and ultralow ice adhesion in a humid environment, which is fundamen...

Anti-icing epoxy resin surface modified by spray coating of PTFE Teflon particles for wind turbine blades

Epoxy resins are widely used for the outer surface of wind turbine blades and many other engineering applications. An anti-icing epoxy resin surface was generated by a spray coating of polytetrafluoroethylene (PTFE; commonly known as Teflon) nanoparticles. The Teflon particles with a mean diameter of 300 nm were dispersed in acetone to achieve 5 % weight fraction. The static contact angle and the roll-off angle for deionized water were measured at 154° and below 2° respectively. The ice detachment strength at the temperature of −10 °C and 16 % relative humidity was approximately 30 kPa on average, which was about 2.5 % of the ice detachment strength of an aluminum substrate and was about 20 % of the ice adhesion strength of plain epoxy. This spray coating method has no limit on the application coverage surface area. To demonstrate the scalability of this coating method, a 101.6 mm by 101.6 mm aluminum surface was successfully produced in the laboratory and demonstrated the same superhydrophobic and icephobic surface characteristics as the smaller test surfaces.

Electrospun nanofibre membrane based transparent slippery liquid-infused porous surfaces with icephobic properties

Icephobic surfaces have attracted increasing attention due to their wide ranging application areas from wind and solar energy systems to aviation. Slippery liquid-infused porous surfaces (SLIPS) are being explored for passive ice protection due to their lower ice adhesion strength. In this study, we present a cost-effective and scalable electrospinning technique to produce freestanding nanofibrous polymeric surfaces for the fabrication of transparent icephobic SLIPS. The diameter of the electrospun fibres produced varied from 200 to 400 nm and the membranes had a theoretical porosity of 71.6 ± 4.1%. Furthermore, three different lubricants polychlorotrifluoroethylene oil (PcTFE), silicone oil and liquid paraffin, were used and it was observed that when silicone oil and PcTFE were used as lubricants for SLIPS, they provided high optical transparency (>90%) in the visible light spectrum compared to PVDF-co-HFP itself. All SLIPS were subjected to centrifugal ice adhesion testing which revealed their ice adhesion strengths lower than 1 KPa with significant delay in droplet icing compared to aluminum reference, from 5 up to 41 s. The results indicated that enhanced icephobic properties of electrospun membranes have been clearly demonstrated.

Fabrication of transparent icephobic surfaces with self-reparability: Effect of structuring and thickness of the lubricant-elastomer layer

Biomimetic lubricant-infused slippery surface (LISS) has attracted extensive attention as an alternative to a superhydrophobic surface (SHS) for icephobic applications. In this work, the impact of the material parameters of LISS with a lubricant-elastomer layer on icephobic performance is reported. A layer of polydimethylsiloxane elastomer and silicone oil on smooth and structured polypropylene (PP) surfaces was spin-coated by a simple one-step procedure. Results demonstrate that the ultra-smooth lubricant-elastomer layer (LEL) has an extremely low water contact angle hysteresis. Compared to SHS and smooth surface, the LISSs reduced ice adhesion by an order of magnitude due to its molecular homogeneity, low contact area, and strain mismatch. The LISSs exhibited excellent dynamic mobility at −10 °C, shear stability, evaporation resistance, mechanical robustness, and transparency. Physically damaged LISS can self-repair at 80 °C. The change in structures and LEL thickness of structured PP has little effect on ice adhesion. As the LEL thickness on a smooth PP increases, the ice adhesion decreases. The smooth PP with a thick LEL has very low ice adhesion, indicating that the roughness is not necessary for maintaining the slippery properties. Transparent, stable, anti-dusting, and self-repairing LELs on smooth materials have potential for icephobic applications.

Novel Superhydrophobic Surface with Solar-Absorptive Material for Improved De-Icing Performance.

Ice accretion is detrimental to numerous industries, including infrastructure, power generation, and aviation applications. Currently, some of the leading de-icing technologies utilize a heating source coupled with a superhydrophobic surface. This superhydrophobic surface reduces the power consumption by the heating element. Further power consumption reduction in these systems can be achieved through an increase in passive heat generation through absorption of solar radiation. In this work, a superhydrophobic surface with increased solar radiation absorption is proposed and characterized. An existing icephobic surface based on a polytetrafluoroethylene (PTFE) microstructure was modified through the addition of graphite microparticles. The proposed surface maintains hydrophobic performance nearly identical to the original superhydrophobic coating as demonstrated by contact and roll-off angles within 2.5% of the original. The proposed graphite coating also has an absorptivity coefficient under exposure to solar radiation 35% greater than typical PTFE-based coatings. The proposed coating was subsequently tested in an icing wind tunnel, and showed an 8.5% and 50% decrease in melting time for rime and glaze ice conditions, respectively.