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Highlights • Durable superhydrophobic coating was fabricated via a facile spray method. • The ice adhesive strength was one order of magnitude lower for coated concrete. • A simplified theoretical model was built for coated and uncoated concrete for the first time. Abstract Road icing has brought huge potential safety hazards and hundreds of millions of losses every year. However studies for anti-icing or de-icing coatings on concrete are still rare due to the special features of concrete surfaces. Here superhydrophobic coating was performed on concrete via spray method and the icephobicity was studied experimentally and theoretically. The low ice adhesive strength and good durability of sprayed coatings represent the potential for icephobic concrete and our theoretical model provides effective route for the design of icephobic concrete. [ABSTRACT FROM AUTHOR]

Ice-building up on the leading edge of wings and other surfaces exposed to icing atmospheric conditions can negatively influence the aerodynamic performances of aircrafts. In the past, research activities focused on understanding icing phenomena and finding effective countermeasures. Efforts have been dedicated to creating coatings capable of reducing the adhesion strength of ice to a surface. Nevertheless, coatings still lack functional stability, and their application can be harmful to health and the environment. Pulsed laser surface treatments have been proven as a viable technology to induce icephobicity on metallic surfaces. However, a study aimed to find the most effective microstructures for reducing ice adhesion still needs to be carried out. This study investigates the variation of the ice adhesion strength of micro-textured aluminum surfaces treated using laser-based methods. The icephobic performance is tested in an icing wind tunnel, simulating realistic icing conditions. Finally, it is shown that optimum surface textures lead to a reduction of the ice adhesion strength from originally 57 kPa down to 6 kPa, corresponding to a relative reduction of ~90%. Consequently, these new insights will be of great importance in the development of functionalized surfaces, permitting an innovative approach to prevent the icing of aluminum components.

Ice accumulation on aerodynamic surfaces is a well-known aspect in various industries, including wind turbines. Many solutions have been developed for several years to deal with this problem, but until now no suitable and energy-sufficient method available for industrial applications has been found. A potential solution is using hydrophobic and/or icephobic coatings, which would allow one to reduce ice adhesion to surfaces. In this study, modifications of a gelcoat based on unsaturated polyester resin with in-house synthesized polysiloxanes dual-functionalized with allyl glycidyl ether (AGE) and hexyl (HEX) or octyl (OCT) groups were used. Most of the chemical modifications used resulted in an increase in surface hydrophobicity (an increase in water contact angle and a decrease in contact angle hysteresis) and an improvement in icephobicity - a reduction in ice adhesion. The lowest ice adhesion achieved a value equal to 221 kPa (the decrease in ice adhesion was 36 % compared to the unmodified surface). The highest water contact angle exhibited a value of 96 °C. Furthermore, correlations were observed between roughness/wettability and ice adhesion: as roughness and wettability decrease, ice adhesion is reduced. The study also determined the durability of the produced surfaces after 100 icing/deicing cycles and the zeta potential surface. • The addition of organosilicon compounds having non-polar alkyl groups results in an increase in the hydrophobicity. • Chemical modification with functionalized polysiloxanes caused a decrease in ice adhesion. • A trend was observed that as the water contact angle increases and the roughness decreases, ice adhesion decreases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrophobic concrete specimens were created by top-treatment with a DCE solution. • The hydrophobic concrete specimens have contact angles greater than 90°. • Ice-concrete adhesion was measured using a customized direct shear apparatus. • The hydrophobic concrete specimens show more than 83% reduction in ice adhesion. Ice when formed on structural materials exhibits strong bonds, which poses a major challenge to many industries. To remove the ice, the creation of hydrophobic surfaces is used as a passive ice removal technique by reducing ice adhesion. Concrete surfaces treated by Pavix Dual Crystallization Engineered (DCE) material show strong water-repelling characteristics. However, the effect of such treatment on ice adhesion is yet to be studied. To quantify this effect, a series of direct shear tests were performed on concrete specimens with the top surface treated with a Pavix DCE material. TxDOT standard Class S concrete was used as control concrete and mixed at two water-cement ratios, 0.45 and 0.43. Ice-adhesion shear tests were performed on control and DCE-treated concrete disks using a customized direct shear test device at two controlled sub-freezing temperatures, −1 °C and −10 °C. In addition, water-repellent properties and contact angle were measured using a tensiometer under static and receding conditions. Results show reductions of more than 83% in ice adhesion of ice adhesion and more than 98-degree contact angles for DCE-treated concrete specimens. The measured results quantify the anti-icing benefit of DCE treatment and provide insights into understanding the anti-icing mechanism of the treated concrete. [ABSTRACT FROM AUTHOR]

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.

Formation and accretion of ice on the leading edge surface of aircrafts wings may lead to disasters. The current de-icing system for aircraft will build up weight, increase energy consumption and add complexity to the aircraft systems. Development of icephobic coatings is a potential solution to prevent ice formation and/or reduce accretion on the critical surface of aircraft. Icephobic coatings based on poly(dimethylsiloxane) (PDMS) with modification by fluorosilane and incorporation of silica nanoparticles have been fabricated. The hydrophobicity of the coatings has been measured in normal conditions with atmospheric pressure and room temperature, showing improvement of hydrophobicity by the fluorination of PDMS and incorporation of silica nanoparticles. The water droplet icing behaviour shows better anti-icing performance for fluorinated PDMS (F-PDMS)/silica coatings with a rough surface. The ice adhesion strength test results show that F-PDMS coatings without silica nanoparticles have lower ice adhesion strength implying better de-icing performance. The wettability of the coatings was also measured at reduced pressure and temperature, to study the mechanism of higher ice adhesion strength of F-PDMS/silica coatings comparing with F-PDMS based coatings. For the design and fabrication of icephobic coatings, compromise on the roughness induced hydrophobicity may become a critical requirement to avoid mechanical interlock between the ice and the rough surface. [ABSTRACT FROM AUTHOR]

Abstract: Superhydrophobic surfaces have been fabricated on flexible fluorinated ethylene propylene (FEP) foils using nanoimprint lithography (NIL) and roughening by plasma etching. The combination of these two techniques results in hierarchical structures and superhydrophobic properties. The icephobic behavior of the surfaces has been studied with measurements of the freezing delay time (FDT) of water droplets on cooled surfaces. It is demonstrated in this paper that the variability of the FDT values is due to the electrostatic surface potential Vs. The impact of this parameter is explored and it is shown that the delay of freezing increases when the surface potential decreases from 0 to −500 V, and decreases for lower surface potentials. This decrease is related to the saturation effect of contact angle, which is well known in electrowetting literature. Contact angles analysis confirms that this saturation effect occurs around −500 V in the present experimental case. The effect of potential surface polarity is also discussed. By optimizing surface potentials of FEP hierarchical structures, it is possible to obtain FDT higher than 40 min at −15 °C. [ABSTRACT FROM AUTHOR]

The durability of the superhydrophobic coatings is an important factor in the lifetime of a coating under extreme environmental conditions. In this study, a superhydrophobic surface was developed by using low pressure plasma polymerized HMDSO coatings on an anodized aluminum surface. The stability of coating was studied under accelerated aging conditions such as several icing/de-icing cycles, UV degradation, immersion in distilled water as well as corrosion. It was found that the developed surface can keep its superhydrophobicity (contact angle ~156°) as well as its icephobic properties even after up to 15 icing/de-icing cycles. It was also observed that the coating has a relatively good stability against UV degradation. In addition, the superhydrophobic surface can keep hydrophobic properties after 1000 h immersion in distilled water. Finally, the superhydrophobic plasma polymerized HMDSO coating also provides anti-corrosion protection for the aluminum substrate. [ABSTRACT FROM AUTHOR]

The deposition of ice, snow, pollution or their mixtures on the surface of outdoor insulators may severely affect their performance, resulting in electrical and or mechanical failures. Various preventative methods are used to minimize the problems of ice and pollution build up on the surface of outdoor insulators. In the last few decades, advanced coatings have been developed for better performance of outdoor insulators in contaminated and freezing environments. These advanced coatings offer the advantage of low wettability, high thermal and ultraviolet resistance, self-cleaning, self-healing, low ice adhesion strength and delayed freezing time. It is believed that these benefits will not only increase the reliability of transmission systems but may also reduce the capital cost of transmission infrastructure. This paper presents a detailed review on the properties and applications of superhydrophobic coatings in outdoor high voltage insulation. This review can be beneficial to scientists and engineers in evaluating the performance and durability of superhydrophobic coatings in polluted and freezing conditions. It also highlights the need for standardized tests and procedures for better understanding the behavior of superhydrophobic coatings in different environments and their long-term durability. [ABSTRACT FROM AUTHOR]

Surface icing almost invariably derives from the precursory step of liquid water encountering the surface. Thus, slippery liquid infused porous surfaces, SLIPS, must possess steady wetting durability, and lubricant stability to function as a reliable hydro−/icephobic surface design especially in outdoor applications. Additionally, they should maintain their phobic performance under shear forces, and possess low sliding friction to act as a slippery, multirepellent surfaces. These characteristics are needed in variable applications ranging from moving and rotating blades to steady surfaces, operating in altering climate conditions. More profound durability testing is needed to examine the loss of surface functionality when the lubricant is depleted from the structure via various routes. In addition, the durability tests should be designed to serve the application-related purposes and thus, to reveal performance differences between slippery surfaces for further analysis and targeted end-use development. Here, we tested the wetting durability and stability of SLIPS with multicycle Wilhelmy plate by dipping the surfaces multiple times in water bath. Additionally, we examined the effects of centrifugal and friction-based shear stress to investigate the lubricant depletion from the structure. Tests that measure the durability and the stability of SLIPS designs are in great need in further developing functional slippery surfaces for real outdoor application coatings which encounter environmental stresses, e.g., wetting and icing. Acknowledging the material differences under specific stresses will guide designing the slippery surfaces towards more specific and functionable end-use applications. • Slippery surfaces have unique properties based on material pairs used. • Thermal expansion of porous solid material influences lubricant depletion. • Forced wetting still challenging for lubricant stabilty. [ABSTRACT FROM AUTHOR]

Fluorinated polysiloxanes with different grafting densities of fluorinated groups were synthesized via hydrosilylation reaction between polymethylhydrosiloxane and tridecafluorooctyl methacrylate (13FMA). By further introduction of vinyltriethoxysilane (VTES), the produced polymers underwent self-crosslinking to generate icephobic coatings. Characterizations of surface chemical composition and morphology of the fluorinated polysiloxanes coatings suggested that the fluorine content and the surface roughness of the coating surface increased with the amount of 13FMA. When the fluorinated polysiloxanes grafted a suitable amount of 13FMA and VTES, supercooled water droplets could easily slip away from the tilted coating surface at − 15 °C, ascribing to its high receding contact angle, and the ice shear strength could reduce to 83 ± 2 kPa. Results of this study further demonstrated the importance of the synergistic effect of silicon and fluorine for contribution to the enhanced icephobicity, and the self-crosslinking fluorinated polysiloxane coatings could find more feasible applications for anti-icing. [ABSTRACT FROM AUTHOR]

Freezing wave propagation among condensed droplets plays an important role in determining ice invasion and subsequent frost growth during condensation frosting processes. Many researchers have shown the use of superhydrophobic surfaces with nanoscale or hierarchical roughness for retarding interdroplet freezing wave propagation. Here we report effective reduction of interdroplet freezing wave propagation by using micropillar patterned superhydrophobic surfaces with emphasis on pillar pitch effect. Systematic experiments were carried out to examine the dependence of the freezing wave propagation velocity and the ice coverage ratio on pillar pitch. We found that given a pillar diameter there is a critical value for pillar pitch where the minimum freezing wave propagation velocity and ice coverage ratio occur. Our results also showed that compared to the smooth hydrophilic/hydrophobic surfaces, with proper pillar pitches the freezing propagation velocity can be reduced by more than one order of magnitude and the ice coverage can be reduced to 1/3. Additionally, our experimental findings revealed three distinctive physical mechanisms/modes. A quantitative mapping of three regimes was obtained to elucidate the significant effects of pillar pitch on interdroplet freezing wave propagation on superhydrophobic substrates with patterned micropillars. [ABSTRACT FROM AUTHOR]

Recent emerging strategies to prepare icephobic coatings have focused on slippery surfaces containing a liquid lubricant with low surface energy, which significantly reduces ice adhesion. In this work, a facile technique was developed for preparation of polysiloxane coatings with efficient and durable icephobicity. Fluorinated polyhedral oligomeric silsesquioxanes (F-POSS-SiH) with different fluorinated groups and Si-H active sites were synthesized via hydrosilylation between fluorinated methacrylates and octakis(dimethylsiloxy) octasilsequioxane. The F-POSS-SiH hybrid compound was subsequently applied as a co-crosslinker in the system of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane to create silicone coatings. The low surface energy of fluorinated groups could drive F-POSS-SiH towards the coating surface, leading to a gradient distribution in which F-POSS-SiH was self-assembled on the top surface, while silicone was rich in the bottom layer. Meanwhile, wavy surfaces were generated spontaneously by compressive stress during the coating formation. The wavy microstructure of coatings provided space for the unreacted silicone oil, i.e., low molecular weight PMHS, that could be considered as a liquid lubricant and controlled by the dosage. Therefore, the slippery wavy coatings showed highly icephobic properties with extraordinarily low ice shear strengths at a lowest value of 3.8 ± 1.8 kPa, only 5 percentage of Sylgard 184. Moreover, the coatings remained icephobicity after 15 icing/deicing cycles, demonstrating excellent durability. [ABSTRACT FROM AUTHOR]

We present a study on materials formulation, self-assembled surface structure, and the correlation between room temperature water contact angle and contact angle hysteresis (CAH) and the icephobic property at −20 °C. Coating materials are based on TiO-modified polysiloxane (PDMS) incorporated in the inorganic-organic hybrid (sol-gel) materials with a self-assembled surface structure induced by fluoroalkylsilane (FAS) additive and nanoparticle dispersion. A home-made single-drop ice tester is used to record the ice formation and ice sliding process on the tilted surfaces with adjustable chamber temperatures below 0 °C. It is found that a CAH less than 10°, surface roughness in the range of 10-80 nm, and a two-scale surface structure with nanospikes are the essential features for automatic ice sliding at −20 °C at a tilting angle of 30°. We achieve such features by a proper formulation of sol-gel matrix containing PDMS and 2 % FAS, with incorporation of 0.5-1 wt% alumina nanoparticle dispersion in water/solvent 1:1 ratio. Preferred particle size is about 100 nm with single peak distribution as measured by a Marvin Zetasizer. Surface morphologies of coatings are measured by atomic force microscopy technique. Coatings are applied by an air atomizing spraying process and thermally cured. Chemical analyses by XPS, FTIR, and SEM-EDX evidenced the designed composition with PDMS and fluoro-group on the coated surface. Accelerated weathering test proved the stability of the coating for at least 1000 h. Graphical Abstract: Home-made single-drop ice tester (a) and the video-captured image of ice droplets on uncoated glass (b) and icephobic-coated glass during ice sliding down (c) at −20 °C. [ABSTRACT FROM AUTHOR]

The ability of phase change materials (PCMs) to absorb and release large amounts of latent heat has led to great interest in their use in anti-icing applications. Combining PCMs and other passive icephobic strategies such as self-lubricating coatings could enhance anti-icing performance. Here, an icephobic coating is fabricated by impregnating an elastomeric matrix containing PEG-PDMS copolymers with PCM microcapsules. First, a selected mixture of n-dodecane and n-tetradecane is encapsulated within urea–formaldehyde shells using in-situ polymerization. Various concentrations of microcapsules are then added into the self-lubricated PDMS coating and 2.5 wt% of hydroxyl-terminated PEG-PDMS copolymer. Differential scanning calorimetry confirms that the PCM-embedded coating has colder ice nucleation temperatures than the self-lubricating coatings lacking microcapsules. The release of latent heat by the PCMs likely preserves the liquid-like layer for a more extended time and delays ice nucleation. The presence of PCM microcapsules can positively affect self-lubricating characteristics of the matrix containing the PEG-PDMS copolymer to further reducing ice adhesion. The presence of a liquid-like layer lowers ice adhesion strength and decreases ice accumulation on surfaces. These particular properties are further enhanced by the incorporated PCM microcapsules and their ability to release latent heat. Finally, the durability of the fabricated coatings is confirmed after multiple icing/de-icing cycles. Such PCM-impregnated coatings therefore offer potential uses for diverse icephobic applications. [Display omitted] • The synergistic effect of combining different anti-icing strategies can enhance icephobic performance. • Phase change materials (PCMs) release a large amount of energy as latent heat. • The presence of a liquid-like layer lowers ice adhesion strength. • Embedding PCM microcapsules into the PEG-PDMS copolymer–containing matrix enhances anti-icing properties. [ABSTRACT FROM AUTHOR]

Although the superhydrophobic surfaces are preferable for passive anti-icing systems, as they provide water shedding before initiation of ice nucleation, their practical usage is still under debate. This is so, as the superhydrophobic materials are not necessarily icephobic and most of the synthesis techniques are characterized with low fabrication scalability. Here, we describe a rational strategy for the atmospheric icing prevention, based on chemically functionalized carbon soot, suitable for large-scale fabrication of superhydrophobic coatings that exhibit and retain icephobicity in harsh operational conditions. This is achieved through a secondary treatment with ethanol and aqueous fluorocarbon solution, which improves the coating’s mechanical strength without altering its water repellency. Subsequent experimental analyses on the impact dynamics of icy water droplets on soot coated aluminum and steel sheets show that these surfaces remain icephobic in condensate environments and substrate temperatures down to −35 °C. Furthermore, the soot’s icephobicity and non-wettability are retained in multiple icing/de-icing cycles and upon compressed air scavenging, spinning and water jetting with impact velocity of ∼25 m/s. Finally, on frosted soot surfaces, the droplets freeze in a spherical shape and are entirely detached by adding small amount of thermal energy, indicating lower ice adhesion compared to the uncoated metal substrates. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis of the pH-dependent contact angles, freezing temperatures and ice adhesion on aluminium samples is presented. It is not yet known whether externally applied electric fields or charged interfaces sufficiently affect the heterogeneous freezing and ice adhesion in order to provide technical solutions for refrigeration engineering, de-icing techniques and food preservation. It was found that surfaces charges that are generated on polished aluminium samples by changing the pH value of the adjacent KCl solution significantly reduce the advancing contact angle. The effect of surface charges on the freezing behaviour was determined by cooling an array of droplets of KCl solutions with pH values between 3 and 12 with a cooling rate of 1 K min−1. Ice adhesion was evaluated using an in-house developed pusher test at -10 °C in a climate chamber. Both icephobicity tests revealed that surface charges seem ineffective to significantly change the freezing behaviour and ice adhesion strength on polished aluminium samples. [Display omitted] • The advancing contact angles reach their maximum at the potential of zero charge. • Higher ion contents increase the achievable supercooling and decreases ice adhesion. • There is no significant effect of pH-generated surface charge on icephobicity. • Heterogeneous freezing follows a generalised extreme probability density function. • Naturally occurring charges are insufficient to provide icephobicity on Al samples. [ABSTRACT FROM AUTHOR]

With the passage of the 2018 Farm Bill that removed hemp from the Controlled Substances Act altogether, production of hemp is experiencing a renaissance. Building on this revival and re-emergence of hemp, we designed and fabricated hemp-based sustainable and robust slippery surfaces by coating hemp paper with beeswax and subsequently infusing it with hemp oil. A wide variety of aqueous liquids and beverages easily slide on our hemp-based sustainable slippery surfaces, without leaving a trace. We also fabricated hemp-based sustainable slippery surfaces using different textured metals. Our hemp-based sustainable slippery metal surfaces display good icephobic and antithrombotic properties. With these attributes, we envision that our hemp-based sustainable slippery surfaces will pave the path to more safe, non-toxic, and biodegradable or recyclable slippery surfaces for applications in food packaging, anti-icing or de-icing coatings, and antithrombotic medical devices., Competing Interests: The authors declare no competing financial interest.

The phase change materials (PCMs) have attracted great interest for applications as smart icephobic coatings because of their capability to restore and release energy. PCMs release a large amount of energy as latent heat upon freezing, which is a stimuli-response behavior for anti-icing applications. Such materials embedded within coatings can be applied to exposed infrastructures to protect them against icing. Here, we encapsulated a mixture of PCMs in a urea–formaldehyde (UF) shell by in situ polymerization and then incorporated the microcapsules into a polydimethylsiloxane (PDMS) coating. Microcapsules 5–15 µm in diameter having a shell thickness of about 200 nm were fabricated. Investigating the chemical composition of the fabricated microcapsules confirmed that PCM material was successfully encapsulated within the UF shell. Moreover, the differential scanning calorimetry (DSC) analysis showed that the PCM preserved its phase-change characteristics when encapsulated and embedded within the matrix. Increasing the abundance of microcapsules within the coating lowered the ice nucleation temperature, verified by DSC, and increased the freezing-delay time because of PCM latent heat release. We utilized a custom-made apparatus, called micro-push-off set-up that allowed us to measure ice adhesion at the exact moment that the water droplet was completely frozen. Therefore, it was observed that the presence of the PCM microcapsules reduced ice adhesion strength, through either possible mechanism of the formation of quasi-liquid layer (QLL) or thermal expansion differences. Furthermore, lower ice adhesion resulted in reduced ice accumulation on the PCM-containing coatings, verified by the static accumulation test (SAT). [Display omitted] [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces serving as icephobic surfaces are a passive means of limiting the icing of surfaces. Ice nucleation time depends on not only liquid properties and environmental conditions but also surface features; however, it is challenging to investigate ice nucleation time and the influencing parameters simultaneously. This manuscript presents two approaches, experimental testing and machine learning, to study ice nucleation time on exposed surfaces. Hydrophobic/superhydrophobic silicone rubber surfaces were fabricated, and these surfaces varied in their wettability and roughness parameters. Superhydrophobic surfaces characterized by a higher arithmetic average, root mean squared, ten-point height, maximum height of the profile, and a Gaussian roughness distribution—skewness near 0—had longer ice nucleation times. We then used neural networks to model icephobicity in relation to ice nucleation time. The predicted ice nucleation time of the model, trained using some of the experimental results, demonstrated a good agreement with the experimental outcomes. Furthermore, this machine learning approach determined the relative importance of roughness parameters, surface wettability, temperature, and droplet volume in determining surface icephobicity. The proposed approach provides a starting point for studying heterogeneous ice nucleation prediction through an understanding of the key parameters required to optimize the icephobic behavior of superhydrophobic surfaces. [Display omitted] • Ice nucleation time of water droplet on hydrophobic/superhydrophobic surfaces has been studied experimentally. • The effect of surface wettability, roughness parameters, temperature and droplet volume on ice nucleation time are evaluated. • An innovative method for predicting ice nucleation time using machine learning algorithms is shown. [ABSTRACT FROM AUTHOR]

Low surface energy materials have been extensively investigated for building icephobic surfaces in recent years. Polydimethylsiloxane (PDMS) and fluoropolymers have been introduced to this field, while control of their structures is of importance to produce deicing surfaces. In this work, fluorinated methacrylate block copolymers containing polyhedral oligomeric silsesquioxane (POSS) moieties were synthesized by reversible addition-fragmentation chain transfer polymerization and transformed into thiolated-copolymers by aminolysis to adjust the self-assembly and modify surface morphology. The icephobic coatings were developed via UV-curable thiol-ene reaction with tunable amounts of thiol-modified POSS-fluorinated methacrylate diblock copolymers with vinyl-functionalized PDMS and thiol-functionalized PDMS. Characterizations of atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle showed the evidence of the POSS-fluorinated diblock copolymers on the outmost surface of the coatings. Owing to the crystallization of perfluoroalkyl side groups, the coatings containing thiol-modified poly(methacrylisobutyl POSS)- b -poly(2-perfluorooctylethyl methacrylate) ( S17F ) exhibited excellent icephobicity, and water droplets could rebound completely on all S17F -containing surfaces at both normal and tilt modes before freeze even at −15 °C. The ice shear strengths of the prepared UV-cured coatings were about one-eighth of that on bare aluminum surface, while the coating containing 5% S17F achieved the lowest ice shear strength of 105 ± 12 kPa. It was found that the icephobicity of these coatings were attributed primarily to the synergistic effect of the POSS-fluorinated methacrylate diblock copolymer and the PDMS component. [ABSTRACT FROM AUTHOR]

Tribology involves the study of friction, wear, lubrication, and adhesion, including biomimetic superhydrophobic and icephobic surfaces. The three aspects of icephobicity are the low ice adhesion, repulsion of incoming water droplets prior to freezing, and delayed frost formation. Although superhydrophobic surfaces are not always icephobic, the theoretical mechanisms behind icephobicity are similar to the entropically driven hydrophobic interactions. The growth of ice crystals in saturated vapor is partially governed by entropically driven diffusion of water molecules to definite locations similarly to hydrophobic interactions. The ice crystal formation can be compared to protein folding controlled by hydrophobic forces. Surface topography and surface energy can affect both the icephobicity and hydrophobicity. By controlling these properties, micro/nanostructured icephobic concrete was developed. The concrete showed ice adhesion strength one order of magnitude lower than regular concrete and could repel incoming water droplets at -5 °C. The icephobic performance of the concrete can be optimized by controlling the sand and polyvinyl alcohol fiber content. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxane (POSS)-containing fluorosilicone multi-block methacrylate copolymers (PDMS- b -(PMAPOSS- b -PFMA) 2 ) were synthesized via RAFT polymerization of methacryloisobutyl POSS (MAPOSS) with hexafluorobutyl methacrylate (HFBMA) or dodecafluoroheptyl methacrylate (DFHMA) as different fluorinated side groups. A macro-RAFT chain transfer agent of polydimethylsiloxane with dithiobenzoate groups at both ends was initially used. Characterizations of surface chemical composition and morphology of the copolymer films suggested that the PDFHMA chains with longer fluorinated side groups, as compared with PHFBMA chains, were easy to migrate onto the surface and the surface roughness was enhanced by introducing PMAPOSS segments. The film of multi-block copolymer PDMS- b -(PMAPOSS- b -PDFHMA) 2 produced a fluorine-rich surface due to the enrichment of fluorinated blocks and exhibited the highest receding contact angle (103.8 ± 0.5°) and lowest water contact angle hysteresis (8.7 ± 1.4°) among all the samples, attributed to the introduction of PMAPOSS segments and the synergistic effect of silicon and fluorine. Measurements of icephobic properties demonstrated that the supercooled water droplet could easily slip away from the tilted PDMS- b -(PMAPOSS- b -PDFHMA) 2 surface (45°) at −20 °C and the ice shear strength tended to decrease from 361 kPa to 264 kPa with incorporation of PMAPOSS blocks in comparison with PDMS- b -(PFMA) 2 . However, it was found that decreasing wettability of the block copolymer film did not have significant effect on reducing the ice shear strength. The prepared POSS-containing fluorosilicone multi-block methacrylate copolymers with good icephobicity can be used as icephobic coating materials potentially. [ABSTRACT FROM AUTHOR]

The mesoscale, multitier texture of the lotus leaf has served as an inspiration to fabricate surface designs with controllable superhydrophobic properties, targeting a broad range of applications. The choice of material for such designs is directly related to surface performance, in particular under adverse and realistic conditions. Due to its importance in many applications, here aluminium is employed as a material platform and identify key porous hierarchical textures, yielding extraordinary impalement-resistant behavior: Droplet repellency is demonstrated consistently for water impact velocities up to 12 m s−1 (extreme Weber number, We ≈ 3500). Despite impressive superhydrophobic behavior, if ice forms on such surfaces, ice adhesion is markedly stronger than on less hydrophobic alumina nanotube array structures. In a departure from the findings of the well-accepted shear stress-based ice adhesion criterion, a deviation between decreasing ice adhesion strength and increasing hydrophobicity is observed. This is explained with ice adhesion mechanism, depending strongly on the applied stress field orientation and the respective effective ice-substrate contact area. Our results indicate that ice adhesion criteria for the performance of icephobic surfaces should account for the simultaneous presence of shear and tensile stresses, instead of shear stresses alone. [ABSTRACT FROM AUTHOR]