Micro/Nano Hierarchical Crater-Like Structure Surface With Mechanical Durability and Low-Adhesion for Anti-Icing/Deicing.

Superhydrophobic surfaces have attracted significant attention for their ability to prevent ice formation and facilitate deicing without requiring external energy. However, these surfaces are often vulnerable to damage from external forces, leading to functional failure due to poor mechanical stability, which limits their widespread use. Drawing inspiration from the hierarchical groove of rose petals and the micropapillae of lotus leaves, a simple laser-based method is proposed to create a superhydrophobic surface with a micro/nano hierarchical crater-like structure (HCLS). To enhance the surface, boiling water treatment is applied to induce dense nanostructures, resulting in an optimal contact angle (CA) of 162° and a desirable sliding angle (SA) of 2.0°. The initial ice adhesion strength of HCLS is as low as 1.4 kPa and remains below 10 kPa even after 300 cm sandpaper abrasion. Furthermore, the HCLS demonstrates excellent mechanical durability, maintaining its performance under conditions that simulate the continuous impact of water and sand in extreme weather. This approach offers an innovative design concept that has the potential to advance the development of anti-icing and deicing surfaces for future aircraft.

De-icing performance evolution with increasing hydrophobicity by regulating surface topography.

It is of great significance to grasp the role of surface topography in de-icing, which however remains unclear yet. Herein, four textured surfaces are developed by regulating surface topography while keeping surface chemistry and material constituents same. Specifically, nano-textures are maintained and micro-textures are gradually enlarged. The resultant ice adhesion strength is proportional to a topography parameter, i.e. areal fraction of the micro-textures, owing to the localized bonding strengthening, which is verified by ice detachment simulation using finite element method. Moreover, the decisive topography parameter is demonstrated to be determined by the interfacial strength distribution between ice and test surface. Such parameters vary from paper to paper due to different interfacial strength distributions corresponding to respective situations. Furthermore, since hydrophobic and de-icing performance may rely on different topography parameters, there is no certain relationship between hydrophobicity and de-icing.

The role of surface topography in de-icing is verified to be determined by the interfacial strength distribution between ice and surface experimentally and numerically, unveiling the relationship between hydrophobicity and de-icing.

Transparent and Robust Amphiphobic Surfaces Exploiting Nanohierarchical Surface-grown Metal-Organic Frameworks.

Highly amphiphobic (repelling both water and low surface tension liquids) and optically transparent surface treatments have widespread demand. By combining a rational growth of metal-organic frameworks (MOFs) with functionalization by environmentally safe, flexible alkyl groups, here we present surfaces with nanohierarchical morphology, comprising two widely differing nanoscale features. These nanohierarchical MOF films show excellent amphiphobicity. We further present three key features. First, we demonstrate the need to use flexible alkyl chains to achieve low drop sliding angles and self-cleaning. Second, our thin (∼200 nm) MOF films display excellent optical transparency and robustness. Third, the nanohierarchical morphology enables a unique combination of additional desirable properties, e.g., resistance to high-speed liquid impact (up to ∼35 m/s, Weber number >4 × 104), thermal stability up to 200 °C, scratch resistance, low ice adhesion for >10 icing/deicing cycles, stability in harsh acidic and basic environments, and capability to remove carcinogenic pollutants from water.

Anti-ice coating inspired by ice skating.

Accumulation of ice to surfaces brings dangerous and costly problems to our daily life. In this paper, an anti-ice coating inspired by ice skating is reported. Hyaluronic acid is used in the anti-ice coating to form aqueous lubricating layer benefitting from its high water absorbing property. Dopamine, the main component of the mussel adhesive protein, is introduced to anchor the hyaluronic acid to the solid surfaces to render the coating applicable to all types of solid surfaces. At the same time it serves as the crosslinking agent for hyaluronic acid, thus the thickness of the water collecting film could be easily varied. Ice adhesion strength on surfaces coated with such kind of coating could be more than one order of magnitude lower than that of uncoated ones. The results indicate that this anti-ice coating with the aqueous lubricating layer has great potential for fighting against icing problems.

Ice Adhesion Properties on Micropillared Superhydrophobic Surfaces.

In this work, we investigate the freezing behavior and ice adhesion properties of sessile drops on micropillared superhydrophobic surfaces (SHSs) with various sizes, which are of practical importance for anti/deicing. First of all, it is demonstrated that the recalescence is related only to the supercooling degree of drops but not to the geometrical parameters of micropillars. The freezing time of sessile drops first increases and then decreases with the area fraction of the SHSs, which demonstrates the nonmonotonic dependence of the icing time on the area fraction. Moreover, the influence of the geometrical parameters of the micropillars on the ice adhesion is discussed. With the decrease of the substrate temperature, the wetting state of the adhesive ice can be transformed from the Cassie ice to the Wenzel ice. For the Cassie ice, the adhesive force is proportional to the area fraction of the SHSs. Interestingly, experimental results show that there exist two interfacial debonding modes of the Wenzel ice: translational debonding and rotational debonding. Furthermore, it is found that the rotational debonding mode contributes to a much lower adhesive force between the ice and the micropillared surface compared to that of the translational debonding mode. By analyzing the critical interfacial energy release rate of the two modes, we deduce the threshold between the two modes, which is quantified as the geometrical parameters of the micropillars. In addition, quantitative relations between the geometrical parameters and the adhesion strengths of the two modes are also obtained. We envision that this work would shed new light on the design optimization of anti/deicing materials.

A Molecular Dynamics Analysis of the Thickness and Adhesion Characteristics of the Quasi-Liquid Layer at the Asphalt-Ice Interface.

The quasi-liquid layer (QLL), a microstructure located between ice and an adhering substrate, is critical in generating capillary pressure, which in turn influences ice adhesion behavior. This study employed molecular dynamics (MD) methods to obtain QLL thickness and utilized these measurements to estimate the adhesive strength between ice and asphalt. The research involved constructing an ice-QLL-asphalt MD model, encompassing four asphalt types and five temperature ranges from 250 K to 270 K. The QLL thickness was determined for various asphalts and temperatures using the tetrahedral order parameter gradient. Additionally, capillary pressure was calculated based on the QLL thickness and other geometric parameters obtained from the MD analysis. These findings were then compared with ice adhesion strength data acquired from pull-off tests. The results indicate that QLL thickness varies with different asphalt types and increases with temperature. At a constant temperature, the QLL thickness decreases in the order of the basal plane, primary prism plane, and secondary prism plane. Furthermore, the adhesion strength of the QLL diminishes as the temperature rises, attributed to the disruption of hydrogen bonds at lower temperatures. The greater the polarity of the asphalt's interface molecules, the stronger the adhesion strength and binding free energy. The MD simulations of the asphalt-ice interface offer insights into the atomic-scale adhesive properties of this interface, contributing to the enhancement in QLL property prediction and calibration at larger scales.

Icephobic Coating Based on Novel SLIPS Made of Infused PTFE Fibers for Aerospace Application.

The development of slippery surfaces has been widely investigated due to their excellent icephobic properties. A distinct kind of an ice-repellent structure known as a slippery liquid-infused porous surface (SLIPS) has recently drawn attention due to its simplicity and efficacy as a passive ice-protection method. These surfaces are well known for exhibiting very low ice adhesion values (τice < 20 kPa). In this study, pure Polytetrafluoroethylene (PTFE) fibers were fabricated using the electrospinning process to produce superhydrophobic (SHS) porous coatings on samples of the aeronautical alloy AA6061-T6. Due to the high fluorine-carbon bond strength, PTFE shows high resistance and chemical inertness to almost all corrosive reagents as well as extreme hydrophobicity and high thermal stability. However, these unique properties make PTFE difficult to process. For this reason, to develop PTFE fibers, the electrospinning technique has been used by an PTFE nanoparticles (nP PTFE) dispersion with addition of a very small amount of polyethylene oxide (PEO) followed with a sintering process (380 °C for 10 min) to melt the nP PTFE together and form uniform fibers. Once the porous matrix of PTFE fibers is attached, lubricating oil is added into the micro/nanoscale structure in the SHS in place of air to create a SLIPS. The experimental results show a high-water contact angle (WCA) ≈ 150° and low roll-off angle (αroll-off) ≈ 22° for SHS porous coating and a decrease in the WCA ≈ 100° and a very low αroll-off ≈ 15° for SLIPS coating. On one hand, ice adhesion centrifuge tests were conducted for two types of icing conditions (glaze and rime) accreted in an ice wind tunnel (IWT), as well as static ice at different ice adhesion centrifuge test facilities in order to compare the results for SHS, SLIPs and reference materials. This is considered a preliminary step in standardization efforts where similar performance are obtained. On the other hand, the ice adhesion results show 65 kPa in the case of SHS and 4.2 kPa of SLIPS for static ice and <10 kPa for rime and glace ice. These results imply a significant improvement in this type of coatings due to the combined effect of fibers PTFE and silicon oil lubricant.

Recent progress in understanding the anti-icing behavior of materials.

Despite the significant progress in fundamental research in the physics of atmospheric icing or the revolutionary changes in modern materials and coatings achieved due to the recent development of nanotechnology and synthetic chemistry, the problem of reliable protection against atmospheric icing remains a hot topic of surface science. In this paper, we present a brief analysis of the mechanisms of anti-icing behavior that attracted the greatest interest of the scientific community and approaches which realize these mechanisms. We also note the strengths and weaknesses of such approaches and discuss future studies and prospects for the practical application of developed coatings.

Enhanced Anti/De-Icing Performance on Rough Surfaces Based on The Synergistic Effect of Fluorinated Resin and Embedded Graphene.

Icing negatively impacts various industrial sectors and daily life, often leading to severe safety problems and substantial economic losses. In this work, a fluorinated resin coating with embedded graphene nanoflakes is prepared using a spin-coating curing process. The results shows that the ice adhesion strength is reduced by ≈97.0% compared to the mirrored aluminum plate, and the icing time is delayed by a factor of 46.3 under simulated solar radiation power of 96 mW cm-2 (1 sun) at an ambient temperature of -15 °C. The superior anti/de-icing properties of the coating are mainly attributed to the synergistic effect of the fluorinated resin with a low surface energy, the rough structure of the sandblasted aluminum plate, which reduces the contact area, and the embedded graphene nanoflakes with a superior photothermal effect. Furthermore, the hydrogen bonding competition effect between the exposed-edge oxygen-containing functional groups of the embedded graphene nanoflakes and water molecules further improves the anti-icing properties. This work proposes a facile preparation method to prepare coatings with excellent anti/de-icing properties, offering significant potential for large-scale engineering applications.

Icephobic Durability of Molecular Brush-Structured PDMS Soft Coatings.

The accumulation of ice can pose numerous inconveniences and potential hazards, profoundly affecting both human productivity and daily life. To combat the challenges posed by icing, extensive research efforts have been dedicated to the development of low-ice adhesion surfaces. In this study, we harness the power of molecular dynamics simulations to delve into the intricate dynamics of polymer chains and their role in determining the modulus of the material. We present a novel strategy to prepare ultralow-modulus poly(dimethylsiloxane) (PDMS) elastomers with a molecular brush configuration as icephobic materials. The process involves grafting monohydride-terminated PDMS (H-PDMS) as side chains onto backbone chain PDMS with pendant vinyl functional groups to yield a molecular brush structure. The segments of this polymer structure effectively restrict interchain entanglement, thereby rendering a lower modulus compared to traditional linear structures at an equivalent cross-linking density. The developed soft coating exhibits a remarkably ultralow ice adhesion strength of 13.1 ± 1.1 kPa. Even after enduring 50 cycles of icing and deicing, the ice adhesion strength of this coating steadfastly stayed below 16 kPa, showing no notable increase. Importantly, the molecular brush coating applied to glass demonstrated an impressive light transmittance of 92.1% within the visible light spectrum, surpassing the transmittance of bare glass, which was measured at 91.3%. This icephobic coating with exceptional light transmittance offers a wide range of applications and holds significant potential as a practical icephobic material.

Multifunctional Anti-Icing Gel Surface with Enhanced Durability.

Materials with low ice adhesion and long-lasting anti-icing properties remain an ongoing challenge in ultralow temperature environments (≤-30 °C). This study presents a gel material consisting of a polymer matrix (copolymer of polyurethane and acrylamide) and an anti-icing agent, ethylene glycol (EG), designed for anti-icing applications at ultralow temperatures. The surface shows a prolonged droplet freezing delay of ca. 322 s at -30 °C and frost resistance properties. It also exhibits an ice adhesion strength of 1.1 kPa at -10 °C and 39.8 kPa at -50 °C, resulting from the interaction between EG and water molecules that hinders the crystallization of ice as well as the significant mismatch between elastic gel and ice. In addition, the gel surface exhibits favorable anti-icing durability, with an ice adhesion strength below 20.0 kPa after 25 icing/deicing cycles and mechanical scratch tests. The gel demonstrates remarkable thermal durability, achieved through the H-bonds between the EG and polymer matrix. The H-bonds further enhance the anti-icing performance, thereby remarkably decreasing EG depletion and improving anti-icing durability. Overall, these properties suggest the potential application of this gel material in harsh environments including polar regions.

Influence of Preparation Methods and Nanomaterials on Hydrophobicity and Anti-Icing Performance of Nanoparticle/Epoxy Coatings.

Despite their effectiveness in preventing icing, hydrophobic coatings possess drawbacks such as susceptibility to detachment and limited wear resistance, leading to inadequate longevity in melting ice/snow. To enhance the surface stability and durability of superhydrophobic coatings, nanoparticle/epoxy formulations were developed using three types of nanoparticles, two dispersion techniques, three application methods, and two epoxy resin introduction approaches. Testing encompassed water contact angle measurements, assessment of ice adhesion force, and determination of icing rates on asphalt concrete coated with these hydrophobic formulations. Fourier-transform infrared spectroscopy was employed to analyze the molecular structures of the coatings, while scanning electron microscopy facilitated observation of the surface morphology of the hydrophobic coatings. The findings indicated that nano-ZnO, TiO2, and SiO2 particles could be modified into hydrophobic forms using stearic acid. Application of the hydrophobic coating improved the concrete's hydrophobicity, reduced ice adhesion strength on both concrete and asphalt, and delayed the onset of icing. Furthermore, optimal dosages of stearic acid, nanoparticles, and epoxy resin were identified as crucial parameters within specific ranges to ensure the optimal hydrophobicity and durability of the coatings.

Reducing Ice Adhesion to Polyelectrolyte Surfaces by Counterion-Mediated Nonfrozen Hydration Water.

Hydrophilic anti-icing coatings can be energy-effective passive solutions for combating ice accretion and reducing ice adhesion. However, their underlying mechanisms of action remain inferential and are ill-defined from a molecular perspective. Here, we systematically investigate the influence of the counterion identity on the shear ice adhesion strength to cationic polymer coatings having quaternary alkyl ammonium moieties as chargeable groups. Temperature-dependent molecular information on the hydrated polymer films is obtained using total internal reflection (TIR) Raman spectroscopy, complemented with differential scanning calorimetry (DSC) and ellipsometry. Ice adhesion measurements show a pronounced counterion-specific behavior with a sharp increase in adhesion at temperatures that depend on the anion identity, following the order Cl- < F- < SCN- < Br- < I-. Linked to the freezing of hydration water, the specific ordering results from differences in ion pairing and the amount of water present within the polymer film. Moreover, similar effects can be promoted by varying the cross-linking density in the coating while keeping the anion identity fixed. These findings shed new light on low ice adhesion mechanisms and may inspire novel approaches for improved anti-icing coatings.

Sustainable Manufacturing of Multifunctional Fluorine-Free Superslippery Flexible Surfaces.

Surface contamination and friction result in significant energy losses with widespread environmental impact. In the present work, we developed fluorine-free super-slippery surfaces employing environmentally friendly and simple biofuel-based flame treatment of polydimethylsiloxane (PDMS). Through a unique combination of processing parameters, highly transparent (>90%) and flexible films were engineered with omniphobic, anti-icing, and ultra-low friction properties. The processed films showed an extremely low tilting angle (<5°) and contact angle hysteresis (<4°) against different liquids, even under subzero temperatures. The coefficient of friction (COF) reduced to 0.01 after processing compared to ∼1 for PDMS. Extremely low ice adhesion of <20 kPa and enhanced freezing time ensured anti-icing behavior. The exceptional multidimensional traits were derived from the extremely stable silicone lubricant layer ensured by the hierarchically structured wrinkles. Wind tunnel tests showed that an air drag velocity of less than 0.5 m/s was sufficient to initiate droplet motion, highlighting low interfacial friction that leads to an anti-staining nature. Sustaining the self-cleaning and anti-staining characteristics, the processed surface showed utmost durability under different harsh conditions. The super-slippery surfaces with multifunctional characteristics fabricated through a sustainable route can be effectively used for various engineering and industrial applications.

Anti-icing performance of hydrophobic coatings on stainless steel surfaces.

This study aims to prevent ice accumulation on the surface of drilling tools by investigating the effectiveness of hydrophobic coatings, which is one of the most promising methods to solve drilling difficulties in warm ice. Herein, four types of hydrophobic organic coatings that can be used on metal surfaces were tested to evaluate their anti-icing performance, service durability, and friction properties. All of them possess rough surfaces with microstructure characteristics such as pores, stripes, or micropapillae. They also exhibit hydrophobicity, with water contact angles of 101.6°, 100.0°, 103.1°, and 108.5°. They can significantly prolong the required freezing time of water droplets on their surfaces, effectively reduce ice adhesion, and decrease the friction between ice and their surface. The ice adhesion in the axial, tensile, and tangential directions can be reduced by 65.64 %, 56.31 %, and 72.11 %, respectively, for the coating with silicon (Si)-based and fluorine (F)-containin compounds (coating-C) at -30 °C; while it can be reduced by 85.05 %, 73.9 %, and 94.2 %, respectively, for the coatings with Si-based and polytetrafluoroethylene (PTFE) compounds (coating-D). The two coatings mentioned above lose their anti-icing performance after 20 icing and de-icing cycles, and their hydrophobicity after 120 abrasion cycles under a load of 6 N.

Thermomechanically Resilient Polyionic Elastomers with Enhanced Anti-Icing Performances.

Anti-icing gels inhibit ice formation and accretion; however, current iterations face prevalent drawbacks such as poor strength, weak substrate adhesion, and limited anti-icing properties. Herein, we propose a novel approach to address these challenges by developing a thermomechanical robust polyionic elastomer (PIE) with enhanced anti-icing properties. The PIE surface exhibits an icing delay time up to 5400 s and remains frost-free after exposure to -10 °C for 3.5 h, attributed to the inhibitory effect on ice formation by ions from ILs and the polyelectrolyte network. Moreover, the PIE exhibits remarkable anti-icing durability, with ice adhesion strengths below 35 kPa after undergoing 30 icing/deicing cycle tests at -20 °C. Following sandpaper abrasion (300 cycles), scratching, and heat treatment (100 °C, 16 h), the adhesion strength remains ca. 20 kPa, highlighting its resilience under various thermal and mechanical conditions. This exceptional durability is attributed to the low volatility of the IL and the robust ionic interactions within the PIE network. Furthermore, the PIE demonstrates favorable self-healing properties and strong substrate adhesion in both low-temperature and ambient environments, facilitated by the abundance of hydrogen bonds and electrostatic forces within PIE. This work presents an innovative approach to developing high-performance, durable, and robust anti-icing materials with potential implications across various fields.

Enhancing Icephobic Coatings: Exploring the Potential of Dopamine-Modified Epoxy Resin Inspired by Mussel Catechol Groups.

A nature-inspired approach was employed through the development of dopamine-modified epoxy coating for anti-icing applications. The strong affinity of dopamine's catechol groups for hydrogen bonding with water molecules at the ice/coating interface was utilized to induce an aqueous quasi-liquid layer (QLL) on the surface of the icephobic coatings, thereby reducing their ice adhesion strength. Epoxy resin modification was studied by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy (NMR). The surface and mechanical properties of the prepared coatings were studied by different characterization techniques. Low-temperature ATR-FTIR was employed to study the presence of QLL on the coating's surface. Moreover, the freezing delay time and temperature of water droplets on the coatings were evaluated along with push-off and centrifuge ice adhesion strength to evaluate their icephobic properties. The surface of dopamine-modified epoxy coating presented enhanced hydrophilicity and QLL formation, addressed as the main reason for its remarkable icephobicity. The results demonstrated the potential of dopamine-modified epoxy resin as an effective binder for icephobic coatings, offering notable ice nucleation delay time (1316 s) and temperature (-19.7 °C), reduced ice adhesion strength (less than 40 kPa), and an ice adhesion reduction factor of 7.2 compared to the unmodified coating.

Icephobicity of Hierarchically Rough Aluminum Surfaces Sequentially Coated with Fluoroalkyl and PDMS Alkoxysilanes.

Superhydrophobic surfaces fabricated by grafting 1H,1H,2H,2H-heptadecafluorodecyl trimethoxysilane (FD-TMS) and polydimethylsiloxane triethoxysilane (PDMS-TES) onto a nano-micro hierarchical aluminum (Al) surface are considered to possess substantial anti-icing functionality, with delayed freezing and low ice-adhesion strength (IAS). Verifying the impacts of PDMS and the synergism of PDMS and FD on the anti-icing performance is the goal of this study. Roughness, one of the prerequisites for superhydrophobicity, was obtained by etching Al substrates in aqueous HCl, followed by immersion in boiling water. FD-TMS and PDMS-TES were then coated on the rough Al substrates layer by layer; a congener coated with a single layer was also prepared for comparison. The FD-PDMS1.92 (1.92 wt.%) coating, in which FD-TMS and PDMS-TES were used as primary and secondary coating materials, respectively, exhibited superior icephobicity, with the lowest IAS of 28 kPa under extremely condensing weather conditions (-20 °C and 70% relative humidity, RH) and the longest freezing delay time of 230 min (at -18 °C). These features are attributed to the incorporation of a dense coating layer with a low-surface-tension FD and the high mobility of PDMS, which lowered the contact area and interaction between the ice and substrate. The substrate coated with FD-PDMS1.92 exhibited improved durability with an IAS of 63 kPa after 40 icing/melting cycles, which is far less than that achieved with the FD single-layer coating.

Interdependence of Surface Roughness on Icephobic Performance: A Review.

Ice protection techniques have attracted significant interest, notably in aerospace and wind energy applications. However, the current solutions are mostly costly and inconvenient due to energy-intensive and environmental concerns. One of the appealing strategies is the use of passive icephobicity, in the form of coatings, which is induced by means of several material strategies, such as hydrophobicity, surface texturing, surface elasticity, and the physical infusion of ice-depressing liquids, etc. In this review, surface-roughness-related icephobicity is critically discussed to understand the challenges and the role of roughness, especially on superhydrophobic surfaces. Surface roughness as an intrinsic, independent surface property for anti-icing and de-icing performance is also debated, and their interdependence is explained using the related physical mechanisms and thermodynamics of ice nucleation. Furthermore, the role of surface roughness in the case of elastomeric or low-modulus polymeric coatings, which typically instigate an easy release of ice, is examined. In addition to material-centric approaches, the influence of surface roughness in de-icing evaluation is also explored, and a comparative assessment is conducted to understand the testing sensitivity to various surface characteristics. This review exemplifies that surface roughness plays a crucial role in incorporating and maintaining icephobic performance and is intrinsically interlinked with other surface-induced icephobicity strategies, including superhydrophobicity and elastomeric surfaces. Furthermore, the de-icing evaluation methods also appear to be roughness sensitive in a certain range, indicating a dominant role of mechanically interlocked ice.

Hydro- and Icephobic Properties and Durability of Epoxy Gelcoat Modified with Double-Functionalized Polysiloxanes.

Anti-icing coatings have provided a very good alternative to current, uneconomic, active deicing methods, and their use would bring a number of significant benefits to many industries, such as aviation and energy. Some of the most promising icephobic surfaces are those with hydrophobic properties. However, the relationship between hydrophobicity and low ice adhesion is not yet clearly defined. In this work, chemical modification of an epoxy gelcoat with chemical modifiers from the group of double organofunctionalized polysiloxanes (generally called multifunctionalized organosilicon compounds (MFSCs)) was applied. The anti-icing properties of manufactured coatings were determined by means of measurements of shear strength between the ice layer and the modified surface, conducted using a tensile machine. In the work, tests were also performed on the roughness, wettability, and durability of the properties in an aging chamber. It was found that the performed modifications of the coating's chemical composition by the addition of polysiloxanes enabled us to reduce ice adhesion by 51% and to increase the water contact angle by 14% in comparison to the neat gelcoat. A reduction in ice adhesion was also observed with the increasing water contact angle and with decreasing surface roughness. In addition, only one modification recorded an increase in ice adhesion after exposure in the aging chamber.