Icephobic Materials Research Articles

Chitosan electrolyte hydrogel with low ice adhesion properties

Icephobic materials can prevent or reduce ice formation, e.g. by ensuring easy detachment, a desirable property for those applications where ice accumulation is critical to human safety. Herein, we develop a chitosan electrolyte hydrogel to create a bio-based surface with low ice adhesion. The chitosan electrolyte hydrogel is physically crosslinked and infused with salted water at concentrations from 4.5 to 30 g/L, including that of seawater (23 g/L). Depending on salt content in the hydrogel, we could obtain very low ice adhesion down to 140 kPa (at – 10°C). We hypothesize that the chitosan electrolyte hydrogel exploits the colligative properties of water avoiding the ice nucleation at the ice-hydrogel interface. To confirm the hypothesis, we investigate the chitosan electrolyte hydrogel structure by contact angles analysis, DSC, TGA, FTIR, XRD, and by rheometry for mechanical properties. We quantify the presence of non-freezing water, which creates a lubricating liquid water layer at the ice-hydrogel interface, affecting the ice detachment mechanism and lowering ice adhesion. In conclusion, the proposed chitosan electrolyte hydrogel presents a bio-based and cost-efficient strategy for ice detachment across various icing scenarios for systems operating in humid marine environments, such as offshore platforms and ships.

Icephobic materials and strategies: From bio‐inspirations to smart systems

AbstractUnwanted ice formations may cause severe functional degradations of facilities and also have a negative impact on their lifespans. Avoiding and removing ice accumulation is always a hot topic in the industrial and technological field. Bionic functional surfaces have been greatly studied for several decades and have proved to be excellent candidates for passive anti‐/deicing applications. However, the drawbacks limit their potential industrial uses under harsh conditions, like low temperatures and high humidity. Most researches on bionic surfaces are focused on a certain function of natural creatures and their underlined fundamental theories are revealed by taking the interface as the static. Actually, living organisms, either plants or animals, are often sensitive and responsive to their surroundings, avoiding risks and even self‐repairing upon damage. From this prospect, a novel view of the bionic icephobic materials has been proposed in the present review, which is expected to be studied and designed by taking the biological species as a system. As two representative icephobic materials, the anti‐/deicing theories of superhydrophobic and slippery surfaces are first discussed. Further, the recent progress of smart icephobic strategies is summarized from interfaces to substrates. We aim to provide new bionic insights on designing future icephobic strategies.

Towards the icephobicity evolution of metallic surfaces affected by transitional wettability

In light of the escalating demands for ice protection related applications in diverse fields, including wind energy, power lines and aerospace, there is a notable surge in interest and attention toward the icephobic materials. The increased focus reflects a growing recognition of the crucial role of materials that demonstrate superior resistance to icing phenomenon. However, the intricate correlation between material wettability and icephobicity remains inadequately elucidated. This study aimed to investigate the factors that influence the relationship between icephobicity and different wetting states. The impact of varying surface topographies was examined within the scope of this investigation. A comprehensive analysis was conducted to evaluate the anti-icing and de-icing performances of the surfaces, encompassing anti-frost, ice shear adhesion strength and electro-thermal heating de-icing aspects. Furthermore, the static and dynamic wettability, along with surface free energy measurements, were also performed to enhance the comprehension of icephobicity variation. The detailed water condensation on various surfaces was meticulously observed using environmental scanning electron microscopy (ESEM). The findings elucidated a strong correlation between the icing behaviour and surface topography. It was observed that the surface topography acted as an amplifier, intensifying the deteriorating effect in icephobicity: the formed glaze per unit area exhibited a significant increase with rough asperities; the ice adhesion strength suffered an obvious increase with rough surface and lower hydrophobicity as well as the prolonged ice detachment and overall energy consumption. Therefore, careful consideration should be devoted to the tailoring of surface morphology and wettability when designing and fabricating icephobic surfaces.

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.

Effect of the experimental parameters on the ice-asphalt adhesion strength and corresponding theoretical model based on the energy-balanced principle

Ice adhesion behavior plays a crucial role in assessing ice-phobic materials. However, the variation of ice-adhesion strength across different laboratories is attributed to the neglect of ice/substrate characteristics. In this work, ice-adhesion strength under different geometric parameters of ice/substrate on asphalt surfaces was examined through an optimized methodology. Additionally, a theoretical model was developed based on the energy balance principle to analyze the influence of various parameters on ice-adhesion strength and to make predictions. The results suggested that the ice-adhesion strength was positively correlated with the substrate thickness and negatively correlated with both the asphalt thickness and the ice diameter. The detachment process of the ice-asphalt interface was divided into two regions, the non-linear mechanical response region, and the linear damage region. The slope of the linear damage region can be defined as the interfacial stiffness of the ice-asphalt system, which was the main reason leading to the change in ice adhesion strength. The increase in ice-adhesion strength was observed as the interfacial stiffness increased. Moreover, the theoretical model of ice-adhesion strength illustrated the effect of ice/substrate geometric characteristics on ice-adhesion strength and was verified by the experiments. This study may provide some new references and a theoretical basis for further research on ice adhesion behavior in different laboratories.

The roles of undercooling degree and materials surface configuration in the growth mechanism of ice layer caused by micro-droplets

Effect mechanisms of the undercooling degree and the surface configuration on the ice growth characteristics were revealed under micro-droplets icing conditions. Preferential ice crystals appear firstly on the surfaces due to the randomness of icing, and obtain growth advantages to form protruding structures. Protruding structures block the incoming droplets from contacting the substrates, causing voids around the structures. The undercooling degree mainly affects the density and the growth rate of preferential ice crystals. With the increase of undercooling degree, the preferential ice crystals have higher density and growth rate, resulting in stronger growth advantage and higher porosity. The surface configuration affects the growth mode, and the ice layer grows with uniform mode, spreading mode and structure-induced mode on the aluminum, smooth Polytetrafluoroethylene (PTFE) and rough PTFE surface respectively, causing the needle-like, ridge-like and cluster-like ice crystals. The rough structures effectively improve the porosity of the ice layer, which is beneficial for optimizing the icephobic property of the materials. This paper provides important theoretical guidance for the design of subsequent icephobic materials.

Robust polyurea icephobic coatings with static large-scale de-icing and dynamic anti-icing performance

Ice accumulation significantly affects the operation of infrastructure and the safety of transportation. Passive icephobic materials utilize inherent properties to achieve anti-icing performance, which has the benefits of no energy consumption and environmental protection. However, their degraded robustness in harsh environments severely limits practical applications. It is still a challenge to prepare icephobic materials that maintain both icephobicity and robustness. In this study, we propose a rational strategy for revolutionarily achieving both icephobicity and robustness by adopting a combination of soft and hard segments impregnated with the lubricant agent. Based on the strategy, the polyurea icephobic coating (PUIC) developed by the NCO-terminated prepolymer, polyaspartic ester, and dimethyl silicone oil ensures rapid and nondamaging ice detachment on the interface (low ice adhesion strength ∼23.7 kPa) via the synergistic effects of hydrophobicity, elastic deformation, and interfacial slippage. In addition, the resulting PUIC can reserve icephobicity under not only continuous 5000 Taber abrasion cycles before the complete wearing off the coating, but also 50 icing/de-icing cycles, 72 h acid/alkali immersion, 72 h UV radiation, and 240 h neutral salt spray. Furthermore, the destroyed PUICs can be recovered by organic solvents and maintain excellent icephobicity. Together with icephobicity, robustness, and scalability, PUICs are effective in static large-scale de-icing and dynamic anti-icing, with broad prospects in practical applications.

Reframing ice adhesion mechanisms on a solid surface

Mitigating icing hazards is of interest for many technological applications. One solution is to employ low ice adhesion coatings, either passively or in combination with active de-icing systems. Nevertheless, comparing different low ice adhesion surfaces can be challenging. Studies generally report the average shear stress, calculated as the ratio of applied force to the ice-substrate contact area; however, the fracture mechanism at the ice-substrate interface is rarely reported. There are two fracture mechanisms that can occur at the interface: stress-dominated and toughness-dominated. Average shear stress is only meaningful when performing adhesion tests in a stress-dominated regime; otherwise, interface stresses are underestimated and misleading. This study presents a new understanding of ice adhesion mechanisms combining experimental and numerical methods, demonstrating how the traditional ice adhesion reporting method can lead to errors up to 400%. Using a simple fracture model, the study shows that the stress-dominated fracture regime in the horizontal push test is favored by smaller ice diameter and greater ice thickness, and is also affected by the load force position. The identification of the two fracture regimes is required for the correct understanding and reproducibility of ice adhesion results, enabling better design and characterization of icephobic coatings and materials.

Fabrication of Slippery Surfaces on Aluminum Alloy and Its Anti-Icing Performance in Glaze Ice

Slippery liquid-infused porous surfaces (SLIPS) have received growing attention as promising icephobic materials. In this study, SLIPS were prepared on aluminum alloys by combining anodization and infusion of common silicone oil. An SLIPS with low ice-adhesion strength (6 kPa) was obtained by optimizing the anodizing time parameters (10 min). In addition, the frosting process and freezing of water droplets on the as-prepared SLIPS at −10 °C were delayed for 2000 s and 4800 s, respectively. Simultaneously, the as-prepared SLIPS also exhibited excellent anti-icing performance in glaze ice, since the supercooled water drips/ice slipped from the surface. The ice weight of the as-prepared SLIPS was significantly lower than that of the bare aluminum surface and the anti-icing-fluid-coated aluminum surface, which was reduced by 38.2%–63.6% compared with the bare aluminum surface. The ice weight increased with decreased temperature and inclination angle. This work proposes a method suitable for large-area preparation of SLIPS that achieves excellent anti-icing performance and significantly reduces the weight of glaze ice.

Stiffening surface lowers ice adhesion strength by stress concentration sites

Mechanically softening materials have been intensively investigated to reduce ice adhesion strength based on the adhesion failure mechanism. Achieving icephobic surfaces with both low ice adhesion strength and mechanical robustness is challenging. The surface stiffening-induced stress concentration sites on elastomer should be possible to improve the mechanical robustness and lower the ice adhesion strength simultaneously, as it can build material inhomogeneity (stiffness mismatch) and geometry irregularity-induced cracks on the surface layer of elastic materials. To reveal this hypothesis, the stress concentration sites are introduced to obtain the robust low ice adhesion surface (RLAS) by implementing rigid nanocomposites with the elastic modulus of GPa scales (e.g. silica nanoparticles, SiO2NPs, ca. 68.9 GPa) into the surface layer of elastomers (e.g. polydimethylsiloxane, PDMS, ca. 2.7 MPa). The effects of the material inhomogeneity (stiffness mismatch) and geometry irregularity-induced stress concentration sites on the reduction of ice adhesion strength are revealed. The minimum ice adhesion strength of the RLAS is down to 10.5 kPa, and its ice adhesion strength remains at 13.8 kPa after 25 icing/deicing cycles. Originating from abundant potential crack initiation sites and stiff nanoparticles, our designed nano-composite materials remarkably lower the ice adhesion strength and are over 2-fold mechanically stiffer than pure elastomer. This strategy offers an unconventionally hardening surface approach for designing icephobic materials with combined durability and robustness.

Crack-Initiated Durable Low-Adhesion Trilayer Icephobic Surfaces with Microcone-Array Anchored Porous Sponges and Polydimethylsiloxane Cover

Reducing unfavorable ice accretion on surfaces exposed in cold environment requires effective passive anti-icing/deicing techniques. Icephobic surfaces are widely applied on various infrastructures due to their low ice adhesion strength and flexibility, whereas their poor mechanical durability, common liquid infusion, weak resistance to contamination, and low bonding strength to substrates are the major remaining challenges. According to the fracture mechanics of ice layer, initiating cracks at the ice-solid interfaces via the proper design of internal structures of icephobic materials is a promising way to icephobicity. Herein, a crack initiating icephobic surface with porous PDMS sponges sandwiched between a protective, dense PDMS layer and a textured metal microstructure was proposed and fabricated. The combination of high- and low- stiffness PDMS layers anchored by the structured metal surface give the sandwich-like structure excellent icephobicity with both high durability and low ice adhesion (5.3 kPa in the icing-deicing cycles). The porosity and the elastic modulus of the PDMS sponges and the periodicity of the metal surface structures can both be tailored to realize enhanced icephobicity. The sandwich-like icephobic surface remained insignificantly changed under solid particle impacting and the durability characterized via linear abrasion tests was elevated compared with PDMS coating on flat metal surfaces. Additionally, the trilayer icephobic surface possesses durability, low ice adhesion strength, and improved resistance to contamination and is applicable on various surfaces.

Internal and interfacial microstructure characterization of ice droplets on surfaces by X-ray computed tomography

HypothesisCharacterizing the microstructure of an ice/surface interface and its effect on the icephobic behavior of surfaces remains a significant challenge. Introducing X-ray Computed Tomography (XCT) can provide unprecedented insights into the internal (porosity) and interfacial structures, i.e. wetting regime, between (super)hydrophobic surfaces and ice by visualizing these optically inaccessible regions. ExperimentsFrozen droplets with controlled volume were deposited on top of metallic and polymeric substrates with different levels of wettability. Different modes of XCT (3D and 4D) were utilized to obtain information on the internal and interfacial structure of the ice/surface system. The results were supplemented by conventional surface analysis techniques, including optical profilometry and contact angle measurements. FindingsUsing XCT on ice/surface systems, the 3D and 4D (imaging with temporal resolution) structural information can be visualized. From these datasets, qualitative and quantitative results were obtained, not only for characterizing the interface but also for analyzing the entire droplet/surface system, e.g., measurement of porosity size, shape, and location. These results highlight the potential of XCT in the characterization of both droplets and substrates and proves that the technique can aid to develop hydrophobic surfaces for use as icephobic materials.

Microporous metallic scaffolds supported liquid infused icephobic construction

Hypothesis: Ice accretion on component surfaces often causes severe impacts or accidents. Liquid-infused surfaces (LIS) have drawn much attention as icephobic materials for ice mitigation in recent years due to their outstanding icephobicity. However, the durability of LIS constructions remains a big challenge, including mechanical vulnerability and rapid depletion of lubricants. The practical applications of LIS materials are significantly restrained, and the full potential of LIS for ice prevention has yet to be demonstrated.Experiments: A universal approach was proposed to introduce microporous metallic scaffolds in the LIS construction to increase the applicability and durability, and to prompt the potential of LIS for ice mitigation. Microporous Ni scaffolds were chosen to integrate with polydimethylsiloxane modified by silicone oil addition.Findings: The new LIS construction demonstrated significantly improved durability in icing/de-icing cyclic test, and it also offered a solution for the rapid oil depletion by restraining the deformation of the matrix material. Low ice adhesion strength could be maintained via a micro-crack initiation mechanism. The results indicated that the multi-phase LIS construction consisting of microporous Ni scaffolds effectively addressed the shackles of the icephobicity deterioration of LIS materials, confirming a new design strategy for the R&D of icephobic surfaces.

Fluorine‐free, highly transparent, chemically durable and low ice adhesion icephobic coatings from biobased epoxy and polydimethylsiloxane

AbstractPassive icephobic surfaces have been extensively studied by researchers due to their advantages of delaying icing time and reducing ice adhesion strength. However, icephobic materials with petroleum‐based resources and toxic fluorine‐containing chemicals, as one of the excellent icephobic materials, are very unfavorable for resource conservation and environmental protection. In this study, we report fluorine‐free, highly transparent, chemically durable and low ice adhesion icephobic coatings prepared by glycerol triglycidyl ether (GTE) derived from natural glycerin and bis(3‐aminopropyl) terminated polydimethylsiloxane (PDMS) via one‐pot method. On the one hand, PDMS with multiple methyl groups and two amine groups acts as a hydrophobic modifier to modulate the surface energy of the coatings, and also acts as a structure modifier to modulate the mechanical properties of the coatings, which allow us to design and synthesis the coating with excellent deicing performance (ice adhesion strength can reach about 16 kPa). On the other hand, GTE with multiple epoxy groups works as cross‐linker to endow the coatings with good cross‐linked networks, so that the coatings showed good durability after being subjected to different temperature treatment and different solution treatments. In additional, the transmittance of the coating is above 91.4%, which is expected to be applied to windows and sensors.

Sebaceous gland-inspired self-lubricated de-icing coating by continuously secreting lubricants

In recent years, oil-contained deicing materials have aroused peoples' concern due to their weak ice adhesion feature. Yet the loss of lubricant on oil-contained surface caused by contact or volatilization should be considered. Oily sebum secreted by sebaceous glands lubricates and moisturizes our skin, and can be reproduced continuously even after daily cleaning. In this work, inspired by sebaceous glands, a self-lubricant (SL) coating with ultra-low ice adhesion and excellent deicing durability was designed via continuously secreting lubricants. To determine the suitable simulant of oily sebum, the tribological tests and theoretical simulation analysis of lubricant on ice were conducted, confirming the effect of polydimethylsiloxane (PDMS) lubricants. By well mixing lubricant and resin, and sebaceous glands-like structures formed in coating matrix after curing, which endowed coating with lubricant storage feature and sebum-like secretion structure. The affinity of PDMS molecules to ice and the regeneration of lubricant film ensured the deicing durability of coating. Ice adhesion strength can be kept below 100 kPa even after 100 icing-deicing cycles, and can recover low ice adhesion strength (~50 kPa) via lubricant secreting. This work highlights the importance of lubricant selection and gives a new vision to designing durable icephobic materials.

Novel Intrinsic Self‐Healing Poly‐Silicone‐Urea with Super‐Low Ice Adhesion Strength (Small 22/2022)

De-Icing Technologies Achieving self-healing anti-icing with low ice bonding force is quite attractive but is still a challenge. In article number 2200532, Yijun Shi and co-workers develop an anti-ice material, which shows an obviously higher self-healing capability and the lowest ice adhesion strength (7 ± 1 kPa) compared with all known ice phobic materials, which can maintain well after healing.

A Family of Frost-Resistant and Icephobic Coatings.

Anti-icing and icephobic materials play a crucial role in demanding applications ranging from energy to transportation systems operating in frigid climates. Despite remarkable advancements in the development of such surface coatings, the use of anti/de-icing chemicals remains one of the go-to solutions for ice management. However, they are notoriously prone to removal by shear forces and dissolution. Herein, the design rationale for developing a family of cryoprotectant and phase-change material (PCM)-based compositions in the form of mixtures, non-aqueous emulsions-creams, and gels that can substantially overcome such challenges is reported. This is achieved through the sustenance of an in-situ-generated surface hydration layer that protects the underlying substrate from a variety of foulants, varying from ice to disease-causing bacteria. Each formulation utilizes unique chemistry to curtail the embodied cryoprotectant loss and can be easily applied as an all-in-one sprayable/paintable coating capable of significantly outperforming untreated industrial materials in terms of their ability to delay condensation-frosting and shed ice simultaneously. Concomitantly, an array of formulation-specific functionalities is observed in the family, which includes optical transparency, mechanical durability, high shear-flow stability, and self-healing characteristics.

Self‐Repairing Performance of Slippery Liquid Infused Porous Surfaces for Durable Anti‐Icing (Adv. Mater. Interfaces 10/2022)

Icephobic Surfaces for Aerospace Application In article number 2101968, Yuan Yuan, Huiying Xiang, and co-workers design durable icephobic slippery liquid infused porous surfaces (SLIPS) on aerospace aluminum alloy. The SLIPS exhibits low ice adhesion strength even after frosting and excellent self-repairing performance, which can withstand ≈150 icing/deicing cycles and 100 abrasion cycles via 4≈5 times of 1 h self-repair. It is promising in the field of durable icephobic materials for aircrafts.

On the icephobicity of damage-tolerant superhydrophobic bulk nanocomposites.

To address the increase in demand for superhydrophobic and icephobic surfaces with greater mechanical robustness, we fabricated damage-tolerant, abrasion-insensitive, and icephobic superhydrophobic bulk nanocomposites using a facile, cost-effective, industrially applicable, and environmentally benign strategy. We prepared nanocomposites composed of high-temperature vulcanized silicone rubber through the highly controlled incorporation of nanosized fumed silica and microsized aluminum trihydrate particles. The produced nanocomposites did not require additional processing, such as sand abrasion or plasma treatment, to acquire their superhydrophobic properties. The extended roughness throughout the whole bulk of the nanocomposites imparted the volumetric superhydrophobicity and resistance to mechanical damage. The presence of micro-nanoparticles also enhanced the thermal stability and icephobic properties of the silicone rubber. The icephobic behavior of the developed nanocomposites was assessed based on freezing delay and push-off tests both of which denoted improved icephobic properties, i.e., high freezing delay time and low ice adhesion strength. We verified the extended duration of superhydrophobicity within the bulk nanocomposite using sandpaper abrasion, severe cutter scratching, tape peeling, and water-jet impacts. This study represents the first evaluation, to the best of our knowledge, of the icephobic properties of both the surface and bulk of the produced nanocomposite subjected to several cycles of sandpaper abrasion. Interestingly, even after multiple abrasion cycles, the samples demonstrated considerably low ice adhesion strength confirming their bulk icephobicity. In a nutshell, our findings are very promising for the fabrication of mechanically robust icephobic materials.

Ice adhesion of PDMS surfaces with balanced elastic and water-repellent properties

HypothesisIce adhesion to rigid materials is reduced with low energy surfaces of high receding contact angles. However, their adhesion strength values are above the threshold value to be considered as icephobic materials. Surface deformability is a promising route to further reduce ice adhesion. ExperimentsIn this work, we prepared elastomer surfaces with a wide range of elastic moduli and hydrophobicity degree and we measured their ice adhesion strength. Moreover, we also explored the deicing performance of oil-infused elastomeric surfaces. The ice adhesion was characterized by two detachment modes: tensile and shear. FindingsThe variety of elastomeric surfaces allowed us to simultaneously analyze the ice adhesion dependence with deformability and contact angle hysteresis. We found that the impact of these properties depends on the detachment mode, being deformability more important in shear mode and hydrophobicity more relevant in tensile mode. In addition, oil infusion further reduces ice adhesion due to the interfacial slippage. From an optimal balance between deformability and hydrophobicity, we were able to identify surfaces with super-low ice adhesion.