Designing scalable elastomeric anti-fouling coatings: Shear strain dissipation via interfacial cavitation

Erosion-resistant materials demonstrate low interfacial toughness with ice and superior durability

The strong adhesion of ice to surfaces results in unwanted effects in various industrial activities. However, current strategies for passive ice-phobic purposes lack either scalability or durability, or both, in industrial applications. In this study, erosion-resistant materials, including ceramic-based (WC, SiC, and alumina) and metal-based (a quasicrystalline coating, QC), were studied for their ice-phobic properties via push-off tests with bulk-water ice from -5 to -20 °C. Although their ice adhesion strengths were high (>400 kPa), their interfacial toughness with ice was quite low (1.1 to 2.6 J m-2) and comparable to polymeric surfaces. The force per width required to remove ice on the QC surface was even lower than that of a silicone (Sylgard 184) surface for an ice length of 7.0 cm. The low interfacial toughness of the erosion-resistant materials with ice was also retained after 1000 cycles of linear abrasion under a pressure of 27.0 kPa. The findings of this work expand the material selection options for durable large-scale ice-phobic applications and could enlighten the use of erosion-resistant materials in harsh industrial environments requiring effective de-icing.

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.

Effect of Doping SiO2 Nanoparticles and Phenylmethyl Silicone Oil on the Large-Scale Deicing Property of PDMS Coatings

Recently, low interfacial toughness (LIT) materials have been developed to solve large-scale deicing problems. According to the theory of interfacial fracture, ice detachment is dominated by strength-controlled or toughness-controlled regimes, which are characterized by adhesive strength or constant shear force. Here, a new strategy is introduced to regulate the interfacial toughness of poly(dimethylsiloxane) (PDMS) coatings using silicon dioxide nanoparticles (SiO₂ NPs) and phenylmethyl silicone oil (PMSO). By systematically adjusting the doping proportion of SiO₂ NPs and PMSO, it is found that a lower interfacial toughness can be achieved with a lower constant shear force. The synergistic effect of the two dopants on the adhesive strength and interfacial toughness is analyzed. Meanwhile, finite element method (FEM) analysis of ice detachment is conducted to show the cracking process intuitively and explicate the mechanism of lowering the interfacial toughness of PDMS by doping SiO₂ NPs and PMSO. It can be concluded that the cohesive zone material (CZM) model is effective for simulating the deicing process of PDMS coatings and provides a comprehensive understanding of the modulation of interfacial toughness.

Suspended Kirigami Surfaces for Multifoulant Adhesion Reduction

High foulant adhesion remains a critical issue in a wide range of industries, such as ice accretion on aircraft, biofoulants on ships, wax build-up within pipelines, and scale formation in water remediation. Previous anti-fouling surfaces have only shown promise for reducing the adhesion of a single foulant system; a multi-foulant anti-fouling technology remains elusive. Here, we introduce a mechanical metamaterial-based approach to develop anti-fouling surfaces applicable to a wide range of fouling substances. The suspended kirigami inverted nil-adhesion surfaces, or SKINS, show significantly reduced adhesion of ice, different waxes, dried mud, pressure-sensitive adhesive tape, and a marine hard foulant simulant. SKINS mimic the wrinkling of hard films adhered to soft substrates. Foulant adhesion can be minimized by this wrinkling, which may be controlled by tuning the kirigami motif, sheet material, and foulant dimensions. SKINS reduce adhesion mechanically and were found to be independent of surface energy, enabling their fabrication from commonplace hydrophilic polymers like cellulose acetate. Optimized SKINS exhibited extremely low foulant adhesion, for example, ice adhesion strengths less than 5 kPa (a >250-fold reduction from aluminum substates), and were found to maintain their performance on curved surfaces like transmission cables. The low foulant adhesion persisted over 30 repeated foulant deposition and removal cycles, demonstrating the anti-fouling durability of SKINS. Overall, SKINS offers a previously unexplored route to achieving low foulant adhesion that is highly tunable in both geometry and material selection, is applicable to many different fouling substances, and maintains extremely low foulant adhesion even on complex substrates over large fouled interfaces.

Enhanced Surface Icephobicity on an Elastic Substrate

Ice accumulation on exposed surfaces is unavoidable as time elapses and the temperature decreases sufficiently. To mitigate icing problems, various types of icephobic substrates have been rationally designed, including superhydrophobic substrates (SHSs), aqueous lubricating layers, organic lubricating layers, organogels, polyelectrolyte brush layers, electrolyte-based hydrogels, elastic substrates, and multicrack initiator-promoted surfaces. Among these surfaces, elastic substrates show excellent enhanced surface icephobicity during dynamic processes (i.e., water-impacting and de-icing tests). Herein, we summarize recent progress in elastic icephobic substrates and discuss the reasons that surface icephobicity can be enhanced on elastic substrates in terms of enhanced water repellency and further lowering the ice adhesion strength. For enhanced water repellency, we focus on reducing the contact time of water impacting such that water droplets can be easily shed from an elastic substrate before ice occurs. Reducing the contact time of water impacting various substrates (i.e., micro/nanostructured rigid SHSs, macrotextured rigid SHSs, and elastic SHSs) is discussed, followed by exploring their mechanisms. We argue that the ice adhesion strength can be further lowered on an elastic substrate by rationally tuning the elastic modulus and surface textures (i.e., surface textured and hollow subsurface textured) and combining elastic substrate with other passive anti-icing strategies (or functioning passive icephobic substrates with an electrothermal or photothermal stimulus). In short, the introduction of an elastic substrate into a passive or active icephobicity surface opens an avenue toward designing a versatile icephobic surface, providing great potential for outdoor anti-icing applications.

Quasicrystalline Coatings Exhibit Durable Low Interfacial Toughness with Ice

Ice accretion can adversely impact many engineering structures in commercial and residential sectors. Although there are many reports of low-ice-adhesion-strength materials, a scalable and durable deicing solution remains elusive, as ice detachment is dominated by interfacial toughness for large interfaces. In this work, durable metallic coatings based on Al-rich quasicrystalline alloys were prepared and applied on aluminum substrates using high-velocity oxyfuel thermal spray. X-ray diffraction patterns confirmed the quasicrystalline phases of the coating, and its large-scale deicing capability was studied by evaluating the coating's ice detachment mechanics using long lengths of ice. A toughness-controlled regime of interfacial fracture was observed for ice lengths longer than ∼2 cm, and a low shear strength of ∼30 kPa was achieved for a 20 cm ice length. The metallic coatings exhibited excellent ice repellency even after being abraded, scratched, heated, UV-irradiated, and exposed to chemical contaminations, demonstrating promising durability for real-world, large-scale ice removal.