Special Section on “Materials Technologies for Controlling Liquid–Surface Interactions from Wetting to Icing”

Abstract

The control of liquid–surface interactions is a fundamental principle in materials science and engineering, influencing a vast array of applications, from energy systems, where tailored wettability enhances heat transfer and fluid dynamics, to biomaterials, where surface properties dictate cell adhesion, biofouling prevention, and drug delivery, liquid–surface interactions remain pivotal. Their role extends further into microfluidics, enabling precise manipulation of droplets in lab-on-a-chip devices and into stimuli-responsive materials, where controlled wetting behavior dictates adaptive and functional performance.

A cornerstone in our understanding of wetting behavior was Young's equation (1805), which established the balance of interface forces at the three-phase contact line, defining the equilibrium contact angle of a liquid droplet on a solid substrate. Followed by the pioneering studies by Wenzel (1936) and Cassie–Baxter (1944), which further refined this knowledge by introducing wetting models that explain how surface roughness and chemistry influence liquid behavior. The Wenzel model describes liquid infiltration into textured surfaces, leading to strong adhesion, while the Cassie–Baxter model highlights the formation of air pockets on structured surfaces, resulting in extreme water repellency. These principles laid the groundwork for modern surface engineering, guiding the development of superhydrophobic coatings, icephobic materials, and adaptive wetting surfaces. Building upon these fundamentals and drawing inspiration from nature, including the hierarchical microstructures of lotus leaves, the rose petal effect, and hydrophobic adaptations in animal fur and insect legs, scientists have engineered precise wettability control to create surfaces with remarkable water management properties. These innovations have unlocked new functionalities, including self-cleaning coatings, enhanced water repellency, and responsive wetting control, with materials ranging from superhydrophobic and oleophobic surfaces to slippery liquid-infused porous films (SLIPS) and amphiphilic coatings.

The control of liquid–surface interactions has been critical in the design of icephobic surfaces, where the behavior of water droplets before freezing determines ice nucleation, adhesion, and removal mechanisms. Ice accretion presents a severe challenge, affecting not only daily life but also critical industrial applications. Frozen power lines, traffic signals, and transportation systems suffer from efficiency losses and increased maintenance demands, while wind turbines, solar panels, and aeronautical surfaces face performance degradation and safety risks.

Developing next-generation icephobic solutions requires interdisciplinary advancements in surface engineering, ice adhesion reduction, and mechanical durability, ensuring optimal performance under extreme environmental conditions. Thus, research efforts are expanding across three major domains: 1) Anti-icing surfaces and coatings (passive solutions): Materials designed to reduce ice formation, minimize ice adhesion, and delay freezing. 2) De-icing technologies: Active systems enabling ice removal with minimal environmental and energy costs. 3) Smart and responsive surfaces: Integrated materials featuring real-time ice detection with adaptive anti-icing and de-icing mechanisms.

Within the category of passive anti-icing surfaces, superhydrophobic coatings have long been regarded as a leading approach for mitigating ice. By exploiting surface roughness, these materials minimize the solid–liquid contact area, thereby delaying freezing and improving icephobic properties. However, superhydrophobic surfaces often suffer from high ice adhesion, prompting researchers to explore alternatives such as SLIPS and amphiphilic coatings, which introduce lubricating layers and molecular-scale tunability to improve ice release efficiency. An ideal icephobic surface must combine three critical attributes: 1) high water repellency to reduce droplet retention; 2) delayed ice nucleation for extended freezing resistance; and 3) low ice adhesion strength for efficient ice removal. Yet, despite ongoing research, a perfect icephobic surface that meets all these requirements has yet to be fully realized. An additional challenge is that icephobic materials must be designed to withstand harsh environmental conditions, requiring mechanical robustness and long-term stability to endure repeated freeze-thaw cycles, abrasion, and weather exposure without degradation.

Active systems require energy from an external source and can involve mechanical, thermal, chemical, or electrical components. Standard de-icing methods, including electrothermal approaches and the use of chemical lubricants, impose significant environmental and energy costs. To overcome this shortcoming, over the past five years, the application of high frequency surface-engineered bulk and surface acoustic waves has emerged as a promising alternative for energy-efficient deicing and ice monitoring, enabling compatibility with passive anti-icing thin films and the development of smart sensing deicing surfaces.

This Advanced Engineering Materials special section will present groundbreaking research on superhydrophobic and anti-icing surfaces, spanning from fundamental principles to applied engineering solutions. In addition to passive coatings, it will explore innovative de-icing strategies, such as acoustic wave activation for ice removal and antifogging, and the development of advanced characterization tools.

A critical challenge in icephobic materials lies in accurately assessing ice adhesion strength and freezing dynamics. Traditional detachment force measurements often fail to account for shear force evolution, which plays a major role in ice removal efficiency. To address these limitations, this issue will highlight high-resolution experimental techniques, computational simulations, and novel diagnostic tools aimed at enhancing scientific understanding of ice adhesion mechanisms. Thus, in the article adem.202401463, Maslov et al. presented an advanced protocol to analyze dynamic contact angle, including molecular dynamics simulations. The tool uses a convex hull algorithm and an optimized ellipsoidal fitting process to determine the contact angle distribution along the droplet contact line with high efficiency and reliability. This methodology offers valuable insights into droplet asphericity and liquid–solid interactions at the nanoscale. In the effort for elucidation of icephobic properties, Sarkari et al. reported in the article adem.202402996, on the critical role of shear force-time evolution to accomplish the precise description of ice adhesion strength. Authors compare different ice adhesion test systems and reveal how traditional approaches may overlook factors such as viscoelastic coating response and failure mechanisms, presenting a more comprehensive approach to understanding icephobicity and durability. In the step forward to unravel the dynamic interactions between supercooled water droplets and highly repellent surfaces, Bonnacurso et al., in adem.202402202 thoroughly analyzed how droplet impalement and surface texture influence ice adhesion strength on surfaces exposed to high-speed impacts.

Environmental considerations have shifted attention away from fluorinated compounds, historically favored for their low surface energy and water repellency. Fluorinated materials, including PFAS-based coatings, raise long-term environmental concerns due to persistence and bioaccumulation. Thus, modern anti-icing solutions must be free from fluorinated compounds and PFAS. The article by Coclite et al., adem.202401532, tackled this pressing issue by developing gradient polymer coatings coupled with electromechanical deicing systems. In this case, the polymer coating, deposited via initiated chemical vapor deposition, enhances ice adhesion reduction while maintaining durability against abrasion, water erosion, and delamination. In adem.202401736, Dignes et al. presented a robust superhydrophobic surface for textiles based on hierarchical nanostructured coatings and inspired by the lotus leaf effect. The coating is formed by silica nanoparticles and long-alkyl-chain silanes that maintains breathability and flexibility while demonstrating durability even under wash cycles. Hydrophobicity is also exploited to harvest water, as reported by Akbari et al. (adem.202402378). The article explores fog water harvesting using superhydrophobic steel meshes obtained through copper electrodeposition and silica-sol modification. The study demonstrates how modifying mesh surfaces enhances water collection efficiency by reducing droplet adhesion and promoting rapid drainage.

Moving toward smart deicing, the review article by Ong et al. (adem.202402139) presented the implementation of acoustic waves in piezoelectric thin-films and plates for deanti-icing, antifrosting, and antifogging applications, focusing on transparent substrates that reflect the current scalability of this technology to lens and outdoor optics systems. In addition, to advance in this topic from the energy efficiency point of view, Pandey et al. in the article adem.202401820 advanced in the discovery of the de-icing mechanisms of Rayleigh and Lamb waves, comparing experiments with sessile droplets and in the IWT with finite element simulations.

This special section of Advanced Engineering Materials integrates advanced material processing, surface engineering, and dynamic liquid-surface control. With innovations in adaptive anti-icing and water harvesting strategies, acoustic wave activation, and fluorine-free coatings, this collection marks a significant step toward technological and environmental advancements in the field.