Recent advances in repelling snow and ice unravel the key differences between the two forms and present novel solutions for keeping surfaces free of both.
There are many reasons to keep surfaces free of snow and ice—from safety issues for walking or driving to structural considerations for power lines, solar panels, and transportation infrastructure. But while ice-phobic surfaces with low adhesion strength are becoming commonplace, the design of snow-repellent surfaces still lags behind.
Snow vs. Ice Adhesion
Although closely related, ice and snow exhibit contrasting adhesion mechanisms and fracture mechanics on solid surfaces. This is due in part to how snow forms and accumulates, since it can happen in a variety of different atmospheric conditions.
The differences in formation processes lead to various types of snowflakes—wet or dry, dense or fluffy—all of which display varying adhesion mechanics. Designing a universal platform that can repel diverse snow types therefore remains a significant challenge.
One key difference between snow and ice is that snow must undergo melting to strongly adhere to a surface. Melting during atmospheric descent results in wet snow with a relatively high liquid water content, but this rarely leads to thick adhesive ice.
However, when snow accumulates on a surface initially above 0 °C, extensive melting and refreezing can occur and lead to a highly adhesive ice layer.1 In contrast, icing occurs when supercooled water droplets touch surfaces that are themselves below the freezing point.
Solutions Inspired by Nature
To mitigate snow adhesion from melting, several recent studies offer advances in passive snow-repellent technology, enabling shedding of snow without external input of chemicals, heat, or mechanical forces.
A research team in Canada worked to develop a passive snow-repellent surface that combines the characteristics of both thermal insulation and superhydrophobicity.1 While neither approach alone is sufficient for passive shedding, the researchers report that combining the two may enable real-world snow repellency.
The group found that an air gap or silica aerogel used as a thermal barrier minimized snow melting and prevented formation of the adhesive ice layer. The addition of superhydrophobicity repelled interfacial meltwater droplets and reduced the contact area, further lowering the snow adhesion strength.
Interestingly, both approaches have a basis in nature: some plants trap liquid as a lubricating layer between solid surfaces and accreted ice to reduce the interaction, while others have hydrophobic self-cleaning properties.2,3
Adding Some Texture
Anti-icing superhydrophobic surfaces and water contact angles have previously attracted interest due to their repellency and low ice affinity. These kinds of smooth, hydrophobic solid surfaces exhibit low ice adhesion values, potentially because increased water depletion at the interface weakens van der Waals’ interactions between the ice and substrate. However, weak durability has been a limitation for widespread applications, and some argue that a textured surface might provide increased utility.4
In a study published in ACS Applied Materials & Interfaces, researchers fabricated a robust textured surface by chemically oxidizing ultrafast-laser-prepared periodic copper microstructures and modifying the periodic micro–nano structure (PDMS) to create a surface composed of microcones, nanowires, and tightly combined PDMS, resembling hedgehog-like spines.5 This triple-scale superhydrophobic surface demonstrates long-term anti-icing performance with low adhesion.
Traditional active anti-ice or -snow systems use include electro-thermals, mechanical vibration, or chemical application, all of which consume mass energy and rely on external input. These new advances in passive snow- and ice-repellent materials and bio-inspired approaches may therefore find immediate real-world use on surfaces ranging from solar cells to overhead transmission cables and car windshields.
Explore Related Research in ACS Journals
Triple-Scale Superhydrophobic Surface with Excellent Anti-Icing and Icephobic Performance via Ultrafast Laser Hybrid Fabrication
Icephobic Surfaces Induced by Interfacial Nonfrozen Water
Robust Superhydrophobic Surfaces via the Sand-In Method
In Situ Activation of Superhydrophobic Surfaces with Triple Icephobicity at Low Temperatures
Key Factors Affecting Durable Anti-Icing of Slippery Surfaces: Pore Size and Porosity
- Zhao, X. et al. Thermal Insulation and Superhydrophobicity Synergies for Passive Snow Repellency. ACS Appl. Mater. Interfaces 2022, 14, 18, 21657–21667
- Lv, J. et al. Bio-Inspired Strategies for Anti-Icing. ACS Nano 2014, 8, 4, 3152–3169
- Cao, L, et al. Anti-Icing Superhydrophobic Coatings. Langmuir 2009, 25, 21, 12444–12448
- Meuler, A. J. et al. Relationships between Water Wettability and Ice Adhesion. ACS Appl. Mater. Interfaces 2010, 2, 11, 3100–3110
- Chen, C. et al. Micro–Nano-Nanowire Triple Structure-Held PDMS Superhydrophobic Surfaces for Robust Ultra-Long-Term Icephobic Performance. ACS Appl. Mater. Interfaces 2022, 14, 20, 23973–23982