In many countries during winter, ice forms on many surfaces, including on cars, aircraft, roads, bridges and overhead power lines. The impact of winter on exposed structures and transportation poses significant dangers and costs to various industries.

Ice is a complex material. It is a disorganized collection of individual crystals formed in circumstances that are sensitive to the conditions. As a consequence, stopping it forming on or removing it from surfaces can be quite challenging. To make things worse, climate change is bringing with it different types of ice.

De-icing involves removing ice from a surface. Anti-icing either prevents the adhesion of ice to a surface (making mechanical removal easier) or liquifies the ice using chemicals that remain on the surface to delay the reformation of ice for a short time. De-icing uses mechanical methods (scraping or pushing), applies heat or uses solid or liquid chemicals that lower the freezing point of water.

De-icing roads and bridges is usually done by spreading salt, often mixed with sand or gravel. However, since salt water still freezes at -18°C (0°F), it is of no help when the temperature falls below this. It also has a tendency to cause corrosion, rusting the steel used in most vehicles and the rebar in concrete bridges.

De-icing aircraft on the ground is usually done either by spraying them with fluids that liquefy the ice and delay its reformation or by blowing heated air to melt the ice and blow off loose snow. Aircraft anti-icing systems are used when the aircraft is in the air, to either prevent the formation of ice or to physically remove it from vulnerable surfaces.

Surfaces that are resistant to the accumulation of ice on them have been developed for several decades, to reduce winter-related impacts. Non-wetting, liquid-infused and hydrated surfaces have been developed. However, high freezing temperature, high ice adhesion strength and subsequent ice accretion, low mechanical durability and high production costs have restricted their application in practice.

Numerous factors, including reducing and preventing ice accumulation, significantly decreasing ice adhesion and/or delaying water solidification, need to be considered in order to create such icephobic surfaces. An icephobic surface is similar to an anti-icing surface, which may then be amenable to rapid de-icing.

Using mechanical methods such as centrifugal force and push-off tests to measure ice adhesion on surfaces may not always correlate or provide the required information for specific applications and may not realistically replicate how ice is removed from surfaces. Measuring ice-on-ice friction may not provide the information either.

Now, a team lead by Professor Jean-Denis Brassard at Université du Québec à Chicoutimi has developed a novel device called the human motion–inspired automated apparatus (HMA) that mimics manual de-icing performed by humans in a scraping mode.¹ The method aims to better assess icephobic properties of surfaces.

The researchers developed a unique procedure using low icing conditions, which are challenging to evaluate using conventional methods.¹ They assessed four surfaces: an epoxy-based hydrophilic coating, a hydrophobic silicone elastomer coating, a hydrophobic epoxy–silicone coating and aluminum as a reference. The device differentiates surfaces according to several important parameters, including the normal force required to initiate ice scraping removal, the maximum force achieved, the angle of attack and the equivalent force.¹ All of these are consistent with validation tests conducted by humans. Of the surfaces, the silicone coating required the lowest normal force and the epoxy–silicone coating had the lowest maximum and equivalent forces.

The HMA aims to transform the evaluation of icephobic materials by providing improved accuracy, repeatability and versatility in testing, while emulating removal of ice from surfaces by humans. This may lead to the development of improved icephobic surfaces.

REFERENCES
1. Brassard, J.-D., Sobahni, S., Osorio, M.-L. and Momen, G. 2024, “New insights into icephobic material assessment: Introducing the human motion–inspired automated apparatus (HMA),” Cold Regions Science and Technology, 229 (32), 104351. DOI:10.1016/j.coldregions.
David Whitby is chief executive of Pathmaster Marketing Ltd. in Surrey, England. You can reach him at pathmaster.marketing@yahoo.co.uk.