Research Briefs, Science & Technology

Penguin feathers and the ice cube tray effect

One thing that is always on the mind during a Montreal winter is the cold and, more specifically, the ice. Living in Montreal makes slipping on ice inevitable. A painful landing on your behind, however, is not the only inconvenience associated with this crystalline structure. The buildup of ice on power lines, utility poles, and other structures can often spell disaster for those dependent on this infrastructure, putting out the lights and preventing heating systems from functioning during the winter months.

The Great Ice Storm of 1998 is a prime example of the damage this weather and ice can cause. Nearly 30,000 utility poles were felled, leaving millions of people in Quebec without power. Another instance of dangerous inclement weather occurred in China in 2008, when  winter storms left millions without power and damaged 80 per cent of power supply stations in the Guizhou province alone.

Even the successful removal and prevention of ice buildup often comes with unintended side effects. The chemicals used in some de-icers can seep into the environment during their use, transport, and storage, getting into the water supply and damaging the ecosystem. Other methods of de-icing may not involve chemicals, but any active method that relies on machinery requires consistent upkeep.  

A team of McGill researchers led by Anne Kietzig, associate professor in McGill’s Department of Chemical Engineering, looked to nature for inspiration in designing a new de-icing technique that avoids these pitfalls. The researchers found that penguin feathers possess an unique structure that allows them to shed ice more easily. When they copied the structure of the penguins’ feathers and applied it to a steel mesh, they found that the mesh was 95 per cent more effective at de-icing than an unenveloped sheet of polished stainless steel. 

Initially, the penguins’ feathers seemed like those of any other bird. But upon closer inspection under the microscope, Kietzig and her team discovered that the primary structures, or central beam of the feathers, had a superimposed nanostructure that formed a “groovy texture.” This is in addition to the microstructure—barbs and barbules—that are also part of the feather. Since Kietzig’s lab specializes in laser micromachining, the structure of penguin feathers was easy enough to replicate.

These feathers work, in a way, like an ice cube tray: The structure of the feather has pore-like areas where the water is left to freeze, and when it does, it expands, breaking the ice that formed around it and allowing that ice to slide off. The research team realized that the mesh’s pores could function in the same way as the barbs and barbules of a feather. Using a laser, researchers copied the feather’s groove-like texture in their mesh prototype. The final product—the overlap of microstructure and nanostructure—is what makes this mesh so efficient at preventing ice buildup and formation.

Although the uses for this technology seem obvious, like coating utility poles and airplane wings, putting it into practice isn’t so simple. It is still unknown if the mesh could be properly and stably attached to surfaces.

“I am not sure that metallic woven mesh will be suitable to attach to other surfaces,” Kietzig said in an interview with The McGill Tribune. “You have to imagine it’s like your kitchen tinfoil in thickness and rigidity. I can’t glue, I can’t solder.”

In addition to the lack of structural integrity in practice, the process of applying this coating could be prohibitively expensive for many industries. The project, therefore, is a starting point for future testing of this sort of structure.

“This is why I think [in the] very long run, what we want to do is use the mesh as a template to learn more about the relevant parameters in that mechanism, and then extract to structural surfaces out of which things are made,” Kietzig added.

Though more practical research is in order, it seems that the flightless, ice-sliding birds featured in countless kids’ books could just be the key to preventing future ice-related power outages.

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