Poison dart frog inspires new way to deice planes
Among the hazards of winter flying is being stuck on a plane as it's being sprayed down with antifreeze to prevent ice build-up on the wings. While this removes the ice and snow, it can be expensive and wasteful, as well as being harmful to the environment. A mix of a chemical called glycol and water is sprayed on in bulk, causing travel delays especially when airports have run out, as happened at Charles de Gaulle Airport in Paris in December. Now, a researcher from Arizona State University believes he has found a more economical way to fight the problem. Writing in the journal Advanced Materials Interfaces, Konrad Rykaczewski and his colleagues describe how they have come up with a system that would allow a plane to prevent ice build while in the air. The system, which was tested out in a lab setting, works on two levels. The first includes superhydrophobic coatings that make freezing raindrops bounce off the surface of the wing instead of forming ice and sticking. But should that system fail, as it might with excessive frost, a backup system releases antifreeze to ensure the wings stay ice-free. "The results were quite impressive," Rykaczewski said. "Ice accumulation was delayed ten times longer on our samples than on superhydrophobic or lubricant impregnated-surfaces in all the icing scenarios. Furthermore, we also saw about a ten-time delay in ice accumulation during freezing rain when compared to surfaces flooded with antifreeze."Rykaczewski says his inspiration for the concept had little to do with cold weather. Rather, he began to envision a two-tiered system after seeing a poison dart frog while on a vacation in Panama with his wife. He returned to the United States and began examining just how the frog releases toxin through its skin. He found one layer is in contact with the outside environment and an inner layer contains the toxin that it releases when threatened."This was exactly the functionality that we wanted from the anti-icing surfaces," he said. "We wanted to secrete antifreeze only in response to the presence of ice on the surface, irrelevant of form - frost, glaze." If used with airplanes, Rykaczewski envisions the two layers as thin as paper being sprayed onto the wing of the airplane. The first layer would be infused with the antifreeze while a second layer on top would be exposed to the atmosphere and contain the superhydrophobic layer to repel the rain droplets. "When the surface starts icing over, e.g. due to frost, the pores fill up with condensate or ice and make contact with the antifreeze," he said. "Due to the contact, the antifreeze starts melting ice and diffusing. This is quite nice since in a way it is passive - the release of antifreeze happens by itself and does not require any external input from an operator." For larger planes or longer flights, Rykaczewski said a syringe with a pump could be added to ensure there is enough antifreeze for the journey. Other experts who study deicing said Rykaczewski's approach holds promise, though, like all innovative ideas, it still needs to be proven commercially feasible. "The work in this paper is very elegant and novel," said Neelesh A. Patankar, the Charles Deering McCormick Professor of Teaching Excellence at Northwestern University, who was not involved in the study. "Taking inspiration from nature, this team has demonstrated a clever approach where they combine the advantages of anti-freeze sprays and textured surfaces," he told CBS News. "This idea is new and in my opinion seems to be the most promising among various approaches presently being explored by the research community. " Washington State University's Xianming Shi called the approach "new and innovative." But he also said it could be improved upon, including finding a way to continuously replenish the antifreeze reservoir.He also warned the cost would likely be higher than conventional methods and additional work needed to be done to ensure the system wouldn't cause problems for the plane itself. "This study takes things one step further but it certainly isn't the silver bullet yet," he said. "The idea is intriguing but there are practical constraints. One of them is the cost and this would also significantly manipulate the surface (of the wing) so there might be some unintended consequences." Rykaczewski acknowledged that it would take time before his method could find its way the commercial runway. Until then, he hopes to try it out on a smaller scale with possible candidates being wind turbines in cold weather climates or drones that fly in regions like the Arctic. "The benefit of the drones is that you don't have a person on board but it has the same physics with flying," Rykaczewski said. "When you build up ice on the wing, it changes lift and changes shape."