While some parts of the world are still experiencing the sweltering summer heat, other places are already preparing for what could be a potentially brutal winter. That's the case for MIT researchers who developed a new way to combat ice buildup.
Ice plagues everything from airplane wings to powerlines to wind turbines during winter months. These issues can cause a domino effect until problems are resolved. Current prevention methods to deal with the ice involve energy-intensive heating circuits or dangerous chemical sprays involving ethylene glycol that prevent buildup entirely.
The MIT solution is relatively simple by comparison. It's a three-layered material that can be applied to surfaces and collects solar radiation. It converts that radiation to heat, and then distributes the heat so the melting doesn't only occur in the direct sunlight.
Associate Professor of Mechanical Engineering Kripa Varanasi worked with postdoctoral candidates Susmita Dash and Jolet de Ruiter on the project.
“Icing is a major problem for aircraft, for wind turbines, power lines, offshore oil platforms, and many other places,” Varanasi said. “The conventional ways of getting around it are de-icing sprays or by heating, but those have issues.”
Taking cues from the sun
As the MIT team pointed out, airlines opt for de-icing sprays with ethylene glycol to bypass active heating. Varanasi looked into using superhydrophobic surfaces to prevent icing, but those coatings can sometimes fall to frost which gives enough surface tension to stick.
Instead, the team wondered if there was "a way to capture [the sun's] heat and use it in a passive approach."
They discovered there was, and that producing a volume of heat to melt all of the ice wasn't needed. There only needed to be a layer where the ice meets the surface. That would be enough to create a thin layer of water -- a layer that would let the ice slip off the surface.
How the layers melt dangerous ice
How did the team manage to create such a slippery surface? They used the top layer as a sun absorber to trap light and convert it into heat. The efficient material absorbs 95 percent of the sunlight and only loses 3 percent to re-radiation, according to the researchers.
The team also needed a layer to spread out that heat. They used a 400-micrometer thick aluminum heated by the absorber layer above it to spread the heat throughout the entire surface.
The bottom layer is just a foam insulation that keeps heat from being wasted and locks it into the surface.
“In addition to passive de-icing, the photothermal trap stays at an elevated temperature, thus preventing ice build-up altogether,” Dash said.
The three layers are all relatively inexpensive, and the coating was tested in real-world settings with detailed measurements. The research was published in a recent edition of the journal Science Advances.
“Scalability of these approaches and thinking about appropriate packaging, specific weight, etc., of the de-icing layer are important practical challenges going ahead, especially when it comes to the aerospace application. The paper also opens up intriguing possibilities around smart and flexible thermal packaging, and thermal metamaterials research to realize its full potential. Overall, an excellent step forward,” he said.