June 13, 2012

Researchers Create Anti-Ice Surface

Derek Walter for redOrbit.com

A team of Harvard researchers has developed a superior method for keeping metal surfaces free of ice and frost.

It´s a difficult task, but one that could have substantial implications for metal surfaces used in wind turbines, aircraft, refrigeration systems, marine vessels and the construction industry. Airplane wings, railings, and other fabrication parts are just a sample of how often metal is used throughout the world in most of the largest industries.

The Harvard team, led by Joanna Aizenberg, a professor of materials science at the Harvard School of Engineering and Applied Sciences, has been seeking to find ways to minimize the impact of freezing temperatures on metal-based materials.

The inspiration? The water repellant leaves of the lotus flower. This effect is commonly known as the Lotus Effect. The complex architecture of the leaves´ surfaces minimizes adhesion.

Replicating this impact is a tremendous task. High humidity and extreme pressure are two major deterrents to a minimally adhesive surface.

To remedy this issue, the research team created a new technology suited for high humidity and extreme pressure. It´s called SLIPS (Slippery Liquid Infused Porous Surfaces).

SLIPS are designed to create a “molecularly-free” flat surface in which liquids will slide right off. This becomes more difficult to maintain as temperatures, change, however. In the case of airplanes, these metal surfaces are ones that have the most riding on the possibility of ice formation.

Aizenberg and her team found a way to cover the metal with a rugged material that the lubricant is able to attach to. The coating can then be sculpted to lock in the lubricant and then be covered over a large area.

Yet even with these advances, challenges remain, according to the research team.

“The lack of any practical way to eliminate the intrinsic defects and inhomogeneities that contribute to liquid condensation, pinning, freezing, and strong adhesion, have raised the question of whether any solid surface (irrespective of its topography or treatment) can ever be truly ice-preventive, especially at high-humidity, frost-forming conditions,” Aizenberg said.

The SLIPS technique shows the most promise among those that have been tried as of recent. According to the researchers, the SLIPS method demonstrated the prevention of ice forming at some very cold temperatures.

“Unlike lotus leaf-inspired icephobic surfaces, which fail under high humidity conditions, SLIPS-based icephobic materials, as our results suggest, can completely prevent ice formation at temperatures slightly below 0°C while dramatically reducing ice accumulation and adhesion under deep freezing, frost-forming conditions,” said Aizenberg.