Ice-prevention materials developed

Scientists develop a new ice-prevention method which could lead to new type of coating.

Last Updated: Nov 15, 2010, 16:57 PM IST

Washington: Drawing inspiration from mosquitoes and water striders, scientists have developed a new ice-prevention method which they say could lead to new type of
coating on planes and roads, reducing icing-related accidents.

The Harvard University researchers who created the new nano-materials that prevent ice formation by repelling water droplets, said their findings can be used to develop a new
type of coating that can be directly integrated into various materials and commercialised in the near future.

It would be soon give birth to a new ice-prevention method that`s more efficient and environmentally friendly than the traditional deicing chemicals used on planes and roads,
they said.

"We wanted to take a completely different tact and design materials that inherently prevent ice formation by repelling the water droplets," said study researcher Joanna Aizenberg, an engineer at Harvard University.

"From past studies, we also realised that the formation of ice is not a static event. The crucial approach was to investigate the entire dynamic process of how droplets impact
and freeze on a supercooled surface," Aizenberg was quoted as saying by LiveScience.

For their research, Aizenberg and colleagues first looked at how nature deals with water (the precursor to ice). They found, for example, that mosquitoes can defog their eyes, and
water striders can keep their legs dry thanks to an array of tiny bristles that repel droplets by reducing the surface area each one encounters.

"Freezing starts with droplets colliding with a surface," Aizenberg explained. "But very little is known about what happens when droplets hit surfaces at low temperatures."

The team created surfaces to mimic some of those found in nature, with teensy bristles, blades and interconnected patterns, such as honeycombs and bricks. Then they used high-speed videos to observe supercooled droplets hitting these surfaces.

They saw that when a cold droplet hit one of their nanostructured surface, it first spread out, and then the process ran in reverse: The droplet retracted to a spherical shape and bounced back off the surface before ever having a chance to freeze.

By contrast, on a smooth surface without the structured properties, the droplets remained spread out and eventually froze, the scientists reported in the journal ACS Nano.

The nanostructured materials prevent the formation of ice even down to temperatures as low as low as minus 25 to minus 30 degrees Celsius.

Below that, due to the reduced contact area that prevents the droplets from fully wetting the surface, any ice that forms doesn`t adhere well and is much easier to remove than the stubborn sheets that can form on flat surfaces.

"We see this approach as a radical and much needed shift in anti-ice technologies," Aizenberg said. "The concept of friction-free surfaces that deflect supercooled water droplets before ice nucleation can even occur is more than just a theory or a proof-of-principle experiments."

In fact, the team has just begun testing the technology in real-world settings.