Tag Archives: anti-icing

McGill University’s proposed anti-icing technology inspired by penguin feathers

An October 24, 2022 news item on Nanowerk announces new research from McGill University (Montréal, Canada),

Ice buildup on powerlines and electric towers brought the northern US and southern Canada to a standstill during the Great Ice Storm of 1998, leaving many in the cold and dark for days and even weeks. Whether it is on wind turbines, electric towers, drones, or airplane wings, dealing with ice buildup typically depends on techniques that are time consuming, costly and/or use a lot of energy, along with various chemicals.

But, by looking to nature, McGill researchers believe that they have found a promising new way of dealing with the problem. Their inspiration came from the wings of Gentoo penguins who swim in the ice-cold waters of the south polar region, with pelts that remain ice-free even when the outer surface temperature is well below freezing.

An October 24, 2022 McGill University news release, which originated the news item, provides more detail, Note: A link has been removed,

“We initially explored the qualities of the lotus leaf, which is very good at shedding water but proved less effective at shedding ice,” said Anne Kietzig, who has been looking for a solution for close to a decade. She is an associate professor in Chemical Engineering at McGill and the director of the Biomimetic Surface Engineering Laboratory. “It was only when we started investigating the qualities of penguin feathers that we discovered a material found in nature that was able to shed both water and ice.”

Fine wire mesh replicates water-shedding and ice-shedding qualities of feathers

“We found that the hierarchical arrangement of the feathers themselves provides water-shedding qualities, while their barbed surfaces lower the adhesion of ice,” explains Michael Wood, a recent PhD graduate who worked with Kietzig, who is one of the co-authors on a new paper in ACS Applied Material Interfaces. “We were able to replicate these combined effects through a laser-machined woven wire mesh.”

Kietzig adds, “It may seem counter intuitive, but the key to ice shedding is all the pores of the mesh which draw water in under freezing conditions. The water in these pores is the last to freeze, creating cracks when it expands, much like you see in the ice cube trays in your freezer. We need such little force to remove ice from our meshes because the crack in each of these pores easily snakes along the surface of those woven wires.”

Promising results from early tests

The researchers carried out wind-tunnel testing of surfaces covered by the steel mesh and found that the treatment was 95% more effective at resisting ice build up than an unenveloped sheet of polished stainless steel. Because there are no chemical treatments involved, the new approach provides a potentially maintenance-free solution to ice buildup on wind turbines, electric towers and power lines as well as drones.

“Given the number of regulations in place in passenger aviation and the risks involved, it is unlikely that airplane wings will ever be simply wrapped in metal mesh,” adds Kietzig. “It is, possible, however, that the surface of plane wings may one day incorporate the kind of texture that we are exploring, and that de-icing will occur thanks to a combination of traditional de-icing techniques working in concert in wing surfaces that incorporate surface texture inspired by penguin wings.”

Although more research is needed, the results thus far are promising.

The image on the left shows the microstructure of a penguin feather (the 10 micrometer closeup of the inset is the equivalent of 1/10th of the width of a human hair, to give a sense of scale) Those barbs, and barbules are branches off the feather’s central stem. The ‘hooks’ serve to attach individual feather hairs together into a mat. On the right is the stainless-steel wire cloth that the researchers decorated with nanogrooves that copy the hierarchy of the penguin feather structure (wire-like with nanogrooves on top). [downloaded from https://www.mcgill.ca/newsroom/channels/news/penguin-feathers-may-be-secret-effective-anti-icing-technology-342980]

Here’s a link to and a citation for the paper,

Robust Anti-Icing Surfaces Based on Dual Functionality─Microstructurally-Induced Ice Shedding with Superimposed Nanostructurally-Enhanced Water Shedding by Michael J. Wood, Gregory Brock, Juliette Debray, Phillip Servio, and Anne-Marie Kietzig. ACS Appl. Mater. Interfaces 2022, 14, 41, 47310–47321 DOI: https://doi.org/10.1021/acsami.2c16972 Publication Date: October 4, 2022 Copyright © 2022 American Chemical Society

This paper is behind a paywall.

Effective anti-icing with nanostructures modeled on moth eyes

According to an August 4, 2020 news item on ScienceDaily the ‘Ice-phobic’ properties of moths’ eyes have inspired a new technology,

Researchers have been working for decades on improving the anti-icing performance of functional surfaces. Ice accumulation on aircraft wings, for instance, can reduce lifting force, block moving parts and cause disastrous problems.

Research in the journal AIP [American Institute of Physics] Advances, from AIP Publishing, investigates a unique nanostructure, modeled on moth eyes, that has anti-icing properties. Moth eyes are of interest because they have a distinct ice-phobic and transparent surface.

An August 4, 2020 AIP news release (also on EurekAlert), which originated the news item, delves further into how they fabricated ‘moth-like eye’ structures at the nanoscale,

The researchers fabricated the moth eye nanostructure on a quartz substrate that was covered with a paraffin layer to isolate it from a cold and humid environment. Paraffin wax was chosen as a coating material due to its low thermal conductivity, easy coating and original water repellency.

“We evaluated the anti-icing properties of this unique nanostructure covered with paraffin in terms of adhesion strength, freezing time and mimicking rain sustainability,” said Nguyen Ba Duc, one of the authors.

Ice accumulation on energy transmission systems, vehicles and ships in a harsh environment often leads to massive destruction and contributes to serious accidents.

The researchers found the moth eyes nanostructure surface coated in paraffin exhibited greatly improved anti-icing performance, indicating the advantage of combining original water repellency and a unique heat-delaying structure. The paraffin interfered in the icing process in both water droplet and freezing rain experiments.

The number of air blocks trapped inside the nanostructure also contributed to delaying heat transfer, leading to an increase in freezing time of the attached water droplets.

“We also determined this unique nanostructure sample is suitable for optical applications, such as eyeglasses, as it has high transparency and anti-reflective properties,” said Ba Duc.

The high transparency and anti-reflective effects were due to the nanostructure being modeled on moth eyes, which have these transparent and anti-reflective properties.

Ice accumulation on a bare coated, nanostructure (NS) and nanostructure covered in paraffin (NSP) samples after a freezing test CREDIT: Nguyen Ba Duc

Here’s a link to and a citation for the paper,

Investigate on structure for transparent anti-icing surfaces by Nguyen Ba Duc and Nguyen Thanh Binh. AIP Advances 10, 085101 (2020); https://doi.org/10.1063/5.0019119

This paper is open access.

Special coating eliminates need to de-ice airplanes

There was a big airplane accident years ago where the chief pilot had failed to de-ice the wings just before take off. The plane took off from Dulles Airport (Washington, DC) and crashed minutes later killing the crew and passengers (if memory serves, everyone died).

I read the story in a book about sociolinguistics and work. When the ‘black box’ (a recorder that’s in all airplanes) was recovered, sociolinguists were included in the team that was tasked with trying to establish the cause(s). From the sociolinguists’ perspective, it came down to this. The chief pilot hadn’t flown from Washington, DC very often and was unaware that icing could be as prevalent there as it is more northern airports. He did de-ice the wings but the plane did not take off in its assigned time slot (busy airport). After several minutes and just prior to takeoff, the chief pilot’s second-in-command who was more familiar with Washington’s weather conditions gently suggested de-icing wings a second time and was ignored. (They reproduced some of the dialogue in the text I was reading.) The story made quite an impact on me since I’m very familiar with the phenomenon (confession: I’ve been on both sides of the equation) of comments in the workplace being ignored, although not with such devastating consequences. Predictably, the sociolinguists suggested changing the crew’s communication habits (always a good idea) but it never occurred to them (or to me at the time of reading the text) that technology might help provide an answer.

A Japanese research team (Riho Kamada, Chuo University;  Katsuaki Morita, The University of Tokyo; Koji Okamoto, The University of Tokyo; Akihito Aoki, Kanagawa Institute of Technology; Shigeo Kimura, Kanagawa Institute of Technology; Hirotaka Sakaue, Japan Aerospace Exploration Agency [JAXA]) presented an anti-icing (or de-icing) solution for airplanes at the 65th Annual Meeting of the APS* Division of Fluid Dynamics, November 18–20, 2012 in San Diego, California, from the Nov. 16, 2012 news release on EurekAlert,

To help planes fly safely through cold, wet, and icy conditions, a team of Japanese scientists has developed a new super water-repellent surface that can prevent ice from forming in these harsh atmospheric conditions. Unlike current inflight anti-icing techniques, the researchers envision applying this new anti-icing method to an entire aircraft like a coat of paint.

As airplanes fly through clouds of super-cooled water droplets, areas around the nose, the leading edges of the wings, and the engine cones experience low airflow, says Hirotaka Sakaue, a researcher in the fluid dynamics group at the Japan Aerospace Exploration Agency (JAXA). This enables water droplets to contact the aircraft and form an icy layer. If ice builds up on the wings it can change the way air flows over them, hindering control and potentially making the airplane stall. Other members of the research team are with the University of Tokyo, the Kanagawa Institute of Technology, and Chuo University.

Current anti-icing techniques include diverting hot air from the engines to the wings, preventing ice from forming in the first place, and inflatable membranes known as pneumatic boots, which crack ice off the leading edge of an aircraft’s wings. The super-hydrophobic, or water repelling, coating being developed by Sakaue, Katsuaki Morita – a graduate student at the University of Tokyo – and their colleagues works differently, by preventing the water from sticking to the airplane’s surface in the first place.

The researchers developed a coating containing microscopic particles of a Teflon-based material called polytetrafluoroethylene (PTFE), which reduces the energy needed to detach a drop of water from a surface. “If this energy is small, the droplet is easy to remove,” says Sakaue. “In other words, it’s repelled,” he adds.

The PTFE microscale particles created a rough surface, and the rougher it is, on a microscopic scale, the less energy it takes to detach water from that surface. The researchers varied the size of the PTFE particles in their coatings, from 5 to 30 micrometers, in order to find the most water-repellant size. By measuring the contact angle – the angle between the coating and the drop of water – they could determine how well a surface repelled water.

While this work isn’t occurring at the nanoscale, I thought I’d make an exception due to my interest in the subject.

*APS is the American Physical Society