Science

Eco-friendly anti-frost system tells ice where to go

Doctoral student Farzad Ahmadi sets up a scale model of a passive anti-frosting surface
Doctoral student Farzad Ahmadi sets up a scale model of a passive anti-frosting surface
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Doctoral student Farzad Ahmadi sets up a scale model of a passive anti-frosting surface
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Doctoral student Farzad Ahmadi sets up a scale model of a passive anti-frosting surface
A scale model of the team's anti-frosting technology applied to a small sheet of untreated aluminum
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A scale model of the team's anti-frosting technology applied to a small sheet of untreated aluminum

In order to keep ice from forming on surfaces such as airplane wings, toxic chemicals are typically applied. And while there are experimental chemical-free alternatives, they still require a power source or involve coatings that can wear off. A new system, however, gets around those issues.

Developed by a team at Virginia Tech, the technology doesn't keep surfaces completely ice-free, but it drastically reduces the area that is ice-covered.

It centers around microscopic arrays of elevated grooves that could conceivably be etched into the surface of materials such as the aluminum used to build an airplane wing, or the glass for a car's windshield. In cold, wet environments, water wicks into these grooves and freezes into stripes of ice, which cover about 10 percent of the surface.

"These ice stripes siphon all nearby moisture from the air, preventing any condensation or frost from growing on the intermediate portions of the surface (the other 90 percent)," assistant professor Jonathan Boreyko tells us. "This is because ice is a low-pressure chemical, analogous to salts."

A scale model of the team's anti-frosting technology applied to a small sheet of untreated aluminum
A scale model of the team's anti-frosting technology applied to a small sheet of untreated aluminum

The problems with simply using salt, he adds, is that it gets diluted as it draws in more water, plus it's environmentally unfriendly once it gets washed off of the surface. By contrast, the ice in the micro-grooves simply becomes more ice as it attracts moisture. That said, it grows at a much slower rate than it would if it were forming a single continuous sheet.

So far, the system has been successfully tested on ordinary aluminum (seen above). It could reportedly be used on just about any material, however, as long as the grooves were applied in the correct pattern.

A paper on the research was recently published in the journal ACS Applied Materials and Interfaces.

Source: Virginia Tech

4 comments
akarp
Why does the ice grow slower? I can understand how attracting water vapor that would freeze in a single uniform layer could be 'directed' to freeze in a 10% coverage channel, leaving 90% open say for vision. But why would the ice grow slower? If its cold enough to freeze the water vapor in the air...it must freeze somewhere...unless energy or chemistry is added?
Bob Stuart
I got how it works, but isn't an "elevated groove" a ridge? When ice gets into micro-cracks in rock, it makes gravel. I'd be careful.
owlbeyou
I don't get it. Is there a reason why a network of heating wires aren't built in to every new plane under the skin? Then, while the jet is on the tarmac waiting, it can be plugged in to keep any ice from forming. Voila! No chemicals! I must be missing something because this solution seems too easy.
KungfuSteve
I wonder if it would be better to use (or combine) a method which vibrates or condenses the wings surface. A birds wing would not get Icy, as they are flexing and moving constantly. Wings are fixed on a plane... however, if every so often the wings are Yanked into flexing a bit (such as by using a metal cable and motor ..or solenoid) ... that would crack any formed ice, and send it off into the blue skies. Vibrational transducers, that change frequency, may also be an option. This might effect fuel efficiency if left on constantly... but then again... it might also improve it too. Not sure if microvibrations are adequate to prevent formation or not... but it seems to make sense in my mind. The other thing I wonder about... is how flexible are the wings themselves? If wings can be made to be more fluid... that might actually solve a lot of turbulence issues. Ive studied and practiced high level, combat martial arts, for over 20yrs. The highest levels in these arts are found in the "Internal" systems... such as Tai Chi. In this art.. one learns how to utilize the ability to become softer and more fluid... yet retaining great power and strength. If a far larger and stronger Op tries to push a high level TC practitioner... the TC Op will twist and shift ever so slightly, and send them flying... all without using much energy nor strength. The more Rigid the Op's attacking forces (and tightly linked body structure)... the greater the power the TC practitioner will have to use against the Op. As for the idea of heating wires... that would require a Lot more juice than one may realize... as well as being very difficult to install. Also, the amount of heat needed to overcome that amount of ice-cold rushing air flow... would probably be way too great... to be practical. As for the Ice cracking wings like Ice cracks rocks... I believe this depends on the Geometry of the Groove. If its a squared groove.. Ice would push the walls apart... where as if the groove is in a "V" shape... the ice would push itself out of the "V", without causing much, if any, stress to the walls of the grooves. The only potential issue... is the grooves getting chipped out, and or dirty... and thus the channels could become more "squared" and or Pitted. This could be caused from debris, hail, birds...etc... which is another thing that All of these ideas have to consider. Biologically speaking... we as humans use flowing liquid, as a temperature regulator... (as well as a transport mechanism). Some serious engineering could potentially make a plane that cycled engine heat into a flowing vein system... but... being liquid based, would add weight to the system. There may be similar options, that may be more effective / efficient.