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Professor Stuart Rowan at Case Western led a team of researchers to develop a self-healing coating.  (Source: Case Western Reserve University via YouTube)

When exposed to UV light, the polymer disassembles and reforms, patching scratches or cracks.  (Source: Case Western Reserve University via YouTube)

The material is shown here, healing from a razorblade scratch.  (Source: Case Western Reserve University via YouTube)
New coating is ready for commercial applications

A major emerging field of materials science is to formulate new materials which, like living organisms, can self heal from macroscopic or microscopic damage.  An international team of researchers has created a new kind of coating that could form the basis of true self-healing car paints [press release 1press release 2; video].  

Nissan implemented a primitive form of self-healing car paint in its EX and G lines, but the actual real world results of that endeavor have been mixed.

This new effort is comprised of teams from Case Western Reserve University in Cleveland, Ohio, led by Stuart J. Rowan; the Adolphe Merkle Institute of the University of Fribourg in Switzerland, led by Christoph Weder; and the U.S. Army Research Laboratory at Aberdeen Proving Ground in Maryland, led by Rick Beyer.

They have created a new self-healing coating that could be used as the basis of paint.  The coating is formed via a technique called supramolecular assembly.  Whereas usual polymers are single large molecules with thousands of atoms, the special new coating is an ionic polymer composed of metal ions and smaller polymeric molecules.  The metal ions act as ”glue", linking the smaller molecules together to form chains.

The polymer's special character shows up when you expose it to UV light.  The polymer enters a "molten" state, filling gaps and scratches.  It then resolidifies.  

Stuart Rowan, a professor of macromolecular engineering and science and director of the Institute for Advanced Materials at Case Western Reserve University, describes, "These polymers have a Napoleon Complex.  In reality they're pretty small but are designed to behave like they're big by taking advantage of specific weak molecular interactions."

Researchers created large scratches and dings on the test coat, then shined a UV light on it, locally.  The material "healed" itself in seconds.  And unlike the self-healing found in living creatures, the material exhibited the ability to go through numerous scratching/healing cycles in a brief time without a loss of integrity.

The researchers evaluated a number of metal ion polymers before picking their current target.  They found that mechanical properties (strength, flexibility without breaking, etc.) increased as the order of the resulting polymer increased.  But as the mechanical strength increased, the ability to be healed decreased.  So scientists opted for a moderate polymer with decent healing and mechanical traits.

As we discussed in our previous piece on self-healing plastics, microcracks -- microscopic scratches or cracks -- ultimately lead to big damage over time.  Aside from resisting macroscopic scratches, the materials could undergo periodic treatments with the UV lamp to prevent wear from microcracks as well.

The research team feels the coating is ready for prime time.  Professor Rowan says the next step is commercialization, stating, "One of our next steps is to use the concepts we have shown here to design a coating that would be more applicable in an industrial setting."

The study on the work was published [abstract] in the journal Nature, perhaps science's most prestigious journal.  

The work was funded by the Army Research Office of the U.S. Army Research Laboratory, the U.S. National Science Foundation, and the Adolphe Merkle Foundation.

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RE: uv???
By tastyratz on 4/24/2011 6:24:11 PM , Rating: 2
I did, but I could sell you a bridge too.
They could have it in practice but melting does not happen at one light level while it remains hard at slightly lower levels. This means on a hot southern sunny day after the clear coats uv inhibitors have begun to wear in a few years you might find the paint soft and less forgiving. Maybe it will smear if you lean on your car, etc. Maybe it could eventually run very slowly in florida for example. Old houses with old windows are wavy because glass still is not completely solidified.

Ever notice how glow in the dark pigments capture UV light and over time do not glow so well? What happens when this ages?

They can make all the claims in the world but only time can tell. Sure it sounds impressive on paper now...

RE: uv???
By LRonaldHubbs on 4/25/2011 6:51:48 AM , Rating: 2
Old houses with old windows are wavy because glass still is not completely solidified.

No, that is a variation on a common misconception that has long been debunked.

RE: uv???
By Manch on 4/25/2011 3:46:23 PM , Rating: 2
Fine, you can try to sell me a bridge after you've completed you SRA reading comprehension cards.

In the above article, read the paragraph:
The researchers evaluated a number of metal ion polymers before picking their current target......So scientists opted for a moderate polymer with decent healing and mechanical traits.

You keep saying "melting" like they invented paint with the hardness of a crayon. That's not what it is. It will not drip off your car or take an imprint of your hand. Also look at the link IN THE ABOVE ARTICLE about the clearcoast Nissan used. This is an advance form of an already commercially used product. They're using metal ions instead of chitin

I'll drop it down for you. When you scratch the polymer, you distrub it's natural/ideal chained structure made up of spheres(metal ions) and sticks (polymeric molecules). When this broken structure is exposed to UV light it activates the metal ions, which in turn atracts the ends of the polymeric molecules. They then self assemble. Once it's back into this chained structure even with continued UV exposure it will do nothing else since it's back to its natural/ideal structure.

Like the earlier version Nissan was using this polymer will eventually lose it's ability to self repair and the scratches will be unable to fix themselves Dont worry tho, you will not walk out to the parking lot one day and shriek in horror because your car now has a bare metal finish.

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