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 1; press release 2; video].
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
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.