Research Could Lead To More Durable Surface Coatings
Scientists from the University of Dayton Research Institute have
manipulated the process of shell and pearl formation in oysters to
demonstrate a method for depositing pearl-like coatings onto
various metal surfaces. University personnel tell ANN this
biomimetic research could lead to new lightweight, durable coatings
able to protect aircraft from impact and corrosion.
The significance of this Air Force Office of Scientific
Research-funded project is that biological ceramic coatings are
naturally derived and do not involve the high-temperature,
high-pressure environment required by existing methods for ceramic
deposition.
The Air Force currently uses protective ceramic coatings on
aircraft for various purposes, but officials say a nonhazardous
process that creates ceramics at room temperature and pressure
would be an interesting alternative.
Doug Hansen, a UDRI senior research scientist, is building on a
fellow investigator's recent discovery that oysters use blood cells
to deposit crystals that form shell and pearl. Clemson University's
Dr. Andrew Mount made the discovery, which negated scientists'
long-held belief that oysters create their shells by precipitating
calcium carbonate from seawater.
"We have taken those blood cells and manipulated them to deposit
crystals in an ordered manner on a variety of metal surfaces,
resulting in a multilayered ceramic coating," Hansen said.
The goal of the program is to understand the process that the
cells use to form and deposit these crystals into layers. Hansen
said he hopes to achieve a high level of control over the thickness
and placement of the ceramic coatings on materials that require
strong but lightweight protection.
Hansen and his wife, Karolyn, also a UDRI senior research
scientist, maintain live oysters in their lab and use them to
demonstrate ceramic deposition inside and outside of the organism.
The Hansens insert small pieces of metal into the oysters, which
triggers the formation of pearl. They also take blood cells out of
the oysters, which when placed on metal behave as if they are
growing a shell on the surface.
Hansen recently reported having successfully deposited
multilayer coatings on four different metal surfaces: two aircraft
aluminum alloys and two biomedical alloys.
Currently the couple is working to characterize the coatings in
terms of corrosion resistance, strength and adhesion. They also are
developing methods to direct the application of the ceramic films
at specific sites on metal surfaces.
Maj. Jennifer Gresham, AFOSR program manager, said she hopes
this research will lead to a better understanding of how biological
systems can formulate ceramic coatings and films. Such knowledge
could allow for the development of synthetic processes to deposit
ceramic films and coatings without the necessity for
high-temperature and high-pressure conditions.