We live in an age when replacement body parts are a major commodity.
Most of us know someone who has had a hip or knee replaced, and work
continues on artificial elbows, backs, sacrums, and similar body
skeletal parts. The problem is that none of the man-made body parts
available have the strength and endurance of the original bone.
Stainless steel and titanium are great materials, but they are not
good as bone. Bone does not shatter and, when a crack develops in a
bone, the crack does not run. Bone has an organized network of
fibers which toughen the bone. There is a lattice of little struts
bone which form a spongy energy-dissipating framework. As bone ages
can lose some of these properties, but the man-made substitutes do
begin to measure up to the bone itself.
In nature there is a material known as nacre. Nacre makes up most shells and is made up of layers of calcium carbonate interwoven with layers of organic glue. You might think of the napoleon, a pastry that is made up in somewhat the same way, but without the glue and of a softer material. In nacre the layers are incredibly thin--about the width of a wavelength of light, which is why shells made of nacre reflect a rainbow of colors (like in an abalone). A crack cannot run through the nacre, because when it gets started it hits a glue layer and is stopped. That makes the nacre incredibly hard to break and virtually impossible to shatter--the ideal bone material.
Biomimetics is the art and science of transforming biological designs into human use. So far no one has been able to make synthetic nacre, but a major push is being made to do so. There is a huge need to be able to make hips and knees and other bone parts that act more like bone. It is remarkable that in studying bone we have been able to see how incredible it is, and when we look for a material to replace bone we find that it is present in sea shells and not in metallic fabricating plants. The materials God uses in making his creatures is of the highest quality, and man is challenged in his attempts to come close to that original.
--Reference: Scientific American, June 2006, page 28.
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