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August 17, 2009

Antlers, Shells and Beaks

What nature can teach us about making things stronger, lighter and sharper

The old saying 'ram tough' is something some researchers at the University of California, San Diego (UCSD) are taking seriously. Ram horns are among many naturally tough objects that these scientists analyze, scrutinize and magnify thousands of times in their lab.

Marc Myers, a materials science professor, says it all started with the abalone--a sea snail with a shell as tough as nails. You think horns and antlers are tough, just try to break an abalone shell in two.

"About ten years ago, I was involved in a project for the Army," says Myers. "We were developing armor. The abalone is made out of a chalk-like material, calcium carbonate, and although chalk is very weak, the abalone shell is thousands of times stronger than chalk. You can try to break it, you cannot succeed."

Discovering that a simple material like chalk could be so strong left Myers curious about how shells and others objects in nature are structured for strength and durability.

Extraordinary properties

Today, the UCSD research team, led by Myers and fellow materials science professor Joanna McKittrick, studies horns, antlers, teeth, beaks and more. "The goal of our research is to understand the extraordinary properties of these biological samples to see if we can duplicate them in the lab," says McKittrick.

For example, how can ram horns and elk antlers withstand impacts without breaking apart? And who knew horns were so different from antlers?

"The first thing we do is cut it and look at the cross section and that's how we identify what's known as the microstructure of the materials," says McKittrick. "We look at it at the higher magnifications so we can see the features that we can't see with the naked eye."

Using a state-of-the-art scanning electron microscope (SEM) purchased with support from the National Science Foundation, scientists are seeing details they've never seen before. The antler and other materials can be magnified as much as fifty-thousand times.

"What's surprising about the elk antler is it's really a bone," McKittrick explains. "It has very similar composition and structure to our skeletal bone."

Made for fighting

McKittrick says they're learning that antlers have a porous bony center surrounded by a sturdy, dense outer shell that evolved over millions of years to do one thing: fight.

"It doesn't serve any structural purposes," she says. "Our bones serve a structural purpose, they create bone marrow--they are calcium reserves. But antlers, they're just used for fighting so they have to be very robust."

The same can be said about ram horns. But horns are different from antlers. Horns are hollow and made essentially of keratin, the same stuff found in our fingernails and hair. In the lab, horn samples, like antlers, are tested for endurance and strength.

Undergraduate Brandon Reynante, a member of the research team, built his own version of a crash test simulator. Taking a stamp-size sample of a ram horn, Reynante sets it at the bottom of a four-foot, tower-shaped machine.

"The machine is designed to simulate rams butting heads during fighting," says Reynante. "Once we have the machine set up, we just press the button to drop the impactor."

The impactor smashes the sample. Surprisingly, only the center portion of the horn sample is damaged. The rest stays intact.

How can these hollow horns withstand such impacts? McKittrick says it has something to do with microscopic tubules running lengthwise that help horns withstand intense forces.

From horns to teeth

Myers became fascinated with the serrated teeth found in certain meat-eaters, including sharks and Komodo dragons.

"You can see the serrations, the tiny serrations along the tooth," says Myers. "The tooth of the Komodo dragon, even though it's a huge and dangerous animal, the teeth are fairly small, but vicious. And, it can cut through meat very easily, through tiny serrations."

Then there's the rainbow-colored toucan bird. Its beak is one-third the size of its entire body. You would think the bird would be too beak-heavy to fly, but a toucan can soar and its beak weighs almost nothing.

"It has a structure that is utterly fantastic," says Myers. "The inside, it's almost hollow and it has foam; and on the outside, it has a shell and it's extremely strong."

Materials of the future?

If you wonder why we should bother knowing about all of this, think 'gecko.' Scientists studying and magnifying the gecko's feet and its uncanny ability to stick to surfaces led to the creation of a new surgical tape.

Similarly, studying horns and antlers could help engineers create better helmets and knee pads. Knowing more about the rugged shells of armadillos and tortoises could lead to better armor for the police and military. Keying in on the sharp details of the serrated teeth in sharks and Komodo dragons could bring us a step closer to better tools.

And remember the toucan bird? Well, one day, the structure of its beak may inspire a new lightweight, super-strong material to build better boats, planes and automobiles.

Miles O'Brien, Science Nation Correspondent
Ann Kellan, Science Nation Producer

Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.