Engineers Are Seeking A New Material For Planes, So Open Wide
It might surprise you to learn that although teeth are part of your skeleton, they are not made of bone. They're enamel, a much harder material that withstands both the friction of chewing and the pressure of biting. As it turns out, the microscopic structure of enamel might provide the basis for DARPA's next building materials.
Why we're covering this:
Nature's Recipe For Strong Teeth
So what makes enamel stronger than bone? According to a study by Nicholas Kotov, a professor of chemical engineering at the University of Michigan, and post-doctoral researcher Bongjun Yeom, every set of teeth they've studied has the same microscopic structure—row after row of overlapping vertical columns. The other ingredient that explains enamel's ability to hold up to constant strains is the soft, organic material that surrounds these columns. The column pattern reinforces the strength of the enamel, and the soft tissue prevents brittleness by redistributing any pressure.
An Ancient Pattern
In their research into the microstructure of enamel, the team studied the tusks of an ancient walrus, the razor-sharp jaws of a Tyrannosaurus rex, and Kotov's own wisdom tooth. Every single one displayed the same pattern—and other discoveries indicate that the substance evolved even before fish first crawled onto land. Though most living fish don't produce it, well-preserved fossils of a 415 million-year-old fish called Psaroepis romeri revealed enamel on its scales and skull (but not its teeth).
Synthesizing Enamel's Strength
The Defense Advanced Research Projects Agency, better known as DARPA, had put out a call for a strong, lightweight material that could withstand various types of stress, and Kotov and Yeom believed that a man-made enamel could fit the bill. Synthesizing it, however, was more difficult than they had anticipated. They had to grow a type of zinc oxide crystals known as nanowires from a substrate up, and interface it with a polymer matrix to act as the soft material. Because of the way it is grown, it can easily be layered for additional strength, and the material is notably lighter than others of its kind. For now, however, mass production is a long ways off.