Bend, but don't break.
That's the key to many resilient materials, from Kevlar to the dizzying steel-and-glass structure of a skyscraper. Researchers at the University of California San Diego can now add one more to the list: flexible ceramics.
Today's strong but flexible synthetic materials are indeed tough, but they have their limits. In pursuit of new solutions, UCSD's researchers took inspiration from Brazil's 300-lb. Arapaima fish, which has the distinction of being among the few species in the Animal Kingdom that can co-habitate with a pack of hungry piranhas.
Researchers found that the Arapaima's scales hold the key to its success. Biomimetics professor Marc Meyers and colleagues examined how the Arapaima resists piranhas by building a machine that forcefully presses piranha teeth into Arapaima scales. After running the materials through their paces, they found that the Arapaima's scales allow partial penetration by piranha teeth, but crack them before they puncture the underlying muscle.
How does it manage the feat? A "heavily mineralized" outer layer with a peculiar arrangement keeps the softer materials beneath protected. It's a formula that nature uses often: take materials that alone aren't especially strong, but combine them in such a way that they function in ways greater than the sum of their parts, from your teeth to the skin of a leatherback turtle.
The research holds promise for the next generation of flexible ceramics, which could assist in furthering research and development for a variety of applications, including soldiers’ body armor, fuel cells, insulation and in aerospace.
"We've produced materials with much higher performance, but we're reaching the limit with synthetic materials," Meyers said. "Now we are looking back at those natural materials and asking, 'how does nature put these things together'?"
Their work is published in the journal Advanced Biomaterials.
Illustration: UCSD Jacobs School of Engineering