The mantis shrimp is something of a wonder-animal. They have incredible eyes, which inspired a novel sensor that can spot cancer, and they can pull the fastest punch on the planet. Moving at around 23 meters per second (75 feet per second), their immensely strong “smashers” help them to kill shellfish, concaving their shells with a force of 1,500 newtons per punch.
"Think about punching a wall a couple thousand times at those speeds and not breaking your fist," said mantis shrimp specialist David Kisailus, a University of California-Irvine professor of materials science and engineering, in a statement. "That's pretty impressive, and it got us thinking about how this could be."
Kisailus and colleagues were able to answer this question in a study recently published in the journal Nature Materials as they discovered these smashers are protected by an impact-resistant nanoparticle coating. The super-strength coating contains a rare combination of structures that outperform most man-made materials and could have many applications for future engineering.
The researchers used transmission electron and atomic force microscopy to understand what made the mantis shrimp’s smashers so strong. Focusing on the peacock mantis shrimp (Odontodactylus scyllarus), their inspection of the appendages showed a dense matrix of hydroxyapatite, a mineral, which had formed into a nanocrystal structure. When delivering a punch, the mineral would rotate, breaking the nanocrystal structure, which later reformed.
"At relatively low strain rates, the particles deform almost like a marshmallow and recover when the stress is relieved," said Kisailus. “When you break something, you're opening up new surfaces that dissipate significant amounts of energy."
The mechanism means that when the mantis shrimp punches its prey, their smashers can absorb the energy through a process called damping without sacrificing the stiffness of the appendages. This is achieved thanks to the combination of stiff inorganic and soft organic materials in the network of oscillating, mineralized nanocrystals.
"It's a rare combination that outperforms most metals and technical ceramics," Kisailus said.
"We can imagine ways to engineer similar particles to add enhanced protective surfaces for use in automobiles, aircraft, football helmets, and body armor."