Mantis shrimp dactyl clubs may hold secrets for tougher surfaces for human use

Materials science researchers at the University of California at Irvine are learning about the resilience of the mantis shrimp. The ancient crustaceans are armed with two raptor hammer-shaped appendages called dactyl clubs that they use to club and crush their prey. These fists, capable of accelerating from the body to over 50 mph, deliver powerful punches while appearing intact afterwards.

UCI researchers have found that clubs have a uniquely designed coating of nanoparticles that absorbs and dissipates energy. The results, published today in Materials from nature, have important implications for engineering materials in the automotive, aerospace and sports industries.

“Consider hitting a wall a few thousand times at these speeds and not breaking your fist,” said David Kisailus, UCI professor of materials science and engineering, who has studied mantis shrimp for over a decade. . “It’s pretty impressive, and it got us thinking about how that could be.”

He and postdoctoral researcher Wei Huang used transmission and atomic force electron microscopy to examine the nanoscale architecture and material components of the surface layer of clubs. They determined that nanoparticles are bicontinuous spheres, made up of interlocking organic (proteins and polysaccharides) and inorganic (calcium phosphate) nanocrystals.

3-D inorganic nanocrystals are mesocrystalline, essentially stacked like Lego pieces, with small differences in orientation where they meet. Crystalline interfaces are crucial for the resilience of the surface layer, as they fracture and break upon high velocity impact, halving the depth of penetration.

“High-resolution TEM has really helped us understand these particles, how they are architectured, and how they react under different types of stress,” Kisailus said. “At relatively low strain rates, the particles deform almost like a marshmallow and recover when stress is relieved.”

He noted that the behavior of structures under high strain impact is very different. “Particles stiffen and fracture at nanocrystalline interfaces,” Kisailus said. “When you break something, you open up new surfaces that dissipate significant amounts of energy.”

The team, which included researchers from Purdue University, Oxford Instruments and Bruker Corp., were also able to measure and characterize the coating’s impressive damping capabilities.

“The rigid inorganic and flexible organic materials in an interpenetrating network impart impressive damping properties to the coating without compromising rigidity. It’s a rare combination that outperforms most metals and engineering ceramics, ”Kisailus said.

He added that he was now focused on translating these findings into new applications in a variety of fields: “We can imagine ways to design similar particles to add improved protective surfaces for use in automobiles, airplanes, football helmets and bulletproof vests. ”