Context:

Researchers from the US and France have recently discovered that the mantis shrimp's dactyl club contains a specialized microstructure that enables phononic shielding. This ability allows the mantis shrimp to blunt the flow of acoustic waves and weaken the recoil, protecting itself from the intense forces generated by its own strikes.

About mantis shrimp:

The mantis shrimp is a marine crustacean, approximately 10 centimeters long, found in tropical and subtropical waters. It is known for its specialized appendages that deliver rapid, forceful strikes, generating shockwaves in water. Despite the intensity, the organism remains unaffected, due to a complex microstructure in its appendages that functions as a natural energy-absorbing system.

Mechanics of the Strike

The mantis shrimp uses a hammer-shaped appendage called the dactyl club, which strikes at speeds of up to 23 meters per second. This rapid movement vaporizes water and releases high-frequency shockwaves, strong enough to break the shells of hard-shelled prey like clams and mussels. Remarkably, the shrimp itself remains unharmed.

Structural Adaptations for Impact Resistance

The dactyl club has a hierarchical structure composed of mineral and organic materials arranged in three layers:

• Impact Surface: Made of hydroxyapatite, this hard outer layer distributes recoil and prevents force from concentrating in one area.
• Impact Layer and Periodic Region: Beneath the surface, biopolymer fibers are arranged in a helicoidal pattern, allowing the structure to endure repeated, high-intensity impacts without significant damage.

Phononic Shielding Mechanism

The internal structure of the dactyl club acts as a phononic bandgap, blocking or attenuating energy waves of certain frequencies. This shielding is achieved through the precise arrangement of materials, allowing the mantis shrimp to protect itself from the shockwaves generated by its own strikes.

Implications for Materials Science

• The discovery of the mantis shrimp's natural energy shield has notable implications for materials science. Researchers are examining the potential to develop synthetic sound-filtering materials modeled after the microstructure of the mantis shrimp. Such materials may have applications in protective equipment, including earmuffs for military personnel, and in strategies aimed at reducing blast-related injuries in both military and sports settings.
• The findings of this study also challenge the long-standing assumption that materials capable of directing energy flow in specific ways can only be engineered in laboratory settings. The mantis shrimp's natural energy shield demonstrates how biological systems can optimize material structures at multiple levels, offering potential inspiration for future materials design and development.

Conclusion:

The mantis shrimp's natural energy shield is a fascinating example of the incredible adaptations that have evolved in nature. By studying this remarkable creature, scientists can gain insights into the development of new materials and technologies that can benefit society in various ways.