Boxfish shell could inspire new form of body armour

Engineers that have been researching the shell structure of the boxfish claim that its unique structure could form the inspiration for new types of armour, robots and flexible electronics.


The boxfish has survived in the oceans for the past 35 million years.
The boxfish has survived in the oceans for the past 35 million years.

The research, conducted by a team from the University of California, San Diego, examined the hexagonal-shaped scales – or scutes – of the boxfish. It found that the scutes were connected by sutures similar to the structure of a baby’s skull, where bones fuse together as the baby grows.

In their findings, published in the journal Acta Materialia, the researchers claim the boxfish sutures are different to those found elsewhere in nature. On impact, the sutures’ zigzag patterns essentially lock in and keep the scutes from breaking apart.

“The most common form of suture structures in nature are those that have a roughly triangular shape and consist of two important components: rigid suture teeth and a compliant interface,” said Steven Naleway, a materials science and engineering Ph.D. student and co-author of the paper.

Boxfish shell, scutes and sutures.
Boxfish shell, scutes and sutures.

“To the best of our knowledge, there is no compliant phase in the interface of the boxfish’s sutures. In addition, the teeth themselves have a much lower aspect ratio – meaning that they are shorter and wider – than most other examples.”

Each of the fish’s scutes has a raised star-shaped structure at its centre, which distributes pressure across the entire surface. Beneath the scutes, a layer of interlocking collagen fibres provides an added layer of protection, as well as flexibility.

“We were able to demonstrate that even if a predator manages to generate a crack in the outer layer, the collagen fibres will help to prevent the structure from failing,” said Wen Yang, a UC San Diego alumna now working at the Swiss Federal Institute of Technology in Zurich, and the lead author of the paper.

Each hexagonal scute in the boxfish's armour has a raised, star-like structure in the centre that distributes stress across the entire surface.
Each hexagonal scute in the boxfish’s armour has a raised, star-like structure in the centre that distributes stress across the entire surface.

The research project, which is part-funded by the U.S. Air Force, is now exploring how the structure of the boxfish’s shell could guide bio-inspired designs that offer improved protection against impact.

“We are currently investigating what mechanical advantage scutes and sutures might provide,” Naleway said in a statement. “We know that the boxfish has survived for 35 million years with this armour, so the design has proved very successful in nature.”