Researchers develop environment-adapting material inspired by sea worms

Sea worms have the incredible natural ability to adapt rigidity to fit its environment. The specific species, called Nereis virens, with a gelatinous jaw that is able to become hard or flexible, has been the inspiration for Massachusetts Institute of Technology researchers who have developed a new material that mimics this characteristic.

The Nereis virens worm’s jaw is made of soft organic material, but is as strong as harder materials such as human dentin. Photo credit: Alexander Semenov/Wikimedia Commons

“The jaw of Nereis virens is composed of a protein that contains large amounts of histidine, an amino acid that interacts with the ions of the environment and makes it more or less flexible depending on the environment in which it finds itself,” explains chemical engineer Francisco Martín-Martínez, a Spanish researcher at the MIT Laboratory for Atomistic and Molecular Mechanics and co-author of the paper.

With a texture similar to gelatin, the worm’s jaw has the ability to adopt the hardness of dentin or human bone. The team was able explore this natural phenomenon and apply it to a new material structure.

The material itself has been developed in collaboration with the US Air Force Research Laboratory (AFRL) and is composed of hydrogel made from synthesized protein, similar to the one that makes up the jaw of the sea worm, which gives it a structural stability and impressive mechanical performance, explains Martín-Martínez.

“When we change the ions of the environment and the salt concentration, the material expands or contracts,” he adds.

Research scientists Francisco Martin-Martinez and Zhao Qin sketch the molecular background of their research on Nereis virens, a marine worm with a remarkably strong and adaptable jaw. Photo credit: Allison Dougherty.

The researchers created a model to predict how the substance will operate and conducted a theoretical study to explain the molecular mechanisms responsible for its behaviour.

At the molecular level, when the environment contains zinc ions and certain pH indexes, the structure of protein material is strengthened. The Zinc ions create chemical bonds with the structure of the compound. These bonds are reversible, and can form or break at convenience, making the material more dynamic and flexible.

Martín-Martínez believes that the material could have significant applications when it comes to soft robotics and sensors.

“Its ability to contract and expand makes it especially suited to creating devices that work as muscles for so-called soft robots, which are made of polymers,” he says. “It could also be used in the development of sensors that do not need to use external power supplies and control devices for complex electronic systems.”

Martín Martínez, who specializes in the design and modelling of materials, believes that most of the problems that are being addressed with technology “have already been solved by nature, almost always in a much better way than we humans can develop, so for us it is a great source of inspiration.”

The material is described in a study published in the journal ACS Nano.

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