Seashells inspire chemists to develop new, stronger and more durable glues


WEST LAFAYETTE, Ind. – Humans depend on the ocean for a vast array of resources: food, energy, minerals, even the less tangible for inspiration and recreation. But one oceanic by-product may not be obvious: glue.

Seashells have clung to rocks for eons longer than humans have used glue. And their natural adhesives tend to be much stronger and more durable than anything developed by humans, even the strong, fast-acting glues found on store shelves and advertised on TV. Which led the chemists at Purdue University to ask: why don’t we just use what they use? Anyone who has ever tried to lift a barnacle off a rock knows that it is almost impossible.

This success is something Jonathan wilker, professor of chemistry and materials engineering, and his laboratory hope to learn from them and build on them.

Shells and seawater: an underwater grip that works

“We start by looking at the animals that make adhesives,” Wilker said. “We’re still working to understand the fundamentals of how animals like mussels and oysters do what they do, how chemistry and engineering work together. We even see how the environment around them and the surface they adhere to influences what they do.

Jonathan Wilker, professor of chemistry, studies seashells to develop adhesives that are more durable and resistant, and that work in a wider range of environments than current adhesives. (Purdue University Photo / Rebecca McElhoe) Download Image

Critters such as barnacles, mussels and oysters live in places where they are continually battered by waves and wind and searched by potential predators. Their very life depends on their ability to cling to nearby rocks and seashells.

Sutures, screws, and staples are all widely used to close wounds, bind tissue, and fix bones, but they are all very damaging and extremely painful. If doctors had a chemical adhesive they could use instead, healing would increase and collateral damage would decrease. However, the body is a tough environment for adhesives: wet and constantly in motion. A bit like the sea.

Scientists at Wilker’s lab – which includes two postdoctoral fellows, five graduate students, four undergraduate researchers and 1,000 seashells – are studying how seashells create materials, which components of adhesives play an active role in bonding, and are testing new synthetic and biomimetic glues to determine their effectiveness, feasibility and performance. They are building on this understanding to develop new adhesives that work underwater, are stronger, more durable, made from food products, and can be peeled off when needed.

“We make adhesives with new features,” Wilker said. “We can add new chemical groups to target all kinds of properties, whether it’s wet bonding, rubber-like flexibility, or the ability to bind and then peel off. One of our systems may even be more powerful than what animals make underwater. In this case, we’re using shell-inspired chemistry, but overall our system is a simplification of what animals produce.

Wilker notes that not everyone in his lab has a chemistry degree; some of the lab members are crustaceans – about 1,000 of them. Seashells play a valuable role in demonstrating how they make adhesives so that scientists can build on their biological strategies. (Purdue University Photo / Rebecca McElhoe) Download Image

Gunning for new glue: make adhesives non-toxic and reversible

Every product in the glue aisle at the hardware store has a downside. Many are poisonous. Particleboard, laminate flooring, and hardwood plywood are all held together by formaldehyde-based resins, which can be carcinogenic. In addition, many adhesives are permanent. There is no way to dissolve the bond when a product is at the end of its life, which often prevents the recycling of components.

“Almost all common glues are petroleum based and non-degradable,” Wilker said. “When your laptops or cellphones, shoes or furniture are no longer needed, most of them go straight to the landfill. Even materials like cardboard are often not recycled because of the adhesives.

Many glues are almost permanent, a factor many people have discovered when trying to remove the gum from a sticker or price tag on a product – or, more sadly, from a car window where a child was seated. Being able to reverse stiffness at will would give humans more control over their environment.

Increasing the durability and functionality of adhesives can improve human life in multiple ways: by limiting exposure to harmful chemicals, making healing more comfortable, and making products more durable and recyclable to save resources and the planet. . Wilker’s laboratory is working to manufacture glues from bio-based compounds and even food.

Membership is a rapidly evolving field with enormous potential. It is an area in which Wilker is a recognized expert, thanks to a stray thread of curiosity encountered in the ocean.

“The basic ideas of our lab come from time spent underwater,” Wilker said. “I was scuba diving, saw seashells sticking to the rocks and thought: I wonder how this works. When I returned to the lab, I was surprised to learn what was still unknown. There are so many possibilities and exciting applications to explore if we can figure it all out. “

Both a professor of chemistry in the College of Science and a professor of materials engineering, Wilker connects the worlds of science and engineering in his efforts to harness the natural world to find innovative solutions to adhesion problems. The Office of Naval Research and the National Science Foundation help fund his research.

Wilker worked with the Purdue Research Foundation Office of Technology Commercialization apply for patents on its adhesives with the United States Patent and Trademark Office. He begins to market them through commercial companies, including a startup, Mussel Polymers Inc.

Editor, Media Contact: Brittany Steff; 765-494-7833; [email protected]

Source: Jonathan Wilker: [email protected]

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