Shellfish inspire chemists to develop stronger, more sustainable adhesives

Purdue University’s (Lafayette, Ind., U.S.) Jonathan Wilker, professor of chemistry and materials engineering, is pursuing a study on shellfish to help develop new adhesives that work underwater, are stronger, and more sustainable, are made from food products and that can be un-stuck when needed. The professor was initially inspired by the shellfish that have been clinging to the ocean rocks for eons, reportedly by a natural adhesives that tends to be stronger and more durable than anything developed by humans. 

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

Critters such as barnacles, mussels and oysters live in places where they are continually battered by waves and wind and pried at by potential predators. Their very lives depend on being able to cling to rocks and their neighboring shellfish. 

Further, sutures, screws and staples are all widely used to close wounds, bind tissues and set bones, but they are all very damaging and extremely painful. If doctors had a chemical adhesive that they could use instead, Wilker believes, healing would increase and collateral damage would decrease. However, the body is a challenging environment for adhesives: wet and constantly in motion. A lot like the sea.

Scientists in Wilker’s lab — which includes two postdoctoral researchers, five graduate students, four undergraduate researchers and 1,000 shellfish — have been studying how shellfish create materials, what components of the adhesives play active roles in bonding and test new synthetic and biomimetic glues to determine their efficacy, feasibility and performance. Within the same lab, Wilker and his team are also working to make glues out of bio-based and food-based compounds.

“We’re making adhesives with new functionalities,” Wilker says. “We can add in new chemical groups to target all sorts of properties, be that wet bonding, rubber-like flexibility or the ability to bond and then de-bond. One of our systems can even be stronger than what the animals make underwater. In that case, we are using chemistry that is inspired by the shellfish but, overall, our system is a simplification of what the animals produce.”

Overall, increasing the sustainability and the functionality of adhesives may improve human life in a myriad of ways, by limiting exposure to harmful chemicals, by making healing more comfortable and by making products more sustainable and more recyclable to preserve resources and the planet. 

“Almost every common glue is petroleum-based and not degradable,” Wilker says. “When your laptops or cell phones, shoes or furniture are no longer needed, most of them go straight to a landfill. Even materials like cardboard often do not get recycled because of the adhesives.”

Adhesion is a rapidly evolving field with huge potential, according to the university. It’s a field in which Wilker is a recognized expert, thanks to a stray thread of curiosity encountered in the ocean.

“The core ideas in our lab come from spending time underwater,” Wilker says. “I was scuba diving, saw shellfish sticking to rocks and thought, ‘I wonder how that works.’ When I got back into the lab, I was surprised to learn about what remained unknown. There are so many exciting possibilities and applications to pursue if we can figure it all out.”

As both a professor of chemistry in the College of Science and a professor of materials engineering, Wilker is said to bridge the worlds of science and engineering in his efforts to tap the natural world for innovative solutions to adhesion problems. The Office of Naval Research and the National Science Foundation help fund his research.

Wilker has worked with the Purdue Research Foundation Office of Technology Commercialization to apply for patents on his adhesives from the U.S. Patent and Trademark Office. He is starting to make them commercially available through commercial ventures including a startup, Mussel Polymers Inc. (Bethlehem, Penn., U.S.).