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“We have been using inspiration from sea creatures to develop several new adhesives,” said Jonathan Wilker, a Purdue professor of chemistry and materials engineering, who helped lead the research team. “Recently we have been seeking strategies for making adhesives tougher. One way to get there can be viewed as making the materials tougher, by first making them weaker.”
The Purdue team added bonds that are broken easily throughout the material. When pressure or stress is applied to the glue, these ‘sacrificial bonds’ are designed to absorb energy and break apart. Meanwhile, the rest of the adhesive remains intact.
“The idea is somewhat similar to how a brick wall is made of bricks that are offset from each other,” said Wilker. “You stagger the bricks and cement so that a crack does not shoot right down through the cement lines. A crack hits the middle of a brick and the forces get spread out toward both sides, eventually decreasing to the point that the wall stays intact.
“We added weak bonds within the adhesive so that mechanical forces and growing cracks lose energy by breaking these bonds instead of having the whole, larger material fracture. The idea is to manage how energy moves through the material. The overall adhesive system can become tougher and less likely to break apart when placed under mechanical stress.”
The researchers tested this idea with several types of bond and found the ones that worked best were neither too weak nor too strong. Wilker said the technique for managing energy in adhesives might be a general phenomenon, which could be applied to adhesives in industries ranging from consumer electronics, to construction, to manufacturing aeroplanes and cars. They are looking for partners to develop the technology.
The team has hundreds of mussels and oysters growing in its laboratory, to study the proteins used for natural adhesion.
The work was published in Journal of the American Chemical Society.
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