New polymer shifts shape with changing body temperature

"Our shape-memory polymer is like a rubber band that can lock itself into a new shape when stretched," said Mitch Anthamatten.
By Brooks Hays  |  Feb. 12, 2016 at 10:25 AM
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ROCHESTER, N.Y., Feb. 12 (UPI) -- Researchers at the University of Rochester have invented at a polymer that changes shape when triggered by body temperature. The material could enable new and improved medical implant devices and technologies.

Material scientists have developed a variety of temperature-activated polymers, but this is the first time a polymer has been designed to react to a temperature change subtle enough to be supplied by the human body.

Researchers say the material's ability to shift shapes can be used in a variety of ways.

"Tuning the trigger temperature is only one part of the story," Mitch Anthamatten, an engineering professor at Rochester, said in a news release. "We also engineered these materials to store large amount of elastic energy, enabling them to perform more mechanical work during their shape recovery."

When polymers are bent or stretched, to what extent they hold their shape is determined by the crystalline structures that form. Anthamatten and his research partner, grad student Yuan Meng, found the quantity and distribution of molecular linkers -- which bind polymer strands -- can control the level and growth of crystallization.

The researchers experimented with the levels of molecular linkers until they found a balance that allows the warmth of the body to melt the crystals and trigger the polymer to return to its original shape.

"Our shape-memory polymer is like a rubber band that can lock itself into a new shape when stretched," said Anthamatten. "But a simple touch causes it to recoil back to its original shape."

The polymer's precise temperature sensitivity is just one advantage. It's also quite strong, capable of exerting considerable force as it recoils.

"Nearly all applications of shape memory polymers will require that the material pushes or pulls on its surroundings," said Anthamatten. "However, researchers seldom measure the amount of mechanical work that shape-memory polymers are actually performing."

The polymer can lift or manipulate an object 1,000 times its weight. The technology could be used to improve sutures, time-release drugs, artificial skin and more.

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