Although polymers that change shape in response to differences in temperature are nothing new, a team of researchers from the University of Rochester now created a material that changes shape in response to body heat alone, providing many new opportunities in the realm of medicine and other applications, including artificial skin, sutures and self-fitting clothing.
The material is a type of shape-memory polymer that is designed to take form of a temporary shape until it is triggered to return to its original form. This trigger, typically heat, was fine-tuned in order to respond to human body heat in particular.
"Tuning the trigger temperature is only one part of the story," Mitch Anthamatten, who led the research team, said in a press release. "We also engineered these materials to store large amount of elastic energy, enabling them to perform more mechanical work during their shape recovery."
During the deformation process, polymer chains are stretched and crystallites, which are small segments of polymers aligned in the same area, are what fix the material into its temporary shape. As crystallite numbers increase, the polymer's shape becomes more rigid and much more difficult to revert back to its initial state.
In order to create the unique polymer, the team determined how to control the crystallization process that occurred when the materials cooled or stretched. Anthamatten and his team accomplished this by adding molecular linkers that connected each individual polymer strand, which inhibited crystallization during the stretching process. After altering the number and types of links used in the polymer, the team was able to adjust the material's stability and set its melting point to near 35 degrees Celsius, just below body temperature.
"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 findings were published in the Jan. 13 issue of the Journal of Polymer Science Part B: Polymer Physics.
