University of Rochester researchers created a material that undergoes a shape change when triggered by body heat alone. The shape-memory polymer can be programmed to retain a temporary form and then revert back to its original structure.
As the material is deformed, polymer chains are locally stretched, and small segments of the polymer align in the same direction in small areas—or domains—called crystallites, which fix the material into a temporarily deformed shape.
As the number of crystallites grows, the polymer shape becomes more and more stable, making it increasingly difficult for the material to revert back to its initial—or “permanent”—shape.
Chemical Engineering Professor Mitch Anthamatten and his team tuned the trigger temperature by connecting molecular linkers to individual polymer strands. By altering the number and types of linkers used, the Rochester researchers adjusted the material’s stability and precisely set the melting point at which the shape change is triggered.
Heating the new polymer to temperatures near 35 °C, just below the body temperature, causes the crystallites to break apart and the material to revert to its permanent shape.
The shape-memory polymer is capable of lifting an object one-thousand times its weight.
Possible applications for the polymer include sutures, artificial skin, body-heat assisted medical dispensers, and self-fitting apparel.
