As anyone who has ever straightened their hair knows, water is the enemy. Hair painstakingly straightened by heat will bounce back into curls the minute it touches water. Why? Because hair has shape memory. Its material properties allow it to change shape in response to certain stimuli and return to its original shape in response to others.
What if other materials, especially textiles, had this type of shape memory
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a biocompatible material that can be 3-D-printed into any shapeand pre-programmed with reversible shape memory. The material is made using keratin, a fibrous protein found in hair, nails and shells. The researchers extracted the keratin from leftover Agora wool used in textile manufacturing.
The research could help the broader effort of reducing waste in the fashion industry, one of the biggest polluters on the planet. Already, designers such as Stella McCarthy are reimagining how the industry uses materials, including wool.
“With this project, we have shown that not only can we recycle wool but we can build things out of the recycled wool that have never been imagined before,” said Kit Parker, the Tarr Family Professor of Bioengineering and Applied Physics at SEAS and senior author of the paper.
“The implications for the sustainability of natural resources are clear. With recycled keratin protein, we can do just as much, or more, than what has been done by shearing animals to date and, in doing so, reduce the environmental impact of the textile and fashion industry.”
The key to keratin’s shape-changing abilities is its hierarchical structure, said Luca Cera, a postdoctoral fellow at SEAS and first author of the paper.
A single chain of keratin is arranged into a spring-like structure known as alpha-helix. Two of these chains twist together to form a structure known as a coiled coil. Many of these coiled coils are assembled into protofilaments and eventually large fibers.
“The organization of the alpha helix and the connective chemical bonds give the material both strength and shape memory,” said Cera.
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