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Researchers at the School of Engineering and Applied Sciences have invented a wool-like material that remembers shape and changes form when soaked in water.
The biodegradable material — which might be safely inserted in the human body — can be 3D-printed into a variety of shapes, including clothing or medical device components.
To develop the novel material, researchers extracted keratin — a naturally-occurring fibrous protein found in hair, nails, and shells — from leftover Angora wool used in textile manufacturing.
Bioengineering and Applied Physics Professor Kevin “Kit” Parker said the researchers “did origami with the keratin sheets,” folding the recycled wool into many different forms.
“We used a chemical trigger, hydrogen peroxide, to set the memory of these keratin sheets into an initial shape, such as a star,” Parker said. “Once the initial shape was set, we dunked it in water and the keratin sheet became malleable, which allowed us to roll the sheet into a compact tube.”
“To reverse the process, we could dunk the keratin sheet back into the water, and it unfolds back into a star,” Parker added.
Luca Cera, a postdoctoral fellow and first author on a paper about the substance published in Nature Materials, described the research as biologically inspired, exploring “what nature already does in terms of shape memory.”
“Many materials we are dealing with in engineering nowadays are completely based on synthetic chemicals, synthetic materials,” Cera said. “But we often forget that nature is much better than us when it comes to engineering nanostructures.”
“Nature has already engineered shape-memory material, and keratin is basically the protein which nature uses to take care of this,” Cera added.
Parker — a co-author of the paper — described keratin as having a “hierarchical structure” which conferred the protein with its strength and ability to retain various shapes, similar to how human hair maintains particular wave patterns.
“So a single chain of keratin is helical in shape, which is known as an alpha-helix,” Parker said. “And when there are two of these chains, they form a structure that is called a coiled coil. Then these coiled coils are assembled into a proto-filament, which brought together further can form a fiber.”
Parker said one major potential application for the material could be medical innovations such as dressings that change their shape as the underlying wound heals.
Cera also noted potential applications in the fashion industry, such as clothing that “physically adapts to the body, that basically is custom-fit.”
Although the wool-like material currently requires water hydration in order to be reprogrammed and molded into new conformations, Cera said further research could unlock other mechanisms for shape-memory reversibility.
“If the material is modified, and there are ways to do this, we could make the shape-memory material even more responsive to other environmental stimuli besides water, such as temperature or light,” Cera said.
Opportunities for commercial application aside, Cera said he has enjoyed the process of seeing the project come to fruition in their lab.
“On the one hand, you can read that something is feasible on paper, yet you might not know exactly how that will translate in your own work,” Cera said. “It has been very rewarding to see how the nanoscale conformational changes of the structure of keratin, as already described in the scientific literature, can now be visualized through macro-scale reconfiguration of our 3D-printed material.”
—Staff writer Meera S. Nair can be reached at firstname.lastname@example.org.
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