Materials that can be deformed and then return to their original state as desired, such as shape memory alloys, could mean big things for aerospace, robotics, and even fashion if a new smart textile from Harvard University is anything to go by. Made from leftover wool products, the programmable material can be bent out of shape in response to stimuli and bounce right back to its original form, with the team imagining putting it to use in shape-shifting clothing items that adapt to different scenarios.
The starting point for this new shapeshifting material is a fibrous protein found in hair, nails and shells called keratin, which can also be found in wool. Keratin carries some useful properties for materials scientists, in that as a single chain it forms a spring-like coil structure called an alpha-helix.
Put enough of these together and you have a strong, large fiber with shape memory characteristics. As the material is stretched, the coils unfurl and new bonds are formed that create stable sheets. The material remains this way until it is exposed to stimuli that returns the coils back to their original shape.
"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,” says Kit Parker, senior author of the paper.
The team started by 3D printing keratin sheets of differing shapes, with these programmed as their “permanent” states by setting them in a solution of hydrogen peroxide and monosodium phosphate. From there, the materials can be molded into other shapes on a temporary basis, in response to different stimuli.
In one experiment, the team permanently set a keratin sheet as a complex origami star. When the star was submerged in water, however, it unfolded and took on a malleable form, enabling it to be rolled into a tight tube, which became its own stable and functional structure as the sheet dried. The tube was then placed back in the water, which caused it to unroll and fold back up into the original origami star.
“This two-step process of 3D printing the material and then setting its permanent shapes allows for the fabrication of really complex shapes with structural features down to the micron level,” says Luca Cera, first author of the paper. “This makes the material suitable for a vast range of applications from textile to tissue engineering.”
The researchers imagines some interesting uses for the new shape-shifting material. They say it could be used to make brassieres with customizable shapes and cup sizes, one-size-fits all t-shirts, or garments with air vents that open in response to moisture. In this way, they hope it can help address wastage in the fashion industry.
“The implications for the sustainability of natural resources are clear,” says Parker. “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 research was published in the journal Nature Materials, while you can see the material in action in the video below.
Source: Harvard University