Shape-memory materials are nifty little things that can recover their original shape after having been altered. Researchers have now been able to create shape-memory textiles from recycled wool used in textile manufacturing.

As reported in Nature Materials, the team developed a material that is biocompatible, can be 3D-printed in any shapes, and is pre-programmed to reverse to its original shape.

In one example, the team programmed a sheet of the material to take the form of an origami star. They then dunked it in water so it became malleable. It was then rolled into a tube and it stayed like that until it was put into the water again. The material then returned to its original shape, self-folding back into an origami star like it was never anything but this carefully folded shape.

"This two-step process of 3-D 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," lead author Dr Luca Cera, from the Harvard John A. Paulson School of Engineering and Applied Sciences, explained in a statement. "This makes the material suitable for a vast range of applications from textile to tissue engineering."

The key to this is keratin, a fibrous protein present not only in wool but also in human hair and nails. The keratin in this new material was fixed into its permanent memory-shape in a solution of hydrogen peroxide and monosodium phosphate.

Human hair is an excellent example of a shape-memory material. If you have ever tried curling your hair, you will know that water and humidity will send it straight back to its original shape. Avoiding water is a cardinal rule.

While certainly complex applications of this material can be envisioned, having a self-ironing material would be pretty great. The fact it comes from recycled material is the cherry on top. 

"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 Professor Kit Parker, 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."