Researchers from the Harvard School of Engineering and Applied Sciences. John A. Paulson (SEAS) developed a biocompatible material that can change shape in response to certain stimuli and return to its original shape in response to others. Research published in Nature Materials.
Anyone who has straightened their hair at least once knows that water will return it to its original shape. Hair, carefully straightened using high heat, turns back into curls as soon as it touches the water. Why? Because hair has shape memory. It is also the properties of a material that 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 shape memory? Imagine a T-shirt with cooling holes that open when exposed to moisture and close when dry or versatile clothing that stretches or shrinks to fit a person’s size.
A group of scientists tried to make such material. Their formulation is made from keratin and a fibrous protein found in hair, nails, and shells. Researchers have extracted keratin from the remaining agora wool used in textile manufacturing.
When the fiber is stretched or exposed to a certain stimulus, the spring structures are unwound and the bonds are aligned, forming stable beta layers. The fiber remains in this position until it returns to its original shape.
To demonstrate this process, the researchers printed three-dimensional keratin sheets in various shapes. They programmed a constant shape of the material, one to which it will always return when a trigger is fired, using a solution of hydrogen peroxide and monosodium phosphate.
For example, one keratin leaf was folded into a complex origami star, this was its permanent form. After the memory was established, the researchers dipped the star into the water, where it turned around and became malleable. Then they rolled the sheet into a tight tube. The fabric dried up and its permanent shape remained in the form of a tube.