If you dream of owning a "supersuit" like Daredevil or Batman, you’re in luck. Chemists from UC San Diego have just developed the ideal protective material.
The team developed an adaptive protein crystal with an unusual "auxetic" property: When the material is compressed in one direction, it shrinks in the other direction rather than expanding, making the material denser. This property has never previously been demonstrated at a molecular level. The results are published in Nature.
"We found a way to create strong, flexible, reversible bonds to connect the protein tiles at their corners," said Akif Tezcan, senior author of the study, in a statement. "These materials are very easy to make, yet provide many new research directions both in terms of materials applications and understanding the fundamental principles of nanoscale self-assembly."
This material can be used, for example, to make better running shoes, as they would provide better shock absorption for heels, or to make more protective body armor.
Tezcan’s group used a square-shaped protein called RhuA to create a sheet-like tiled material: The proteins in this crystal are in a regular, repeating pattern and linked with reversible bonds. The flexibility of the bonds allows the proteins to rotate and fill in the open spaces.
The bonds in the protein tiles allow them to rotate to open spaces after a compression has been applied. Yuta Suzuki and Timothy Baker, UC San Diego
This property allows for the material to respond to physical stress equally in all directions. If the material is stretched or compressed in one direction, all the proteins turn together, which generates a stretch or compression, respectively, in the other direction too.
This quality is represented in physics by the Poisson ratio, which is just the ratio between the contraction strain in one direction and the extension strain in another direction in a material. Normal materials have a positive Poisson ratio, with rubber being closer to the possible upper limit. The material created by Tezcan has a Poisson ratio of -1, which is the lowest possible value for it.
While there’s more to do before this material can be used commercially, it seems like it’s a goldmine of useful properties. Under the right chemical conditions, the material even heals itself.
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