Auxetics

The earliest published example of a material with negative Poisson's constant is due to A. G. Kolpakov in 1985, "Determination of the average characteristics of elastic frameworks"; the next synthetic auxetic material was described in Science in 1987, entitled "Foam structures with a Negative Poisson's Ratio"[1] by R.S.

[11] However, although Auxetics are promising structures and have a lot of potential in science and engineering, their widespread application in multiple fields is still a challenge.

[12] At the macroscale, auxetic behaviour can be illustrated with an inelastic string wound around an elastic cord.

Auxetic behaviour at the macroscale can also be employed for the development of products with enhanced characteristics such as footwear based on the auxetic rotating triangles structures developed by Grima and Evans[13][14][15] and prosthetic feet with human-like toe joint properties.

For example, the nuclei of mouse embryonic stem cells in a transition state display auxetic behavior.

In footwear, auxetic design allows the sole to expand in size while walking or running, thereby increasing flexibility.
Production of auxetic metamaterials through the introduction of patterned microstructural cuts using direct laser cutting . The thin rubber surface with perforated architecture covers a spherical surface (orange) [ 37 ]