How NASA Reinvented The Wheel
Nickel-Titanium

Nitinol is a memory shape alloy made of Nickel and Titanium. What is special about this material is that it has two rare properties:

Shape memory

Superelasticity

Shape memory

Shape memory is the property of a material of undergoing deformation and then be able to return to its original shape when the heat is applied to it. An object made of Nitinol can be bend and deformed at room temperature, but as soon as you apply some heat it returns to its previous shape. It remembers its original shape.

The secret of this material lays in its crystal structure.

When Nitinol is under a certain temperature, its crystal structure is called martensite. The atoms in this structure are organized in a way that allows it to offer an easy path for the deformation. When stress is applied the atoms move and align to absorb it. This is different from the traditional materials where, when a stress is applied what happens is that the bonds of the atomic structure are stretched.

When we release the stress the object maintains that shape until heat is applied. When we apply heat to Nickel-Titanium its crystal structure change again and becomes austenite. This structure is the most stable at high temperature but as soon as the material cools down it returns to a martensitic structure.

This property means that the shape of the object made of Nitinol can return to its original one by absorbing energy from the heat we apply to it.

And that is not all. By modifying the percentage of the two elements we can tailor the temperature at which the transformation happens. More specifically, by increasing the percentage of Titanium we also increase the transformation temperature.

This is a property really unique that has already found many uses.

As an example, in the medical field, Nitinol is used to produce stents. Before the use of this material, they were made of other metals. After being inserted in the blood vessel they have to be plastically deformed into the shape wanted. To do that a small balloon is inflated inside the stent. This a complicated and dangerous procedure because the pressure can damage the tissue of the artery

When used in stents, Nitinol transformation temperature is set to human body temperature. In this way, when the stand is inserted in the artery, it returns to its original shape and doesn’t put any excessive pressure on the blood vessel.
['Alessandro Bazzi']
['Mars', 'Future Technology', 'Technology', 'NASA', 'Space']