Shape Memory Alloy - Metal that returns to its original shape when heated


This paper clip is made from a nickel-titanium alloy (NITI/Nitinol) wire, which can have two distinct types of internal crystal structures. The crystal structure changes when the metal is heated above its activation temperature. Below the actuation temperature, the alloy is flexible and can be bent easily into any shape. When heated above its actuation temperature the wire will transform to the other crystal structure and the wire will spring back to its "remembered" shape.

See this video of a nitinol paper clip in action:

Used for:
Nitinol wire is used for super-elastic spectacle frames. It is also used to make surgical stents, which are small tubes that expands outwards to open blocked arteries. 

It is possible to "teach" nitinol wire a new shape by holding it in the desired shape and then heating it to 500°C before it is rapidly cooled. The metal is available as wire, bar, tube, or sheet. It can be machined to obtain other geometries. It is possible to change the composition of the alloy, so that the metal returns to its original shape at temperatures between -100°C and +110°C.  

Try it:
Bend the sample to any shape and then heat it in hot water, with a heat gun, or with a lighter to experience the shape change. It is truly magic! The paper clip can be bent and heated many times, but it will start to "forget" its shape if it is mistreated or bent excessively.

The sample:
We stock two variants of nitinol paper clips:
  • 1 mm diameter wire - actuation temperature 50°C
  • 0.5 mm diameter wire - actuation temperature 90°C
They both measure 3 cm in height and have a length of 12 cm when unfolded. 

All samples come with a laminated information card, which includes contact details for the supplier.