Nitinol   is an alloy of nickel and titanium. It is a  shape memory alloy (SMA) (also known as memory metal or smart wire) that remembers its shape. After it is deformed and  heated to a specific temperature it regains its original shape by itself. It is often made into springs. The temperature at which it changes form can be tuned to reasonable requirements by adding different metals to it.                                          


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A spring made of shape memory metal in its martensite phase.

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The same spring stretched to a new shape.

In warm water or with a stream of hot air, the spring returns to its
"trained" shape by heating it to above the temperature of the phase change into the more rigid austenite phase.























The archwire of these braces used in orthodontia
is made of memory metal to apply pressure
uniformly to the teeth.


  Flexible eyeglass frames. Bending the memory metal eyeglass
frames converts the metal from the rigid austenite structure
to the more flexible martensite structure. When this mechanical
stress is removed, the frames return to their original shape
and austenite structure. See this exact pair of frames distort
when exposed to liquid nitrogen.

A NanoMuscle actuator, visible on top of the bug, allows this demonstration toy to walk without the sound of a traditional motor.

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Applications of NITINOL

Robotic Muscle

Bone plates

aircraft maneuverability