Nitinol Shape Memory Alloy

Nitinol, a nickel-titanium alloy, demonstrates shape memory by returning to a pre-set shape when heated. Unlike ordinary wire, Nitinol “remembers” its original form and straightens itself when exposed to sufficient thermal energy.

1. Provide volunteers with two types of wires: straight ordinary wire and straight Nitinol wire.
2. Ask volunteers to bend the wires into any shapes such as coils, springs, or zigzags.
3. Select a volunteer with ordinary wire. Hold the wire with pliers and heat it using a heat gun; the wire will simply get hot without changing shape.
4. Retrieve a bent Nitinol wire from a volunteer. Hold it with pliers and heat it using the heat gun; the wire will straighten and return to its original shape.
5. Allow the wire to cool, then have a volunteer bend it again. Reheat to show that the shape-memory effect is repeatable.
6. Explain that the effect occurs because Nitinol atoms shift back to their “remembered” structure at a certain transition temperature.

Nitinol Amazing Shape Memory Alloy - Action Lab Shorts:

📄 Shape-Memory Alloys - David Pogue: https://www.pbs.org/wgbh/nova/assets/education/making-stuff/stuff-toolkit-smarter-demo.pdf

• Compare Nitinol to other smart materials, such as shape-memory polymers, to highlight differences.
• Use different thicknesses of Nitinol wire to observe how the heating time changes.
• Perform the demonstration with multiple Nitinol wires bent into different shapes for a dramatic visual effect.

• Use heat-resistant gloves when handling wires and the heat gun.
• Do not point the heat gun toward the audience.
• Ensure wires are completely cooled before allowing audience members to handle them.
• Place the heat gun out of reach after use to cool safely.

• Why does Nitinol return to its original shape when heated? (Its crystal structure undergoes a phase change at the transition temperature, restoring its “remembered” shape.)
• How is Nitinol different from ordinary metals? (Ordinary metals expand with heat but do not retain memory of a previous shape.)
• Where are shape-memory alloys like Nitinol used in real life? (Examples include orthodontic braces, thermostats, medical stents, and automatic valves.)