Nitinol paper clip

The adventures of a stubborn paper clip!

Difficulty:
Danger:
Duration:
15 minutes
Nitinol paper clip

Safety

  • Carefully review the general safety advice in the instruction book before starting the experiment.
  • Observe safety precautions when working with boiling water.
  • Avoid touching heated objects with bare hands.

Step-by-step instructions

You’ll need a hot surface for this experiment. The thermosticker will turn yellow to warn you when the lid heats up.

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Observe what happens to the nitinol paper clip on the hot surface! Does this work for any deformation? Compare the unbent nitinol paper clip with a regular paper clip!

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Will the nitinol paper clip be able to extricate itself from more complex situations?

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To speed up the heating of the nitinol paper clip and, as a result, its self-folding process, dip it in hot water.

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Disposal

  • Dispose of solid waste together with household garbage.

Scientific description

Everything around us consists of small particles  known as atoms. In solid materials and objects, such as furniture, stones , ice , and more, the particles are arranged in a particular order. Solids seem to consist of many identical cells , where the particles  are located in certain places, for example, in the corners of each cell .

Solids behave differently when bent or compressed. They can be elastic (inclined to return to their original form) like an eraser , flexible like clay, or even fragile like pencil lead . When a solid is bent, the cells in its structure change shape, so the particles shift to another comfortable place. In elastic solid objects , particles  have a hard time finding another suitable position and they return to their old spots, restoring the object to its old form. The reverse is true for flexible materials : after bending , when the cell’s shape is changed, the particles can find another decent location and stay in it. That is why the regular paper clip keeps its form after bending.

What is nitinol? It is an artificial material composed of a mixture of the metals nickel (Ni) and titanium (Ti), hence the name Ni-Ti-nol. Moreover, it exhibits both elastic and flexible properties! At room temperature, objects made from nitinol behave like flexible materials: both nitinol  and a regular paper clip will retain their new shape  after deformation. But when heated , nitinol begins to exhibit elastic properties, similarly to a bath duck , so the object recovers into its pre-deformed shape . This is called the shape memory effect.