Nitinol crane

Heat it—lift it!

Difficulty:
Danger:
Duration:
15 minutes
Nitinol crane

Safety

  • Carefully review the general safety advice in the instruction book before starting the experiment.
  • Read the "Working with Batteries" section of the safety guidelines carefully before proceeding. Always disconnect the setup after finishing the experiment.
  • Keep a bowl of water nearby when working with fire.
  • Keep flammable materials and hair away from the setup.
  • Avoid touching heated objects with bare hands.
  • Disassemble the setup after the experiment.

Step-by-step instructions

Imagine you are an engineer! Start by building a secure support for the crane.

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Now you need a load for your crane. Let’s use water! Fix a string in the bottle and attach “hooks” to the spring to secure its ends to the crane and the load.

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The foil underlay is necessary to prevent the box the crane is on from overheating.

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Manually stretch the spring to lower the weight.

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Use electricity to heat the spring! When the button is pressed, electrons begin to move through the entire spring from the “–” terminal of the first battery to the “+” terminal of the last one. The moving electrons heat the spring, which contracts and lifts the weight.

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Disposal

  • Dispose of solid waste together with household garbage.
  • Dispose of used batteries in accordance with local regulations.

Scientific description

As you have already seen, nitinol displays flexibility at room temperature and elastic properties (inclination to return to its original form) when heated. It turns out that it can be heated not only with fire, but also with electricity! How does this work?

When two wires  are used to connect the spring  to both ends of the battery , an electrical circuit is formed. In this circuit, electric current starts to flow. Electric current in metals is actually the movement of tiny particles called electrons . It moves from the “–” terminal  to the “+” terminal  of the battery . The running electrons collide with the spring  particles  and heat them .

This experiment shows how one can apply the non-ordinary properties of nitinol to lift weight. Nitinol is also used to make the dental arches used in braces! The orthodontist changes the arc shape at room temperature. Then, in the mouth, at body temperature, the arc begins to revert to its previous form, thereby gradually exerting pressure on the teeth and forcing them to move.