```
Shape-memory alloy is a material that has a shape memory effect due to thermal elasticity and martensitic transformation and its reverse transformation. After undergoing plastic deformation at one temperature, it can revert to its original shape at another temperature.
When Xiang Shan first folded the paper airplane, he did so in a constantly changing magnetic field, heating the metal foil by cutting the magnetic lines of force to then fold it at a higher temperature. Later, at room temperature, he further processed these paper airplanes. Inside the paper airplanes, he installed a lithium battery-powered infrared emitter and a Longbo Lens.
Inside the metal foil, the infrared rays were reflected, heating the interior, and causing the shape-memory alloy metal foil paper airplane to heat up and unfold its wings.
