This mechanism shrinks when pulled

Veritasium

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The video shows a seemingly paradoxical mechanism: a lattice made of scissor-like crossed bars shortens in the longitudinal direction as soon as you pull on it, and lengthens when you compress it. This behavior contradicts everyday experience with normal materials, which become longer under tension. Derek first demonstrates the phenomenon with a hand-made model and then records force- and displacement-curves to make the unusual characteristic visible.

The effect is due to geometry, not magic. The bars form a kinematic structure with degrees of freedom that let the pivots shift while the individual members remain rigid. When you pull axially, the scissors rotate and the overall length shrinks—the system exhibits “negative linear compressibility.” In an energy diagram, this process corresponds to skipping over an unstable region, comparable to the snap of a metal clicker plate.

Researchers are transferring this principle to microscopic metamaterials by repeating the scissor cells millions of times using 3-D printing or lithography. This yields materials that can amplify forces, damp vibrations, or act as mechanical fuses. Applications range from impact protection in vehicles and flexible medical stents to actuators that generate large movements from small drives.

The video makes it clear how the deliberate arrangement of simple components can add up to entirely new material properties. Through smart geometric design, engineers can realize mechanisms that defy classical intuition yet strictly obey the laws of physics. The clip ends by inviting viewers to experiment with simple parts themselves and develop a feel for the possibilities offered by metamaterials

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