Physics
Bistable Spring Mechanisms in Slap Bracelets
Quick fact
A slap bracelet is a pre-stressed cylindrical shell with a curved cross-section. This geometry creates two stable shapes—straight and coiled—between which it can snap through when a small force overcomes an energy barrier.
Why this is interesting
Why does a slap bracelet snap from a straight strip into a tight coil around your wrist with just a light tap? The secret lies in its built-in tension and curved cross-section.