World's Smallest Keypad Lock

First published: January 2007

The “buttons” are an acidic molecule, an alkaline compound, and ultraviolet light, and must be given in the right sequence for the molecular “lock” to change state.

Earlier descriptions of locks that require specific substances and light to open can be found in Tolkein’s “The Hobbit” and “The Lord of the Rings”, and the film “The Fifth Element”.