Invisible Tags Write, Read, and Erase Using Light

A method was developed that enables information to be contained in simple plastic foils with a thickness of less than 50 μm, which is thinner than a human hair. Organic luminescent molecules are introduced into the transparent plastic foils. In the beginning, these molecules are in an inactive, dark state; by locally using ultraviolet irradiation, it is possible to turn this dark state into an active, luminescent one.