Patterned Thin Films for Applications in Security Documents

The purpose of this project is the development of novel strategies to manufacture devices that render the unauthorised duplication or falsification more difficult. With the rapidly increasing quality of publicly available replication technology (e.g. colour printers and photo-copying machines), the counterfeit of bank notes and identity documents is becoming and increasing problem. To counteract this field of organised crime, new approaches to manufacture security documents are necessary.In a collaboration with the world's largest security printer and paper maker, De La Rue, the objective of this project is to develop novel devices for security documents. Based on techniques that are available in Prof. Steiner's laboratories, surface patterns will be developed that show a brilliant coloured effect that change when the angle of illumination or observation is changed. This effect arises from the interference of white light on a surface with a micrometre-sized dielectric pattern. To achieve this a combination of strategies are planned, including the use of fluorescent nanoparticles, multilayer structures, lateral gratings, etc., all deposited by spin-coating, or soft lithographic methods.