Cluster optical coding - from biochips to counterfeit security

摘要

Spatially tuned resonant nanoclusters allow high local field enhancement when excited by electromagnetic radiation. A number of phenomena has been described and subsequently applied for the construction of novel nano- and bionano-devices. Easy to manufacture, cost efficient and high throughput transducers using metal cluster resonance technology are based on surface-enhancement of metal cluster light absorption (SEA). The optical phenomenon driving SEA in metal cluster films is the so-called anomalous absorption. At a well defined nanometric distance of a cluster to a mirror the reflected electromagnetic field has the same phase at the position of the absorbing cluster as the incident fields. This feedback mechanism strongly enhances the effective cluster absorption coefficient. Such a system is characterized by a narrow reflection minimum. Based on this SEA-phenomenon (licensed to and further developed by november AG) a number of commercial products has been constructed. Brandsealing~R uses the patented SEA cluster technology to produce optical codings. Cluster SEA thin firm systems show a characteristic color-flip effect and are extremely robust. Both properties are vital for application as a unique security feature. The specific narrow band multi-resonance of the cluster layers allow easy authentication of the optical code. This can be achieved with a hand-held reader being developed by november AG and Siemens AG. SEA features are machine-readable which makes them superior to comparable technologies. Cluster labels are available in two formats: as a label for tamper-proof product packaging, and as a direct label, where label and logo are permanently applied directly and unremovable to the product surface. Together with Infineon Technologies and HUECK FOLIEN, the SEA technology is currently developed as a direct label for e.g. SmartCards.