Invisible Tags: Physicists At TU Dresden Write, Read And Erase With The Use Of Light
A team of physicists headed by Prof. Sebastian Reineke of TU Dresden developed a new kind of storing information in fully transparent plastic foils. Their innovative idea is now published in the renowned online journal “Science Advances”.
Prof. Reineke and his LEXOS team work with simple plastic foils with a thickness of less than 50 µm, which is thinner than a human hair. In these transparent plastic foils, they introduced organic luminescent molecules. In the beginning, these molecules are in an inactive, dark state. Using ultraviolet irradiation, it is possible to turn this dark state locally into an active, luminescent one. By mask illumination or laser writing, activated patterns can be printed into the foil having a resolution comparable to common laser printers. Similar to glow-in-the-dark stickers, the patterns can be brought to shine and the imprinted information can be read out. By illuminating with infrared light, the tag is erased completely and new data can be written into it.
The working principle of these programmable transparent tags is based on the well-known molecule oxygen. Oxygen is present in the plastic foil and steals the light energy from the glowing molecules. Ultraviolet radiation induces a chemical reaction which efficiently removes the oxygen from the layer. In consequence, the luminescent molecules are activated and able to emit light. The deactivation process using infrared light is based on a temperature rise of the foil, leading to an increased oxygen permeability and therefore a refilling of the layer with oxygen.
These novel tags can be manufactured in any size. The low material costs of fewer than two dollars per square meter promise a wide range of application scenarios: Information like barcodes, serial numbers or addresses can be hidden for on-demand readout only. Also, these invisible tags could lift document security and anti-counterfeiting to a whole new level.
Prof. Reineke: ‘Those invisible and re-writable tags can be used in a multitude of ways, while at the same time offering minimalistic physical foot-prints. We can manufacture such tags thinner than conventional barcode stickers. These tags can become a versatile alternative to many often technology-loaded solutions for information exchange in our daily life. These luminescent tags make electronics obsolete at the location, where the information is stored. The development and optimization of such systems open a broad research field bringing together material development, process engineering, and fundamental research in an interdisciplinary fashion.’
About The Light-Emitting and eXcitonic Organic Semiconductor (LEXOS) Group
The LEXOS group is part of the Dresden Integrated Center for Applied Physics and Photonics Materials (IAPP) and the Institute of Applied Physics of the Technische Universität Dresden and led by Prof. Sebastian Reineke. One focus of the LEXOS group is the investigation of excitonic and luminescent systems covering organic and other related emerging materials. The group has strong expertise in the optical spectroscopy of such systems. One current example is the investigation of organic biluminescence, where luminophores show both fluorescence and phosphorescence at room temperature. Further, the LEXOS group has long-standing expertise in the research and development of organic light-emitting diodes (OLEDs). The current OLED research comprises stack and concept development, devices optics, charge transport and recombination studies, long-term stability investigations, material development (dopant and emitter materials), and device integration.
Source: Technische Universität Dresden