Rainbows without pigments offer new defence against fraud
Scientists from the University of Sheffield have developed pigment-free, intensely coloured polymer materials, which could provide new, anti-counterfeit devices on passports or banknotes due to their difficulty to copy.
The polymers do not use pigments but instead exhibit intense colour due to their structure, similar to the way nature creates colour for beetle shells and butterfly wings.
These colours were created by highly ordered polymer layers, which the researchers produced using block copoylmers (an alloy of two different polymers). By mixing block copolymers together, the researchers were able to create any colour in the rainbow from two non-coloured solutions.
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This type of polymer then automatically organises itself into a layered structure, causing optical effects similar to opals. The colour also changes depending on the viewing angle. This system has huge advantage in terms of cost, processing and colour selection compared to existing systems.
The complexity of the chemistry involved in making the polymer means they are very difficult for fraudsters to copy, making them ideally suited for use on passports or banknotes.
The academics used Diamond Light Source, the UK's national synchrotron science facility in Oxfordshire, to probe the ordered, layered structures using high power X-rays. This helped them understand how the colours were formed, and how to improve the appearance.
Dr Andrew Parnell, from the University of Sheffield's Department of Physics and Astronomy, said: "Our aim was to mimic the wonderful and funky coloured patterns found in nature, such as Peacock feathers. We now have a painter's palette of colours that we can choose from using just two polymers to do this. We think that these materials have huge potential to be used commercially."
Professor Nick Terrill, Principal Beamline Scientist for I22, the Diamond laboratory used for the experiment, explained: "Small Angle X-ray Scattering is a simple technique that in this case has provided valuable confirmatory information. By using Diamond's X-rays to confirm the structure of the polymer, the group was able to identify the appropriate blends for the colours required, meaning they can now tailor the polymer composition accordingly."
Notes for Editors: The institutions involved in the research include the University of Sheffield, the University of Hull and Diamond Light Source in Oxfordshire.
To view the paper, 'Continuously tuneable optical filters from self-assembled block copolymer blends', published in Soft Matter, please visit the link below.
Diamond Light Source is funded by the UK Government via the Science and Technology Facilities Council (STFC) and by the Wellcome Trust.
The Diamond synchrotron generates extremely intense pin-point beams of light of exceptional quality ranging from X-rays, ultra-violet and infrared. Diamond's X-rays are around 100 billion times brighter than a standard hospital X-ray machine.
Over 2000 researchers use Diamond to conduct experiments in a wide range of disciplines including health and medicine, structural biology, energy, engineering, earth and environmental sciences, solid-state physics, materials & magnetism, nanoscience, electronics, chemistry and cultural heritage.
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Fusion IP plc (Fusion) was established in 2002 to commercialise university-generated intellectual property. It has long-term exclusive agreements with two of the UK's leading research intensive universities, the University of Sheffield and Cardiff University, giving it exclusive access to a combined R&D spend of over £185m a year.
Fusion's first agreement was a ten-year exclusive arrangement with the University of Sheffield giving it the right to commercialise (through both the creation of spin-out companies and licensing) research, owned by the University, initially in the area of medical life sciences. This agreement was expanded in July 2008 to include all non-life science research-generated IP such as energy, engineering and electronics. Fusion has significant shareholdings in a portfolio of Sheffield University spin-out companies including Simcyp, Magnomatics, Diurnal and Phase Focus. For more details please visit the link below.
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