SEM image of concavities is covered by a conformal multilayer stack of 11 alternating layers of titania and alumina (Image: Mathias Kolle, University of Cambridge)
Counterfeiting is a crime as old as money itself. It causes a reduction in the value of real money and can add to company losses, as they are not reimbursed for counterfeits. In 1996 Australia became the first country to have a full series of circulating polymer banknotes, which are difficult to counterfeit because they cannot be successfully reproduced by photocopying or scanning. Now scientists have discovered a way of mimicking the stunningly bright and beautiful colors found on the wings of tropical butterflies, that could help make banknotes and credit cards even harder to forge.