London: A team of researchers has devised a new method for stacking microscopic marbles into regular layers, producing intriguing materials which scatter light into intense colours and which change colour when twisted or stretched.
The team, led by the University of Cambridge, used a new method called Bend-Induced-Oscillatory-Shearing (BIOS) to produce hundreds of metres of these materials, known as 'polymer opals', on a roll-to-roll process.
The results, reported in the journal Nature Communications, has allowed such sheets to be manufactured on industrial scale, opening up applications ranging from smart clothing for people or buildings, to banknote security.
Some of the brightest colours in nature can be found in opal gemstones, butterfly wings and beetles. These materials get their colour from the systematically-ordered microstructures they contain.
When stretched, the material shifts into the blue range of the spectrum and when compressed, the colour shifts towards red. When released, the material returns to its original colour.
"Finding a way to coax objects a billionth of a metre across into perfect formation over kilometre scales is a miracle," said Professor Jeremy Baumberg, the paper's senior author.
"It is wonderful to finally understand the secrets of these attractive films," said PhD student Qibin Zhao, the paper's lead author.