Throughout history, man has marveled at the beauty of nature’s colours, including those in beetles, butterfly wings and opals. Until now, creating manmade substances with such refractive colour intensity has not been possible. This is because these magnificent colours are not pigment based, but instead reflect light brilliantly through the systematic ordering of their microstructures.
Recently though, a team led by the University of Cambridge invented a method called Bend-Induced-Oscillatory-Shearing (BIOS), that makes it possible to manufacture “hundreds of metres of these materials, known as ‘polymer opals’ (PO), on a roll-to-roll process.”
“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. “But spheres are only the first step, as it should be applicable to more complex architectures on tiny scales.”
As the online journal Phys.org reports, “In order to make polymer opals in large quantities, the team first needed to understand their internal structure so that it could be replicated. Using a variety of techniques, including electron microscopy, x-ray scattering, rheology and optical spectroscopy, the researchers were able to see the three-dimensional position of the spheres within the material, measure how the spheres slide past each other, and how the colours change.”
The research team, which has published its results in the journal Nature Communications, is optimistic about the potential for this discovery, stating that, “In addition to a clear demonstration of large-scale assembly using this BIOS method, our work provides the first experimental determination of the detailed PO structure, and new physical insights into the microscopic mechanisms behind crystallization of this rheologically unique system. The general principles underpinning BIOS can thus be applied in many ways including ordering of widely varying nanoparticle sizes, and even mixtures with polydispersity exceeding 20% which are normally impossible to order. For instance, anisotropic nanoparticles should have even further improved degrees of ordering, delivering a range of nematic phases in flexible films. This may be particularly interesting in the case of cellulose nanorods, which are known to produce intense structural colours but take days to form chiral nematic phases. The shearing of nanoparticle systems in this fashion also acts to segregate nano components into stacks of ordered two-dimensional layers, opening up many new possible architectures. ”
Looking to the future, the University’s commercial arm has received 100’s of enquiries from chemical companies interested in the new material, such that a spin-out company called Phomera Technologies, has been founded.
As well as studying ways to fully industrialize the process or in how to amend production to meet specific commercial needs, the company is hoping to monetize the venture further with a view to using the product in heat reflective coatings for buildings, smart clothing and footwear, or for packaging applications and banknote security features.
Beyond the money, much of the scientific community is simply happy to have met a challenge set by nature. As PhD student Qibin Zhao, the paper’s lead author said, “It’s wonderful to finally understand the secrets of these attractive films.”