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Beetle scales could hold the key to sustainable white paint

30th August 2019 - Scientists have used STFC’s ISIS Neutron and Muon Source (ISIS) research facility to investigate how to mimic one of the brightest whites in nature, the wing scales of the Cyphochilus beetle, found in South East Asia, with the aim of producing more environmentally-friendly paint in the future.

This new research potentially paves the way not only for new paints that would have a much lower carbon footprint but could also help tackle the challenge of recycling single-use plastics.

The Cyphochilus beetle has scales on its wings that are very white and reflective, properties that do not often occur in nature. The colour is not due to pigmentation, but is due to the complex nanostructure of the scales on the beetles’ wings, which reflect light in a certain way. These structural characteristics are also what gives some bird feathers their iridescent colour and even the fur of mammals like polar bears its white appearance.

A study led by Dr Andrew Parnell from the University of Sheffield has been looking at how to replicate the structures that produce this white in the Cyphochilus beetle in order to replace the pigment currently used to make white paints. The work at ISIS has been looking at a more environmentally friendly source of whiteness: a plant-based polymer, cellulose acetate.

Dr Parnell said: “In the natural world, whiteness is usually created by a foamy Swiss cheese-like structure made of a solid interconnected network and air. Until now, how these structures form and develop and how they have evolved light-scattering properties has remained a mystery.

“Having understood these structures we were able to take plastic and structure it in the same way. Ideally, we could recycle plastic waste that would normally be burnt or sent to landfill, structure it just like the beetle scale and then use it to make super white paint. This would make paint with a much lower carbon footprint and help tackle the challenge of recycling single-use plastics.”

White paint contains nanoparticles of titanium oxide –a compound also used in sunscreen – and it has the potential to damage soil and marine ecosystems. It also has a significant carbon footprint due to the carbon dioxide emitted during industrial processing and is the most expensive component used in paint. Replacing it with a plant-based polymer would make white paint much less damaging to the environment.

At ISIS, researchers used neutron techniques to look at the beetle scales and the cellulose acetate at the nanoscale. Using ISIS’ LARMOR instrument, the team applied small angle neutron scattering techniques to measure the nanostructure of just one or two scales from the Cyphochilus beetle. The sensitivity of the LARMOR instrument to large length scales makes it uniquely useful for investigating the properties of the beetle wings that give it its structural white colour.

ISIS Beamline Scientist Dr Adam Washington said: “The structures we studied in these beetle scales are only accessible through a small number of techniques.  Out of those techniques, only LARMOR and the brightness of the ISIS source would let us examine hundreds of these scales in just a few days, instead of months.”

The OffSpec instrument at ISIS was also used to measure some of the fundamental neutron scattering properties of the cellulose acetate films that were used in the analysis of small angle scattering data.

Other measurements were taken using X-ray tomography techniques at the European Synchrotron Research Facility (ESRF) in Grenoble, France.

In the future, the ability to replicate structural colour in paint using cellulose could see recycled food or agricultural waste replace the potentially polluting chemical pigment currently used.

Notes:

Previous research by this team has looked at the way structural colouration in polar bear fur could be used to give paint heat-retentive, insulating properties.

You can read more about the work here

Last updated: 04 September 2019

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