Structural colour in beetles

Beetle shells inspire colour-changing nanoparticles

Image credit: Dreamstime

A team of Korean researchers has developed a cheap and simple method for creating nanoparticles which can be made to change colour even when implanted within a material.

Their method was inspired by the dazzling rainbow of colours that shine from beetle shells. The shells of beetles – as well as the feathers of some birds and components of some plants – are covered with tiny biological structures of crystalline shapes, which through interference with the passage of light produce an intense, iridescent display of colour.

The phenomenon was first observed by rivals Isaac Newton and Robert Hooke and is based on the principal of wave interference.

This type of colour – structural colour – has been a phenomenon that scientists have spent years attempting to recreate in the lab. Unlike many other pigments, structural colour is resistant to fading. Artificial structural colour could have uses in cosmetics, dyes, paints and countless other products.

However, all of the techniques currently used to integrate structural colour into materials tend to be expensive, tedious and inflexible: once these pigments are fixed to a surface, it is nearly impossible to modify them.

The group of materials scientists – from Pohang University of Science and Technology and Andong National Univerity in Korea – report a new method which could allow nanoparticles to change colour, even after being embedded into a material.

According to their ACS Applied Materials and Interfaces paper, the nanoparticles can be created through a process called hydrothermal growth, in which flower-like nanostructures of zinc oxide are synthesised quickly in ordinary warm water.

This technique allowed the researchers to control the size, shape and spacing of the nanostructures during synthesis by adjusting the speed of synthesis, even after having been implanted within a material.

The researchers report that the inexpensive technique for creating tuneable structural colour could lead to the production of anti-tampering tags and microelectrodes for easier-to-read sensors.

Recently, a Japanese research team used the molecular structure of iridescent bird feathers to create new artificial pigments and demonstrate new ways to control the interaction of light and materials.

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