Diatoms to make the world iridescent

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The tiny single-celled diatom, which first evolved hundreds of millions of years ago could be about to bring a shine into our lives. The tiny creature has a hard silica shell which is iridescent, displaying vivid colours that change depending on the angle at which it is observed. This effect is caused by a complex network of tiny holes in the shell which interfere with light waves.

UK scientists have now found an extremely effective way of growing diatoms in the laboratory, with potential for scale-up to industrial level. This would enable diatom shells to be mass-produced, harvested and mixed into paints, cosmetics and clothing to create stunning colour-changing effects, or embedded into polymers to produce difficult-to-forge holograms.

Manufacturing products with these properties currently requires energy-intensive, high-temperature, high-pressure industrial processes that create tiny artificial reflectors. But farming diatom shells could provide an alternative that takes place at normal room temperature and pressure, dramatically reducing energy needs and so cutting carbon dioxide emissions. The process is also extremely rapid – in the right conditions, one diatom can give rise to 100 million descendants in a month.

This advance has been achieved by scientists at the Natural History Museum in London and Oxford University, with funding from the Engineering and Physical Sciences Research Council. The project involved a range of experts from disciplines including biology, chemistry, physics, engineering and materials science.

“It’s a very efficient and cost-effective process, with a low carbon footprint,” says Andrew Parker, who led the research. “Its simplicity and its economic and environmental benefits could in future encourage industry to develop a much wider range of exciting products that change colour as they or the observer move position”.

 The shells are completely biodegradable, aiding eventual disposal and further reducing the environmental impact of the process life cycle.

By changing the precise make-up of the culture medium, the exact iridescent properties of the diatoms, and therefore the final optical effects that they create, can be varied. The researchers estimate that up to 1 tonne/day of diatoms could be produced in the laboratory in this way, starting from just a few cells. Within as little as two years, an industrial-scale process could be operational.