"A new technique using microscopic ocean organisms could lead to cheaper, greener methods for producing iridescent cosmetics, paints and holographic plastics.
"The whole industrial process has a low carbon footprint when compared to conventional [methods]," said Andrew Parker, a professor of biology at Green College, at Oxford University in England.
The new method, developed by Parker and his team, enlists the light-altering properties of diatoms — plant-like microorganisms that live in oceans, fresh water and soil.
A diatom's ability to alter light comes from the silica shell encasing it. Each shell is comprised of a complex network of tiny holes — called photonic structures — that allow some colors in the rainbow spectrum of light to pass through, while rejecting others.
We see the rejected wavelengths of light. And when viewed from different angles, the colors seem to shift and become opalescent. Different species of the tiny phytoplankton have differently shaped shells, which in turn reflect light in a unique way.
The idea is to use specific species of diatoms to produce iridescent colors in consumer products.
By immersing a few living diatoms in a nutritious solution that encourages them to divide and multiply, Parker says his team can produce up to a ton of the single-celled organisms per day.
Once enough diatoms are grown, the researchers raise the temperature of the solution or introduce a weak acid to kill off the organic matter, leaving the light-reflecting structures behind.
Those structures can then be added to a transparent paint mixture, for example, to produce anything from iridescent car paint to opalescent cosmetics. The structures could also be added to a polymer solution and used to make holographic security codes on credit cards."
