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Though small, glitter can be a big environmental problem. When glitter is added to\u00a0cosmetics<\/a>, it often ends up getting washed off, and the microplastic pieces make their way into rivers and oceans. So-called sustainable glitters haven\u2019t been much better. While some plant-based glitters do already exist, they\u2019re usually wrapped in materials like aluminum or plastic polymer film in order to give them their shimmer, coatings that don\u2019t biodegrade; or, they need\u00a0perfect composting conditions<\/a>\u00a0to disappear.<\/p>\n\n\n\n Mica and titanium dioxide, minerals used in \u201cnatural glitters,\u201d have their own issues: mining the former is a practice fraught with child labor; the latter has been banned in the European Union because of its potentially toxic, carcinogenic effects, especially if digested.<\/p>\n\n\n\n Researchers at the University of Cambridge say their cellulose-based glitter solves all these problems, for a safer, sustainable sparkle. The first pieces of this glitter were made from wood-pulp, which the researchers detail in the journal\u00a0Nature Materials,<\/em><\/a>\u00a0but any plant product with easily extractable cellulose could be used, like cotton or even a \u201cwaste product\u201d such as mango peels, banana peels, or coffee bean skins, says Silvia Vignolini, a chemistry professor at the university and senior author of a paper. (And since it\u2019s only made from cellulose, it can also be safely eaten, the researchers say.)<\/p>\n\n\n\n To get their cellulose glitter to give off that iconic, multicolored twinkle, they didn\u2019t add any plastic coatings or aluminum layers. Instead, they used a process called \u201cstructural coloration,\u201d in which microscopic structural surfaces bend light waves in such a way that they produce pigments. Structural colors can be seen in nature, like on an iridescent peacock feather or the metallic-looking blue of marble berries<\/a>.<\/p>\n\n\n\n \u201cThe cellulose nanocrystals are organized in such a way that they can make color,\u201d says Benjamin Droguet, also from the school\u2019s chemistry department and first author of the paper. The nanocrystals form a\u00a0helicoidal structure<\/a>, meaning the layers rotate as if arranged in a spiral. Think of it as a staircase, he says. \u201cThe way to control the color is by simply changing the size of those helicoids, so we can imagine a staircase with levels that are different distances from each other. The larger the features, the longer the wavelengths of light that will be reflected,\u201d which then changes the colors that we see.<\/p>\n\n\n\n The cellulose particles they used from wood pulp spontaneously form these structures through a process called self-assembly: the cellulose crystals align, and then twist. But to actually turn this into glitter, the researchers had to create large-scale cellulose films, and they did that by packing cellulose into water, As the water evaporates, it forces the materials to contract, which prompts that self-assembly into those spiraling, light-reflecting colors. They could then grind that film of colorful cellulose down into tiny particles of glitter. Because the only ingredient is plants, no matter what happens to the glitter, it will eventually biodegrade.<\/p>\n\n\n\n With this method, the researchers don\u2019t need to add anything to the cellulose to create shimmering colors. \u201cCellulose by itself is a transparent material,\u201d Vignolini says. It\u2019s when you organize and structure it on this kind of scale that it can provide color. \u201cThink about a soap bubble,\u201d she says. \u201cWater is transparent, but as soon as you create that soap bubble layer, then you start to see colors.\u201d The researchers\u2019 main goal, she adds, is to find a more sustainable solution for pigment in general. The way we make any artificial colors often requires a chemical-heavy, energy-heavy process.<\/p>\n\n\n\n