Almost all of the glitter that has been used by human’s, albeit visually appealing, poses a significant environmental problem due to the long-term persistence of microplastics. A new formulation by a group at the University of Cambridge addresses this problem by using a new formulation based on cellulose polymers from plants, while being just as shimmery as the original product.
Figure 1. Cellulose nanocrystal structures are picture in 3 different media from left to right; water, water:ethanol, and ethanol. Colour differences are observed due to differences in water-uptake and swelling that causes red-shifting of the coloured particles. Figure taken from reference 2.
Everyone at some point in their lives has used glitter for arts and crafts and has been stuck with the epidemic of these shimmery pieces of small plastic that are almost impossible to clean up. Glitter is undeniably difficult and gets everywhere, and since most glitter is made of plastic, it does not go away very easily. It has become the bane of almost every parent and schoolteacher, and also acts as a toxic and unsustainable material that contributes to the ever-growing global plastic pollution problem.
When used in cosmetic products it is inevitably washed off and microplastic pieces end up in our bodies of water. Sustainable efforts have been made to try and reduce this problem with plant-based glitters which are already in production, but these still struggle from complete sustainability due to necessary aluminum or plastic films that are required to generate their shimmery effect. In Europe alone, the cosmetics industry is responsible for the production of over 5500 tons of microplastic every year, showing that this is a present and significant problem.
Researchers at the University of Cambridge have been working to address this problem and have published an article in Nature Materials about using cellulose-based glitter that can provide a safer alternative without comprising visual appearance.1 The group has found a way to produce glitter from this main building block of the cell walls in plants, fruits, and vegetables, with successes in extracting and producing materials from wood-pulp, cotton, and mango peels. And quite interestingly, since the glitter is only made from cellulose, it can be safely eaten.
The glitter is composed of cellulose nanocrystals, which contain microscopic structures that can bend light to produce vivid colours in a manner known as Structural Colour. This same phenomenon is seen all throughout nature in the bright colours of butterfly wings and peacock feathers, which produce colours through their interactions with light. The nanocrystals arrange in a fashion that produces a helicoidal structure, which means that the layers rotate in a spiral pattern, similar to a staircase. The way in which these structures can be modified to produce different colourations depends on the distances between the “stairs” in this helicoidal structure. The larger the features present, the longer the wavelengths of light that end up being reflected, which can have a major impact on the observed colour. Additionaly, viewing angle, distance, and even liquids used for dispersions can affect the interaction with light, leading to different observed colours. The best part about this process of colour formation is that the resulting hues do not fade over time, even after hundreds of years.
Figure 2. Cellulose nanocrystal on glass slide showing different colours based on angle of viewing and incident light.. Figure taken from reference 3.
The films of these cellulose nanocrystals can supposedly be made at scale using roll-to-roll processes like those used in wood pulp processing to make paper, resulting in spontaneous formation of these cellulose nanocrystal structures in a process known as Self Assembly. This is when the helical twisting occurs, aligning the crystals for colour production. Through careful optimization of the roll-to-roll process, the team was able create large-scale cellulose films by packing cellulose into water to cause swelling. As the water evaporates, the cellulose film begins to contract and self-assemble into the spiraling, light reflecting colours that are desired. This film can then be easilyground into tiny particles that resemble glitter. Most importantly, unlike its plastic counterpart, this tiny particle is composed entirely of biodegradable materials that are completely plastic and toxin free. It is also far less energy intensive than the conventional methods used in current production.
Figure 3. Cellulose film produced by roll-to-roll process. Figure taken from reference 2.
The next steps of this work hope to scale up production into more commercial and industrial sized equipment with hopes of reaching the market in the upcoming years. The use of these sustainable cellulose glitter particles is a revolutionary discovery with great potential for large-scale usage in not only the party world, but also in the cosmetic industry. This could allow for a significant reduction in global microplastic production, leading to a safer and more sustainable future, all thanks to Materials Chemists!
The findings of this research has been published in the Journal of Nature Materials:
Droguet, B. E.; Liang, H.-L.; Frka-Petesic, B.; Parker, R. M.; De Volder, M. F. L.; Baumberg, J. J.; Vignolini, S. Large-Scale Fabrication of Structurally Coloured Cellulose Nanocrystal Films and Effect Pigments. Nat. Mater. 2021 2021, 1–7. DOI: 10.1038/s41563-021-01135-8.
References:
1) Droguet, B. E.; Liang, H.-L.; Frka-Petesic, B.; Parker, R. M.; De Volder, M. F. L.; Baumberg,
J. J.; Vignolini, S. Large-Scale Fabrication of Structurally Coloured Cellulose Nanocrystal
Films and Effect Pigments. Nat. Mater. 2021 2021, 1–7.
from-plants. (accessed Nov 15, 2021).
(accessed Nov 15, 2021).