Plant-based pectin and cellulose films reflect over 95% of light

Natural materials, from butterfly wings to mother of pearl, can display a striking range of optical effects. Reproducing those effects has long been difficult when the raw ingredients must be biodegradable and sustainable, because most natural substances reflect too little light and the processing methods available could not build the fine structures needed. A team led by researchers at The University of Osaka now reports in Advanced Materials a process that turns two common plant-derived substances, pectin and cellulose, into surfaces that reflect more than 95% of the light striking them across a variety of wavelengths, including wavelengths outside the visible range.

Earlier work in this field relied on minerals or petroleum-based compounds to synthesize useful products such as pigments. Later efforts shifted to natural organic components, including liquid crystals and cellulose, but those materials struggled to reach the reflectivity that optical systems demand. The low intrinsic reflectivity of natural substances and the absence of advanced processing techniques both held the field back. The Osaka team approached the problem by finding new ways to process polysaccharides, naturally occurring compounds built from chains of sugar molecules.

The foundation of the new method is the xerogel, a highly porous solid made by drying a gel without allowing it to shrink. Lead author Takaaki Kasuga explains that this class of material underpinned the entire study. Because the gel dries without collapse, the internal structure of the solid is preserved, which matters enormously when the goal is to control how light interacts with matter at the microscopic scale.

To build the reflective films, the researchers used a technique called electrodeposition to form 100 alternating layers of pectin, a natural plant material familiar to most people as the setting agent in jams, together with nanofibers of cellulose, the main structural component of plant cell walls. Senior author Masaya Nogi notes that the specific deposition process, combined with the unique properties of the two polysaccharides, produced layers that were either dense or highly porous. The dense pectin xerogel layers and the porous cellulose nanofiber xerogel layers have very different optical characteristics, and it is the contrast between adjacent layers that produces extreme reflectivity in the finished product.

The performance figures are remarkable for an all-biopolymer system. The final material showed greater than 95% reflectance at a variety of different wavelengths of light, including non-visible light. Nature offers few comparable examples, and even the best of them falls far short. The brilliant armor of the jewel beetle Chrysochroa fulgidissima reflects only about 30% of light, meaning the plant-derived multilayer outperforms one of the most celebrated natural reflectors by a wide margin. The team also produced a beetle model coated with the all-polysaccharide multilayer reflector to demonstrate the material’s optical qualities.

Potential applications span several high-technology areas. The researchers point to optical sensors, decorative displays, and anti-counterfeiting technologies as candidate uses for the films. Because the color, pattern, and performance of the layers can all be finely tuned, the same platform could support a much broader family of products. The authors suggest that sustainable coatings, labels, and building materials could one day replace their synthetic, non-biodegradable counterparts.

The materials also address a persistent weakness of earlier bio-derived optical systems: durability against disposal. After some tweaking of the material’s chemical composition, the naturally sourced layers could be made to degrade by up to 80% in just two months. That figure meets the standard benchmark for biodegradability, meaning the films can claim both extreme optical performance and an environmentally responsible end of life, a combination rarely achieved in optical materials research.

One further capability stands out for practical use. The films can reflect near infrared light while allowing visible light to pass through them. Used as windows, such materials could help keep houses cool in the summer, because the near-infrared portion of sunlight carries heat that the film would block while ordinary daylight still enters the room. This selective behavior opens a path toward energy-saving architectural applications without sacrificing natural illumination.

The study, titled “Over 95% optical reflectance from structurally modulated all-biopolymer multilayers,” will be published in Advanced Materials. It demonstrates that sustainable, plant-based raw materials can achieve the high reflectivity once thought to require minerals or petroleum-derived compounds, and that the structural modulation of dense and porous xerogel layers is the key to unlocking that performance. As the researchers describe it, this is likely just the beginning for a processing approach that turns two of the most abundant plant substances on Earth into some of the most reflective biodegradable materials yet reported.

Subject of Research: A plant-based multilayer optical reflector made from pectin and cellulose xerogels that achieves over 95% reflectance and meets biodegradability benchmarks.

Article Title: Making mirrors from plants

Article References: Making mirrors from plants. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: pectin, cellulose, xerogel, electrodeposition, optical reflectance, biodegradable materials, polysaccharides, jewel beetle, near infrared, anti-counterfeiting, University of Osaka, Advanced Materials