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Only a few individuals or teams are awarded by the Guinness Book of World Records for specific actions or research they’ve done. One of those teams is led by the University of Colorado Boulder Professor of Physics Ivan Smalyukh, who, with his research group, developed “the World’s Most Transparent Material.”

This material—a synthetic gel-derived material known as aerogel—is around 97-99% transparent, compared to glass, which is around 92% transparent. While many aerogels are being manufactured worldwide, the aerogel Smalyukh and his team have created involves fibers of cellulose, a protein derived from plants. Their aerogel, which has now been successfully patented, can be added to windows to boost thermal insulation, increasing the overall efficiency of a building.

What is an Aerogel?

Aerogels are often described as “frozen smoke” or “solid air” because they are incredibly light and porous. They are made by removing the liquid from a gel, leaving behind a mostly empty solid network.

“There are different ways people define aerogels, but it’s roughly one percent solid by volume and 99 percent air, so it’s mostly air,” explained Smalyukh.

Despite being extremely lightweight, aerogels are excellent thermal insulators, which means they can prevent heat from passing through them. This makes them useful in everything from space exploration to insulating homes.

“In the U.S., unfortunately, we still have almost 50 percent of single-pane windows,” added Smalyukh. “What that means is that you heat the building, especially during winter, but then a lot of that energy is actually lost through the windows.”

By retrofitting these windows with aerogel, the thermal efficiency of these windows can be increased as more heat is trapped inside.

The Challenge with Transparency

Traditional aerogels, however, despite being effective insulators, have drawbacks—they tend to scatter light, making them appear cloudy or opaque. This limits their use in applications where transparency is important, such as windows.

“They are so hazy because you have many tiny particles that are somehow connected to each other in a network. And the length of the pores between these particles ranges from a few nanometers to micrometers.”

That’s where the new aerogel Smalyukh and his team developed, called SiCellA, comes in. Instead of having various pore lengths and particle sizes like other aerogels, the researchers meticulously controlled the size of the particles, the cellulose fibers, within SiCellA, along with the distance between these particles.

“The cellulose fibers we use are typically under 6 nanometers in diameter. Because the particles themselves have a diameter much smaller than the wavelengths of light and the pores in between them are also much smaller, therefore, the scattering of light is very small.”

This produces a higher transparency percentage of the aerogel, allowing it to let through 97-99% of visible light while scattering and reflecting only 1% of the remaining light.

Boosting Energy Efficiency

To create comfortable indoor environments, buildings consume around 40% of the energy produced worldwide. Windows and skylights are often the weakest points in a building’s insulation, allowing heat to escape in the winter and letting it in during the summer.

“If we only could stop that heat loss, then we would not need to generate this much energy,” Smalyukh elaborated. “That means shutting down some coal-based power plants or using less fossil fuels.”

By using this SiCellA in windows, buildings could become much more energy-efficient, reducing the need for heating and cooling and lowering energy bills. Because SiCellA is so transparent, it can be used in windows without blocking the natural light that makes spaces bright and inviting. This means that homes and offices can stay comfortable all year round while using less energy, contributing to a more sustainable future.

A Guinness World Record

The incredible transparency of SiCellA hasn’t gone unnoticed. The Guinness Book of World Records has officially recognized it as the most transparent material ever created.

When Smalyukh & team presented their results at an ARPA-E project meeting, the program manager suggested submitting SiCellA to the Guinness Book of World Records to help disseminate the project's outcomes. While Smalyukh and his team did submit the record to Guinness back in 2019, the public release of this World Record wasn’t until much later, as the team was patenting SiCellA at the same time and had to wait for the patents and in to be accepted before breaking the news.

“It was interesting and exciting to see the record entry in the Guinness Book of World Records,” Smalyukh added. “We were happy that everything went through.”

Title Image: Senior Research Associates Vladyslav Cherpak and Bohdan Senyuk hold SiCellA aerogel film, suspended in plastic wrap, in front of the foothills. Image courtesy of the Smalyukh Group