13-Aug-2018: Scientists develop a super-insulating transparent gel.

Physicists have developed an insulating gel that could coat the windows of habitats in space, allowing the settlers inside to trap and store energy from the sun—much like a greenhouse stays warm during the winter. And unlike similar products on the market, the material is mostly see-through.

Transparency is an enabling feature because we can use this gel in windows, and we could use it in extraterrestrial habitats. We could harvest sunlight through that thermally insulating material and store the energy inside, protecting ourselves from the big oscillations in temperature that we see on Mars or on the moon.

The defining feature of aerogels is air. By weight, these thin films are 90 percent gas. Engineers achieve this feather weight by generating crisscrossing patterns of solid material that trap air inside billions of tiny pores, similar to the bubbles in bubble wrap. It’s that trapping capacity that makes them such good insulators.

That same network, however, tends to scatter light, making aerogels look cloudy and explaining why some engineers call them “frozen smoke.” To make a more translucent gel, physicists began with the common plant sugar cellulose. By carefully controlling how cellulose molecules link up, the team is able to orient them into a lattice-like pattern. That pattern is so uniform, that it allowed light to pass through giving the gel its transparent appearance. Unused beer wort, or waste liquid produced during the brewing process, can make cellulose when scientists add in specialized bacteria.

Currently, it takes the team about two weeks to culture the cellulose, but the rest of the process of making the aerogel moves quickly. The final product of the team’s efforts is a thin, flexible film that is roughly 100 times lighter than glass. This gel is so resistant to heat that you could put a strip of it on your hand and light a fire on top—without feeling a thing.

While the researchers have their eye on putting this material on space habitats, more immediate applications are already available on Earth. Most windows are poor insulators. Roughly one-quarter of the energy that is expended to heat and cool buildings in the United States goes toward offsetting the loss of heat through windows, potentially costing building operators billions of dollars per year.

Covering glass in sheets of the aerogel, however, could dramatically slow down the loss of heat, said Hess, who also leads the project’s tech-to-market transfer work. And you wouldn’t have to replace the windows in the process. On a larger scale, cities could use the gel to retrofit windows on skyscrapers, dramatically increasing energy efficiency.