Wouldn’t it be nice to live in a world where technology enables us to pay less on energy bills? Aerogels offer one potential solution.

These materials have exceptional thermal insulating properties, which help boost the energy efficiency of the apparatus they are integrated with. Energy-saving aerogels can be found in windows, refrigerators, and even spacecraft insulation. So, how did this mysterious material originally appear?

Essentially, aerogels are a spin-off of traditional gels. Whereas traditional gels (think, Jell-O) are chains of linked particles submersed in a liquid, aerogels are formed by replacing all the liquid with air. This gives the aerogel many fine, nanometer-sized pores and a curious combination of being both lightweight and durable. Counterintuitively, the air replacement needed for aerogels can’t be achieved by drying — this is because as liquid evaporates, the gel structure collapses before air can be substituted. You can see this phenomenon occur when Orbeez (a gel-based water toy from the 2000s) shrink under air-drying, and it is one of the major reasons that aerogels were not more swiftly discovered. 

In 1931, to overcome the drying phenomenon, Stanford University researcher David Kistler flushed gels with alcohol at the supercritical condition — a special state that is both liquid and gas — and created the world’s first aerogel. However, the aerogel didn’t initially provide commercial value, so it hid in plain sight until it was rediscovered in the 1980s. This time, Arlon Hunt from Lawrence Berkeley National Laboratory (LBNL) realized that the aerogel had great untapped potential, as long as it underwent a few chemistry tweaks.

The first major change was to make the aerogel more compatible with manufacturing. The original aerogel was expensive and hazardous to make (in fact, the first aerogel factory exploded from the chemical ingredients). By switching alcohol with non-flammable carbon dioxide, the process for making supercritical fluids could use lower temperature and pressures and avoid accidental ignition.

Next, the thermal properties of aerogels needed to be vastly superior to their commercial competitors. Although aerogels were technically a better insulator than the leading foams, it needed justification for the slightly higher cost and risk. Hunt found that aerogel pores could block most modes of heat transfer, but it couldn’t block infrared radiation. To fix this, Hunt realized aerogels needed to have an infrared-blocking sidekick: micro-sized carbon black particles. This addition enabled aerogels to use far less material for the same insulation effect as competing foams, and secured aerogel’s niche in refrigerator insulation.

In 1990, Hunt and LBNL won the FLC Excellence in Technology Transfer Award for their work on the aerogel. But there were still unresolved opportunities to improve the technology. At that time, aerogels were insulating enough for applications in building walls, but weren’t clear enough to be integrated into windows, which is a major source of household energy loss. The lack of clarity did not come from the aerogel’s internal chemistry, but from the occasional impurities that leaked and interfered with the fabrication process. However, aerogels just needed time for manufacturing standards to improve, and eventually, it became easier to operate with cleanliness and produce clearer aerogels.

As aerogels became more refined, they caught the eye of other laboratories and industry partners for commercial use. Fast forward several years to when aerogels became clear enough to inspire breakthroughs in thermochromic thin film material for windows. In 2018, Sandia National Laboratories (Sandia) won the FLC Excellence in Technology Transfer Award with IR Dynamics, a New Mexico-based Nanotech startup, for developing windows with smart regulation of solar heat. This meant that the windows could adjust their solar transmittance and reflectance according to the temperature of the day, while maintaining its insulating properties — making heating and cooling the building more efficient, and, well, “pane-less.”

The window of opportunity really came about when Sandia combined its insulating aerogels with the IR Dynamic’s thermochromic nanoparticles. The term “thermochromic” refers to a change of color or transmissivity via temperature, which is useful because if light transmission can be controlled, so can solar heat-gain through the window. In the future, temperature-sensitive insulation can also be useful for things like architectural plastics. 

Sandia not only used the technical arsenal of IR Dynamics, but also a tailored combination of technology transfer mechanisms. These entailed several licenses, a Cooperative Research and Development Agreement, New Mexico Small Business Assistance program projects, a User Facility Agreement, and outside consulting. The initial development for retrofitting window films using IR Dynamics technology was also partially funded by a $1.95 million Department of Energy Advanced Research Projects Agency-Energy grant.

More recent aerogel technology breakthroughs include a University of Colorado aerogel made of recyclable materiels that was recognized by the Guiness Book of World Records for being the world's most transparent material, as well as Aeroshield's aerogel that has high clarity and is currently being tested at LBNL.

Aerogels and dynamic solar control tell a technology transfer journey that was more of a marathon than a sprint. Nearly a century after its invention, many details have been refined in the aerogel, but its fundamental existence remains steadfast. Now, aerogels have a clear future in influencing the efficiency of our infrastructure — and possibly more.