“It’s like holding a slab of San Francisco fog,” says Pamela M. Norris, a UVA professor of mechanical and aerospace engineering. She’s doing her best to describe a solid that’s actually 98 percent air. Called an aerogel, it consists in its various incarnations of either silica, zirconia or alumina, which makes up the remaining 2 percent. Dry, delicate and almost completely transparent, aerogels are the lightest solids ever produced.
The substance was first developed in the 1930s by a California scientist who was interested in removing the liquid from gel while keeping the structure intact. The highly combustible production process made them dangerous to make at first, and it’s only recently that aerogels have been rediscovered for their useful capacities.
“They’re an amazing class of material possessing a lot of world records,” says Norris. Aerogels have the lowest speed of sound and the lowest electric conductivity of any known material, making them excellent acoustic and electric insulators. They’re also the world’s best thermal insulator, and, as such, were used to line electronics in the recent Mars rover mission. “They’re the only material that would have worked,” says Norris.
NASA has also been using aerogels in an ongoing mission to collect particles in space. The material forms a butterfly net that collects tiny fragments, such as those left by comets, which can then be studied and identified.
But stardust and space travel aren’t the only applications for this high-performing material. Norris, who directs UVA’s Aerogel Research Laboratory, the only facility of its kind in the country, is working to realize its full potential here on the ground.
When Norris came to UVA in 1994, her first grant entailed a study of the way energy moves through different materials on a microscopic level. She needed aerogels for this research, but found their cost prohibitive. “So I made them myself,” she says. In doing so, Norris became fascinated with the material and has since made aerogels one area of her expertise. She founded the research lab and got funding from the U.S. Department of Defense for a project in which aerogels could be used to detect biological warfare agents in the air. Morris was studying how aerogels could function as a sort of sponge embedded with air-specific receptors. When they detected hostile agents, the receptors would cause the sponge to change properties, indicating an emergency.
Contrary to what you might expect, though, funding for that project dried up after the terrorist attacks of Sept. 11, 2001. “After 9/11, only people who could produce a product in six months to a year would get a contract,” says Norris. “We weren’t close enough to product development, so funding for basic research stopped.”
The aerogel lab, however, is busier than ever. Norris is now focused on other aspects of aerogel synthesis such as the sol-gel process, a production process that allows scientists to alter the material’s density, pore-size distribution and surface chemistry according to specific needs. Norris is working with UVA chemistry professor James P. Landers on lab chip technology, where sol-gels are used for purification of DNA from biological samples. She also has several undergraduates busy on a range of research projects, from the design of an ultra-insulating sleeping bag to fiber-reinforced aerogels that bounce.
For such a light material, aerogels hold a lot of potential. Still, you’d think that after more than 10 years of research, Norris would tire of concentrating on something that barely seems to exist. “No way,” she says when asked about slowing down. “It’s the coolest substance ever.”