It looks like glass and feels like solidified smoke, but the most interesting features of the new silica aerogels made by UC Davis and Lawrence Livermore National Laboratory researchers are too small to see or feel. Lighter than styrofoam, this strange material is riddled with pores just nanometers in size, leaving it 98 percent empty.
Water can soak into the material, but in the confined space the water molecules arrange themselves in unusual ways, said Subhash Risbud, professor of chemical engineering and materials science at UC Davis. For example, a lipid membrane can spread across a wet aerogel just as it does around a living cell.
Scientists studying such lipid membranes usually put them on a wafer of silicon or gold. Instead, the aerogel provides a wet cushion for the membrane, allowing it to have moisture on both sides and act more like a real cell in which membranes are studded with proteins. Researchers at Stanford University, led by engineering professor Curtis Frank and Risbud, recently patented the concept.
The invention could be used for investigating diseases such as lupus and rheumatoid arthritis and for biological testing devices.
Aerogels are made by taking a wet gel -- a meshwork of molecules in liquid, such as water -- and removing the water to leave a spongy structure. The first aerogels were made in the 1930s by Samuel Kistler, and the technology was further developed by Lawrence Hrubesh and colleagues at the Lawrence Livermore National Laboratory over 40 years later.
Silica aerogels also have many other applications in fibre optics, insulation against sound or heat, and miniature pumps for built-in refrigeration systems in packaging, Risbud said.
The research project was part of the Center on Polymer Interfaces and Macromolecular Assemblies, a collaboration between Stanford, UC Davis, UC Berkeley and the IBM Almaden Research Center. Risbud also continues to collaborate with Joe Satcher and John Poco of the Lawrence Livermore National Laboratory on silica aerogels.