Researchers at ETH Zurich have accomplished a bit of modern-day alchemy, transforming 20 carat gold into a lightweight foam. Well, technically it's an aerogel: an exceedingly light and porous matrix of material. It's so porous, in fact, that the foam doesn't conduct electricity because, at atmospheric pressure, the gold atoms within the structure don't actually touch. "The so-called aerogel is a thousand times lighter than conventional gold alloys. It is lighter than water and almost as light as air," Raffaele Mezzenga, Professor of Food and Soft Materials at ETHZ, said in a statement.
The foam is created by first heating milk proteins until they break down into nanometer-scale fibers. These are then mixed into a gold salt solution where the two materials fuse and crystalize into a gel-like fibrous mass. It is then delicately dried in an carbon dioxide bath. And while the resulting product looks like natural gold, this aerogel actually is hand malleable at room temperature.
Even cooler, the color of the resulting nugget can be easily manipulated by changing the gold's particle size. "The optical properties of gold depend strongly on the size and shape of the gold particles," the study's lead author Gustav Nyström, said in a statement. "Therefore we can even change the colour of the material. When we change the reaction conditions in order that the gold doesn't crystallise into microparticles but rather smaller nanoparticles, it results in a dark-red gold." The ETH team believes that this new material could find use in a wide variety of applications from jewelry and watch design to use in chemistry and optics.