Good news for lovers of gold watches and jewelry. Researchers from ETH Zurich University have developed a new type of gold that weighs ten times less than a traditional piece of 18-carat gold. This means you can don your favorite set of gold rings and watch without the extra weight.
The standard mixture of gold usually consists of about three-quarters gold and one-quarter copper, leaving you with a density of about 15 g/cm3. However, the newly developed gold has a density of just 1.7 g/cm3 but is still classified as 18-carat gold.
So how exactly did they achieve this? Leonie van‘t Hag, formerly a postdoc in the lab of Raffaele Mezzenga and professor of food and soft materials at ETH Zurich, and colleagues substituted conventional metal alloys such as copper and silver. They replaced those elements with protein fibers and a polymer latex to form a matrix in which they embedded thin discs of gold nano-crystals. An added benefit of replacing those alloys is that microscopic air pockets formed within the gold, substantially reducing the overall weight.
Next, the team of researchers added the aforementioned ingredients to water to create a dispersion. After adding salt to turn the dispersion into a gel, they replace the water with alcohol. The team then placed the alcohol mixture into a pressure chamber where high pressures and a supercritical CO2 atmosphere enables the mixing of the alcohol and the CO2 gas.
When the pressure is released from the chamber, it turns into a homogeneous gossamer-like aerogel (a solid material of extremely low density). Heat can be further applied afterward to harden the plastic polymers, thus transforming the material and compacting into the final desired shape, yet preserving the 18-carat composition.
“As a general rule, our approach lets us create almost any kind of gold we choose, in line with the desired properties,” Mezzenga says.