A new form of plastic gold weighs five to ten times less than traditional 18-carat gold

Formerly a postdoc in the ETH lab headed by Raffaele Mezzenga, Professor of Food and Soft Materials, Leonie van 't Hag set to create a new form of gold that weighs about five to ten times less than traditional 18-carat gold.

Instead of a metal alloy element, van 't Hag, Mezzenga and colleagues used protein fibres and a polymer latex to form a matrix in which they embedded thin discs of gold nanocrystals.

The lightweight gold contains countless tiny air pockets invisible to the eye.

To create the new lightweight gold the researchers first added the ingredients to water and created a dispersion. After adding salt to turn the dispersion into a gel, next they replace the water in it with alcohol.

Placing the alcohol gel into a pressure chamber, high pressures and a supercritical CO2 atmosphere enables miscibility of the alcohol and the CO2 gas; when the pressure is released, everything turns it into a homogeneous gossamer-like aerogel.

Heat can be further applied afterwards to anneal the plastic polymers, thus transforming the material and compacting into the final desired shape, yet preserving the 18 carat composition.

In addition the researchers can adjust the hardness of the material by changing the composition of the gold. They can also replace the latex in the matrix with other plastics, such as polypropylene.

Since polypropylene liquifies at some specific temperature, "plastic gold" made with it can mimic the gold melting process, yet at much lower temperatures.

The plastic gold is suitable for the manufacturing of watches and jewellery and is also suitable for chemical catalysis, electronics applications or radiation shielding.

The researchers have applied for patents for both the process and the material.