Considering that gold has a very high density, and is one of the heaviest metals per volume in the world, the fact that researchers at ETH Zurich have succeeded in creating gold aerogel so light that it can float is quite an accomplishment!
Aerogels, also called ‘frozen smoke’ are produced synthetically with solids and a high porosity. Since the voids between particles fill with air, they have very low density.
Although at first glance, this particular aerogel appears as a sprayable gold ingot, it is in fact a thousand times lighter. The material, which is a type of rigid foam, is actually lighter than water – its density is close to that of air. Gold aerogel can also be freely shaped, even with bare hands!
Interestingly, this new spray has quite a bit of intrinsic value, as it is composed of 83% pure gold. The remainder consists of air bubbles and a little bit of milk (that is not a typo – yes, milk).
The process used to create the gold foam makes use of heated milk proteins, which form miniature amyloid fibrils. These are then placed in a solution containing positively charged ions of gold. After a period of evaporation, the fibers are arranged into a 3D structure, around which crystallized gold forms a kind of ‘grid.’
In addition to perhaps leading to the creation of super-lightweight jewellery, gold aerogel has numerous potential engineering applications. Its usefulness is primarily due to its catalytic properties and thus its ability to carry a current, but this requires subjecting the gel to high pressure so that the gold particles come into contact with one another.
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