By Josh Perry, Editor
[email protected]

Researchers from the Lawrence Livermore National Laboratory (LLNL) created ultra-low-density metal foams out of typically heavy metals such as gold, copper, and silver that are tiny enough to ride on the back of a mosquito, according to a report from the lab.

A mosquito standing on cotton fibers carries a sample of ultra-low density gold aerogel.
(Joshua DeOtte/LLNL)

This is the product of nearly a decade’s worth of work into metal nanowire-based aerogels to use as laser X-ray sources. It is not a traditional foam, but rather “a spaghetti-like web of randomly connected nanometer-sized wires, formed into the shape of a miniature marshmallow and containing the same or fewer number of atoms as air.”

Previous attempts ran into challenges such as the foam aging in the air before it got to the test section, falling apart too easily, or coming out of the molds distorted.

Scientists froze nanowires inside a mold containing a water-glycol mixture. The material is then placed in an acetone bath to remove the frozen water. The acetone is removed by drying it with liquid carbon dioxide, which leaves only the material and air. “Supercritical drying ensures the liquid transforms into a gas phase without creating a meniscus that could damage the fragile ultra-low-density metal foam structure,” the article noted.

Copper and silver foams have been the best-performing so far, but there is progress on creating gold material as well.

Read the full article at https://www.llnl.gov/news/making-metal-lightness-air.