����ý

A team of engineers claims to have created the world's lightest material.

The substance is made out of tiny hollow metallic tubes arranged into a micro-lattice - a criss-crossing diagonal pattern with small open spaces between the tubes.

The researchers say the material is 100 times lighter than Styrofoam and has "extraordinarily high energy absorption" properties.

Potential uses include next-generation batteries and shock absorbers.

The research was carried out at the University of California, Irvine, HRL Laboratories and the California Institute of Technology and is published in the latest edition of Science.

"The trick is to fabricate a lattice of interconnected hollow tubes with a wall thickness 1,000 times thinner than a human hair," said lead author Dr Tobias Schaedler.

Low-density

The resulting material has a density of 0.9 milligrams per cubic centimetre.

By comparison the density of silica aerogels - the world's lightest solid materials - is only as low as 1.0mg per cubic cm.

The metallic micro-lattices have the edge because they consist of 99.99% air and of 0.01% solids.

The engineers say the material's strength derives from the ordered nature of its lattice design.

By contrast, other ultralight substances, including aerogels and metallic foams, have random cellular structures. This means they are less stiff, strong, energy absorptive or conductive than the bulk of the raw materials that they are made out of.

William Carter, manager of architected materials at HRL, compared the new material to larger low-density structures.

"Modern buildings, exemplified by the Eiffel Tower or the Golden Gate Bridge are incredibly light and weight-efficient by virtue of their architecture," he said.

"We are revolutionising lightweight materials by bringing this concept to the nano and micro scales."

Robust

To study the strength of the metallic micro-lattices the team compressed them until they were half as thick.

After removing the load the substance recovered 98% of its original height and resumed its original shape.

The first time the stress test was carried out and repeated the material became less stiff and strong, but the team says that further compressions made very little difference.

"Materials actually get stronger as the dimensions are reduced to the nanoscale," said team member Lorenzo Valdevit.

"Combine this with the possibility of tailoring the architecture of the micro-lattice and you have a unique cellular material."

The engineers suggest practical uses for the substance include thermal insulation, battery electrodes and products that need to dampen sound, vibration and shock energy.