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Scientists create lightweight champ

Dan Little / HRL Laboratories

A new type of nickel-phosphorus lattice is so light it can sit atop a ball of dandelion fluff without disturbing it.

Researchers have created a new kind of metal that rates as the world's lightest material — and just might show up in future batteries and shock absorbers.

The nickel-phosphorus "microlattice," which is described in this week's issue of the journal Science, is the stuff that gee-whiz is made of: It actually consists of 99.99 percent air. The other 0.01 percent is made up of interconnected hollow tubes with a wall thickness of 100 nanometers. That's 1,000 times thinner than a human hair.

To get technical about it, the density of the material is 0.9 milligrams per cubic centimeter. In comparison, the lightest sample of aerogel, the stuff that's been called "solid smoke," has a density of 1.1 mg/cc.

The microlattice is made through a process that's completely different from the "cooking" technique that gives rise to aerogel. The researchers start by setting up a matrix of polymer lattices, and then deposit thin films of nickel-phosphorus. When the polymer is etched away, tiny metal tubes are left behind in the shape of the lattice.

Aerogel is foamy stuff that makes a great insulator but chips off easily. In contrast, the highly ordered structure of the microlattice makes it strong and resilient.

"Modern buildings, exemplified by the Eiffel Tower or the Golden Gate Bridge, are incredibly light and weight-efficient by virtue of their architecture," William Carter, manager of the architected materials group at California-based HRL Laboratories, explained today in a news release. "We are revolutionizing lightweight materials by bringing this concept to the nano and micro scales."

Lorenzo Valdevit, a materials scientist at the University of California at Irvine, said materials actually get stronger when the scale is reduced to the nanometer level. "Combine this with the possibility of tailoring the architecture of the microlattice, and you have a unique cellular material," he said in a UC-Irvine news release.

The material is strong enough to bounce back after being compressed by 50 percent, yet light enough to sit on top of a fluffy dandelion without disturbing it, as shown in the photo above. The stuff's properties make it ideal for applications that involve soundproofing or shock absorption, and it could also lead to lighter battery electrodes. It's no wonder that the material was developed for the Pentagon's Defense Advanced Research Projects Agency. (And yes, the developers have applied for a patent on the microlattice structure and formation process.)

Update for 10:15 p.m. ET: Valdevit provided a little more perspective on the "lightest material" claim in a follow-up phone call. "You might argue that it's a 'structure' rather than a 'material,'" he acknowledged. But the key factor has to do with how strong and resilient the microlattice is for its weight. That's what will determine how widely it's used.   

Science's Brandon Bryn narrates a video showing how an ultralight metallic microlattice recovers from compression. (Credit: HRL Laboratories / AAAS)

More material about materials science:

In addition to Carter and Valdevit, authors of "Ultralight Metallic Microlattices" include Tobias Schaedler, A.J. Jacobsen, A.E. Sorensen, J. Lian and J.R. Greer.

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