Press outlets around the world were bowled over last week by an especially lite news item: The announcement that researchers at several California universities and HRL Laboratories managed to create the world’s lightest material, “metallic micro lattice,” which has a density of 0.9 mg per cubic centimeter, about 100 times lighter than styrofoam. Their breakthrough is described in a paper published in the journal Science (paywall).
Metallic mirco lattice is 99.99 percent air, yet is actually a metal that can balance atop the head of a dandelion without crushing it, and exhibits complete elastic recovery from being compressed with greater than 50 percent strain, as seen in this incredible video.
As such, the material, which was synthesized over a four-year period with a grant from the Defense Advanced Research Projects Agency (DARPA), is anticipated to have a wide variety of applications in everything from the military to infrastructure to batteries even a new generation of biomedical tissue scaffolding.
But just how was the miraculous metallic micro lattice made, and what is it made up of? TPM contacted one of the scientists involved in the effort to get the backstory. As it turns out, the achievement was truly a collaborative effort.
“I think I actually had the idea to push for super-low density,” said said HRL’s William Carter, one of the authors of the new paper, in an email to TPM.
“The main invention (the process to make microlattices) was done here at HRL by Dr. Alan Jacobsen in 2007. The process to get ultra-light materials was refined by Dr. Tobias Schaedler over the past year. We collaborated with Prof. Valdevit’s group at UC Irvine to understand the mechanical properties, and Prof. Greer’s group at Caltech to understand the base material properties.”
Carter further explained to TPM that “final material is a common alloy between nickel and phosphorous typically called ‘electroless nickel.’”
That said, Carter added that he thinks his team can “make the same structure out of many different materials,” including polymers, and even ceramics. The main achievement lies in how the material is assembled, not its raw components.
“Aerogels,” the lightest materials prior to metallic micro lattice, “can be super-light, but at a microscopic scale they are very random, making them very fragile,” Carter said.
“I figured if we could order the material at the micro-scale, we could make a much more robust material. Dr. Schaedler made it happen - he developed the actual process to get down to ultra-low density.”
That process involves a pouring a liquid material into the micro lattice pattern and hardening it by exposing it to ultraviolet light. The “electroless nickel” was then poured onto the pattern very precisely, forming a 100-nanometer thin uniform coating.
Carter told TPM that so far, his team has synthesized a “few dozen ‘coffee-cup coaster’ sized samples,” actually an enormous achievement, given the nano-scale of the material. And Carter said his team can “easily make more/bigger ones.”
“This is a very early study, and we will probably see more concrete applications” in the near future, Carter added.
On another fun note, Carter told the Los Angeles Times that the material floats to the ground like a feather if dropped from the air, taking 10 seconds to reach the ground when released from shoulder-height.
A semi-related aside: HRL Laboratories, formerly Hughes Research Laboratories, is a 51-year-old company started by legendary American billionaire industrialist Howard Hughes as the research wing of his Hughes Aircraft Company. It is now co-owned by Boeing and General Motors.