Lightest Metal in the World

A team of scientists has revolutionized the world of chemical engineering by successfully designing a metal so thin it can rest on top of a dandelion without crushing it.

The UC Irvine research group sought to develop the new metal, whose nano-structure makes it 100 times lighter that Styrofoam. Comprised of 99.99 percent air, the material is merely 0.01 percent metal. Moreover, the material’s density is reported to be 0.9 mg/cc.

The finding can be attributed to a collaborative effort between Hughes Laboratory of Research (HRL), the University of California Irvine, and the California Institute of Technology (Caltech).

HRL was responsible for all aspects of manufacturing, UCI for macro-mechanical characterization, modeling and optimal design, and Caltech for nano-scale materials and mechanical characterization.

Organizations ranging from aerospace to consumer electronics have been very interested in exploring possible applications of this new material.

The entire project was funded by The Defense Advanced Research Projects Agency (DARPA), an agency of the United States Department of Defense, which develops new technology for military use.

UCI’s team, led by Lorenzo Valdevit, assistant professor in the Department of Mechanical and Aerospace Engineering, with a joint appointment in Chemical Engineering and Materials Science, has been developing the metal for over a year.

“We had a very important role in the Science paper that led to the press coverage, and will be playing an even more important role in the future mechanical improvement of these metallic — and possibly non-metallic — micro lattices, hopefully improving their already exciting properties even further,” Vadevit said. “The credit for the invention and fabrication of the material goes entirely to HRL Laboratories.”

UCI is playing an integral role in understanding and optimizing its mechanical properties, from stiffness to strength, damping and energy absorption.

The material’s careful design resulted in it possesing unusual properties such as the ability to absorb energy and to recover its shape after having undergone enormous compression. Empirically, the material has been able to restore itself after enduring compression surpassing 50 percent strain.

“It might open a number of opportunities for use in acoustic and vibration damping as well as energy-absorbing structures,” continued Vadevit. “The physics underlying these fascinating properties is currently being investigated, with UCI playing a major role.”

Lightweight cellular materials have been investigated for applications in aerospace and transportation systems for some time. Nevertheless, HRL initiated this pursuit with novel hierarchical concepts involving macro-scale materials emerging out of a three-dimensional arrangement of thin films. For this specific material, each film is as thin as 100 nanometers approximately 1,000 times thinner than a human hair.

According to Dr. William  Carter, manager of the Architected Materials Group at HRL, correlated the unique properties of the metal to structures on a much larger scale. Well-known buildings such as San Francisco’s Golden Gate Bridge or Paris’ Eiffel Tower are simultaneously lightweight and durable, with respect to their size.

Until recently, incredibly lightweight materials were restricted in use because of a fatal flaw: the inability to endure pressure.

Because this novel metallic lattice has an orderly structure, it is more conductive, stiff and strong, and thus capable of withstanding greater pressure than previous designs.

This achievement is noteworthy because the metal’s unprecedented combination of properties may inspire the innovation and expansion of more of these materials.

“When they sent us one of the first samples, we could hardly believe our eyes,” recalled Vadevit. “You can drop this entirely metallic material from shoulder level, and it floats like a feather, taking 10 seconds to reach the ground. It’s really super cool!”

The physics underlying the architecture of the metal can be read about in depth in the Nov. 18 issue of Science.