Researchers at the University of Pennsylvania’s School of Engineering and Applied Science, the University of Illinois at Urbana–Champaign, and the University of Cambridge have built a sheet of nickel with nanoscale pores that make it as strong as titanium but four to five times lighter.

The empty space of the pores, and the self-assembly process in which they’re made, make the porous metal akin to a natural material, such as wood. Infusing the empty space with anode and cathode materials would enable this metallic wood to serve double duty: a plane wing or prosthetic leg that’s also a battery.

The study, published in Nature Scientific Reports, was led by James Pikul, assistant professor in the department of mechanical engineering and applied mechanics at Penn Engineering.

The struts in the researchers’ metallic wood are around 10 nanometers wide, or about 100 nickel atoms across. Other approaches involve using 3D-printing-like techniques to make nanoscale scaffoldings with hundred-nanometer precision, but the slow and painstaking process is hard to scale to useful sizes.

“We’ve known that going smaller gets you stronger for some time,” Dr. Pikul said, “but people haven’t been able to make these structures with strong materials that are big enough that you’d be able to do something useful. Most examples made from strong materials have been about the size of a small flea, but with our approach, we can make metallic wood samples that are 400 times larger.”

Dr. Pikul’s method starts with tiny plastic spheres, a few hundred nanometers in diameter, suspended in water. When the water is slowly evaporated, the spheres settle and stack like cannonballs, providing an orderly, crystalline framework. Using electroplating, the same technique that adds a thin layer of chrome to a hubcap, the researchers then infiltrate the plastic spheres with nickel. Once the nickel is in place, the plastic spheres are dissolved with a solvent, leaving an open network of metallic struts. Roughly 70% of the resulting material is empty space. With a density on par with water’s, a brick of the material would float.

Replicating this production process at commercially relevant sizes is the team’s next challenge.