Caltech Develops Nanoscale Metal Additive Manufacturing

A nanoscale lattice prepared using a new technique developed by the lab of Julia R. Greer.

Last year, California Institute of Technology (Caltech), Pasadena, California, researchers revealed that they had developed a new fabrication technique for printing microsized metal parts containing features about as thick as three or four sheets of paper. Now, the team has reinvented the technique to allow for printing objects a thousand times smaller: 150 nanometers. These parts can be three-to-five-times stronger than similarly sized structures with more orderly atomic arrangements.

The new process starts with preparing a photosensitive "mixture" that is comprised of a hydrogel, a type of polymer that can absorb many times its own weight in water. This mixture is selectively hardened with a laser to build a 3-D scaffold in the same shape as the desired metal objects. In this research, those objects were a series of tiny pillars and nanolattices.

The hydrogel parts are then infused with an aqueous solution containing nickel ions. Once the parts are saturated with metal ions, they are thermal treated until the hydrogel is burned out, leaving parts in the same shape as the original but consisting entirely of metal ions that are now oxidized. The oxygen atoms are chemically stripped out of the parts, converting the metal oxide back into a metallic form.

The work was conducted in the lab of Julia R. Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics, and Medical Engineering; and Fletcher Jones Foundation Director of the Kavli Nanoscience Institute. Funding for the research was provided by the U.S. Department of Energy.