Caltech engineers have developed a new 3D printing technique that helps create complex nanoscale metal structures.
The process, once scaled up, could be used in a wide variety of applications, from creating 3D logic circuits on computer chips to engineering ultralightweight aircraft components.
According to Caltech materials scientist Julia Greer, it could also usher in a new class of materials with unusual properties that are based on their internal structure.
The professor and her team have thus built 3D lattices whose beams are just nanometers across – far too small to be seen with the naked eye.
According to the researchers, these materials exhibit unusual, often surprising properties; Greer’s team has created exceptionally lightweight ceramics that spring back to their original shape, spongelike, after being compressed.
Greer’s group 3D prints structures out of a variety of materials, from ceramics to organic compounds. Metals, however, have been difficult to print, especially when trying to create structures with dimensions smaller than around 50 microns, or about half the width of a human hair.
“Metals don’t respond to light in the same way as the polymer resins that we use to manufacture structures at the nanoscale,” says Greer. “There’s a chemical reaction that gets triggered when light interacts with a polymer that enables it to harden and then form into a particular shape. In a metal, this process is fundamentally impossible.”
Greer’s graduate student Andrey Vyatskikh has however come up with a solution. He used organic ligands – molecules that bond to metal – to create a resin containing mostly polymer, but which carries along with it metal that can be printed, like a scaffold.
Vyatskikh bonded together nickel and organic molecules to create a liquid that looks a lot like cough syrup. The team designed a structure using computer software, and then built it by zapping the liquid with a two-photon laser.
The laser creates stronger chemical bonds between the organic molecules, hardening them into building blocks for the structure.
Since those molecules are also bonded to the nickel atoms, the nickel becomes incorporated into the structure. In this way, the team was able to print a 3D structure that was initially a blend of metal ions and nonmetal, organic molecules.
Moreover since the process vaporized a significant amount of the structure’s material, its dimensions shrank by 80 percent, but it maintained its shape and proportions.
Image and content: California Institute of Technology