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3D printed objects smaller than a human hair, and invisible to the naked eye are commonly produced using a process called two-photon lithography. This method has been used to develop innovative medical treatments, security features, and even castles on the tip of a pencil.
In a new technique developed by the Greer Group at California Institute of Technology (Caltech) researchers have used two-photon lithography to 3D print metal structures. By producing dimensions no larger than 100 nanometeres, the Greer Group’s technique is capable of making metal features “an order of magnitude smaller” than any other metal 3D printing method.
Greer - Group - Researcher - Author - Caltech
Greer Group researcher and lead author of the Caltech research paper Andrey Vyatskikh holds a slide that holds microscopic 3D printed nickel structures.
The metallic reaction
Reaction - Laser - Pulses - Material - Two-photon
Relying on a reaction between laser pulses and light-reactive material, two-photon lithography is necessarily polymer-based. Professor Julia Greer, supervisory author on the Caltech study, explains, “Metals don’t respond to light in the same way as the polymer resins that we use to manufacture structures at the nanoscale,”
“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.”
Polymer - Ink - Process - Particles - Demonstration
And so, the polymer ink used in the process is instead laced with fine metallic particles. As a demonstration, the Greer Group uses nickel, which is bonded to the polymer using ligands.
The Greer Group’s ink is 3D printed using a Photonic Professional GT from Nanoscribe GmbH, a system common to two-photon lithography experiments. Layer-by-layer, the team 3D prints complex lattice samples.
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