Research Team Achieves On-Demand 3D Nanoprinting of Pure Metal Structures with Direct-Writing Method

Have you ever wanted your own tiny 3D printed magic wand? While we unfortunately can’t offer you the real thing, we can tell you about a 3D shape made out of a combination of gold and carbon that looks like one – thanks to a research collaboration between the Graz Centre for Electron Microscopy, the Institute of Physics at Karl-Franzens University, the Center for Nanophase Materials Sciences at Oak Ridge National Laboratory (ORNL), the Department of Materials Science and Engineering at the University of Tennessee, and the Graz University of Technology.

The scientists can now achieve on-demand 3D printing of pure metal structures on the nanoscale, thanks to a new direct-writing technique. The research team created a less costly and time-consuming way to 3D print on any shape or material without using masking steps. These tiny structures built on the nanoscale – remember, a human hair is about 80,000 nanometers wide – could help advance sensors and computers, information storage technologies, and light sources. They could also improve transmission of plasmons – small waves of electron density that occur once light hits an electron conductor, like a metal.

Focused electron beams are used to convert surface-bound molecules of gold and carbon into the gas phase and deposit them to construct precise 3D freestanding structures of pure gold. The ultra-sharp features produce free electron oscillations, or quasiparticles called plasmons, with high efficiency.

The team converts surface-bound molecules that contain carbon and metal in a patterned sequence into the gas phase, and then use a focused electron beam to precisely deposit them into the resulting 3D shape of gold and carbon; if you’re a Tolkien fan, you might see above that this 3D shape looks a bit like the staff of Gandalf the White.

The process is not dissimilar to TU Wien’s direct-write method of using an electron beam to 3D print pure gold. But these collaborative researchers purified the 3D structures inside the growth reactor with water vapor to remove the carbon; the resulting freestanding pure-gold structures were then tested for plasmonic behavior.

The team published a paper on the work, titled “Direct-Write 3D Nanoprinting of Plasmonic Structures,” in ACS Applied Materials & Interfaces; co-authors include Robert Winkler, Franz-Philipp Schmidt, Ulrich Haselmann, Jason D. Fowlkes, Brett B. Lewis, Gerald Kothleitner, Philip D. Rack, and Harald Plank.

The abstract reads, “During the past decade, significant progress has been made in the field of resonant optics ranging from fundamental aspects to concrete applications. While several techniques have been introduced for the fabrication of highly defined metallic nanostructures, the synthesis of complex, free-standing three-dimensional (3D) structures is still an intriguing, but so far intractable, challenge. In this study, we demonstrate a 3D direct-write synthesis approach that addresses this challenge. Specifically, we succeeded in the direct-write fabrication of 3D nanoarchitectures via electron-stimulated reactions, which are applicable on virtually any material and surface morphology. By that, complex 3D nanostructures composed of highly compact, pure gold can be fabricated, which reveal strong plasmonic activity and pave the way for a new generation of 3D nanoplasmonic architectures that can be printed on-demand.”

Jason Fowlkes

Fowlkes, the team leader for the ORNL Center for Nanophase Materials Sciences, also worked with Winkler, Lewis, Plank, and Rack last year to improve the focused electron beam induced deposition (FEBID) nanoscale 3D printing technique with a simulation-guided process.

This new direct-write 3D nanoprinting method can produce on-demand, customized nanostructures from the ground up, and is a precursor to maskless fabrication of architectures in one, two, and three dimensions on any surface shape and material – even materials that have plasmonic behaviors. Plasmonic oscillations actually encode more data than conventional technologies are able to, which will help improve sensor devices, novel light sources, and extremely dense information storage technologies.

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