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Gold ‘glitter’ reveals defects in 3D printing

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Researchers have developed a technique in which gold “shines” inside 3D printed parts to highlight any problems.

“This is one of the first applications using gold for defect detection. We are able to inspect and detect defects that aren’t visible to the naked eye, using the optical properties of embedded gold nanoparticles,” says Cole Brubaker, civil engineering graduate student at Vanderbilt University, and lead author of the study. “That’s a very critical step—being able to say ‘We have a defect. It’s right here.'”

The research team used super-tiny particles of gold, which actually show up as a deep maroon color. The nanoparticles are approximately 100,000 times thinner than a human hair, but they could solve a major problem in manufacturing.

“3D printed materials are becoming increasingly common in our day-to-day life, from consumer goods and products to even demonstrations of 3D-printed automobiles and homes,” says coauthor Kane Jennings, chair and professor of chemical and biomolecular engineering. “But there can be problems in the processing of 3D-printed materials. Small defects or missing print layers can occur. These defects can compromise and weaken the structural integrity of the 3D-printed products, causing failure.”

Researchers decided to try embedding gold inside the printing material to see whether it could help flag those defects.

“It’s similar to the gold in your ring, but it has very unique optical properties that don’t degrade over time,” Brubaker says.

The innovative process involves mixing the gold nanoparticles with a dissolved plastic polymer, dispersing it throughout the medium. When it dries and hardens, the plastic is extruded or pressed into gold nanoparticle-filled polymer filaments, or thin tubing, which can then be used in standard 3D printers.

After a part is printed, it goes into a special UV-Vis spectrophotometer to inspect for defects.

“We’re using the absorbance properties of the embedded gold nanoparticles,” Brubaker says. “You just scan light across the surface of the sample and see where the absorbance decreases inside, signaling a defect in that material. A defect can be found with one single nondestructive measurement. It’s very quick. It takes just a matter of seconds. We don’t have to rely on large sensing systems that have sensors placed all over the part.”

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“There are tremendous possibilities for what we can do with this technology,” Jennings says. “We have demonstrated the 3D printed parts can be self-reporting. They self-report defects. We’re looking now at the possibility to do even more with these smart materials.”

“What really gets me excited is the broad range of applications we can use this technology for,” says Brubaker. “We’ve just scratched the surface.”

The research appears in the ACS Applied Nano Materials.

Additional researchers from Vanderbilt and Fisk University in Nashville also contributed to the work. The US Office of Naval Research funded the research. Patents are pending on the technology.

Source: Vanderbilt University

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