Innovative 3D printing technology creates glass microstructures with rays of light

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Researchers at UC Berkeley have developed a new way to 3D print microstructures of glass, including these 3D printed glass lattices, which are displayed in front of a US dime for scale. Credit: Photo by Joseph Toombs/UC Berkeley

The manufacturing technique allows for faster production, better optical quality and design flexibility.

Researchers at[{” attribute=””>University of California, Berkeley have developed a new way to 3D-print glass microstructures that is faster and produces objects with higher optical quality, design flexibility, and strength, according to a new study published in the journal Science.

3D-Printed Trifurcated Microtubule Model

A 3D-printed, trifurcated microtubule model. Credit: Video by Adam Lau/Berkeley Engineering

Working with scientists from the Albert Ludwig University of Freiburg in Germany, the researchers extended the capabilities of a 3D-printing process they developed three years ago — computed axial lithography (CAL) — to print much finer features and to print in glass. They dubbed this new system “micro-CAL.”

Glass is often the preferred material for creating complicated microscopic objects, including lenses in compact, high-quality cameras used in smartphones and endoscopes, as well as microfluidic devices used to analyze or process minute amounts of liquid. However, present manufacturing methods can be slow, expensive, and limited in their ability to meet the industry’s increasing demands.

The CAL process is fundamentally different from today’s industrial 3D-printing manufacturing processes, which build up objects from thin layers of material. This technique can be time-intensive and result in rough surface texture. CAL, however, 3D-prints the entire object simultaneously. Researchers use a laser to project patterns of light into a rotating volume of light-sensitive material, building up a 3D light dose that then solidifies in the desired shape. The layer-less nature of the CAL process enables smooth surfaces and complex geometries.

This study pushes the boundaries of CAL to demonstrate its ability to print microscale features in glass structures. “When we first published this method in 2019, CAL could print objects into polymers with features down to about a third of a millimeter in size,” said Hayden Taylor, principal investigator and professor of mechanical engineering at UC Berkeley.

“Now, with micro-CAL, we can print objects in polymers with features down to about 20 millionths of a meter, or about a quarter of a human hair’s breadth. And for the first time, we have shown how this method can print not only into polymers but also into glass, with features down to about 50 millionths of a meter.”

3D Printed Tetrakaidecahedron Lattice

Researchers at UC Berkeley have developed a new way to 3D print intricate glass microstructures, including this tetrakaidecahedron lattice structure. Credit: Photo by Adam Lau/UC Berkeley

To print the glass, Taylor and his research team collaborated with scientists from the Albert Ludwig University of Freiburg, who have developed a special resin material containing nanoparticles of glass surrounded by a light-sensitive binder liquid. Digital light projections from the printer solidify the binder, then the researchers heat the printed object to remove the binder and fuse the particles together into a solid object of pure glass.

“The key enabler here is that the binder has a refractive index that is virtually identical to that of the glass, so that light passes through the material with virtually no scattering,” said Taylor. “The CAL printing process and this Glassomer [GmbH]-the materials developed are perfectly matched to each other.

Cubic Glass Lattice

Scanning electron micrograph of a cubic lattice with 20 micron lattice elements. Credit: Photo by Joseph Toombs/UC Berkeley

The research team, which included lead author Joseph Toombs, who holds a Ph.D. student in Taylor’s lab, also performed tests and found that CAL-printed glass objects had more consistent strength than those made using a conventional layer-based printing process. “Glass objects tend to break more easily when they contain more flaws or cracks, or have a rough surface,” Taylor said. “CAL’s ability to create objects with smoother surfaces than other layer-based 3D printing processes is therefore a big potential advantage.”

3D printing of glass microstructures

UC Berkeley graduate student Joseph Toombs uses tweezers to grasp a glass lattice structure created using an innovative new 3D printing technique. Credit: Photo by Adam Lau/UC Berkeley

The CAL 3D printing method offers manufacturers of microscopic glass objects a new and more efficient way to meet customers’ demanding requirements for geometry, size, and optical and mechanical properties. Specifically, this includes manufacturers of microscopic optical components, which are a key component of point-and-shoot cameras, virtual reality headsets, advanced microscopes and other scientific instruments. “Being able to fabricate these components faster and with greater geometric freedom could potentially lead to new device functions or lower-cost products,” Taylor said.

Reference: “Additive volumetric fabrication of silica glass with microscale computed axial lithography” by Joseph T. Toombs, Manuel Luitz, Caitlyn C. Cook, Sophie Jenne, Chi Chung Li, Bastian E. Rapp, Frederik Kotz-Helmer and Hayden K. Taylor, April 14, 2022, Science.
DOI: 10.1126/science.abm6459

This study was funded by the National Science Foundation, the European Research Council, the Carl Zeiss Foundation, the German Research Foundation and the US Department of Energy.

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