Innovative 3D printing technology creates glass microstructures with light rays

Production technology allows faster production, more optical quality and design flexibility.

Researchers in[{” 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.

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.”

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 developed material is perfect for each other.

Scanning electron micrograph of a cubic lattice with 20 micrometer lattice members. Credit: Photo by Joseph Toombs / University of California, Berkeley

A research group that included lead author Joseph Toombs, Ph.D. a student at Taylor’s lab, also conducted tests and found that glass objects printed by CAL have more stable strength than those produced using a conventional layered printing process. “Glass items tend to break more easily if they contain more imperfections 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 a major potential advantage.”

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

The CAL 3D printing method offers manufacturers of microscopic glassware a new and more efficient way to meet customers ’high demands on geometry, size and optical and mechanical properties. Specifically, this includes manufacturers of microscopic optical components that are a key part of compact cameras, virtual reality headsets, advanced microscopes and other scientific instruments. “The ability to make these components faster and with more geometric freedom could potentially lead to new device features or lower cost products,” Taylor said.

Reference: “Volumetric Additive Production of Quartz Glass with Microscale Computer Axial Lithography” by Joseph T. Toombs, Manuel Luitz, Caitlin S. Cook, Sophie Jen, Chi Chung Lee, Bastian E. Rapp, Frederick Kotz K. Heln and Helra K. April 14, 2022 Science.
DOI: 10.1126 / science.abm6459

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