Scientists Develop Innovative 3D Printing Technique To Create Glass Microstructures With Light

According to a new study published in the journal Science, researchers at the University of California, Berkeley have developed a new method for 3D printing glass microstructures. This method is faster and produces objects with higher optical quality, design flexibility and strength.

The researchers, in collaboration with scientists at the University of Freiburg in Germany, have extended the capabilities of a 3D printing process they developed three years ago, Computational Axial Lithography (CAL), to print finer features and print in glass. They called the new system "micro-CAL."

Glass is often the material of choice for making complex microscopic objects, including the lenses of small, high-quality cameras used in smartphones and endoscopes, and microfluidic devices used to analyze or process tiny amounts of liquids. However, current manufacturing methods can be slow, expensive, and limited in their ability to meet the growing demands of the industry.

The CAL process is fundamentally different from today's industrial 3D printing manufacturing process, which builds up objects from thin layers of material. This technique can be time-consuming and can result in rough surface textures. However, CAL 3D prints the entire object at the same time. The researchers used a laser to project a pattern of light into a rotating photosensitive material, building up a three-dimensional light dose, which then solidified into the desired shape. The layer-free nature of the CAL process enables smooth surfaces and complex geometries.

This research pushes the boundaries of CAL, demonstrating 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 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 as small as about 20 millionths of a meter, or about a quarter the width of a human hair. And, for the first time, we have demonstrated this approach Not only can you print in polymers, but you can also print in glass, with features down to about 50 millionths of a meter."

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

"The key factor here is that the refractive index of the binder is almost the same as the refractive index of the glass, so there is little scattering of light as it passes through the material," Taylor said. The CAL printing process and this Glassomer (GmbH) developed material are each other's perfect combination."

The research team also conducted tests and found that CAL-printed glass objects had more stable strength than objects made using traditional layer-based printing processes. "When glass objects contain more defects or cracks, or have a rough surface, they tend to shatter more easily," Taylor said. Therefore, compared to other layer-based 3D printing processes, CAL makes objects with smoother surfaces. Capability is a big potential advantage.”

CAL's 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 that are a key part of compact cameras, virtual reality headsets, advanced microscopes and other scientific instruments. "Being able to manufacture these parts with greater speed and geometric freedom has the potential to lead to new device capabilities or lower costs," Taylor said.