Glass is the preferred material for creating complex microscopic objects, including lenses in compact, high-quality cameras used in smartphones and endoscopes, as well as microfluidic devices that analyze or process minute amounts of liquid. Berkeley engineers have developed a system called micro-CAL, a new way to 3D print glass microstructures that is faster and produces objects with higher optical quality, design flexibility and strength than current manufacturing methods.
Micro-CAL expands the capabilities of a 3D-printing process the researchers developed three years ago — computed axial lithography (CAL) — to print much finer features and to print in glass. “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,” said Hayden Taylor, associate professor of mechanical engineering. “This method can print not only into polymers but also into glass, with features down to about 50 millionths of a meter.”
Unlike today’s industrial 3D-printing, micro-CAL prints the entire object simultaneously. It does so by using 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 material — developed by scientists from the Albert Ludwig University of Freiburg, Germany — contains nanoparticles of glass surrounded by a light-sensitive binder liquid. Digital light projections from the CAL printer solidify the binder; the researchers then heat the printed object to remove the binder and fuse the particles together into a solid object of pure glass.
The researchers, including Ph.D. student Joseph Toombs, found that micro-CAL’s glass objects had more consistent strength than those made using a conventional printing process. “Glass objects tend to break more easily when they contain more flaws or cracks, or have a rough surface,” said Taylor. “CAL’s ability to make objects with smoother surfaces than other, layer-based 3D-printing processes is therefore a big potential advantage.”