Three-dimensional printing of transparent fused silica glass

Using stereolithography 3D printers, a silica nanocomposite is shaped and then fused to produce non-porous, very smooth, highly transparent fused silica glass components. Fused silica glass has long been known for its excellent optical properties, yet processing and patterning this material still requires high-temperature processes and/or hazardous chemical materials. To simplify such processes, Bastian Rapp and colleagues have been developing a system—termed 'liquid glass'—in which a viscous amorphous silica nanocomposite can be patterned into complex shapes by moulding and then photocured to produce optical-quality glass structures. In their latest development, the group have tuned the properties of their nanocomposite to facilitate its use in a 3D printer, yielding high-optical-quality glass structures with features as small as a few tens of micrometres. Glass is one of the most important high-performance materials used for scientific research, in industry and in society, mainly owing to its unmatched optical transparency, outstanding mechanical, chemical and thermal resistance as well as its thermal and electrical insulating properties1,2,3. However, glasses and especially high-purity glasses such as fused silica glass are notoriously difficult to shape, requiring high-temperature melting and casting processes for macroscopic objects or hazardous chemicals for microscopic features3,4. These drawbacks have made glasses inaccessible to modern manufacturing technologies such as three-dimensional printing (3D printing). Using a casting nanocomposite5, here we create transparent fused silica glass components using stereolithography 3D printers at resolutions of a few tens of micrometres. The process uses a photocurable silica nanocomposite that is 3D printed and converted to high-quality fused silica glass via heat treatment. The printed fused silica glass is non-porous, with the optical transparency of commercial fused silica glass, and has a smooth surface with a roughness of a few nanometres. By doping with metal salts, coloured glasses can be created. This work widens the choice of materials for 3D printing, enabling the creation of arbitrary macro- and microstructures in fused silica glass for many applications in both industry and academia.