Of all the materials that can be 3D printed, glass remains one of the most challenging. However, scientists at the ETH Zurich research centre in Switzerland are working to change this with a new and better technology for printing glass.
Printing glass objects is now possible and the most common methods involve either extruding molten glass, or selectively sintering (laser heating) ceramic powder to convert it into glass. The former requires high temperatures and therefore heat-resistant equipment, while the latter does not allow for the production of particularly complex objects.ETH’s new technology aims to improve on both of these disadvantages.
It consists of a photosensitive resin which is made up of liquid plastic as well as organic molecules bonded to silicon-containing molecules – in other words, they are ceramic molecules. Using an existing process known as digital light processing, the resin is exposed to a pattern of ultraviolet light. Wherever the light hits the resin, the plastic monomers are cross-linked to form a solid polymer. The polymer has a labyrinth-like internal structure, with the spaces within the labyrinth being filled with ceramic molecules.
The resulting three-dimensional object is then fired at 600oC, burning off the polymer and leaving only the ceramic. In a second firing, at a firing temperature of approximately 1000oC, the ceramic densifies into a transparent porous glass. The object does shrink significantly when transformed into glass, a factor that must be taken into account during the design process.
Despite the small size of the objects created so far, they are quite complex in shape, the researchers say. In addition, the pore size can be adjusted by varying the UV intensity, or the other properties of the glass can be altered by mixing borates or phosphates into the resin.
A major Swiss distributor of glassware has already expressed interest in using the technology, which is somewhat similar to that being developed at the Technical College in Karlsruhe, Germany.