It is not easy to produce glass objects using 3D printing. Only a few research groups worldwide have attempted to produce glass using additive processes. Some of them created objects by printing molten glass. The disadvantage of this approach is that it requires very high temperatures and heat-resistant equipment. Other researchers used powdery ceramic particles that can be printed at room temperature and later sintered into glass. However, the complexity of the objects made from them has so far been rather low.
Researchers at ETH Zurich have now chosen a different way of producing complex glass objects using 3D printing. Their new process is based on stereolithography, one of the first 3D printing techniques from the 1980s. Researchers David Moore, Lorenzo Barbera and Kunal Masania from the Complex Materials Group of ETH Professor André Studart developed a resin composed of liquid plastic and a siloxane.
The resin can be processed with a commercially available stereolithography device. UV light patterns are radiated onto the resin. Where the light hits, the resin becomes hard. This happens because the two resin components separate completely at the exposed points: the plastic monomers form a labyrinth-like polymer framework, the molecules of the siloxane fill the gaps in the labyrinth.
In this way, an object can be built up layer by layer. The researchers can change various parameters for each layer, such as the pore size: weak light intensity produces large pores, strong irradiation small pores. The researchers can also change the microstructure of the object in layers by adding borate or phosphate to the resin. This makes it possible to produce objects made up of different types of glass.
The researchers then have to burn a blank made in this way at two different temperatures: At 600 degrees Celsius to burn away the polymer framework and then at around 1000 degrees Celsius to compact the objects into glass. During firing, they shrink considerably, but become transparent and hard like window glass.