Producing glass objects using a 3D printer is far from easy. To date, only a handful of research groups around the globe have attempted to produce a variety of glass parts using inventive additive manufacturing methods. These may, for example, include 3D printing of molten glass, but the disadvantage is the extremely high temperatures and heat-resistant equipment. Alternatively, powdered ceramic particles were used that can be printed at room temperature and then sintered to create glass. Without exceptions, all of the objects produced in this way were not very complex in appearance. Now, another interesting approach has come to the scene, from a team researchers at ETH Zurich. Here’s a brief introduction of their approaches and findings to date.

Complex Glass Printing Methodology by ETH Zurich 

Recently, researchers from ETH Zurich, Switzerland, came up with a new inventive methodology to produce complex glass objects with 3D printing. The approach has basically evolved from the process of stereolithography, one of the first invented 3D printing technologies developed back in the 1980’s.

The research team, composed of David Moore, Kunal Masania, and Lorenzo Barbera of  ETH Zurich’s ‘Complex Materials Group’ – which is led by professor Studart, has developed a special resin that contains plastic and organic molecules to which glass precursors are bonded. 

Complex glass objects created by a 3D printer. Image courtesy of ETH Zurich / Group for Complex Materials.

3D Printing Oxide Glasses: A Paradigm Shift

The digital fabrication of oxide glass by 3D printing represents a major paradigm shift in the way glass objects designed and manufactured, opening opportunities to explore functionalities inaccessible by current technologies. The few examples of 3D printed glass objects so far are limited in their chemical compositions and suffer from the low resolution achievable with particle-based or molten glass technologies.

“As most functional properties of glass emerge from their transparency and multicomponent nature, this 3D printing platform may be useful for distinct technologies, sciences and arts”.

ETH Zurich Researchers presented a new breakthrough including a Digital Light Processing printing platform exploiting the photopolymerization-induced phase separation of hybrid resins to create glass parts with complex shapes. High, spatial resolutions can be achieved, as well as multi-oxide chemical compositions. Interestingly, the resin can be processed using commercially available Digital Light Processing technology. This involves irradiating the resin with UV light patterns. Wherever the light strikes the resin, it hardens because of the light-sensitive components of the polymer resin crosslink at the exposed points. The plastic monomers combine to form a labyrinth-like structure, creating the polymer. The ceramic-bearing molecules fill the interstices of this labyrinth.

Analogously to conventional porous glass fabrication methods the ‘phase separation phenomena’ was exploited to fabricate complex glass parts displaying light-controlled multiscale porosity and dense multicomponent transparent glasses with arbitrary geometry. Images courtesy of ETH Zurich / Group for Complex Materials.

How it Works: Build Process Modification by Light

An object can thus be built up layer by layer. The researchers changed various parameters in each layer, including the pore size: weak light intensity results in large pores; intense illumination produces small pores.

The researchers were also able to modify the microstructure, layer by layer, by mixing silica with borate or phosphate and adding it to the resin. Complex objects can be made from different types of glass, or even combined in the same object using the technique.

Then, the researchers set the produced blank on fire at two different temperatures: at 600 degrees Celcius to burn off the polymer framework and then at around 1,000 degrees Celsius to densify the ceramic structure into glass. During the firing process, the objects shrink significantly but become transparent and hard like window glass.

The blank (left image) is ‘fired’ at 600 degrees to eliminate the plastic framework. In a second firing step, the object becomes glass (right image). (Image courtesy of ETH Zurich / Group for Complex Materials )

The Process – Possibilities & Limitations

For these initial trials, the 3D printed glass objects were basically not bigger than a coin. Larger glass objects, such as bottles, drinking glasses or windowpanes, cannot be produced in this way. The aim of the research groups was rather to prove the feasibility of producing glass objects of complex geometry using a 3D printing process. The technology, however, is much more than a gimmick. A patent application was filed and negotiations about the use of the technology have started. The results of the group were reported in the latest issue of Nature’s ‘Materials Journal‘.

SOURCE:

‘Glass from a 3D Printer‘ by Peter Ruegg, ETH Zürich 
https://ethz.ch/en/news-and-events/eth-news/news/2019/11/glass-from-a-3d-printer.html

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