An image showing boro-phospho-silicate (BPS) glasses obtained by 3D printing of phase-separating resins

Source: © David G Moore et al/Springer Nature Limited 2019

Complex resin structures containing inorganic precursors can be printed out and then treated to produce sophisticated glass designs

A simple 3D printing platform can produce complex-shaped glass structures with high resolution and multi-oxide chemical compositions.1 The new approach, which relies on the phase separation of liquid resins, could be useful in several areas including 3D printing of reactionware for organic synthesis.

Automated glass-manufacturing processes have been traditionally restricted to symmetric and predominantly flat geometries. While recent advances in 3D printing technologies have opened new possibilities, enabling the creation of single-phase, multicomponent glass objects using methods such as direct writing2 or stereolithography,3 these techniques still have some drawbacks. Direct ink writing suffers from geometrical limitations and the glasses prepared so far using stereolithography have been based only on quartz, which limits the available chemistries. So, developing new methods that enable a broad compositional design and improve the resolution of the printed items is crucial.

A team led by André Studart at the Swiss Federal Institute of Technology in Zurich has now used a digital light processing printer to create complex multicomponent glass structures. The scientists prepared a liquid resin containing inorganic precursors, a photoactive monomer mixture and a light-absorbing dye. ‘UV light exposure triggers the solidification of the liquid material, as well as the formation of a bicontinuous interdigitating network between a polymer-rich phase and the pre-ceramic-rich counterpart,’ explains co-author Kunal Masania. He points out that the formulation of the ink is the key aspect of the process. ‘By controlling the monomer-to-pre-ceramic ratio and the compatibility between the pre-ceramic species and the polymer, we can produce an ink that is homogenous in the liquid state and undergoes phase-separation when exposed to UV light.’ After a final heat treatment, organics are burnt out and the porous ceramic structure is transformed into a transparent glass with complex geometry and spatially tuneable composition.

An image showing transparent and dense BPS glasses obtained by sintering 3D printed porous objects

Source: © David G Moore et al/Springer Nature Limited 2019

The Swiss team demonstrated a number of different glass structures and say it could be used to produce artwork or scientific glassware

The researchers tested their approach by printing cylindrical and gyroid structures with controlled pore-size gradients, as well as a glass leaf with locally tuneable optical properties. The print resolution was improved by adjusting the monomer composition in the resin.

‘The authors demonstrate that by simply varying the light source power density, they can tune the glass microstructure, and by changing the chemistry of the resin, they can vary the glass composition,’ says Joel Destino a materials scientist at Creighton University, US. ‘Furthermore, they claim their method offers improved print resolution, or the ability to print features that are finer than previously reported methods.’ Destino adds that such advances are critical for making glass 3D printing a viable commercial process.

Masania says that the new results ‘set the ground for geometrical and chemical mass-customisability in glass manufacturing’ and Destino adds that they have the potential to revolutionise many fields. ‘Glass materials are essential in many products, ranging from the smartphone in your pocket to the research-grade telescopes,’ he says.

Lee Cronin of the University of Glasgow, UK, who recently developed a 3D-printed modular reactor for chemical synthesis, sees possible applications in this field too. ‘This article is really interesting since it seems to show a way to 3D print complex oxide glass structures,’ he says. ‘This could be very helpful in the 3D printing of reactionware for organic synthesis where the blueprint of the reaction defines the glassware. We are doing this in plastic, but the chemical and heat resistance here is very exciting for fabrication of chemical generators using 3D-printed chemical synthesis kits.’