3D printing adds glass to its repertoire

One of mankind’s oldest materials can now be 3D printed.

3D printing technology is changing the way we manufacture nearly everything, but glass has been beyond its reaches—until now. Bastian Rapp and colleagues have developed technology that allows them to 3D print high-quality, intricate glass shapes, like tiny pretzels or castles, and produce complex lenses and filters of high optical quality. They achieved this by developing a free-flowing silica nanocomposite called “liquid glass.”

We spoke to Rapp to find out more about his work, which appears in a new Nature study.

ResearchGate: What motivated this study?

Bastian Rapp: We wanted to close an important gap in the material palette for modern 3D printing techniques. 3D printing is the manufacturing revolution of the 21st century, and glass has until now been a material that was not accessible for 3D printing. Because of our work, this is now possible.

A three-dimensional structure of a castle gate printed in fused silica glass. Credit: NeptunLab/KIT.

RG: What applications could this have?

Rapp: Glass has many applications in industry and academia, but also of course in everyday life. From printing your own drinking glasses to precision optics and applications in data transmission (smart glass fibers), this material has many potential applications. Even applications in construction and architecture could be possible using the capability of 3D printing to generate freely curved glass panels, for things like facades. The Elbphilharmonie in Hamburg is a good example of a building that could have used this technology for the complicated glass facade.

RG: How did you achieve this?

Rapp: “Liquid Glass” is a liquid glass nanocomposite which consists of glass nanoparticles suspended in a photocurable prepolymer. We obtained a formulation that behaves similarly to resins commonly used in 3D printers. Because of this, it can be used by commercially available stereo lithography instruments. After a thermal treatment, the resulting components become pure fused silica glass.

A three-dimensional pretzel generated by three-dimensional printing in fused silica glass. Credit: NeptunLab/KIT

RG: Were there any hurdles in this process?

Rapp: Some of the biggest challenges to overcome when designing the "Liquid Glass" was making sure it had a sufficiently low viscosity. This is a prerequisite for the material’s suitability in state-of-the-art stereo lithography instruments. We also required a sufficiently high loading of glass nanoparticles which ensures better optical properties of the final glass. Finally, there needed to be a perfect match in the optical index of refraction of both the nanoparticles and the liquid prepolymer—this is a prerequisite for high resolution 3D printing.

RG: Is this something that anyone with a 3D printer could use? When do you think it could be available to the public?

Rapp: If a state-of-the-art stereo lithography instrument and a suitable high-temperature oven, (such as the ones used in ceramic processing in art schools) is available, this is a process that anyone can do. We are currently working to commercialize this technology.

We believe it will be an important enabler for making glass, one of the oldest materials mankind has used, accessible for the manufacturing revolution of the 21st century.

Feature image is a honeycomb structure printed in fused silica glass. Credit: NeptunLab/KIT.