For the first time, researchers have 3D printed a unique material that demonstrates optical transparency in the mid-infrared range: chalcogenide glass.

The additive-manufacturing achievement supports the creation of new kinds of components and optical fibers for low-cost sensors, telecommunications equipment, and biomedical devices.

With the help of a slightly modified conventional 3D-printer, a team from the Centre d'Optique, Photonique et Laser (COPL) at Université Laval in Canada created the soft chalcogenide glasses.

The work is part of an international project entitled PROTEus: PRinting of exotic multi-maTErial fibers granted by the Canadian NSERC funding agency.

PROTEus aims to combine multiple materials – by using additive manufacturing and direct laser writing approaches – to engineer fiber-based photonic components and devices.

Chalcogenide glass softens at a relatively low temperature compared to other glass. The researchers, led by Patrick Larochelle, therefore increased the maximum extruding temperature of a commercial 3D printer from approximately 260 °C to 330 °C .

The team produced chalcogenide glass filaments with dimensions similar to the commercial plastic filaments normally used with the 3D printer. Finally, the printer was programed to create two samples with complex shapes and dimensions (see the above image).

"3D printing of optical materials will pave the way for a new era of designing and combining materials to produce the photonic components and fibers of the future," said researcher Yannick Ledemi. "This new method could potentially result in a breakthrough for efficient manufacturing of infrared optical components at a low cost."

Ledemi spoke with Tech Briefs about the importance of easy-to-print chalcogenide glass, and what a “new era” of photonic components and fibers might look like.

Tech Briefs: What is chalcogenide glass, and how does it compare to conventional glass?

Dr. Yannick Ledemi: Chalcogenide glass is a unique class of vitreous materials showing optical transparency in the mid-infrared range, like no other type of glasses. For instance, chalcogenide glasses are commercially available as infrared lenses for thermal imaging.

A second specific feature of chalcogenide glasses is their low glass transition and softening temperatures, close to those of polymers. By taking advantage of this property, we adapted a commercial 3D-printer based on the fused deposition modeling approach to enable the 3D printing of chalcogenide glass.

Among all known glasses (silicate, phosphate, heavy metal oxide, fluoride, etc.), chalcogenide glass shows the most extended optical transmission toward longer wavelengths in the infrared. It is an oxide-free glass based on sulfur, selenium, and/or tellurium chalcogen elements. It is a soft glass possessing low characteristic temperatures, making its thermal processing easier at relatively low temperature (for example, fiber drawing at 350-400 °C, extrusion at 350 °C).

Tech Briefs: How does the 3D-printing approach work?

Dr. Ledemi: The fused deposition modeling 3D-printing approach consists in extruding filaments of materials through a die upon heating at a certain temperature, characteristic to the chemical composition of the considered material. As the characteristic temperatures of chalcogenide glasses are only a few tens of degrees higher than those of polymers used in 3D-printing, we modified a commercial 3D-printer to enable material extrusion at higher temperature, to enable the 3D-printing of chalcogenide glass.

Tech Briefs: Why is the printing of this type of material so important?

Dr. Ledemi: This first demonstration of feasibility of printing chalcogenide glass paves the way for the manufacturing of novel glass components whose design and complex geometries were not achievable before with the conventional fabrication techniques.

Tech Briefs: Why has the 3D printing of glass been so challenging?

Dr. Ledemi: We had to modify a commercial printer, including its operation software. We also had to add an additional heating component to allow extrusion of a material at higher temperature than the maximum temperature originally allowed by the printer. Additional parts were also designed and installed to help the glass filament feeding process through the extruder.

Lastly, thanks to our strong hands-on experience in chalcogenide glass fiber development and to our manufacturing and fabrication facilities available at COPL, we were able to produce the chalcogenide glass filaments of required dimensions.

Intense efforts were required to find a printer design capable of attaining and supporting over time the required temperature for glass extrusion, which is about 80 °C higher than its initial maximum working temperature. As soon as this issue was overcome, the 3D-printing process worked extraordinarily well, allowing the production of first specimens.

Tech Briefs: What is possible now that you can 3D print glass? What are the most exciting applications to you?

Dr. Ledemi: The most important innovation of this work is the demonstrated feasibility of chalcogenide glass 3D-printing by using the filament feed approach with a conventional, commercially available 3D-printer. This paves the way to the production of many kinds of optical components, including optical preforms for fiber drawing, not only based on chalcogenide glasses, but also on multi-material assemblies (for example, chalcogenide glass, optical polymers, electro-conductive polymers, etc.).

Complex designs of optical components and optical fiber preforms can now be envisaged, pushing the limits very far. Chalcogenide glass essentially has applications related to its infrared transparency. Besides defense and security where infrared imaging is playing an important role, many environmental sensors required for pollutant monitoring, waste management, CO2 storage, and the mining industry are relying on the infrared chemical signature of molecules. Health and medicine is also a strategic area where infrared components are used to monitor specific information and support diagnosis. 3D-printed chalcogenide-based components could potentially result in a breakthrough for their efficient manufacturing at a low cost.

Tech Briefs: What’s next?

Dr. Ledemi: The next steps of this work are to, firstly, to improve the design of the printer to increase its performance and enable the additive manufacturing of complex parts or components made of chalcogenide glasses, including optical preform for fiber drawing.

Secondly, we want to upgrade the printer by adding new extruders to enable co-printing with polymers having optical and/or electrical functionalities, in order to produce multi-material components or preforms for photonic applications.

What do you think is possible with 3D-printed glass? Share your comments and questions below.