Additive manufacturing, also known as 3D printing, is used to create everything from toys to jet engine parts to dental implants. Materials such as plastic, aluminum, concrete, and even chocolate have been successfully used in printers. Glass remains one of the most challenging materials to 3D print due to its high viscosity, extreme temperature requirements (exceeding 1,000 degrees Fahrenheit), susceptibility to fractures, and tendency to form unwanted bubbles.
Ed Kinzel, associate professor of aerospace and mechanical engineering at the University of Notre Dame, and his lab have pioneered a 3D-printing approach to glass fabrication that promises to advance optics, photonics, and microelectronics. Not only is his team able to make sophisticated scientific instruments, they can use these same techniques to create sparkling Christmas tree ornaments as well.
“While modern techniques still have a long way to go to match the creativity and precision of artisans, our process is more similar to traditional glassworking than to standard 3D printing with plastics,” said Kinzel, who collaborates with artisan Kiva Ford, a master designer of specialty glass apparatuses at Notre Dame’s Radiation Research Laboratory.
A glass artisan can move a workpiece in many directions—up/down, forward/backward, left/right, plus wrist rotations and finger manipulations. With Kinzel’s technique, the glass object moves along five axes relative to a CO₂ laser. This provides a greater range of motion than traditional 3D printing in which the nozzle moves in x and y axes.
“We’re still more constrained with 5-axes compared with the artisan who has 12 degrees of freedom with two hands,” said Kinzel. “However, our technique permits coordinated rotation, and this enabled the printing of the spiral, glass ornament.”
Using their novel, 3D-printing technique, Kinzel’s graduate students Nishan Khadka and Md. Nadeem Azad created the ornament using optical fiber with a diameter of only 1/200th of an inch (125 μm)—thinner than a strand of Christmas tree tinsel. The ornament is just over a third of an inch tall, the height of one Lego brick.
“Our tree doesn’t weigh much either,” said Kinzel. “The fun thing is that these structures are quite flexible. Even with thicker filaments, you can easily flex them with your fingers like a spring.”
Developing an efficient and cost-effective technique for 3D printing glass would enable the production of complex structures, such as photovoltaic glass, without relying on labor-intensive manufacturing processes. The innovation could also lead to a broader use of glass, an eco-friendly material.
“We’re happy that our glass Christmas tree has sparked curiosity about our lab’s work and shown that it’s possible to fabricate these complex, spiral 3D geometries, though we’re clearly not yet ready to compete with Santa’s workshop,” said Kinzel.
— Karla Cruise, Notre Dame Engineering; Photos by Wes Evard, Notre Dame Engineering