Using ultraviolet light instead of extremely high temperatures, a team of Georgia Tech researchers has developed a new approach for 3D printing small glass lenses and other structures that would be useful for medical devices and research applications.

Their process reduces the heat required to convert printed polymer resin to silica glass from 1,100 degrees Celsius to around 220 degrees C and shortens the curing time from half a day or more to just five hours. They’ve used it to produce all kinds of glass microstructures, including tiny lenses approximately the width of a human hair that could be used for medical imaging inside the body.

Led by George W. Woodruff School of Mechanical Engineering Professor H. Jerry Qi, the team described their approach Oct. 4 in the journal Science Advances.

The team’s printing process presents a climate friendlier option for silica glass manufacturing.

Typical additive manufacturing processes for glass require polymer mixtures that must be burned away with heat once the desired shapes are formed. The Georgia Tech team’s approach uses a photoresin that is converted to glass using a kind of ultraviolet light called deep UV light. That allows for lower temperatures that save significant heating energy. And because they don’t have to add extra polymer material, fewer resources are involved in the first place.

The researchers employed a light-sensitive resin based on a widely used soft polymer called PDMS, and they don’t have to add silica nanoparticles to their mix like other 3D printing methods. The result is highly transparent glass without the potential optical issues that can arise with the added nanoparticles. The glass lenses they produced were as smooth as commercially made fused silica glass.

In addition to Qi’s group in the Woodruff School, the research team also included Rampi Ramprasad’s lab in the School of Materials Science and Engineering. Right now, their process creates structures that are 200 – 300 micrometers in size — equivalent to the thickness of a piece of paper or the diameter of a human hair. They’ve started to work on scaling up the glass structures they can 3D print to the millimeter scale.

Qi said advances in 3D printing technology and interest in ceramics — inorganic, nonmetallic materials that are shaped, fired, harden, and become heat- and corrosion-resistant — pushed the group to think about new approaches to their manufacture. And they found a willing partner in the Office of Naval Research, which funded the effort.

“We really want to do the cutting-edge — things nobody has done before in the space of low-temperature conversion of polymers to ceramics within additive manufacturing,” Qi said. “We were encouraged by the Office of Naval Research. They know the risk is high, but they gave us a lot of freedom to try new things.”