According to Georgia Tech, a team of 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 – using ultraviolet light instead of extremely high temperatures.
Their process reduces the heat required to convert printed polymer resin to silica glass from 1,100 degrees Celsius to around 220 degrees Celsius and shortens the curing time from half a day or more to just five hours. They’ve used it to produce a multitude of glass microstructures, including tiny lenses that are approximately the width of a human hair and 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 in the journal Science Advances.
“This is one of the exploratory examples showing that it is possible to fabricate ceramics at mild conditions, because silica is a kind of ceramic,” said Qi. “It is a very challenging problem. We have a team that includes people from chemistry and materials science engaged in a data-driven approach to push the boundary and see if we can produce more ceramics with this approach.”
Along with the miniaturization of lenses for medical endoscopes, these 3D printed glass structures could create microfluidic devices – typically small computer chip-like devices with nano- or micro-scale channels used to study cells or biofluids in motion. Glass chips would offer advantages over current chips made of polymer materials, the researchers said – resisting corrosion from chemicals or body fluids.
According to Mingzhe Li, a postdoctoral researcher in Qi’s lab and the study’s first author, the low-temperature process also would enable the fabrication of microelectronics with glass structures. “We can print in situ, directly into microelectronics,” said Li. “Semiconductor materials used in microelectronics cannot withstand very high temperatures. If we want to print directly on a board, we have to do it at a low temperature, and 200 degrees C can definitely do this job.”
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 – allowing for lower temperatures that save significant heating energy.
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. Their glass lenses were reportedly 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, the 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 manufacturing.
The Office of Naval Research 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,” said Qi. “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.”