KTH Royal Institute of Technology
A team of Swedish scientists has developed a new technology for 3D printing Silica glass Simplifies complex energy-intensive process. As a proof of concept, they printed the world’s smallest wine glass (made of actual glass) using a frame smaller than the width of a single hair, as well as an optical resonator for fiber-optic communication systems—one of several potential applications for 3D-printed silica glass components. They described their new method in The last paper In Nature Communications.
“The backbone of the Internet is based on optical fibers that are made of glass,” said co-author Christine Gilvason from KTH Royal Institute of Technology in Stockholm. “In these systems, all kinds of filters and comparators are needed that can now be 3D printed with our technology. This opens up many new possibilities.”
Silica glass (i.e., amorphous silicon dioxide) is one material that remains challenging for 3D printing, especially at the microscopic level, according to the authors, although several approaches are seeking to address this challenge, including lithography and inking. Direct and digital light processing. Even those were only able to achieve feature sizes on the order of several tens of micrometres, with one exception Study 2021 that reported nanoscale accuracy.
But all of those are used Sol Gel Processes involving different organic mixtures loaded with silica nanoparticles. The final printed structures are therefore composites containing many organic materials, and thus lack the most desirable properties of silica glass (i.e., thermal and chemical stability, hardness, and optical transparency over a wide range of wavelengths). It requires an additional sintering step at high temperatures of about 1,200 °C (2,192 °F) for several hours to remove the organic residues and achieve those properties. This extra energy-intensive step severely limits potential applications as only substrate materials that can withstand higher temperatures can be used. Some approaches also require 3D printed structures to be assembled into a final form, which is challenging on a micrometer scale.
When developing their alternative 3D printing technology for silica glass, Gylfason et al. Turn into hydrogen silsesquioxane (HSQ), an inorganic silica-like material that can be shaped by electron rays, ion rays, and certain wavelengths of ultraviolet light. One major advantage is that their method does not rely on organic compounds to act as photosensitizers or binders that remain on the substrate, as is the case with lithography or direct ink writing. Instead, their method relies on direct cross-linking of inorganic HSQs.
The process has three main steps. First, they dropped HSQ dissolved in organic solvents onto a substrate. Once the HSQ dries, they trace the desired 3D shape using a focused sub-picosecond laser beam. Finally, any uncovered HSQ is dissolved with a plain use of potassium hydroxide solution. Raman spectroscopy of the printed microstructures showed all the expected features of silica glass.
However, there were also residual traces of hydrogen and carbon. For applications requiring more pure silica glass, residual organics can be removed by annealing the structures at 900 °C (1,652 °F)—an additional step granted, but at a much lower temperature than the usual additional sintering step. Then, the spectrum of the structures was matched to a commercial fused silica glass substrate. While annealing the 3-D microstructures can cause them to shrink or distort, the authors found that the maximum shrinkage for their silica glass structures was about 6 percent, compared to between 16 percent and 56 percent for glass objects made using lithography and direct inking methods. . .
In addition to a small proof-of-concept wine glass and optical resonator, the authors imprinted a small version of the KTH logo, a cantilever, and a conical spiral, as well as a silica glass fiber optic tip. They believe their method could be used to make custom lenses for medical devices and micro-robots as well. Coating 3D printed microstructures with nanodiamonds or ferrous nanoparticles could enable further customization of the integration properties of hybrid quantum photonics or magnetically removing control of the motion of the structures, respectively.
“The concerns when integrating 3D printing methods are usually different for different applications,” said co-author Bo Han Huang, a graduate student at KTH. “Although optimization of our method is still required for different applications, we believe that our method provides an important and necessary breakthrough for 3D printing on glass for use in practical scenarios.”
DOI: Nature Communications, 2023. 10.1038 / s41467-023-38996-3 (about DOIs).