Researchers at Vilnius University, Lithuania, have succeeded in 3D printing glass-ceramics on a nanoscopic scale.
Strong and potentially fluorescent or superconductive, these amorphous materials, and their fabrication via additive manufacturing, facilitates the creation of tailor-made quantum dots and unlocks new potential in microdevice manufacturing. Examples of such devices include microrobots or microfluidic chips used in medical research.
Ultrafast laser 3D lithography
For this experiment, the researchers used two-photon lithography technology. A method of 3D fabrication on a photonic scale, the technology employs an ultrafast pulsed femtosecond lasers to precisely cure a light-reactive material. One commercial method of this technology is marketed by Germany’s Nanoscribe in the Photonic Professional GT system, however the Vilnius University system is known as “ultrafast laser 3D lithography” or “3DLL.”
The material selected for study is glass-ceramic, or “sol-gel”, resist SZ2080, a modified silica gel and photopolymer, often researched for medical applications, and used to make UV-protective coating or quantum dots.
Green parts and glass-ceramics
A multi-step process, similar to green part metal sintering, SZ2080 is first 3D printed into a desired shape with features hundreds of nanometers in size. Examples given in this study include a micro-sculpture of Vytis, the coat of arms of Lithuania; a cube; photonic crystal structures and hexagonal scaffolds.
After printing, the parts are sintered at temperatures up to 1500°C. This process decomposes 80% of the material content, causing the part to shrink by 40 – 50 % and produce an even higher resolution than the part as-printed.
The sintering process also creates the object’s glass-ceramic crystalline structure, leading to superior mechanical and chemical properties.
As the research states, “The silica and zirconia precursors present in the resist in the ∼20% mass of inorganic component will lead to emergence of silica and zirconia crystalline phases in the final sintered ceramic material.”
More complex, resilient microdevices
By tailoring this process, researchers will be able to make freeform 3D structures with a complexity impossible to create via other microfabrication methods. In addition, the structures, as stated in the conclusions of this study, will “acquire new features, especially resilience at harsh physical and chemical environments.”
Furthermore, “Since nanoscale materials can initiate precipitation,” (for making pigments and conducting water desalination among other things) “and guide growth of nano-crystallites,” (e.g. quantum dots) “a wide field for experimentation horizons are widened by the presented modality of additive manufacturing.”
‘Additive-Manufacturing of 3D Glass-Ceramics down to Nanoscale Resolution’ is available open-access via ResearchGate. The paper is co-authored by Darius Gailevičius, Viktorija Padolskytė, Lina Mikoliūnaitė, Simas Šakirzanova, Saulius Juodkazis, and Mangirdas Malinauskas.
The research was funded by a grant from the U.S. Army Aviation and Missile Research Development and Engineering Center (AMRDEC), which is seeking to uncover applications in efficient sensing.
Featured image shows uniform scaling of a micro 3D printed Vytis sculpture. Left shows the sculpture as printed. Right shows the same structure after sintering at 1200°C for one hour. Image via Vilnius University