Due to its exceptional transparency as well as its stability in contact with heat or chemicals, glass is relevant for many high-tech applications. However, conventional glass forming processes are often time-consuming, energy-intensive and quickly reach their limits for small and complicated components. Materials scientists from Freiburg, Dr. Frederik Kotz-Helmer and Prof. Bastian E. Rapp, in cooperation with the University of California, Berkeley in the USA, have developed a new process that can be used to produce quickly and with precision of very small components from transparent glass thanks to 3D micro-printing. Possible applications include components for sensors and microscopes, but also for lab systems on a chip. The researchers were able publish results in the famous magazine Science.
Glass powder in a plastic binder
The new technology is based on so-called Glassomer materials, which Kotz-Helmer and Rapp developed at the Department of Microsystems Engineering (IMTEK) at the University of Fribourg. “Glassomer materials are made of glass powder in a special plastic binder,” says Kotz-Helmer, “allowing the glass to be treated like a plastic.” The components thus obtained are then placed in an oven which causes the combustion of the plastic and the sintering, that is to say the densification of the glass. “Ultimately, the components are made of 100 percent highly transparent fused silica glass,” says Kotz-Helmer.
The component is created in one step
Freiburg scientists have now combined Glassomer materials with a new 3D printing process developed by a research team led by Professor Hayden Taylor of the University of California, Berkeley. Conventional 3D printers print their objects layer by layer. However, in the new process, called computed axial lithography (CAL), the component is created in a single step. A container containing liquid light-sensitive material is exposed to two-dimensional light images of the object to be printed from many different angles. When the images overlap and the quantity of light absorbed thus locally exceeds a certain threshold, the material suddenly hardens: in a few minutes, the component is formed. Excess material that is still liquid can be washed away.
Structures with the thickness of a single hair
“In principle, this process also works with the Glassomer material,” says Kotz-Helmer. To this end, the Freiburg scientists have developed a material consisting of glass powder and plastic which is both highly transparent and hardens quickly to an appropriate threshold value. “The devil was in the chemical details here,” says the materials scientist. Previously, moreover, the CAL process was only suitable for relatively coarse structures. By combining the materials science expertise of the University of Freiburg and project partner Glassomer GmbH, a Freiburg spin-off, as well as the further development of system technology at the University of California, it has now possible to combine and improve these technologies. “For the first time, we were able to print glass with structures on the order of 50 micrometers in just a few minutes, which is about the thickness of a hair,” says Kotz-Helmer. “In addition, the surfaces of the components are smoother than with conventional 3D printing processes.”
Glass as a substitute for vulnerable plastic
Kotz-Helmer sees possible applications for the innovative manufacturing process, for example, in the micro-optical components of sensors, virtual reality headsets and modern microscopes: “The ability to manufacture such components at high speed and with great geometric freedom will enable new functions and more cost-effective products in the future.”
Microfluidic channels are also required for so-called lab-on-a-chip systems for research and medical diagnostics. Until now these have been mostly plastic, but they often cannot withstand high temperatures and harsh chemicals. Thanks to the new process technology, complex channel systems can now be made of glass, says Kotz-Helmer: “Thanks to the thermal and chemical stability of glass, many new application areas are opening up, especially in the field of chemistry over-synthesis of a chip.”
– This press release was originally published on the website of the University of Friborg