Researchers at the University of Freiburg have figured out how to injection mold glass. Their new production method yields detailed parts that would be impossible to make using conventional techniques, and at far greater speed.
In conjunction with a startup called Glassomer, the researchers have developed polymer granules that contain silica glass particles. These granules can be injection molded using standard equipment. After being ejected from the mold, the parts are washed, removing some of the polymer (which can be harvested and re-used); then the part is baked in an oven, where the remaining polymer is vaporized by the heat, leaving just the silica glass particles. As the temperature in the oven is cranked up, the glass particles fuse together. The resultant part is pure quartz glass.
Image: Neptun Lab/University of Freiburg
"For decades, glass has often been the second choice when it comes to materials in manufacturing processes because its formation is too complicated, energy-intensive and unsuitable for producing high-resolution structures," explains Prof. Dr. Bastian E. Rapp from the Laboratory of Process Technology at the Department of Microsystems Engineering at the University of Freiburg. "Polymers, on the other hand, have allowed all of this, but their physical, optical, chemical and thermal properties are inferior to glass. As a result, we have combined polymer and glass processing. Our process will allow us to quickly and cost-effectively replace both mass-produced products and complex polymer structures and components with glass."
There is, however, a slight catch that needs to be factored into the design: Because material is being removed from the part after it comes out of the mold, it shrinks--equally in all directions, thankfully--by about 15%.