Complicated gear-like shapes created using a new method
By Robert F. ServiceApr. 8, 2021, 3 p.m.
The production of glass – one of the oldest materials known to man – is being redesigned in the 21st century. A new approach to glassmaking treats the material like plastic, allowing scientists to inject vaccine bottles, tortuous channels for doing laboratory chemistry, and other complex shapes.
“It’s really exciting work,” says André Studart, materials scientist at ETH Zurich. “This is a great way to shape glass into intricate and interesting geometries.”
Glass was first found in Egypt and Eastern Mesopotamia around 3500 BC. Manufactured. Then as now, the material was made by melting silicon dioxide or silicon dioxide at around 2000 ° C and then shaping it using various techniques. Modern glass-making techniques can easily mass-produce certain shapes such as flat window panes and rounded bottles, but they cannot produce the intricate designs required for modern biomedical instruments.
In 2017, researchers headed by Frederik Kotz, microsystems engineer at the Albert Ludwig University of Freiburg, wanted to change this. They redesigned a 3D printer to forge glass instead of printing plastics or metals.
Scientists created a printable powder by mixing silica nanoparticles with a polymer that could be cured with ultraviolet (UV) light. After printing the shapes they wanted, they used UV light to cure the polymer to keep it in shape. They then burned the mixture in an oven to burn off the polymer and fuse the silica particles into a continuous glass structure.
The approach worked and enabled the creation of shapes such as tiny pretzels and replica castle gates. The work attracted the interest of companies that wanted to build tiny lenses and other complex transparent optical components for telecommunications equipment. However, the process was slow and made the components one at a time rather than taking a completely industrial approach where parts could be mass produced, as is the case with plastic.
To speed things up, Kotz and his colleagues have now expanded their nanocomposite approach to injection molding, a process that mass-produces plastic parts like toys and bumpers by the ton. The researchers started again with tiny particles of silica. The team then mixed the silica with two polymers, polyethylene glycol (PEG) and polyvinyl butyral (PVB). The mixture produced a dry powder the consistency of toothpaste. The team fed the paste into an extruder, which pressed it into a pre-formed shape with shapes like a disk or a tiny gear.
Outside of the shape, the parts retain their shape as a myriad of weak attractive bonds, known as van der Waals interactions, form between neighboring silica particles. But the parts are still fragile.
To harden them, the researchers used water to wash off the PEG. The remaining material was then fired in two steps: first at 600 ° C to burn out the PVB and second at 1300 ° C to fuse the silica particles into the final piece.
“What you get in the end is high-purity quartz glass” in any shape you want, says Kotz. The glass parts also have the optical and chemical properties required for commercial telecommunications equipment and chemical reactors, he and his colleagues report in Science today.
This is useful, Studart says, because its transparency, chemical inertness, and stability at high temperatures make glass ideal for diagnosis, drug packaging, and even bumpy surfaces that improve solar cell efficiency. “In my opinion [the method] will trigger a lot of new ideas. “
According to Studart, however, this new approach to mass production of glass parts is still associated with a bottleneck: washing off the PEG must be done slowly over days to ensure that the glass parts do not crack. Speed it up, he says, and injection molding glass could become just as popular as plastic.