The 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 cured the polymer with UV light so it would hold its shape. They then fired the mix in an oven to burn off the polymer and fuse the silica particles into a continuous glass structure. The approach worked, making it possible to craft shapes such as tiny pretzels and replica castle gates. The work garnered interest from companies wanting to build minute lenses and other complex transparent optical components for telecommunications equipment. But the procedure was slow, turning out components one by one, rather than a fully industrial approach that could produce parts en masse, as is done with plastic.
To speed things up, [the researchers] have now extended their nanocomposite approach to work with injection molding, a process used to mass produce plastic parts like toys and car bumpers by the ton. The researchers again started with tiny silica particles. The team then mixed the silica with two polymers, polyethylene glycol (PEG) and polyvinyl butyral (PVB). The mixture created a dry powder with the consistency of toothpaste. The team fed the paste into an extruder that pressed it into a preformed mold with shapes such as a disc or tiny gear. To harden them, the researchers used water to wash away the PEG. They then fired the remaining material in two stages: First at 600C to burn out the PVB, and second at 1300C to fuse the silica particles into the final piece. Outside of the mold, the parts hold their shape because myriad weak attractive bonds, called van der Waals interactions, form between neighboring silica particles. But the parts are still fragile. The report has been published in the journal Science.
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