Transparent and hard – but still it does not shatter in the event of an impact: Researchers have developed an amazingly high-performance material made of glass flakes and acrylic that is inspired by the structures of the shell mother-of-pearl. The features of the new super-glass material surpass previous versions and it is comparatively easy to manufacture. Among other things, it could make the displays of smartphones more robust in the future, say the developers.
Due to its transparency, rigidity and resistance to many stresses, glass is one of the most important useful materials for humans. Unfortunately, however, it also has a problematic property: its low breaking strength limits the possible uses and is the cause of notorious damage: some cell phone or tablet displays are already splintered after a fall. Techniques such as hardening and lamination, although they can help reinforce glass, are costly and stop working once the surface is damaged. For this reason, materials researchers have been devoting themselves for some time to the challenge of developing glass that, in addition to its coveted properties, also has increased breaking strength.
Inspired by mother-of-pearl
A team from McGill University is based on models from nature. “Evolution is a master of design. If you study the structure of biological materials and understand how they work, you can be inspired by them and use them as templates for new materials, ”says senior author Allen Ehrlicher. Specifically, the scientists have been trying for years to transfer the characteristics of mother-of-pearl from mussel shells to glass materials. “Amazingly, mother-of-pearl has the properties of a rigid material, but also the resilience of a soft one,” says Ehrlicher. The secret is based on the combination of tiny, hard lime flakes with soft proteins. This composite material forms a brick wall-like structure in mother-of-pearl. “It gives the mother-of-pearl a strength that is 3000 times higher than that of the individual materials,” says Ehrlicher.
Previous attempts to transfer the system to glass have already led to success. But the transparency of the materials left a lot to be desired and the production was also complex. That is why Ehrlicher and his colleagues have again worked on an alternative approach. The scientists mimicked the architecture of mother-of-pearl with layers of glass flakes in combination with the relatively soft plastic acrylic. The composite material is brought into the brick wall-like structure of the mother-of-pearl model by centrifugation processes.
Promising glass composite material
This comparatively simple and inexpensive method initially resulted in a material that was very hard and break-resistant – but not yet transparent. So the scientists then turned to the challenge of giving the composite optical transparency. “We finally succeeded in adjusting the refractive index of the acrylic so that it merges seamlessly with the glass and results in a truly transparent composite material,” reports first author Ali Amini.
The result is now an easy-to-produce glass composite material that, according to the researchers, eclipses previous versions: “Until now, you had to compromise between high strength, toughness and transparency. Our new material is now five times more break-proof than normal glass, ”concludes Ehrlicher. It could thus be suitable for improving the properties of various glass structures – such as the displays of smartphones and co. Next, the researchers are now planning further optimizations: Among other things, they want to give the glass material the potential, properties such as color, mechanics, by implementing additional components and change conductivity.
Finally, the scientists draw attention to a curious story in connection with their research: flexible glass is supposedly a lost invention from the time of the reign of the Roman emperor Tiberius. According to the traditions of ancient authors, an inventor presented the ruler with a drinking bowl made of a mysterious glass material. Instead of breaking, it just dented instead of breaking when loaded. The story came to a macabre end: after the inventor swore he was the only one who knew how to make the material, Tiberius had him executed because he feared that the glass would devalue gold and silver because it could be more valuable . “When I think of this story, I’m glad that our material innovation only resulted in a publication and not an execution,” says Ehrlicher.
Source: McGill University, Article: Science, doi: 10.1126 / science.abf0277