Bendable glass could toughen up smartphones

January 30, 2014 // By Jean-Pierre Joosting
Apple already use Gorilla glass to provide scratch resistance to their smartphone displays but the glass will still shatter upon impact. There are also numerous rumors that Apple are considering using sapphire coated glass in their next generation iPhone to provide the ultimate in scratch resistance as sapphire is almost as hard as diamond. Not only could the iPhone 6 feature a sapphire-coated glass display according to recent speculation but that it will also come with solar cells embedded into the display.

Bendable glass that does not shatter on impact would enable smartphone manufacturers to address another huge consumer concern, that of broken displays we too often encounter in the real world.

Inspired by the mechanics of natural structures like seashells, professor François Barthelat and his team at McGill’s Department of Mechanical Engineering in order to significantly increase the toughness of glass were able to increase the toughness of glass slides 200 times compared to non-engraved slides. This was achieved by engraving networks of micro-cracks in configurations of wavy lines in shapes similar to the edges of pieces in a jigsaw puzzle in the surface of borosilicate glass, which stops cracks from propagating and becoming larger.

These micro-cracks were then filled with polyurethane, although according to Barthelat, this second process is not essential since the patterns of micro-cracks in themselves are sufficient to stop the glass from shattering.

“Mollusk shells are made up of about 95 per cent chalk, which is very brittle in its pure form,” says Barthelat. “But nacre, or mother-of-pearl, which coats the inner shells, is made up of microscopic tablets that are a bit like miniature Lego building blocks, is known to be extremely strong and tough, which is why people have been studying its structure for the past twenty years.”

Previous attempts to recreate the structures of nacre have proved to be challenging, according to Barthelat. “Imagine trying to build a Lego wall with microscopic building blocks.” Instead, the researchers used lasers to engrave networks of 3D micro-cracks in glass slides in order to create similar weak boundaries that are found in natural materials like nacre.

Barthelat believes that the process will be easy to scale up to any size of glass sheet and that it can also be extended to ceramics and polymers.

‘Overcoming the brittleness of glass through bio-inspiration and micro-architecture’ by F. Barthelat et al in Nature Communications:

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