Flexible glass could offer more rugged smartphone displays

January 31, 2014 // By Jean-Pierre Joosting
Oneof the limitations of big-screen displays on pocketable products - such as smartphones - is that they have to be fronted by a sub-mm-thin sheet of glass. Apple already uses Gorilla glass to provide scratch resistance to its smartphone displays but the glass will still shatter upon impact. There are also rumours that Apple isconsidering using sapphire coated glass in their next generation iPhone to provide even more scratch resistance as sapphire is almost as hard as diamond.

Not only might the iPhone 6 feature a sapphire-coated glass display - according to recent speculation-  but it could also come with solar cells embedded into the display. Bendable glass that does not shatter on impact would enable smartphone manufacturers to address the issue of broken displays - which happens, in the real world.

Inspired by the mechanics of natural structures such as seashells, professor François Barthelat and his team at McGill University’s Department of Mechanical Engineering 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.

“Mollusc shells are made up of about 95% calcium carbonate, which is very brittle in its pure form,” says Barthelat. “But nacre, or mother-of-pearl, which coats the inner shells, 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.

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