Medical News
Technology
27 June 2019
The layered structure of mother of pearl has inspired a new kind of glassEye of Science/SPL
By Michael Le PageA type of glass that bends like plastic has been created by copying seashells. It could be used to make safer windows, more shatterproof screens for phones and even foldable screens that don’t scratch easily.
“We can make a piece of glass that drastically deforms like a piece of plastic,” says Francois Barthelat at McGill University in Canada. “It duplicates what we see in seashells.”
Mother-of-pearl, or nacre – the iridescent material that lines the inside of many seashells – is made mostly of brittle calcium carbonate. But it is extremely tough and strong because the calcium carbonate is arranged in tiny hexagonal platelets joined by flexible biopolymers.
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When this material is struck, the platelets can slide over each other as the polymers stretch, dissipating the energy of the impact instead of shattering. Extreme forces can rip the platelets apart but the resulting cracks don’t spread as they do in materials like glass.
Many teams around the world are working on ways of mimicking these properties. Barthelat’s team have done it by using a laser to engrave patterns on thin sheets of glass. These sheets are then laminated together with a plastic called ethylene-vinyl acetate. During the lamination, the sheets are broken along the engraved lines into tiny squares or hexagons.
The result is a material that has many of the desirable properties of glass, such as being highly transparent and scratch-resistant, but that is far more impact-resistant than either laminated or tempered glass.
The new glass is flexible like plasticYin et al., Science (2019)
When it does break, the damage remains localised rather than spreading through the entire sheet as happens when, say, a laminated car windscreen is broken. “If you press hard on a corner you badly damage that corner but the rest of the glass isn’t affected,” Barthelat says.
The main downside is that it is too bendy for some purposes – nobody wants droopy windows. For many purposes, it will be necessary to add an extra layer or two of plain glass, which makes the material more prone to breaking – but it is still two or three times more impact resistant than tempered glass, says Barthelat.
The glass can be cheaply manufactured and could be especially useful for phones and tablets.
The screens of smart devices are currently made of tempered glass treated to make them more scratch resistant, but they shatter easily when dropped. The latest iPhones have glass backs as well to allow wireless charging, making them even more prone to breaking.
Barthelat says the mother-of-pearl glass could also be used to make foldable screens. Samsung was due to release the first-ever phone with a foldable screen in April, but it has yet to be launched after reviewers found serious flaws, including easily damaged screens.
Journal reference: Science, DOI: 10.1126/science.aaw8988
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