Mollusk Inspired Glass That Bends But Does Not Break

Drawing inspiration from seashells, international scientists have created a glass that bends but does not break when dropped.

Glass shatters easily and is one of the reasons that expensive glass items are kept safely away. But a new tough glass created by scientists does not break although it might get slightly bent on dropping hard.

Researchers at McGill's Department of Mechanical Engineering have developed the new glass drawing inspiration from the mechanics of seashells.

Prof. Francois Barthelat, the study lead, explains that the Mollusk shells consist of 95 percent chalk (calcium carbonate). These shells also have three different layers that give the mollusk strength and also a tough covering. The mother-of-pearl (or nacre), the composite material produced by mollusk that coats the inner shells, consists of tiny tablets that are very brittle and tough. Several attempts were made by scientists to recreate nacre, but none succeeded.

In this study, the researchers focused on the internal weak boundaries found in the nacre. This nacre is 3,000 times more break-resistant when compared to the other minerals, that is why scientists have been studying it for years.

Later, they engraved the networks of 3D micro cracks in glass slides in order to produce similar weak boundaries. They were surprised to see that the toughness of the glass slides increased 200 times in comparison to the non-engraved slides. This was achieved by engraving networks of the micro-cracks in jigsaw-puzzle-like waves, which prevented them from spreading and getting larger. The cracks were stuffed with polyurethane.

Barthelat strongly believes that this process can be easily scaled to any size of glass sheet.

"What we know now is that we can toughen glass, or other materials, by using patterns of micro-cracks to guide larger cracks, and in the process absorb the energy from an impact," says Barthelat. "We chose to work with glass because we wanted to work with the archetypal brittle material. But we plan to go on to work with ceramics and polymers in future. Observing the natural world can clearly lead to improved man-made designs."

The research funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI), is documented in the journal Nature Communications.