Mollusc shells consist largely of chalk, the same soft stuff that comes apart so easily on blackboards. Yet this material provides aquatic life with protection tougher than advanced engineering ceramics. The difference can be seen at the microscopic level, where the shell is revealed as an interlocking series of small tablets, intricately connected to provide remarkable resilience.

The structure of ordinary mollusc shells has been mimicked to create not-so-ordinary, tough-to-break glass. Photo credit: McGill University

This same kind of resilience can now be created in ordinary glass. In a recent issue of Nature Communications, McGill University researchers identified a technique for generating an interior network of microcracks that enhances the strength of glass by two orders of magnitude.

McGill’s François Barthelat led a team that worked with standard glass slides, about 150 microns in thickness and a bit smaller than the average business card. Using a laser beam with a relatively modest 500 milliwatts of power, Barthelat’s team focused the light tightly on the edge of the slide, inducing cracks that appear like the wavy edges of a jigsaw puzzle. “It’s not only on the surface,” says Barthelat, a mechanical engineering professor. “There are thousands of them within the slide.”

Using a miniature mechanical testing machine for measuring how much energy it takes to break the glass, the researchers confirmed that the laser-treated samples had become about 200 times tougher. Barthelat suggests that the glass could be made even stronger by varying laser pulses in a more controlled fashion. Meanwhile, the injection of an optical polyurethane could render the microcracks invisible, so that this glass would be indistinguishable from its more delicate counterpart. “Observing the natural world can clearly lead to improved man-made designs,” says Barthelat, adding that the same approach could work with other materials. “We plan to work with ceramics and polymers in the future.”