Apply a large enough stress to a piece of brittle material and it will break—most likely at a preexisting flaw or weak spot. Flaws thereby reduce the fracture strength of real materials relative to their theoretical maxima, sometimes by orders of magnitude. That reduction can be well predicted by the expected statistical distribution of flaw sizes, which depends on the sample’s size.

Reduce the sample’s dimensions below a micron or so and the picture changes. Submicron single crystals of metal or ceramic, whether they contain flaws or not, are much stronger than their bulk counterparts.1 Furthermore, a submicron sample is no more likely to break at a flaw than anywhere else. The reasons for that size effect remain unclear. But it’s been noted that fracture-resistant biomaterials—such as shells, bone, and tooth enamel—are made up of just such submicron mineral crystals embedded in a protein matrix.2 (For more on...

You do not currently have access to this content.