LAUSR

resistant to cracking — a property that could be exploited to produce safer cars, aeroplanes and power plants. Conventional sheet metals are prone to failure when exposed to repeated stress, because cracks, once formed, easily spread. Inspired by the fracture resistance of bone, Motomichi Koyama of Kyushu University in Fukuoka, Japan, and his colleagues designed an alloy with a similar substructure. The authors packed different metal nanostructures together in a hierarchical way. This helped to deflect and halt the growth of cracks in stress tests, allowing the steel to withstand higher levels and more cycles of applied stress than commonly used steels.