LAUSR

Small, smooth, and bendable diamonds If you manage to deform a diamond, it usually means you have broken it. Diamonds have very high hardness, but they do not deform elastically. This limits their usefulness for some applications. However, Banerjee et al. discovered that diamond nanoneedles can deform elastically after all (see the Perspective by LLorca). The key was in their small size (300 nm), which allowed for very smooth-surfaced, defect-free diamonds. The deformation was close to the theoretical limit for diamond, which opens up the potential for applications in microelectronics and drug delivery. Science, this issue p. 300; see also p. 264 Diamond nanoneedles have smooth surfaces and are defect-free, allowing them to deform elastically. Diamonds have substantial hardness and durability, but attempting to deform diamonds usually results in brittle fracture. We demonstrate ultralarge, fully reversible elastic deformation of nanoscale (~300 nanometers) single-crystalline and polycrystalline diamond needles. For single-crystalline diamond, the maximum tensile strains (up to 9%) approached the theoretical elastic limit, and the corresponding maximum tensile stress reached ~89 to 98 gigapascals. After combining systematic computational simulations and characterization of pre- and postdeformation structural features, we ascribe the concurrent high strength and large elastic strain to the paucity of defects in the small-volume diamond nanoneedles and to the relatively smooth surfaces compared with those of microscale and larger specimens. The discovery offers the potential for new applications through optimized design of diamond nanostructure, geometry, elastic strains, and physical properties.