As one of the world’s hardest materials, we tend to think of diamond as rigid and unyielding. But scientists have succeeded in making diamond needles that are so thin they can bend under pressure.

Diamond is hard but also brittle, and attempts to deform even a small sliver usually result in fractures, rather than bending. But a research team based in Hong Kong and Singapore showed that it is possible to make bendy diamonds by producing tapering, 300nm-wide ‘needles’ of the material. They created the structures by etching them from thin films of diamond synthesised by chemical vapour deposition. When mounted on a silicon sheet so that they stick straight upwards, the pointed ends of these structures can bend without breaking when they are pushed with an indenter – also made from diamond – inside a scanning electron microscope.

Theoretical simulations combined with microscope observations of the needles suggest they have the ability to bend while retaining their high strength because they have fewer defects and smoother surfaces than larger diamonds, which makes them less prone to brittle fractures. The extent to which the needle tips bent is close to the theoretical limit for diamond shown in previous calculations.

Diamond has lots of applications in research, and being able to tinker with its physical properties in this way could open up new opportunities in data storage, optomechanical devices and bioimaging, the researchers say.