Science Focus - the home of BBC Science Focus Magazine

What’s the sharpest knife in the world?

Subscribe to BBC Science Focus Magazine and get 6 issues for just £9.99

Obsidian knife blades: overkill for slicing your sandwich.

Asked by: Lizzie Myers, Andover


The thinnest blades are three nanometres wide at the edge – 10 times sharper than a razor blade. These are made by flaking a long, thin sliver from a core of obsidian (volcanic glass).

Obsidian knives have been tested for use as surgical scalpels but aren’t currently licensed for use on humans, since they could leave glass fragments in the wound.

Read more:


Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.


luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.


Sponsored content