What’s the sharpest knife in the world? © iStock

What’s the sharpest knife in the world?

Obsidian knife blades: overkill for slicing your sandwich.

Asked by: Lizzie Myers, Andover

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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.


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