Researchers claim they've come up with the world's first manufactured non-cuttable material, just 15 percent the density of steel and impervious to drills or angle grinders. They say it could make for indestructible bike locks and lightweight armor.
https://newatlas.com/materials/proteus-non-cuttable-bike-lock-armor
Just because it’s resistant to saws and drills doesn’t mean it can’t be “cut” with some hydraulic shears or blown through by a kinetic penetrator, so it’s applications are rather limited. For it to be of use on a bike lock, I would assume it would need to be used as a cladding on the body and shackle over a tough core material. And composite armors are already a thing.
Would be great cladding for things like safes and vault doors and the like, though.
@estherschindler
...
It’s highly cut resistant, but yes, it has interesting applications.