Researchers from the University of Durham (UK) and the Fraunhofer Institute (Germany) have developed a material whose sole purpose is to resist any attempts to cut it. This does not mean prohibitive strength or even invulnerability - on the contrary, called "Proteus", the new material can be completely destroyed. But precisely cutting or drilling with the help of mechanical devices is completely useless.
Proteus consists of an aluminum base, into which numerous ceramic spheres are evenly inserted into the bun dough like raisins. They are not fixed in place and are not so strong - on the contrary, the outer layer of ceramics actively crumbles under load, turning into grains of sand. Because of this, a viscous mess of ceramics, dust and metal particles forms at the place of deformation, which fills the gap.
This is very similar to how a bullet gets stuck in a sandbag - the farther it moves, the more grains of sand begin to contact it, slowing down its movement. If instead of a metal drill, you take a water cutter, the rounded and movable ceramic particles will rotate under the action of the jet and reflect it in different directions, which ultimately makes it just as useless. You can leave as many cuts as you like on the surface of the Proteus aluminum case, but you will not be able to cut it entirely.
As noted by the co-author of the development Stefan Shinishevsky, trying to cut Proteus is akin to trying to break through a jar of jelly with diamonds. The developers plan to use the novelty to create light armor and protective equipment against melee weapons and other similar threats. It can also be used to make anti-theft cables for bicycles, which are unlikely to be eaten even with bolt cutters.