Picture a rope in a tug-of-war, with two teams pulling in opposite directions. As long as the forces match, the rope holds. But if one team gives a sudden yank, the rope can snap. The same thing happens in rubber with nanoparticles mixed into it.

When rubber is stretched, tension builds up inside it, much like a rope being pulled taut. At first the particles can shift a little, releasing some of the stress. Under strong stretching, though, they line up in rows and get stuck, like people packed into a crowded bus who can no longer move an inch. At that moment the pressure spikes, and a void opens up in the rubber.

Using calculations, the scientists found this happens at a pressure of about 4 MPa, very close to the value for real rubber. That means the mechanism works the same way across different materials. If we can learn to control how the particles move, we could make rubber that holds out longer before it tears.