Stretchy, strangely adhesive, and able to 'self-heal' if cut, the surprising properties of these gels potentially make them useful for a wider range of applications than commonly-used plastics, which are either hard and brittle or soft and easily torn.

"We've created a class of materials that we've termed glassy gels, which are as hard as glassy polymers, but – if you apply enough force – can stretch up to five times their original length, rather than breaking," says Michael Dickey, materials scientist at North Carolina State University (NCSU).

But as with so many fortuitous scientific discoveries, the goal was never to make a whole new class of subtances, Dickey tells ScienceAlert.

"We stumbled into these interesting materials," he says, when NCSU researcher Meixiang Wang was experimenting with ionogels, materials made of a polymer swollen with an ionic liquid that conducts electricity.

Wang was trying to make stretchable, wearable devices that might be used in a pressure sensor, other medical devices or robotics. Altering the composition, Wang produced a gel that looked at first like a "mundane piece of transparent, flexible plastic" before testing showed it was very hard – but not brittle like other common plastics.

"Once we realized they have remarkable properties, we dove in to understand them better," Dickey says.

The glassy gels are made using an ionic liquid, which is similar to water but made entirely of charged particles, allowing it to conduct electricity. When mixed with a polymer precursor the liquid pushes the polymer chains apart, making the material soft and stretchy. At the same time, the ions are also strongly attracted to the polymer chains, preventing them from separating.