Video: A Ball of Metal Bounces Off a Thin Sheet of Super-Tough Hydrogel

We’ve seen hydrogels–the squishy material of the future–do some neat tricks before. Researchers, for example, have already tried to make them autonomous self-healers, ready to repair themselves when they break. But what if they just didn’t break at all under strain? Then you’d get something like this video, which shows a new, super-strong hydrogel shrugging off a ball of metal.

Toughness is a major plus for hydrogels. Their semi-solidity makes them a good choice for add-on biological materials, like contact lenses or drug-delivery systems, and even stronger hydrogels could be used for bigger projects (Nature points to replacement cartilage or scaffolds for growing artificial organs).

This particular gel comes from Harvard University materials engineer Zhigang Suo, who, along with a team, created the gel from two polymers: alginate and polyacrylamide. They work in tandem to create the effect seen in the video. The ionic bonds of the alginate molecules break and reform under pressure, spreading the energy of an impact over a wider area. That also protects the covalent bonds in the polyacrylamide molecules, which hold the gel together.

What does that translate to? A hydrogel as tough as rubber that can stretch 20 times its normal length, and that can do this to a ball of metal.