Tough, super-stretchy gel could make better implants

LOOK out, Mr Fantastic: there’s a new creation in town that is super-stretchy and ultra-strong, despite being 90 per cent water.

The material is a hydrogel, an artificial substance that has similar properties to many tissues in the human body. Familiar to many as soft contact lenses, hydrogels have also been used as wound dressings or cartilage replacement.

There is a limiting factor: “Most hydrogels are brittle, like tofu or Jell-O,” says Zhigang Suo of Harvard University. “To be used in the body, hydrogels have to be flexible and tough.”

Suo and colleagues created their substance by mixing two polymers each crosslinked with different types of chemical bonds. The resulting hybrid gel can stretch to more than 20 times its original length and still bounce back into shape (Nature, doi: 10.1038/nature11409).

Other hydrogels have been made about as stretchy, but they rip easily if they suffer small tears.

“It’s like the rubber of a balloon,” says Suo. “If you cut a small hole in it and then try to stretch it, the hole will get bigger and the rubber will break.”

Even when slightly torn, the new gel can stretch to around 17 times its original length before it tears. The team thinks this toughness may be due to the gel’s hybrid nature.

Costantino Creton at ESPCI ParisTech in France, says the hydrogel has the best balance of properties yet, as well as being easy to make: “It shows promise where you need something soft and flexible but also durable.”