Tough gel material could replace cartilage

A gel material that can stretch 21 times its length, rebound and repair itself could lead to advances in medicine and tissue engineering. U.S. scientists say. Called a hydrogel, because its main ingredient is water, the material is exceptionally tough -- tougher than human cartilage -- self-healing and biocompatible, researchers at Harvard University reported Thursday. "Conventional hydrogels are very weak and brittle -- imagine a spoon breaking through jelly," lead author Jeong-Yun Sun at Harvard's School of Engineering and Applied Sciences said. "But because they are water-based and biocompatible, people would like to use them for some very challenging applications like artificial cartilage or spinal disks." To create the tough new hydrogel, they combined two common polymers to form a complex network of crosslinked chains that reinforce one another. "The unusually high stretchability and toughness of this gel, along with recovery, are exciting," researcher Zhigang Suo said. "Now that we've demonstrated that this is possible, we can use it as a model system for studying the mechanics of hydrogels further, and explore various applications." Beyond artificial cartilage, the researchers say the hydrogel could be used in soft robotics, optics, artificial muscles, as a tough protective covering for wounds or "any other place where we need hydrogels of high stretchability and high toughness."