Soft, Stretchy, And Tough

A hydrogel with record-busting toughness that’s superstretchy to boot has been created by a team of engineers (Nature, DOI: 10.1038/nature11409). The new material could improve the performance of products made from hydrogels, such as flexible contact lenses and tissue engineering scaffolds. It could also open up applications for which hydrogels were previously considered too prone to breakage to be useful, such as in materials for cartilage replacement. Hydrogels are made mostly of water—roughly 90%—held into a solid form by water-insoluble polymers. They don’t typically stretch very far, and they are usually quite brittle, with a fracture energy of only about 10 J/m2. By contrast, the new hydrogel has a fracture energy of about 9,000 J/m2 and can stretch to 20 times its initial length without breaking. The real breakthrough in creating tougher, stretchier hydrogels came in 2003, says Zhigang Suo, the Harvard University mechanical engineering professor who led the development ...