A new jelly-like substance developed by materials engineers in the US and South Korea could one day be used as replacement cartilage. It's a hydrogel - a water-based compound - which means that it's compatible with the workings of the human body. Many of the tissues in the body can be classified as natural hydrogels; the brain, for example, is made up of nearly 80 per cent water.
A combination of two other hydrogels, the new material can stretch up to 21 times its own length and is able to withstand a force 10 times that of natural cartilage. It is also much more resistant than each of its ingredients. One ingredient, polyacrylamide, is used to make disposable contact lenses, while the other, alginate, is mainly used to thicken food.
Ordinarily, molecular chains of alginate knit themselves together with weak ionic bonds, which are quickly broken when the material is stretched. However, in the new compound, when the alginate bonds break, they form much stronger covalent bonds with the polyacrylamide. The result is a material that can withstand all the rigours that natural cartilage endures. As well as replacement cartilage, this gel could one day be used for dressing wounds and in components for soft-bodied robots.
Written by Sacha Torregrosa-Jones