Hydrogels: are they keeping their heads above water?

For as long as biomaterials have been designed, there has been a strong interest in certain water-containing substances known as hydrogels. These have been assumed to be "biocompatible" because of certain similarities they have with tissues of the body, but they also offer a variety of other desirable characteristics. For several reasons, however, hydrogels have not fully realized their potential. This article addresses some of the issues involved.