Intelligent Gels; May 1993; Scientific American Magazine; by Yoshihito Osada and Simon B. Ross-Murphy; 6 Page(s)

Industrial products are generally made of metal, ceramic or plastic. These substances are by nature tough, hard, dry and easy to work with. Most engineers avoid "wet" components, such as liquids and gels. Liquids are entirely unable to maintain their shapes; gels are weak and tend to fail under small loads. Indeed, gels may be chemically unstable, and their properties suffer if they are allowed to dry. At present, they are used only in a few specialized applications, such as foods, water absorbents and soft contact lenses.

Yet a growing number of workers, taking inspiration from nature, have begun to see opportunities in these materials. Biological systems consist mostly of soft and wet substances. Indeed, many creatures live entirely without a rigid frame. The sea cucumber, for example, is essentially a water-swollen gel containing primitive organs; nevertheless, it can feed, reproduce and even defend itself from attackers. The sea cucumber responds rapidly to touch by stiffening its usually flexible body, and if it is further mishandled, it can cause part of its body wall to turn into a viscous fluid mass that prevents it from being grasped firmly.