Biomedical uses of shape memory polymers.

A new type of plastic polymeric material is described which can dramatically change its physical properties with temperature. These changes include hardness, flexibility, modulus of elasticity and shape. These changes occur within a very narrowly defined range of temperatures, which can be controlled in the manufacturing process. These "memory resins" can be formed by casting, extruding, injection molding and solution coating into a rigid form which has low cytotoxicity. Warming followed by cooling allows forming of the material; the new shape is retained until the part is rewarmed and recooled, at which time the part reverts to its original manufactured shape. The author describes several current and proposed uses for these shape memory polymers.