Tensile Properties of Hydrogels and of Snake Skin

Stimulus-responsive or “smart” gels are of potential interest as sensors and actuators, in industrial separations, and as permeable delivery systems [1]. In most applications, a certain degree of mechanical strength and toughness will be required, yet the large-strain behavior of gels has not been widely reported. Some exceptions include work on gelatin [2] and other food gels [3], some characterization of soft gels applicable for in-vitro cell growth studies [4], and toughness determinations on commercial contact lens materials [5]. In general, it can be anticipated that the gel stiffness will increase with increasing degree of crosslinking, but the tensile strength may go through a maximum [6].