Many people fondly remember playing with toys known as Shrinky Dinks—sheets of polystyrene plastic with shapes that kids can color, cut out and heat in an oven, where they shrink into thicker pieces of plastic. Now, researchers have repurposed shrink films for an unexpected use: making strong, durable grippers that could someday encapsulate materials or be incorporated into soft robotics. They report their results in ACS Applied Polymer Materials.
Shrinky Dinks® undergo their dramatic transformation because they are shape-memory polymers. Manufacturers pre-stretch the sheets of polystyrene so that when heated above 217 F, they shrink back to their former size. Michael Dickey, Jan Genzer and colleagues wondered if they could exploit these properties to make inexpensive grippers that would be stronger and retain their shape better than other soft materials used for this purpose, such as hydrogels and elastomers.