Heat-reactive material can learn to transform into multiple shapes

Science : Self-folding materials—polymers that take on a predetermined shape when subjected to certain stimuli, such as heat, electric charge, or magnetic fields—have been around for a while. The first such materials all functioned through elasticity, which is the tendency of a material to return to its default shape, and they could only be designed with two or three shapes to shift into. Combining elasticity with another property known as plasticity, or the ability to be reshaped, was thought to be the key to creating materials that could take on any number of shapes. Now Tao Xie of the State Key Laboratory of Chemical Engineering in Hangzhou, China, and his colleagues have figured out how to combine two such materials. Their compound can transform between different shapes using both properties—with transition temperatures of 70 °C for elasticity and 130 °C for plasticity—and it can make the transition hundreds of times with little sign of fatigue. The next step, says Xie, is getting the material to work at room temperature.