Scientists have developed a photoactive hydrogel capable of increasing its volume by more than 80,000% within just 40 seconds when exposed to visible light. Even more remarkably, the same material can be programmed to bend, twist and form left- or right-handed helices depending on where and from which direction the light is applied. Once the illumination is removed, the programmed shape can be erased, allowing the material to be reconfigured again.The effect is enabled by a light-sensitive molecule called spiropyran embedded within the polymer network. When illuminated, the molecule changes the interactions between the polymer chains, allowing the hydrogel to absorb large amounts of water and expand dramatically. By illuminating selected areas, researchers create differences in expansion across the material, giving them precise control over how it bends and twists.
In laboratory demonstrations, tiny strips of the hydrogel were used to lift loads, operate a light-controlled underwater switch and drive a miniature rotating system. Researchers believe the technology could eventually be useful in soft robotics, adaptive grippers, miniature valves, pumps and other devices that can change their mechanical function without conventional motors. The technology remains at the experimental stage, however, and further development will be required before practical applications become possible.
Source: Nature Communications
