Light-Activated Soft Material Inches Along

Gone are the days when robots were made solely from rigid metal parts and electronic circuitry. Scientists now strive to make flexible, soft, nonmechanical robots that can change shape and delicately handle fragile objects. To help turn that vision into a reality, researchers led by Jian Chen of the University of Wisconsin, Milwaukee, have designed a soft polymeric material that moves when hit with a flash of infrared light (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201210232). The team fabricated the robotic substance by polymerizing and stretching a mixture of acrylate-based liquid-crystal monomers and carbon nanotubes. They attached a sheet of the composite material to the top of a passive layer of silicone. When exposed to IR light, the nanotubes in the liquid crystal-silicone bilayer heat up, causing ordered polymers to undergo a phase transition and become disordered. The motion induces strain that forces the bilayer to bend. To demonstrate the material’s usefulness, the researchers turned a sheet of it into a light-activated gripper that curls around small objects, enabling their transfer from one point to another. The team also added hinges of the polymeric bilayer to a plastic sheet and activated them in sequence to make the whole device walk slowly forward.