A light-powered shape-configurable micromachine

Micromachines that are capable of performing certain tasks in a liquid environment have become one of the major research focuses in the past decade. In this paper, we report a novel light-driven fuel-free micromachine with reversible shape-changing capability. Interestingly, the mechanism to propel the micromachine is the Marangoni flow which derives from the preferential swelling caused by light-induced doping phenomena. More interestingly, under different irradiation conditions, the micromachine not only exhibits on–off–on motion and directional motion, but is also capable of switching between different motion behaviors (moving, outward surface water flow or their combination) in a controllable fashion. Furthermore, the micromachine is able to undergo reversible structural changes to realize a sheet-to-tube transition, which regulates its motion behavior as well. We thus believe that the current work may provide useful insight into the design of micromachines with novel motion behaviors.