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.