Autonomous helical propagation of active toroids with mechanical action.

Self-assembly in nature is fundamentally dynamic, existing in out-of-equilibrium state in which the systems have the ability to autonomously respond to environmental changes. However, artificial systems exist in a global minimum state, which are incapable of conducting such complex functions. Here we report that input of thermal energy can trigger fixed, artificial toroids to spontaneously nucleate helical growth. The helical polymerization undergoes reversible and repeatable cycles with subsequent energy input. When the toroids are located inside lipid vesicles, the polymerization-depolymerization cycle is accompanied by reversible elongation of spherical vesicles. Such liberation from a global minimum state will pave the way to create emergent structures with functions as complex as those of living systems.