Hydrophilic domains compose of interlocking cation-π blocks for constructing hard actuator with robustness and rapid humidity responsiveness

• A robust sturdy actuator combines a rigid matrix and hydrophilic domains. • Rapidly swelling polymer actuator results in unprecedentedly large stresses. • The interlocking cation-π blocks allow actuator to revert to its original shape. • The activating 2D-to-3D shape transformation through thermoreversible S–S bonds. Biomimetic actuators have seemingly infinite potential for use in previously unexplored areas. However, large stresses and a rapid water response are difficult to realize in soft actuators, owing to which their practical applicability is currently limited. In this paper, a new method for designing and fabricating humidity-responsive sturdy hard actuator. By combining a rigid matrix and hydrophilic water domains consisting of dynamic interlocking cation-π blocks, high-performance polymer actuator was synthesized that swell rapidly in response to a water gradient in their environment, resulting in unprecedentedly large stresses. More critically, the strong interlocking cation-π blocks reform and the intermolecular distance is reduced when the water is removed, allowing the deformed actuator to revert its original shape. The proposed design principle can potentially be extended to produce different types of sturdy actuators with rapid water responsiveness.