Porous Organic Cage with Water Vapor-Triggered Structural Transition for Actuation Applications

Fabricatingsmart humidity-responsive actuators that can convertthe potential of humidity into other forms of energy, such as mechanicalenergy and electricity, is of great importance in the context of theintelligence age and energy crisis. Here, a flexible porous organiccage that can undergo a reversible structural transformation between & alpha; and & beta; phases upon humidity stimulation is successfullyfabricated into a humidity-responsive actuator by using a polymerwith intrinsic microporosity (PIM-1) as a matrix. The humidity-responsivemechanism is unveiled in depth by various characterizations. We findthat the inherent porosity of PIM-1 significantly enhances the performanceof the resulting actuator. These actuators can be used to performbionic motions, such as serving as smart grippers and crawling robots.After further coupling with a piezoelectric film, the formed bilayerdevice can output stable voltage-level power upon periodic humidityswitching. This work demonstrates the first example of using a porousmolecular cage as a humidity-responsive actuator and energy transducer,providing new insights into the design and fabrication of smart materialsfor advanced applications.