Programmable and Reversible Self-assembly of 3D Architectures Actuated by Flexible Metal–Organic Frameworks

Respond rapidly and reversibly to external stimuli are critical to mimic biological systems. To design a multi-stimuli responsive actuator, we built a novel type of monolayer composite film that integrates the swellable metal-organic frameworks (MOF-88C) into the polymer P(VDF-CTFE). When exposed to polar solvent vapors (toluene, acetone, dichloromethane, and methanol), the composite-strip produces a reversible shape transformation derived from the intrinsic flexible of MOF crystal. Benefited to the active swelling MOF, the instant reversible bending (angle change >360° within 10 seconds) of the composite strip was realized at minute concentrations of dichloromethane vapor. Furthermore, to realized specific and programmable actuation, we use two fabrication strategies, templates and femtosecond laser system to control over swellable MOF crystals spatial distribution within the polymeric film. Interestingly, the composite film successfully mimicked natural plant tendrils, flowers that blooms or closes and soft robots that wriggle and grab objects. The composite material based on flexible MOF is a promising candidate for smart material of autonomous soft mechanical driving device.