Asymmetric Metal-Organic Framework-Based Mixed Matrix Membrane for Reversible Self-Assembling 3D Architecture

Shape-transformationmetal-organic framework (MOF)-basedsoft actuators that can quickly respond to external stimuli have beenpotential candidates in the areas of biomimetic soft robots, smartmechanical devices, and flexible devices. Herein, we construct a uniqueasymmetric mixed matrix membrane (MMM) consisting of swellable iron(III)fumarate (MIL-88A, MIL= Materials from Institute Lavoisier) on oneside and methacrylate-functionalized polydimethylsiloxane (MA-PDMS)on the other side. Upon variation of the humidity environment, theasymmetric composite membrane exhibits reversible and repeatable bendingbehavior. Through simple graphical programming, the composite membraneobtains a self-folding ability and successfully realizes diversifiedpredictable 3D architectures, including artificial flowers, automaticmechanical claws, and unilateral crawling devices. Moreover, the 3Darchitecture could be restored to a 2D plane through the desorptionof MIL-88A and the thermal expansion of MA-PDMS derived from near-infrared(NIR) light and exhibit continuous motion to imitate living creaturesin nature. This work will offer insight into the fabrication of programmablesoft actuators, thus shining enlightenment for their potential applicationin bioinspired soft robots and smart mechanical devices.