An asymmetric clay film for smart moisture actuators: Film actuation and characterization

Exploring low-cost materials and convenient fabrication is crucial for the development of humidity responsive actuators. Montmorillonite (Mt.), one of the natural layered clays, provides the great potential in the field of smart actuators. We present the self-assembling Mt.bilayer film, which was simply prepared by sequential vacuum filtration of Mt. and organic montmorillonite (OMt) dispersions. When exposed to the uniform humidity, the obtained Mt./OMt bilayer film shows good stable actuation and a large bending deformation with a curvature up to 360 degrees. Several biomimetic devices (window cutain, flower and gripper) was designed using Mt./OMt films and their smart actuation was demonstrated through programmable bendings. Importantly, more complex shapedeformations and more intelligent actuators can be realized by simply printing glue arrays on OMt side of the bilayer film. Additionally, the obtained Mt./OMt film is sensitive to various solvents and shows different bending behaviors upon exposure to the organic solvents vapors. This work may demonstrate a new, simple and promising strategy for potential application of layered clay in flexible robots, biomimetic devices, and solvent sensors.