Photocrosslinking Patterning of Single-Layered Polymer Actuators for Controllable Motility and Automatic Devices

Shape-programmed deformation of soft polymer films is essential for applications in robotics, self-adaptive devices, and sensors. In comparison to bilayer polymer actuators, the challenge remains to manipulate single-layered soft actuators for rapid, reversible, and shape-programmed deformations in response to external stimuli owing to their homogeneous composite structures. Herein, this work reports a soft polymer film actuator that has a single-layered structure, yet demonstrates the shape-programmed motility. The actuator is composed of polyvinylidene fluoride film as a matrix and patterned by photocrosslinking of acrylamide and N', N'-methylenebisacrylamide, which generates soft-hard alternating segments in the structure. As it is exposed to acetone vapors, the soft-hard structures lead to an unequal response that results in the shape-programmed deformation. The actuator is elastic (strain: 160%) and tough (stress: 40 MPa) and can maintain its rapid, reversible, and shape-programmed motions for a few hours, even longer. The soft-hard structure enables the film actuator (3.5 mg) to give a contracting stress of 4 MPa that is used in an automatic device able to lift a cargo of 5.09 g, ∼1453 times heavier than the film itself. The power output reaches 474 J kg^-1, ∼100 times higher than the reported soft actuators. This simple application indicates a potential for the soft actuator used in acetone vapor sensing devices.