Biomimetic shape-morphing actuators with controlled bending deformation and photo-mediated 3D shape programming for flexible smart devices

Biomimetic soft actuators with programmable morphing behaviors and remote actuations have drawn significant attention in recent years. In this work, we present the network architecture of a four-arm crystalline shape memory polymer actuator via efficient thiol-acrylate coupling of polycaprolactone precursor bearing crosslinkable methacrylate end-groups with pentaerythritol, followed by post-approach surface chemistry of polydopamine (PDA) nanospheres coating. The excellent photothermal transfer efficiency of the coated PDA can enable rapid temperature increase over the transition temperature of polymeric matrix and optically drive the shape morphings. Combined with built-in internal stress, anisotropic polymer chain relaxation of the strained thin actuator film would generate asymmetric contractions and thus causes controlled bending deformations via surface directing of an 532 nm green laser. Beyond this, the dynamic nature of transesterification reaction also provides the actuator film with reprogrammability. Remarkably, the morphing behaviors of a flexible plane film into various soft robots including 3D airplane and chiral helix were achieved under a 300 mW/cm2 simulated light irradiation. The results presented in this study clearly provide a new method for designing actuators with spatiotemporally programmable morphing behaviors and will pave way for the construction of flexible smart devices.